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MikeOxon

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  1. MikeOxon

    A Galaxy of Stars

    By MikeOxon,


    General
    In my previous post, I wrote that I needed to make a model of one of the longer-boilered ‘Stars’, to see if it made a better comparison with the photograph taken at Cheltenham shed around 1850.
     
    According to the RCTS booklet Part Two, two ‘Stars’ were built with boilers that were 2 feet longer than the others – these were ‘Rising Star’ and ‘Bright Star’. We are very fortunate that E.T. Lane not only made several sketches of ‘Rising Star’, including end-elevations, but also produced a finished and very detailed drawing of the same engine.
     
    E.T. Lane
    I have made considerable use of sketches by E.T. Lane in my blog posts, so I thought I should find out a little more about him. It proved to be a far from easy search but I eventually found information on the ‘Ancestry’ website.
     
    Edward Theophilus Lane, to give his full name, was one of two sons of the engraver and lithographer Richard James Lane. Both sons died young.
     

     
    Richard James Lane, was born at Berkeley Castle in 1800, He became a Royal Academician and, in 1829, he drew a well-known portrait of the young Princess Victoria, later to become Queen. In lithography, he is reputed to have attained a delicacy and refinement which have never been surpassed.
     
    In addition, Edward’s grandmother was a niece of the celebrated painter Gainsborough, so there was a history of artistic talent running in the family.
     
     
    With that background, it is hardly surprising that Edward should have developed his own artistic talent, with which he chose to provide us with a remarkable series of sketches and drawings of engines and other rolling stock at Swindon, up to his early death at the age of 20. In addition to sketch books, he left 41 sketches of locomotives, carriages, and wagons on separate sheets.
     
    It seems likely that he succumbed to one of the many epidemics that plagued ‘New Swindon’ in those years, including outbreaks of cholera and smallpox. He must have returned home to London, where he was buried at St. Pancras in 1850.
     
    His elegant drawing of ‘Rising Star’ stands as a fine example of his art:
     

    Finished drawing of ‘Rising Star’ by Edward Lane, dated April 25, 1849
     
     
    My 3D-model of Rising Star
    I created my model by modifying the drawings of ‘Evening Star’, described in my previous post. I lengthened the frames by inserting an additional 8 mm (scale 2 feet) between the leading and driving wheels and, similarly, I extended the boiler length by 2 feet. I created a new firebox. which had a reported case length of 5 feet, as opposed to 4’ 10” on ‘Evening Star’. I also created a new ‘haycock’ top, to the profile shown in the Lane drawing. On the sketches by Lane, the smokebox is shown as 1” longer than ‘Evening Star’, while the trailing wheels have only 14 spokes compared with 16 spokes on the leading wheels. (this last is a characteristic shared with his sketch of ‘Vulcan’ and applied to my model of that engine.
     

    My 3D-model created by reference to Lane’s drawing
     
    These various minor differences demonstrate the way in which each of these early engines was ‘hand made’, with various small discrepancies between one engine and the next, apart from any significant design changes. As I pointed out in my earlier post ‘From the Stars to Firefly’, the great innovation by Gooch was to ensure that all his Firefly-class engines were built to standard templates, so that components were interchangeable between different members of the class.
     

    My 3D-model of Rising Star
     
    My two models of ‘Evening Star’ and ‘Rising Star’, rendered in ‘Fusion 360’, appear together below. These are not ‘finished’ models but are intended simply to show the more obvious differences between members of the same class. Neither Lane’s drawing nor his sketches of ‘Rising Star’ show a manhole cover on the ‘haycock’, so I have not included one in my model, although I strongly suspect that one was, in fact, present on the prototype.
     

    My 3D-models of ‘Evening Star’ (left) and ‘Rising Star’
     
    My next ‘test’ is to see how my model of ‘Rising Star’ compares with the engine in the photograph taken at Cheltenham:
     

    My model of ‘Rising Star’ compared with Cheltenham photo
     
    Of course the match is not perfect. It is, in fact, rather difficult to adjust all the display parameters, so that the ‘Fusion 360’ model has the same perspective as the photograph. I do believe though that the longer boiler matches the photo rather well and that the firebox is more appropriate than the one on Lane’s sketch of ‘Evening Star’. Without more information about the photograph, which is probably lost in the mists of time, I can’t take matters any further.
     
    Expanding the Galaxy
    There is another finished drawing by Edward Lane of the last of the Stars, ‘Royal Star’, delivered in November 1841, four years after the first of the class – the famous ‘North Star’ – and some time after many of Gooch’s own Firefly-class had entered service.
     
    ‘Royal Star’ reverted to the shorter (8’) boiler used on ‘Evening Star’ and the most obvious difference from the earlier engine lay in the shape of the firebox casing. This was shorter (4’ 6” length) and taller, with wood-lagged sides in the shape of a ‘Gothic arch’ up to the high-mounted safety valve casing.
     
    I made a ‘haycock’ top some years ago by a rather convoluted method.  With more knowledge of the tools in ‘Fusion 360’, I tried a simpler method but it was soon obvious that adding the wooden lagging to the curved sides of the ‘Gothic’ box was going to be a new modelling challenge!
     
    To create the Gothic box, I first made a cuboid box and then drew the ‘Gothic’ profile on one side. I then used the ‘push-pull’ tool in Fusion 360 to produce the ‘Gothic’ arch in one direction. After that, I rotated the box though 90 degrees and repeated the ‘push pull’, to create the second, orthogonal arched profile. A diagram helps:
     

    Creating ‘Gothic’ Firebox in Fusion 360
     
    That proved to be a very straightforward method but adding the planked lagging needed more thought. I eventually found a solution from watching this video on YouTube..
     
    For this solution, I created a new body by extruding from the inner outline I had already sketched, as shown in the diagrams above. I then slid this body through the firebox body – fortunately, this is allowed in the virtual world, where bodies pass freely through one another! Next, I had to cut the arched faces of this new body to match the profile of the firebox itself. Again, a diagram helps:
     

    Creating the Lagging on Firebox Sides
     
    The finishing touch was to represent the planks of the wooden lagging To do this, I made a single horizontal slot near the bottom of a lagged side. I then used the ‘pattern on path’ command in ‘Fusion 360‘ to repeat this feature upwards, along a path following the profile of the side of the firebox. This procedure almost magically created the feature that I wanted.
     

    My 3D-model of a Gothic Firebox for Royal Star
     
    All that remained was for me to place this firebox into my model of ‘Royal Star’, which was mainly just a copy of ‘Evening Star’:
     

    My 3D-model of Royal Star
     
    Later Re-builds
    Most of the ‘Stars’ were converted into Tank engines during the 1850s. The conversion included replacement of the leading 4’ diameter wheels by pairs of 3’ 6” diameter wheels and lengthening of the boiler to 10 feet, where this had not already been done.
     
    Since I now had the ‘bit between the teeth’, I thought I would illustrate this later development by modifying my model of ‘Rising Star’, which already had a 10’ boiler. The re-design was generally straight-forward: just adding a saddle-tank and bunker. These parts were similar to those I have previously designed for my model of ‘Leo’.  The most difficult modification was to redesign the front end of the frames to accommodate the paired wheels. It didn’t take very long, however, before I had a 3D-model, which I have named ‘Red Star’
     

    My 3D-model of ‘Red Star’
     
    One again, I should point out that these are not ‘finished’ models but are only intended to indicate the different characteristics of the various members of the ‘Star-class’. I hope I have shown that not all GWR engines look the same!
     

    My Galaxy of Stars
     
    There’s a lot more work needed before any of these become printable models but that means I have plenty of material to keep me going through the coming winter months 🙂
     
    Mike
  2. MikeOxon

    A Tangled Web

    By MikeOxon,


    General
    I’ve referred before to the problems that arise from using published drawings as the basis for creating 3D models of early locomotives. The usual dictum of “find a photograph of your selected prototype” simply doesn’t apply to the years before photography became established.
     
    That leads to the next problem – so much of the information we read about early locomotives comes from books that were written decades after the time to which they refer. Even Gooch’s own ‘diary’ is considered suspect, since the pages about the early years were clearly written much later. It’s by no means a new problem either – Sekon, in his book ‘The Evolution of the Steam Locomotive’, published in 1898, made the following comment: “Readers may wonder why such obviously inaccurate statements should be published. One can only conjecture. Many lists of early locomotives have during the past few years been published. These should, however, be accepted with the very greatest caution.”. Matters have got considerably worse with the passage of much more time!
     
    We are very fortunate to have the sketch books and drawings made by the young apprentice at Swindon in the 1840s, Edward Lane, who sadly died at the age of 20. In his short life, he made an invaluable record for posterity of first-hand views of early Broad Gauge locomotives and other rolling stock. Even though many of his illustration are only rough sketches, they present a ‘from life’ impression and many of them are annotated with measurements and additional sketches of small details.
     
    Much later, early in the 20th century, another set of illustrations was produced by G.F. Bird and these appeared in a special supplement to ‘The Engineer’ magazine. Later still, after WW2, the RCTS produced a booklet covering the Broad Gauge Engines of the GWR as Part Two of a series on GWR Locomotives. On page B3, the booklet comments that “Bird's line drawings, the early ones mainly derived from the sketches and drawings made by E. T. Lane at Swindon in 1848/9, still remain a classic. They are the only known illustrations of many of the early engines and some are used yet again in this volume”. We must not, however, forget the caution sounded by Sekon back in 1892 and, from my own experience, Bird appears to have misinterpreted some of the information contained in Lane’s sketches.
     
    In replying to comment in my previous post about Leo-class engines, I wrote that “Another example I have found is the case of 'Evening Star', where Lane shows appropriate-looking safety valve covers but with figures above them that seem to indicate a much larger diameter. Bird has drawn extremely fat covers, presumably based on his reading but, to me, they do not look 'right'.”
     

    Comparison of sketch by Lane and later drawing by Bird
     
    I reported that “One day, I must study this engine in more detail”, so here goes!

    Modelling ‘Evening Star’
     
    In the case of the ‘Stars’, we are especially fortunate to have a couple of very early photographs of three Broad Gauge locomotives outside Cheltenham shed, possibly as early as 1848. One of the engines is alleged to be ‘Polar Star’, although I have not found a good reference to the source of that attribution.
     

    Early Photographs taken in Cheltenham c.1848

    According to the RCTS Part Two, ‘Evening Star’ was similar to ‘Polar Star’, so the photographs shown above are a useful point of reference.
     
    I also wanted a larger version of the Bird drawing than that shown in ‘The Engineer’ supplement published 16th December 1910, which included charts showing various Broad Gauge engines. This led me to another of the pitfalls that are frequently encountered with published drawings! I turned to Arman’s ‘Broad Gauge engines of the GWR, Part1’, published 2018, where on p.82, there is a reproduction of Bird’s drawing from the Locomotive Magazine 1901. It is immediately obvious (from the elliptical wheels) that this reproduction is compressed in the vertical direction. These distortions always have to be watched out for!
     
    Returning to the Lane sketch, I decided to create a sketch in Fusion 360, using Lane’s written dimensions. The result, shown below, looks to be proportioned similarly to the Bird drawing.
     

    My Sketch based on Lane’s Dimensions
     
    Although some Lane sketches appear to be accurately proportioned, this one clearly is not. Even some of his written dimensions appear to be incorrect. For example, the overall length of the boiler between smokebox and firebox is clearly marked as 7’ 9” (31mm in 4mm scale) but there are three figures written below, apparently referring to the boiler rings, that do not add up to this total – they are “2.3”, “4.3”, “3.2”. Perhaps the central figure refers to the boiler diameter over the cladding?
     
    At this point, I must state that I have not made any pilgrimages to Kew or York, to study original drawings. I note that there is a lot of detailed information about dimensions of the various ‘Stars’ in the RCTS booklet but I do not know the original sources. Therefore, please exercise the caution advised by Sekon, when reading the following paragraphs concerning my own speculation.
     
    Now I return to the matter of the safety valve casings. The ‘Polar Star’ photos do not show any fitted on the boiler of ‘Polar Star’, so these photos are of no help. The only guide I have is that Lane’s ‘from life’ sketch shows tall, narrow casings, similar to those on the ‘North Star’ replica in Swindon Museum, rather than the odd-looking fat tubes in Bird’s drawing.
     
    I have been looking at other Lane sketches for clues and found one of ‘Hesperus’, a ‘Sun-class’ engine, with a carefully drawn casing but, unfortunately, without any dimensions being shown. To my eyes, it looks like a better-drawn version of the casings shown on the rough sketch of ‘Evening Star’. The plinth is wider than the main column and I suggest could be the source of the “1” dimension, marked on the ‘Evening Star’ sketch. Perhaps, I am just adding more ‘errors’ by my speculations but I am influenced by the ‘jizz’ of Lane’s sketch.
     
    So I have continued to create a 3D-model in Fusion 360, drawing on the information contained in the photographs and the Bird drawing, as well as the Lane sketch, to re-create the frames and the haycock top of the firebox. The RCTS Part Two states that the firebox casing on ‘Evening Star’ was 4’ 10” long, which agrees exactly with Lane’s dimension, so I am content to use this figure.
     

     

    My 3D-model of ‘Evening Star’ created in Fusion 360
     
    Now, though, I come up against a major discrepancy between the Lane drawing of ‘Evening Star’ and the supposedly similar ‘Polar Star’, alleged to be the engine in the Cheltenham photograph.  In Lane’s sketch, the joint between the rectangular firebox and the ‘haycock’ top is well below the level of the boiler top, whereas the photograph shows a much taller rectangular box with a more ‘squashed’ haycock top.
     
    In the caption to the Cheltenham photographs on p.84 of Arman’s book ‘Broad Gauge Engines of the GWR, Part One’, he asserts that “Polar Star had its frames and boiler lengthened by 2’ 0” by 1849, so we can date the photograph as prior to that work being carried out”. I am not at all sure about that. I oriented my model in Fusion 360 as closely as I could to one of the Cheltenham photographs and the comparison shows that the boiler appears significantly longer in the photo, ahead of the driving wheels, than in my model:

     
    My 3D-model of ‘Evening Star with photograph of ‘Polar Star’
     
    As a further test, following a method I have used on other photographs, I used the ‘perspective’ control in 'Photoshop' to allow comparison between the diameter of the driving wheel (known to be 7’) and the length of the boiler in the photograph of ‘Polar Star’
     

    ‘Cheltenham Photo’ with Perspective Adjustment
     
    Knowing the diameter of the driving wheel was 7 feet, this comparison indicates the boiler length was (330/230) x 7 feet, i.e. 10 feet. This supports my suggestion that, at the time of the photograph, the frames and boiler of the ‘Star’ had been lengthened by 2 feet from the original 8 foot boiler length. The design of the firebox also matches Lane’s sketch of ‘Rising Star’ which was built with the longer boiler.
     
    It now looks as though I shall have to make a model of ‘Rising Star’ to take this investigation further!
     
    Mike
     
     
     
  3. MikeOxon

    Another new 'Old Engine' - 2

    By MikeOxon,


    general
    My first post in this series described how I produced a working drawing for a model of GWR No.184. Now, it's time to consider the tender and, for this, information is less readily available. Wet and windy weather has kept me indoors, so that progress has been rather quicker than I had anticipated.
     
    The various photographs of No.184 show it partnered with a variety of different tenders, so I decided to try to model the tender shown together with its 1893 re-build. I have not found a broadside view of this engine/tender combination, so have had to work from the oblique view shown in my previous post.
     
    In a forum thread on Estimating Dimensions from Oblique Views , I described a technique for correcting the effects of perspective by using the tools in the photo-editing program 'Photoshop Elements' (PSE). This program can adjust the magnification across an image, to correct for the angle between the subject and the camera. Once this has been done, it becomes possible to compare the distances between different points on a photograph, providing these points all lie in the same plane.
     
    In order to use this method on the photograph of No.184, I first identified some parallel lines that are as well-spaced as possible in the image. I chose a line along the top of the boiler and the line defined by the rails below the engine, and marked these in red on the photo, as shown below:
     

     
     
    The next step is to use the 'Perspective' tools in PSE, to distort the image until these two lines are made as parallel as possible,. ( I use an early version of PSE but the principles remain the same in later versions, although the menus may differ in detail.)
     
    First select the whole image (Select | All) and then select 'Transform | Perspective' in the Image Menu. Use the mouse to drag the handles that appear around the image, to offset the effects of perspective by enlarging the more distant parts of the image, as shown below.  It helps to turn 'on' the grid display, when judging when the lines have become parallel.
     

     
     
    Once the image has been 'squared up' in this way, it is possible to compare distances measured along the frames of the engine and tender. The coupled wheelbase of No.184 is known to have been 8 feet, so I used the 'Line' tool to draw a line between the wheel centres, in the plane of the engine frame, and measured the length of this line in pixels. On my image, this length was 188 pixels. I then drew similar lines between the tender wheel centres, which both measured 130 pixels. The 'real' distances between these points are in direct proportion to these lengths, giving an estimated tender wheelbase of 130/188 X 8 feet, or 5' 9" between each pair of axles.
     

     
     
    Unfortunately, the photograph does not show the entire length of the tender, so I could not use this method to determine the overall dimensions of the tender frame. There is, however, a rather similar type of tender, shown behind GWR No. 244, in Part 3 of the RCTS "Locomotives of the GWR" (Fig.C60), which appears to have the same 5' 9" + 5' 9" wheelbase. ( * This is not certain and is based on my assumption that the wheelbase of this re-built engine was 7' 0" + 8' 0" ). This tender scales to 19' 3" platform length.
     

     
     
    I have used the side-on photograph of this tender to produce a line drawing. First, I increased the Contrast of the photo, using PSE, and then selected 'Stylize | Find Edges from the Filters Menu, to produce the rough outline shown below. I used this outline as a template to draw a more refined outline drawing and also included some of the details shown in photos of No.184.
     

     
     
    I adjusted the sizes of both the engine and tender outline drawings, such that 40 pixels correspond to 1 foot on the real engine, and set the scale to 100px/cm, so that they will print at 4mm/foot scale. I then pasted the two drawings (engine and tender) together, to provide an overall impression of the complete 'system' that needs to be modelled:
     

     
     
    Now that I have some scaled sketches, I can start to design the main parts for a model engine. My first step will be to draw, and then cut out, some paper templates, which I shall use to explore a feasible method for construction, and to check clearances for (00-gauge) wheels, motor, etc.
     
    In previous models, I have cut out these templates by hand but, this time, I intend to use my Silhouette cutter.
     
    Mike
     
    Continue to next part
     
    * My assumption is supported by the ratio between the wheelbases being extremely close to 7 : 8. I used a spreadsheet to find that the most precise match to my pixel ratios lay at 6' 10" + 7'10", which would yield a tender wheelbase of 5' 8". The tolerances in my measurements are, however, greater than ± 1" so I have kept my initial estimate.
  4. MikeOxon

    Photographic Evidence

    By MikeOxon,


    General
    Having wandered into South Devon territory with my atmospheric caper, I started to look at some of the steam engines used on that line. I realised that, although I have modelled several early passenger engines, including the Firefly class, I have not tackled any of the early goods engines.
     
    The Leo class 2-4-0 were built as goods engines, starting in 1841. It was soon realised, however, that they had insufficient adhesion weight, so all the engines were converted to carry saddle tanks. We are very fortunate that the young draftsman, E.T.Lane made sketches of ‘Leo’ both before and after conversion at Swindon Works in 1849. In fact, his two sketches were dated 13th September 1849 and 21st September 1849, which indicates how rapidly the conversion was carried out! Although these are only notebook sketches, I found that overlaying the two versions showed how similar they are and indicates that the sketches are actually rather accurate. Many of the key dimensions are written on the sketches, although the later one only shows those which changed as a result of conversion. Unusually, he also sketched end elevations for the tank engine.
     

    Sketches by E.T.Lane of Leo at Swindon in 1849
     
    I decided that the saddle tank version was the one I would like to model and so I started to examine the available information in more detail. I should mention that there was a later ‘upgrade’ to many of these engines, when larger bunkers were fitted and that there are a few photos available of the larger-bunkered form. They must have been useful engines, because many of them survived until the great cull of Broad Gauge stock in the 1870s.
     
    I have mentioned before that caution is needed when taking dimension from drawings. In the present case, G.F. Bird made some more ‘finished-looking’ drawings, clearly based on Lane’s sketches, early in the 20th century. When I looked at one of these, reproduced in Mike Sharman’s book of Broad Gauge drawings, I thought that the tank tops looked very low, in comparison to the Lane sketches drawn from life. This could be seen clearly when I overlaid the Bird drawing over the Lane versions:
     

    Three drawings overlaid
     
    There are actually three drawings here – the first by Lane as a tender engine (Red), the second by Lane after conversion to a tank engine (Black), and the Bird drawing (Blue). Considering they are described as ‘sketches’, the Lane versions appear remarkably consistent in their scaling but the Bird drawing is very different in its portrayal of the tank.
     
    Fortunately, there is a good photo of ‘Aries’ (Leo-class) standing outside Faringdon shed, probably in the late 1860s by which time its bunker had been enlarged. Although it is not quite side-on, it is possible to compare the overall height of the tank with the diameter of the driving wheels (known to be 5 feet). The result looks to be much closer to the Lane sketches than to the much later Bird drawing (overlaid in red).
     

    Comparison of photo with Bird drawing
     
    To take the matter further, I decided to create a 3D model that I could then align with the photograph, to check how well the Lane dimensions agreed. I extruded the tank body, using ‘Fusion 360’, from one of the Lane end-elevation sketches and created the boiler as a cylinder, scaled from the prototype dimensions of 8’ 6” length by 3’ 6” diameter, as shown below:
     

    Extruding from drawings in Fusion 360
     
    I copied the frames and buffer beams, by extruding in my usual way, and ‘borrowed’ a Haycock-style firebox from my earlier ‘Firefly’ model.  Next, I assembled all these parts together, within ‘Fusion 360’, and then imported the photo of ‘Aries’ at Faringdon as a ‘canvas’. I could now rotate my basic 3D model until it appeared to be in a similar orientation to that shown in the photograph.
     

    Model and ‘Canvas’ in Fusion 360
     
    I then overlaid the model and photograph, in order to compare the major dimensions. The result, shown below, confirms that the Lane sketches are an accurate representation of the height of the saddle tank.
     

    Overlay of my 3D model and photo of ‘Aries’
     
    This is one of those rare occasions when one of the early engine designs survived long enough to appear in a good photograph. I have used 3D modelling as a research tool, to validate Lane’s sketch and to show that the much later Bird drawing is not accurate.
     
    Having got this far, I suppose can now proceed with a complete model of a Leo-class tank engine. According to Ian Pope & Paul Karau’s book “The Forest of Dean Branch, Vol.1”, the former station master at Cinderford recorded that the line was opened with a Leo-class engine ‘Virgo’, so I even have an excuse to include this engine in my ‘Bullo Pill’ collection .
     
    Mike
  5. MikeOxon

    3D-Printed Horses

    By MikeOxon,


    general
    After reading some recent posts about horse drawn wagons and the like, I started to wonder if it would be possible to 3D-print my own horses.
     
    A look at the 'Cults' website yielded a 3D-printable horse  by David Mussaffi, described as ‘FDM printer ready’, so I thought that this would be a good place to start.  I looked at the file after loading it into my ‘Cura’ slicing software and found that the model was cleverly split into three parts, such that there were flat surfaces to lie on the printer bed, with no overhangs that would require support structures.  The original design was rather large for 4 mm scale, so I adjusted the ‘scale’ setting in ‘Cura’ until I felt it was a reasonable size for use on my railway. The following illustration shows the three parts, as they appeared on my printer bed,
     

    Three components of downloaded horse by David Mussaffi – as printed
     
    Once separated and carefully trimmed along the edges, these three parts fitted together very well, to make a complete model – in fact, I was pleasantly surprised by the result and decided that a few of these 3D-prints would be useful additions to my railway, for pairing with various vehicles. Differences in texture are visible on this unpainted model but I felt that, with a little more fettling and painting, a very satisfactory model could be produced.
     

    3D-printed horse after assembly of 3 components
     
    I also realised that by adjusting the overall scale and/or individual parameters such as girth, it would be possible to produce a range of different types of horse from the same basic design.
     

    3D printed horse variations
     
    Horse Shunting
     
    A few years ago, when I set up a scene on my layout involving horse shunting, I found myself musing on whether there might be any way of simulating a walking motion.  I wonder if any readers remember the little ‘ramp walker’ toy that once came in cereal packets? A string could be attached to a model horse and hung over the edge of a table, attached to a small weight. This would cause the horse to ‘walk’ to the edge and then stop.

    ‘Cereal Packet’ Horse Walker
     
    When I first thought about it, a few years ago, I could see no way in which I replicate a model of this type at an appropriate size. Now, however, having gained some experience in using a 3D-printer and having created a 3D-printed horse, the thought entered my mind again and I thought it was worth ‘giving it a go’.
     
    Well, I’ve had a go but still haven’t succeeded in making it walk! I suspect that there is a problem of scale. If I halve the linear dimensions, then the surface areas decrease by a factor of four and the weight by a factor of eight. I suspect such changes upset the relationships between movement, weight, and friction that make the model work.
     
    I have documented the steps I’ve taken so far in the hope that someone will be able to suggest which parameters to change, to make it work. After around 3 months of fiddling with it, I’ve run out of ideas!
     
    Downloaded 'Walker'
     
    The trouble from the outset was that I had only a vague idea of how the walking action worked, so I looked on the web and found another model on the 'Cults' website, described as a '4 legs walker'. This model consists of a simple ‘body’ and a set of pivoted legs, which enabled me to examine the principles behind the ‘walking’ motion. I knew, however, that I would have to produce a much more realistic looking ‘body’!
     

    Downloadable 4legs-Walker, showing shaped feet
     
    Now the fun began, as I contemplated how to adapt the ‘realistic’ 3D-printed horse to the ‘walking’ principle! I was encouraged by the fact that the horse model I had downloaded was already divided into separate parts that I might be able to adapt to a suitable new configuration.  So, I started on a new ‘learning curve’! What follows has taken a few months of ‘trial and error’ (mostly the latter) but the main steps are summarised below:
     
    Meshmixer
     
    The first hurdle was to get the downloaded horse model into my 3D-modelling software ’Fusion 360’.  It is possible to import a mesh (STL) file but, when I tried to convert this model into an editable ‘body’, I immediately got a message that there were too many ‘faces’, so that conversion was not possible. It was clear that some basic ‘editing’ was needed before I could start to use my ‘Fusion 360’ modelling tools to adapt the components of my downloaded horse. This sent me on a search for software that could help me to solve this difficulty and I found the very useful (and free) ‘Meshmixer’ program by ‘Autodesk’.  Some of the useful functions of this software are described below:
     
    Separating the three components using 'Meshmixer
     
    After opening the original model that I had downloaded from the ‘Cults’ site, I found that I could use the ‘Select’ tool in ‘Meshmixer’ to separate the three parts of the original model, so that I could work on each of them independently.
     
    Simplifying the model mesh
     
    The next step was to use the ‘Edit’ menu within the ‘Select’ tool in 'Meshmixer', to reduce the complexity of the mesh, choosing the ‘max deviation’ reduce target, so that deviations of less than 0.2 mm were ignored. This seemed a reasonable figure, to match the capability of my 3D printer. This process allowed me to reduce the number of facets on each component, so that they became suitable for importing into ‘Fusion 360’.
     
    Converting the Mesh
     
    Once the STL mesh file has been imported into ‘Fusion 360’, there is an option to convert a ‘mesh’ model into a ‘body’, which can then be operated upon by means of the usual ‘Fusion 360’ tools. During this process, I discovered that my ‘Windows 10’ operating system includes a 3D Viewer App, which not only displays STL files but also shows statistics, such as the number of faces and vertices in the model. The original downloaded horse had 50,474 triangles in its mesh whereas, after simplification as described above, this was reduced to 2,634 triangles.
     
    After carrying out these modifications, I had a model that could be imported successfully into ‘Fusion 360’, where I could start to make the changes needed for a ‘walking’ model.  Before I could do much more, however, I realised that I needed to make the upper body of the horse ‘hollow’, so that it could contain the tops of movable legs and their pivots. My aim was to provide the functionality contained in the the basic ‘4-legs Walker’ that I showed above.
     
    Making a hollow model with 'Meshmixer'
     
    I found that ‘Meshmixer’ contains a simple tool within the ‘Edit’ menu to make a mesh model ‘hollow’, with options to define the thickness of the remaining side walls and the complexity of the inner mesh. This procedure is illustrated below:
     

    Using Meshmixer to create a hollow model
     
    In 'Meshmixer', the inner mesh is described in terms of ‘mesh density’ so, by trial and error, I selected a value that seemed to match the number of triangles in the outer mesh.  Now, I could import the hollow mesh model into ‘Fusion 360’, where I could use the ‘Hole’ tool to make apertures in the sides of the horse body, to accept axles for the pivoted legs.
     
    Adding legs
     
    For the initial trials I created simple rectangular legs with open rings at the top to act as pivots – these were similar to the ones used by the ‘4legs-Walker.’ I reamed out the holes until the legs swung freely on 2 mm diameter steel axles. When printed, the upper body now looked like this:
     

    My 3D printed Hollow Body with Legs
     
    I did quite a lot of fettling of the various components, to make sure that the legs swung freely within the upper body shell.
     
    Lower Body
     
    I imported the original solid version of the lower body into ‘Fusion 360’ and used the ‘Split’ tool to cut off the original legs from this part of the body, just below the belly of the model. I then drew rectangles on the flat top surface of the lower body, to define where the movable legs could pass through, while limiting their angle of travel. I extruded these rectangles into apertures, through the depth of the lower body, using trial and error to adjust the size of these apertures so that they allowed an appropriate amount of free leg movement, fore and aft.
     

    My 3D Printed Lower Body with Slots
     
    Printing the Feet
     
    The shape of the feet is critical to the working of the model, so I started by modifying the ones used by the ‘4legs-Walker’, downloaded from the ‘Cults’ site. Because the lower surface has to be angled, I separated the feet from the legs and provided a flat upper surface to each foot, which could lie on the bed of my 3D printer, when I printed the feet ‘upside down’. I also provided a rectangular socket in the top of each foot to hold a leg securely.
     
    Assembly
     
    Once I had designed all the individual components in ‘Fusion 360’, I printed each of the components: upper body, lower body, head, 4 legs and 4 feet. As mentioned above, a considerable amount of trial and error was needed to achieve the clearances needed for free movement of the legs within a controlled arc of swing.  Fortunately, each of these small parts only took a few minutes to print, so it was easy to make successive ‘tries’.  I show below this collection of parts, as they emerged from the printer.
     

    My 3D printed ‘Walking Horse’ Components
     
    Lessons Learned
     
    I’ve learned quite a lot about how to modify a 3D-printable model downloaded from the web, by means of tools such as ‘Meshmixer’, which I hope will be of interest to other 3D modellers.
     
    Help Requested
     
    Unfortunately, though,  I’ve still not succeeded in achieving an effective walking motion so, if any of my readers can make useful suggestions, I’ll be very pleased to receive them.
     
    In the meantime, I’ll keep trying to find the ‘magic solution’
     
    Mike
  6. MikeOxon
    Assembling the Parts
     
    In tackling the assembly of the components that I printed as described in Part 2 of this series, I was reminded of President Kennedy’s words “We choose to … do the other things, not because they are easy, but because they are hard“
     
    I had realised that the assembly of the parts was not going to be easy but it turned out even trickier than I had expected. To re-cap, the parts I printed were as shown below:
     

    3D printed Atmospheric Apparatus Components
     
    The tricky aspects arise from the need to align the four axle bearings with the appropriate axles. The locations of these axles are, in turn, determined by the placement of the axle boxes on the main carriage under-frame.
     
    My idea was to suspend the hangers, which carry the cylinder frame and the two cylinders, from a brass rod passing across the centre of the octagon. The inboard ends of the longitudinal frames have sockets to accept the ends of this brass road, thus holding together the entire upper part of the apparatus. I included holes in the octagon and hangers, plus sockets in the longitudinal frames, within the 3D models of these components and, rather to my surprise, they actually appeared as required from my basic 3D printer.
     
    A little opening out with a reamer was all that was required to enable a 1mm brass rod to pass through the octagon and the hangers, as I had intended. This stage of the assembly is shown below:
     

    Octagon, with Hangers suspended from Brass Rod
     
    In this photo above, the octagon is actually upside down, as I soon realised, but it does show the method of assembly quite clearly. I used superglue to attach the lower ends of the hangers to the piston frame, then clamped these parts together to allow the glue to harden.
     
    Next, it was time to press the longitudinal frames onto the ends of the brass rod and align the whole assembly with the axles of the carriage wheels. At this point, I realised that the octagon was upside down and also that the brass road had to be removed to allow the central axle to pass through the bearings on the octagon – now turned downwards.
     
    Getting everything to fit together proved to be something of a trial! [understatement] The parts are small and it was difficult to hold every thing still, in order to set up the correct alignments. Fortunately, the brass rod was quite a firm fit into the ends of the longitudinal frames, so this helped me to wiggle everything into place, without it all falling apart.
     
    I think some more thought about this part of the assembly might result in a better method but we are where we are! After a certain amount of cursing and swearing, the assembly looked like this:
     

    Atmospheric apparatus attached to Carriage Chassis
     
    It was a great relief when I found that the sloping longitudinal frames did not clash with the lateral parts of the carriage frame, although it was close! My 3D model proved itself to be accurate!
     
    When in the operating position, the piston carriage hangs below the level of the running rails but, in my model, it is hinged like the prototype, so it can be swung to one side to allow this vehicle to run on normal track.
     
    All that remained was to attach the two pistons, connected by a brass piston rod to the piston carriage and the model was complete – hurrah!
     

    My 4mm scale 3D-printed model Piston Carriage
     
    On the evidence of the contemporary paintings by William Dawson, it seems most probable that the carriages were painted brown overall, so I have adopted this colour for my model.
     
    After fettling, painting, and general ‘tidying up’ of the model, I posed it on my short length of broad gauge track. The roof is covered in self-adhesive vinyl. I used a leather punch to create holes in the vinyl for the oil lamp housings. The windows are glazed with overhead transparency sheet. The piston for the atmospheric apparatus can be seen below the front buffer beam of the carriage.
     

    My 4mm scale model of SDR Piston Carriage
     
     
    The Atmospheric Train in Operation
     
    To add a sense of realism to the scene, I placed a few of my models against a back-scene representing the red sandstone cliffs at Dawlish Warren:
     
     

    Diorama showing some of my Broad Gauge models

    I think it might be useful to add a few notes on how the trains were operated and how the pistons under the carriage were inserted into the propulsion pipe.
     
    The first point is that the system was designed for single-line working only. Because the flap valve was hinged to one side of the slot along the top of the pipe, it had to be raised by the apparatus below the carriage from the side opposite to the hinge. Research by the BGS strongly suggests that the hinge ran along the ‘seaward’ side of this coastal railway, from which it follows that the lifting apparatus must work from the landward side. Surprisingly, the protective metal covers, shown in Samuda’s Patent illustrations, were not fitted, despite the obvious detrimental effect on the leather arising from the seaside environment.
     

    Patent Illustration showing hinged leather seal
     
    Because of this ‘handed-ness’ the carriage always had to work in one orientation and could not be turned. That is why there had to be two pistons and driving compartments at both ends. Brakes were only fitted to the wheels on the landward side, so the drivers position was towards that side, where the brake operating levers were situated.
     
    The propulsion pipes were laid in 3 mile lengths, each length attached to a pumping station. Flap valves at the ends of the pipe were opened in response to a trigger device, operated as a train approached the end of one of the pipes. Once the pistons had entered the evacuated pipe, the driver had no means of regulating the speed of the train other than by applying the brake.
     
    The propulsion pipes stopped short of stations and the train ‘free-wheeled’, in the manner of a slip coach, after leaving the pipe until stopped, hopefully at the station platform, by the driver. Under- and over-runs were apparently not infrequent. At that time, manhandling or horse-shunting of railway vehicles were not unusual and these were, in general, the only methods available, if the train had to be moved when ‘off’ the pipe.
     
    The exception was for starting a train from a station. An auxiliary pipe was laid alongside the track ahead of each station. This pipe contained a piston attached to a length of rope that could be hooked to the front of the piston-carriage. The rope started the train into motion until the pistons entered the main propulsion pipe, when the driver released the staring rope. The flying end of the rope was a potential hazard to any gangers that might be near the line at the time!
     
    Before the train could start, the pumping engine for the appropriate section of pipe had to be operated. This was done according to the timetable so, if a train was late, the pumps had to be run for much longer than was strictly necessary, which increased the costs of running the system. Curiously, although the electric telegraph was installed along the line, it was never used to signal when the pumps were needed!
     
    Whenever the piston carriage had to be taken off the main line, its atmospheric apparatus had to be raised, in order to clear any pointwork and crossings. This was achieved by use of a winding handle fitted into a socket on the seaward side of the carriage.
     
    All these factors were clearly inconvenient, when compared with the flexibility of steam locomotive working.
     
    For any one who wishes to learn more about this railway, I can recommend the book ‘Brunel’s Atmospheric Railway’ which, apart from containing the set of 25 contemporary watercolour illustrations by William Dawson (1790-1877), provides extensive text and drawings, edited and produced by Paul Garnsworthy of the Broad Gauge Society (BGS). A new edition has recently been printed.
     
    Addendum
     
    Robert Stephenson carried out a technical review of the Kingstown & Dalkey atmospheric railway in Ireland in 1844.
     

    Kingstown & Dalkey atmospheric railway
     
    His conclusions were:
     
    1st That the atmospheric system is not an economical mode of transmitting
    power, and inferior in this respect both to locomotive engines and stationary
    engines with ropes.
     
    2nd That it is not calculated practically to acquire and maintain higher
    velocities than are comprised in the present working of locomotive engines.
     
    3rd That it would not in the majority of instances produce economy in the
    original construction of railways, and in many would most materially augment
    their cost.
     
    4th That on some short railways, where the traffic is large, admitting of trains
    of moderate weight, but requiring high velocities and frequent departures, and
    where the face of the country is such as to preclude the use of gradients suitable
    for locomotive engines, the atmospheric system would prove the most eligible.
     
    5th That on short lines of railway, say four or five miles in length, in the
    vicinity of large towns, where frequent and rapid communication is required
    between the termini alone, the atmospheric system might be advantageously
    applied.
     
    6th That on short lines, such as the Blackwall Railway, where the traffic is
    chiefly derived from intermediate points, requiring frequent stoppages between
    the termini, the atmospheric system is inapplicable ; being much inferior to the
    plan of disconnecting the carriages from a rope, for the accommodation of the
    intermediate traffic.
     
    7th. That on long lines of railway, the requisites of a large traffic cannot be
    attained by so inflexible a system as the atmospheric, in which the efficient
    operation of the whole depends so completely upon the perfect performance of
    each individual section of the machinery.
     
    I remain, Gentlemen,
    Your most obedient servant,
    ROBT. STEPHENSON.
     
    Stephenson’s assessment, especially his 5th point, is being re-applied with modern technology in both Indonesia and Brazil. See https://www.youtube.com/watch?v=GM2Zxn7ybNQ
     
     
    Mike
  7. MikeOxon

    My Atmospheric Caper - Part 2

    By MikeOxon,


    General
    Introduction
     
    In Part 1 of this series, I described my model of the piston-carriage for the South Devon (SDR) atmospheric railway, based on drawings by Paul Garnsworthy in the Broad Gauge Society (BGS) Journal ‘Broadsheet’Nos 44 and 46.
     
    It’s been great to receive so many positive comments – clearly some of my viewers like reading about ‘forgotten’ corners of railway history. They spurred me into getting on with the next phase. Thank you!
     
    The carriage body was relatively straightforward, being similar to other broad gauge carriages that I have already modelled. I felt, however, that I should attempt to understand the workings of the system and I find that the best way of doing this is to build a model.
     
    There are several drawings in the Patent Application by Clegg and Samuda but these were only intended to illustrate their ideas and contain features that were never used in practical applications of their idea. It was pointed out to me recently by a fellow member on this site @drduncan that the principle is the same as that used in the steam catapults on aircraft carriers in the Navy. It was in that context that I found some very clear drawings that illustrate the principle very well:
     

    Slotted Pipe for Steam Catapult
     
    In the SDR application, the sealing flap was made from leather strips that were hinged along one side of the slot. This meant that instead of being lifted bodily, as in the illustration above, it had to be raised at an angle, from the side opposite the hinges.
     
    As a result of research by members of the BGS, negatives of drawings of the original SDR piston carriage were found in Bristol Museum and re-drawn by Paul Garnsworthy for the BGS Journal ‘Broadsheet’. This was no mean task, as the originals were not only very faded but consisted of a series of partial or split views, typical of the period. There are various plan and elevation views of the mechanism, which I found needed careful study to determine how the various components were arranged (N.B. I’m no expert in reading engineering drawings!)
     
    The description in the two ‘Broadsheet’ articles helped to shed light on the various complexities. The following is based on those articles
     
    How it Worked
     
    The chassis framing beneath the carriage was quite conventional for the period, except for the central bay, where a wide space was left for the atmospheric apparatus. This apparatus was carried by bearings on the wheel axles, with two bearings on the central axle and one each on the outer axles,
     
    The atmospheric apparatus. had its own substantial frame composed of iron plates, In the centre these formed an octagon, carrying the two bearings on the middle axle. From this octagon, longitudinal plates extended to single bearings located centrally on the outer axles. Two hangers, pivoted from the octagon, suspended a longitudinal plate, which hung below the carriage and passed through the slot in the top of the main propulsion pipe, set between the running rails. These hangers were angled to raise the leather sealing flaps on the opposite side from their hinges, running along one side of the slot.
     
    Once the hangers were inside the propulsion pipe, they were attached to a pair of 11 foot long piston frames. Between these frames there were five rollers, which functioned to raise the hinged sealing flap, fitted along the upper slot of the propulsion pipe, and let it down again, once the plate connecting the pistons to the carriage had passed. There were two additional rollers mounted on the main assembly, above the pipe, to ensure that the flap valve was pressed down firmly after the carriage had passed.
     
    Piston rods extended from each end of the piston frames, inside the propulsion pipe, to the pistons themselves, which were located towards each end of the carriage. The two pistons allowed the carriage to be operated in either direction, so that it did not need to be turned at the end of a journey.
     
    In operation, the propulsion pipe, set between the running rails ahead of the carriage, was evacuated by stationary steam engines. Atmospheric pressure acting on the piston from the back of the carriage then pushed the carriage and its train forwards. Behind the leading piston, the rollers on the piston frame raised the sealing flap so that the blade connecting the carriage to the pistons could pass through and then, towards the back of the piston carriage, a top roller re-made the seal, so that the pipe could be evacuated again for the next train.
     
    Creating my Model
     
    Once I had worked out how all the gubbins were supposed to work, I could start to create a model. The drawings show lots of additional rods and levers, not all of which are understood, so I concentrated on the major elements of the system.
     
    As usual, I started by importing drawings as ‘canvases’ in ‘Fusion 360’ and extruded the various components by tracing over these. Although the following description may seem straightforward, the actual design and fitting together of the various components involved a great deal of trial and error!
     
    I started with the main carriage frame, which provides an overall orientation reference and defined the mounting points for the wheels and axles. I added the springs and axleboxes by the same methods as for my earlier designs.
     

    3D sketch of carriage underframe and wheels
     
    With these key reference points in place, I could then start to create the atmospheric equipment, described above, around them.  As usual, I extruded these parts from a drawing. I placed axle bearings on the central octagonal plates and on the longitudinal plates, in their proper locations over the three axles.
     

    The frame (red) carrying the atmospheric equipment underneath the carriage
     
    The next major component to create was the piston frame and pistons, which ran inside the propulsion pipe when the train was operating. This component is made up of several parts: two frames, the piston rods, the pistons themselves, rollers, and the hangers which couple this component to the octagon and thence to the train..
     
     

    The piston assembly that runs inside the propulsion pipe
     
    In the prototype, the hangers were connected to the octagon on pivots. These allowed the complete piston assembly to be raised clear of the track, in case the piston-carriage had to be attached to a normal train or simply to negotiate points and crossings (which were another problem for the atmospheric system)
     
    Having created the various parts separately by tracing over the drawings, I then used the ‘move’ tools in ‘Fusion 360’ to bring them together into the correct alignment. At this stage, it became apparent that several minor adjustments to dimensions were necessary, to ensure that all the parts fitted together neatly in the correct orientations. I made two screen shots of the assembly: first with the pistons in the operating position and then hinged to one side by 45°, in order to clear normal trackwork.
     
     

    The Atmospheric Equipment in raised and operating positions
     
    I should re-emphasise that these 3-D sketches are simplified, to illustrate the basic operating principles of the atmospheric equipment. The raising of the piston assembly was achieved by pinion gears and shafts, which could be operated by a removable handle, rather like the starting handle on an old-fashioned car. Other control rods could adjust the pressure applied by the flap-closing rollers, as appropriate for the direction of travel. There may also have been linkages to open relief valves in the pistons since, apart from applying the brake, there was no provision for regulating the speed of the train.
     
    This last factor once caused a major panic for the crew of a train on the Kingstown and Dalkey Railway, when they forgot to attach the piston-carriage to its train before starting. It is said that the carriage, operating as a ‘light engine’, reached a speed of 80 mph but, fortunately, was stopped before there was a disaster at the top of the incline!
     
    In addition to the atmospheric gear, a braking system, controlled by handles in both the driving positions at the ends of the carriage, was fitted to operate on one side only.
     
    Printing the Model
     
    It was immediately apparent, from the small sizes of some of the components, that a working model in 4mm scale could not be created solely by 3D printing. In particular the various rollers and the piston rods would need metal components.
     
    Unless, however, I was also prepared to build some miniature slotted pipe and flexible valve strips, the model would not be operational anyway so, simply as a demonstration model, I felt that a realistic ‘impression’ could be obtained by taking a few ‘short cuts’.
     
    These applied mainly to the piston assembly that runs inside the propulsion pipe. I decided to embed the rollers within a solid piston carriage and run a brass wire longitudinally to connect this part to the two pistons. This proved more awkward than it sounds, as I also wanted a flat face, to lay on the printer bed but, after much trial and error, I found a solution that involved splitting the piston carriage into three printable pieces.
     
    I similarly embedded the two flap-closing rollers into the upper frame and fitted another brass wire across the length of the octagon, to carry the pivoting hangers. Now, at last, it was time to think about making some trial prints.
     
    Once I had a collection of what I considered to be ‘printable’ parts, I passed the drawings to the ‘Cura’ slicing program. At this stage, a few more problems emerged. I still don’t know how it happened but some parts were inclined at very small angles, such as 0.3 degrees. I do know that I have never experienced this problem before so, perhaps, there has been some change to the ‘Fusion 360’ software that allowed this to happen. Fortunately, it could be corrected by simple rotations in ‘Cura’, until the components lay flat on the printer bed.
     
    Another problem emerged because I had failed to note that the body of the piston carriage was unusually narrow for a broad gauge vehicle, at only 8’ 4” wide. I should have been warned by the comment in the ‘Broadsheet’ article that “Nevertheless, [the frames] came perilously close to the wheels (7’ 7 ½ ” over wheels / 7’ 8½ ” between solebar flanges”. I had left insufficient clearance between the body sides in my original design to fit around BGS wheelsets, so I have had to widen and re-print the carriage body.
     
    I knew that I was taking risks with some of the ‘printable’ parts I created but, in fact, my old Geeetech printer coped admirably with some rather small dimensions and awkward shapes. The first step was to print the main chassis members and fit the wheelsets. This went well, as shown below:
     

    My 3D-printed underframe and BGS Wheelsets
     
    The next step was printing the octagon and longitudinal members that carry the atmospheric apparatus. I designed these to be linked together by a brass rod passing across the width of the octagon, which I intend to use for suspending the lower parts of the equipment.
     
    Since these are all small parts, I added the piston frames to make a ‘set’ of parts for printing together. The complete set printed in just 19 minutes. As mentioned above, I simplified the design of these parts so that they all had flat faces that could lie on the printer bed. The ‘rollers’ are not movable but printed as integral parts of the frames. After printing, the complete set appeared as below:
     

    My 3D-printed Atmospheric frame parts
     
    I printed the remaining small parts as a separate group, since they all involved more complex shapes, which I anticipated might prove difficult. To minimise the possibility of these parts toppling over while printing, I selected the option in ‘Cura’ to surround each part with a ‘brim’. I prefer to avoid support structures whenever possible, as they can be difficult to remove cleanly – even very thin layers of printed PLA can be remarkably tough!
     
    In fact, even the very small ‘hangers’ came out better than I had expected, though the brim was not easy to remove from these. I find the only successful tool for this job is a finger-nail. I show these parts still in place on the printer bed - note that the cylinders are only 11 mm long. Note also the holes in the hangers, to allow them to be suspended from the octagon. The thin strips attached to the hangers are to allow these very small parts to be glued to the piston frame (the one with 5 rollers) shown in the previous illustration.
     

    My 3D-printed cylinders and hangers on Printer Bed
     
    As I mentioned above, I had to re-print the carriage body a little wider, in order for it to fit over the wheels, after which the whole kit and caboodle looked as below:
     
     

    All parts for my model Atmospheric Piston Carriage
     
    As with many jobs, it all looks quite simple now it’s done. Perhaps it’s down to my increasing age but this one cost me more “tears and sweat” than anything else I’ve made since I started trying my hand at 3D printing.
     
    I shall pause here for a stiff drink and then tackle the job of assembling all those small pieces, which will disappear out of sight underneath the carriage!
     
    I’m still thinking about the colour of the carriage. I think it looks nice and rather ‘rustic’ in brown.
     
    Mike
     
    Feature Photo - William Dawson, "From the Station in St Thomas to the Alphington Meadows", detail
     
  8. MikeOxon

    My Atmospheric Caper - Part 1

    By MikeOxon,


    General
    Introduction
     
    Having worked my way back to the very beginnings of the GWR, it’s been hard to think of where to go next. I’ve enjoyed exploring those odd-ball engines that Brunel ordered for his new concept of a railway, even though they proved to be disastrously undersized. Nevertheless, several of them had quite long lives as branch-line engines.
     
    I do enjoy ‘bringing to life’ forgotten areas of railway history and, for the broad gauge, the ultimate in odd-ball ideas was, perhaps, the atmospheric railway that Brunel decided to recommend for the South Devon Railway.
     

    Atmospheric Railway showing Pipe and Pumping Station at Dawlish
    by Nicholas Condy (1793-1857)
     
    The basic idea was to move things along a pipe by evacuating air from the pipe ahead of the vehicle, so that atmospheric pressure would push from behind. This concept found some long-lived applications in shops and other businesses, where it was used to carry paperwork and cash in small canisters around a building.
     
    In 1840, two engineers, Clegg and Samuda, laid out a half-mile long track at Wormwood Scrubs, where railway carriages were drawn along by a piston, placed within an evacuated iron pipe set between the running rails. Several engineers were invited to view the demonstration and, whereas Stephenson dismissed it as a ‘great humbug’, Brunel was captivated and went on to propose it for use on the South Devon Railway.
     
    He wasn’t alone and the idea was adopted by a few other railways, including the Nanterre to St Germain railway in France. The first to be built, in 1843, was the Kingstown & Dalkey Railway, on the outskirts of Dublin. It was only one and three-quarter miles long and the atmospheric system was used to take trains up an incline, from which they returned by gravity. A trial was also made on a 5-mile stretch of the London, Croydon & Epsom Railway, authorized in 1844 and opened in January 1846. Many problems were encountered and in May 1847 the whole line was converted to locomotive operation.
     
    Typically, Brunel’s plans were more grandiose. On Brunel’s recommendation, the South Devon Railway laid fifteen miles of single track from Exeter St David’s to Teignmouth, later extended by a further five miles to Newton Abbot. The intention was to apply the atmospheric system all the way to Plymouth, so Brunel allowed some unusually steep gradients along his surveyed route, on the assumption that they would be operated by atmospheric traction ... but matters never got that far!
     
    Atmospheric operation of the line was very short-lived: public operation began on 13th September 1847 and within the year it was all over!.  The last atmospheric train arrived at Exeter during the night of 9/10 September 1848. This isn’t the place to go into all the reasons for such a catastrophic failure – suffice to say that the multiple reasons were both technical and economic in nature.
     
    Misconceptions
     
    So why do I want to make a model? My main reason is that there are serious misconceptions about what the railway actually looked like. A lot of credence was given to images based on Clegg and Samuda’s Patent Application, which actually bear very little resemblance to what was actually built. The illustrations were only intended to indicate the principles of operation, as shown below.
     

    Schematic diagram from Samuda and Clegg’s Patent on atmospheric railway. 
     
    Unfortunately, a commercial artist and writer, Robert Barnard Way, active from 1930 to 1958 created an atmospheric railway scene based on Nicholas Condy's painting of Dawlish (above), with the addition of a train headed by a simple flat car, as shown in the Patent diagram. There are now a great many copies of this image in circulation, so I shall avoid perpetrating this error.
     
    A true description of the piston carriage used on the SDR came to light during a meeting of the Broad Gauge Society (BGS), held at Bristol Museum in 1993. There was an opportunity while they were there to browse through the Woodfin Collection, where some BGS members were astonished to discover a real bombshell. Negatives 14471, 14894-14896 and 16141-16150 actually recorded drawings of one of the elusive South Devon Railway piston carriages. Paul Garnsworthy of the BGS created new drawings from the rather faded images and published a pair of articles, including his drawings, in the BGS Journal ‘Broadsheet’ issues 44 and 46. (available to BGS members in digital format)
     
    In order to set the record straight, I decided to create a model based on these drawings, using my usual methods of extruding from drawings by means of ‘Fusion 360’ software.
     
    Creating my Model
     
    The first step was to import the drawings from ‘Broadsheet’ as a ‘canvas’ in ‘Fusion 360’. After scaling to 4mm/foot, I copied the main outlines of the sides and ends, before adding details of doors, windows, and panelling. All these were created by means of the ‘rectangle’ and ‘3-point arc’ drawing tools
     

    My sketches of the carriage side overlaid on the ‘canvas’
     
    I then used the ‘push-pull’ tool to raise the mouldings above the main extrusion of the side, to create a solid model.
     
    The ends of the carriage were created in exactly the same way from the appropriate drawings. The sides and ends were all created as separate ‘bodies’ within ‘Fusion 360’.
     
    The floor was created as a simple rectangle and the roof was similar except for an arc profile. I added two oil lamp housings to the roof, placed to be shared between the 2nd and 3rd class compartments, This was a common practice in the early days, when any sort of lighting was considered a ‘luxury’!
     
    Once all the parts were extruded, I created a rendered image of the complete assembly in ‘Fusion 360’. The colour of these carriages is unknown. Brown was the standard colour used on both the GWR and the SDR but there is evidence that at least some 2nd class SDR carriages were painted green. I decided to use green, simply to provide a contrast to my usual stock.
     
    Accommodation in the prototype comprised two 2nd class compartments towards each end and a central area for 3rd class passengers. The piston carriage was designed to be bi-directional and was not turned at the end of a journey. Because much of the SDR line ran along the coast, the two sides can be referred to as the ‘seaward’ and ‘landward’ sides. Brakes were only fitted on the landward side so the driving position was offset to this side at both ends of the carriage.
     

    my rendered piston-carriage body created in Fusion 360
     
    For printing, I divided the components into just four parts – 2 sides, roof, and a floor combined with ends and partitions.
     

    The four components ready for ‘slicing’ and printing.
     
    This division into components allowed me to lay the sides flat on the printer bad, so that there was no need to provide additional support to the window openings. The roof is flat on the underside and the other parts are printed from the floor upwards. I could separate the ends, if this proved necessary to achieve clear window openings but, in practice, I have found that my printer copes well with small simple rectangular openings like these.
     
    Printing my Model
     
    The printing all went smoothly, including the floor and partitions, where I had hoped that the window openings would print reasonably cleanly without additional supports. There is a little stringing visible (I used the Geeetech printer) but nothing to cause any difficulty.
     

    Floor and Partitions on Geeetech E-180 printer bed
     
    I then printed the two sides and the roof, which included two oil-lamp housings, shared between adjacent compartments. I continue to be amazed by what my printer can achieve. In this case, I could see light through the small holes in the lamp covers that I had included in the 3D model,.
     

    My 3D-printed Piston Carriage Body with oil-lamp housings
     
    Of course, this was just a straight-forward carriage design. I now have to tackle the underframe, with its attachments to the atmospheric pistons. On the prototype, these were pivoted such that they could be raised if the carriage had to pass over crossings in ‘ordinary’ track.
     
    I intend to represent them in the raised position or, if I can manage to do so, I may even make them hinged! I anticipate that creating them, such that they can be 3D-printed, will be a challenge and I suspect that some ‘hybrid’ construction methods will be necessary.
     
    Mike
     
    Feature Photo: watercolour by William Dawson (1790-1877) - "view of Newton station, via Brunel's Atmospheric Railway"
  9. MikeOxon

    Simple Carriage Build

    By MikeOxon,


    General
    As a diversion from the problems I am experiencing in completing my Waverley-class 4-4-0, I have put together a Broad Gauge carriage body, using photo-printed sides.
     
    I have previously described making various standard-gauge coaches by using my Silhouette cutter to cut out several layers, some of which I pre-printed from photographs of actual coaches. I gradually refined and simplified my methods, resulting in the construction of an early Passenger Brake Van (PBV), which I built back in 2015.
     

     
     
    To re-cap, my method was to use my Silhouette cutter to mark out the sides and ends of the main body shell on 20 thou (0.5 mm) plastic card. I then assembled the sides and ends around a rectangular floor plate, cut from 40 thou (1 mm) plastic card, using polystyrene cement, to create a firm, rigid structure. Next, I attached the ‘cosmetic’ side layers using book-binders' adhesive. These layers were pre-printed on photographic paper and used the registration marks, printed by the Silhouette Studio software, to ensure that the window apertures aligned with the openings cut into the inner sides.
     
    The problem is that the Silhouette cutter can only cut through 10 thou plasticard whereas, for rigidity, the body sides need to be much thicker than this. For a PBV, with only one rectangular window aperture in each side, it was easy enough to cut these out by hand but, for a more complex passenger coach, much of the advantage of using a computer-controlled cutter would be lost.
     
    Some time ago, I had the idea of using 40 thou (1 mm) clear (transparent) plastic card for the sides of the main body shell, so that windows only need to be cut in the thin ‘cosmetic’ outer layers. I decided to try out this method in practice, to construct a simple Broad Gauge carriage body.
     
    My chosen prototype was one of the 6-wheel ‘Revised Standard’ composite carriages, built for the GWR between 1854 and 1857. I started by creating a scale image from the dimensioned sketch on the Broad Gauge Society Data Sheet No.154. I then copied my image, as a background layer, into my Autosketch CAD software and traced over the main outlines and the window openings, to create a DXF file for transferring to my Silhouette Studio software. Alongside this cutting diagram, I also produced a coloured image of the carriage sides, using Photoshop Elements software, to create a JPEG image that I also transferred to the Studio software.
     

     
     
    The next step, using the Studio software, was to align the photo image with the cut lines from the DXF file and then to save the composite image in Studio format. After selecting to add registration marks, I printed the file on photo-quality paper, using my HP Deskjet ink-jet printer. After printing, I sprayed a protective coat of matt varnish (I use 'Liquitex') over the photo image. Once the image had dried, I inserted the paper into my Silhouette cutter, which found the printed registration marks and cut out the sides, in alignment with the photo image.
     
    I actually built each side from two photo layers – an inner layer with smaller window apertures, representing the droplights and wooden window frames, and an outer layer, with larger apertures, to allow these window frames to show through, as three-dimensional structures. After gluing the layers together, with book-binders' adhesive, I did some re-touching with Venetian red paint to cover the exposed edges of the cut-outs and so complete the window apertures.
     

     
     
    Now, I constructed the main body shell by cutting rectangular pieces of transparent plastic card for the two sides and ordinary white plastic card for the ends (all 40 thou thickness). I assembled these into a box structure, exactly as I described previously for the PBV. Once the polystyrene cement had cured, all that remained was to glue the coloured sides in place, with the ‘windows’ showing through the transparent body structure.
     

     
     
    My final photo shows this carriage body mounted on a broad gauge chassis, built from a Broad Gauge Society kit. Of course there is a lot of detailing that needs to be added, to represent door handles, hinges, etc. but the basic form of the body proved very simple to construct.
     

     
     
    To return to my ‘Waverley’ 4-4-0 locomotive, I had the idea of using some filter conversion rings, as used by photographers to fit different sizes of filters to their lenses, as a basis for constructing the splashers.
     
    I managed to find some rings on the web of the correct diameter and waited patiently for them to arrive from China. At first, it looked promising, and I cut off the protruding threaded portions, to leave a rim representing the brass outer edge of the close-fitting splashers on the prototype. Unfortunately, the rings were just too shallow to cover the full depth of the wheel and, being made from aluminium, I could not solder them to an inner structure.
     

     
     
     
    I have paused again, for further thought, but may use these rings as templates, around which I can form some brass splashers of the correct depth.
     
    Mike
  10. MikeOxon

    In the Beginning ...

    By MikeOxon,


    General
    When I started my first pre-grouping blog in 2013, I entitled my first post “Turning Back the Clock”. Ever since then, I seem to have been turning it further and further back, until I’ve reached the very first engines of the GWR.
     

    Some early GWR Engines
     
    Although the story of Swindon Works is well documented and there is some information and illustrations of the first establishment at Paddington, I have so far found virtually nothing about the original engine-house at West Drayton, to which the first engines were delivered and then worked on by Daniel Gooch.  MacDermot in his ‘History of the GWR, Vol.1’ tells the delightful tale of Vulcan’s delivery: “the first engine actually tried in steam was Vulcan. It was shipped by Messrs Tayleur to London Docks, whence it came by canal to West Drayton, arriving at the latter place, together with Premier, from Mather, Dixon & Co, about 10th November 1837. Gooch had to get them and two other engines, which arrived later, from the wharf to the engine-house about a mile distant. An elm tree, which happened to be handily situated, was used to support the tackle for lifting the engines from the barge.”  I can’t imagine the Directors having been over-pleased, when they learned how their precious engines had been hauled aloft!
     
    The canal tow-path remains a pleasant walk but the wharves have long since disappeared, along with the elm trees. The earliest large scale map I have found is the OS 6 inch, surveyed in 1864, after the Uxbridge branch had been added but while West Drayton station was still located West of the road bridge - the station was moved to the East side in 1884. This map shows the De Burgh Arms already present, although whether it was there in time for Gooch to enjoy a welcome pint after a day’s hard work on the engines is uncertain. I found an artist’s impression of the first station but nothing about the first ‘works’ of the GWR.
     

    OS 6-inch – extract showing West Drayton Station, surveyed 1864
     
    Nevertheless, this was the place where Gooch wrestled with the problems posed by all those engines that were delivered against Brunel’s specifications.
     
    My current model of ‘Eagle’ is one of those engines and it has been difficult to find much information about its detailed design. By looking at early illustrations of other engines built by Sharp, Roberts & Co. for the standard gauge, I have found a few indicative details of how the boiler was mounted on the frames. An illustration of ‘Vortimer’, built for the SER, indicates supports for the boiler at the motion plate and at the side of the firebox, so I have appropriated these features for my model of ‘Eagle’
     

    Standard gauge 2-2-2 by Sharp, Roberts & Co., 1842
     
     
    Creating the Tender for ‘Eagle’
     
    The illustration above also shows the style of tender produced by the firm, although this one is a few years later than ‘Eagle’. On the other hand, there is a similar-looking but smaller tender shown with the earlier engine ‘Hibernia’ that was supplied to the Dublin and Kingstown Railway in 1834.
     
    Overlaying the drawings of ‘Eagle’ and the ‘Hibernia’ tender suggests what might have been used as the tender to ‘Eagle’:
     
     

    My suggestion of a Tender for ‘Eagle’
     
    Furthermore, E.T.Lane made some contemporary sketches of a tender supplied by Charles Tayleur & Co. for the engine ‘Venus’:
     
     

    Tender for Venus, sketch by E.T.Lane
     
    The style looks familiar and shows the interesting point that the wheels were mounted outside the frames, suggesting that this is simply an adaptation for the broad gauge of one of the firm’s usual tenders.
     
    In correspondence with the GWR Directors, Sharp, Roberts & Co. wrote: “The engine tenders made by us are entirely of metal, and consequently much more durable than those made of wood. We have not however had time to make drawings of one adapted to your line, and therefore cannot name an exact price, but we presume it will be from £220 to £250.”. This seems to confirm my ‘adaptation’ theory.
     
    So, on the basis of all the above sources of information, I set about designing my own interpretation of a tender for my model of ‘Eagle’. I suppose it is fair to say that any resemblance to the prototype is largely coincidental!
     
    I amalgamated the design of the tender for ‘Hibernia’ with the wheels and splashers from the ‘Venus’ tender, keeping the standard-gauge body inside the wheels. The result does look rather high-sided but this must be balanced against the body being narrower than on other broad gauge tenders.
     

    My planned Tender for ‘Eagle’ over illustration of ‘Vortimer’
     
    As usual, I imported this sketch into Fusion 360 as a ‘canvas’ and then drew over the outlines and extruded the body and chassis panels. I then added splashers outside the frames, as on the engine itself, to produce the 3D model shown below:
     

    My conjectural model of a Tender for ‘Eagle’
     
    Following my usual method, I printed the various components separately to produce the ‘kit of parts’ shown below:
     

    3D-printed Tender Components
     
    I have found that my basic printer does remarkably well with small items such as handrails. The axles even print with a clear 1 mm diam. hole thought the centre!
     

    3D printed Small Parts
     
    PLA plastic is remarkably tough and those fine railings were easily removed from the printer bed without damage.
     
    Into the Paint Shop
     
    One of the advantages from constructing both the engine and tender from several components is that this simplifies the painting. There is no need to mask off parts, since there is no risk of paint spreading onto adjacent parts.
     
    Current opinion appears to take the view that the wooden cladding on early boilers was painted from the start and not left polished, as it is on the replicas at Didcot. I have taken the ‘painted’ approach and used a mix of black and ‘Rustoleum Painter’s Touch’ dark green paints, to create my interpretation of the ‘dark blue-green’ appearance, as described for early broad-gauge engines. I used chocolate brown on the frames and black for the tops of the splashers. Final touches were brass effect for the bright-work and china-red for the buffer beams.
     

    My 3D printed model of ‘Eagle’ with its Tender
     
    There are various rods and pipes to add to this model and this view also highlights the absence of any motion. This view demonstrates the unusual layout of the running gear, with the leading axle placed in front of the smokebox.
     
    ‘Eagle’ is my third model of the first group of engines that were built for the GWR.  Both ‘Eagle’ and ‘Aeolus’ became useful branch line engines, after modifications made by Gooch. These engines taught Gooch a lot about the problems of maintaining a fleet of engines, each one of which had its own individual problems. His solution was to introduce a high degree of standardisation to his own designs, the first of which appeared in March 1840 as ‘Fire Fly’.
     
    For my final illustration, created with help from Photoshop, I show my three models together, against a backdrop of the engine house at Paddington in 1846.
     

    My models of Eagle, FireFly, and Aeolus at Paddington shed, 1845
     
    Mike
     
    footnote:
     
    The engine shed at Paddington in 1845 was of the ‘round house’ style, with a central turntable. Before the present terminus was built on the site of the old Goods Shed, the station offices were located in the arches of Bishop’s Road Bridge, with the platforms and Engine Shed to the west of this bridge:
     

     
     
  11. MikeOxon

    3D-printed Double Fairlie

    By MikeOxon,


    general
    Background
     
    Several years ago – 2006 in fact – I was driving away from a visit to Blaenau Ffestiniog slate quarries and noticed that the last train of the day was due to arrive at the railway station.
     
    It turned out to be quite a long wait, as the train on the Festiniog Railway was in trouble and eventually arrived with a broken flexible steam pipe to one of the power bogies. With a sense of ‘make do and mend’, the trailing end of the pipe was lashed up and the train then made a very late start for Porthmadog, relying on just one power bogie for the downhill trip
     

    Broken Steam Pipe of ‘David Lloyd George’
     
    At that time, my small model railway was in abeyance, although I did think briefly about the Langley Models kit, which seemed rather basic and also required the purchase of an American diesel to provide the chassis.
     
    Now, there is the Bachmann model, which looks very nice but, at £200, this is too expensive just to satisfy a vague whim. It’s too long anyway for my rather tortuous narrow gauge track around the North Leigh quarries.
     
    I did feel an ‘itch’, however, to try one as a 3D modelling task. I felt it provided an interesting challenge to lay out the components in such a way that they could be printed on my basic FDP printer.
     
    Steps to Creating My Model
     
    I found a drawing by Ian Beattie of a ‘typical’ Festiniog Double Fairlie in ‘Railway Modeller‘ November 1992, which I have used as a basis for my model. I also found a very helpful photo of an unclad ‘Merddin Emrys’ at Boston Lodge on the Festiniog ‘Facebook’ pages. This showed me several normally hidden details of the boiler and its supporting structures.
     
    The Footplate
     
    Following my usual method, I imported the Ian Beattie drawing, as a ‘canvas’, into Fusion 360. I started by extruding the footplate from the plan view in this drawing collection, as shown below. I designed this so that the top surface was completely flat and could be laid on the bed of my FDP printer
     

    Extruding the Footplate in Fusion 360
     
    Since I do not have a practical application for this type of engine, I am treating it simply as a design exercise.
     
    The Cab and Firebox
     
    The next challenge was the central cab. Since I had included the parts of the sides below the footplate and the firebox plinth in my initial footplate component, I had to create a part that would sit flat on the firebox plinth. I first drew the front and back ends of the cab by tracing over the drawing. The sides were a little more complex, because of the ‘joggle’ in the width, at mid-height.
     
    I created a 1mm ‘offset’ drawing inside the edges of one of the end walls of the cab and then extruded this profile along the length of the cab to create both sides and the roof. I then drew the outline of the side opening on one side of the cab and used the ‘push-pull commend to cut out these openings through the entre width of the cab. These stages of my construction are illustrated in the following drawing:
     

    Steps in designing the Cab for my Model
     
    After the extrusion described in Step 1, my next Step 2 was to add the other end wall to the cab and then complete the assembly by adding a floor, which would sit on the firebox plinth, when printed.
     
    Step 3 shows the twin firebox, which was a separate extrusion and, as in the case of the cab, I drew the detail of the fire doors on one side of the box before using the push-pull tool to emboss the details of the two doors. I also added the shaft for the handbrake. Similarly, I added some details of the reversing lever on the opposite (Driver’s) side of the firebox.
     
    Step 4 shows the complete cab with the firebox inside, aligned over the footplate, which I had extruded first. Note that the large holes through the length of the firebox and cab ends are to allow a brass tube to be passed along the whole length of the printed model, to act as a ‘spine’, both to align the two boilers and to hold everything together.
     
    The Side Tanks
     
    The next challenge was presented by the four side tanks. Those on the Fireman’s side contain coal bunkers while, on the Driver’s side, there are tool boxes on top. These tanks form mirror-image pairs at each end of the engine.
     
    To create the tanks, I started by extruding from a rectangular base to the height shown on the drawing,. On the prototype, the tanks have extensions on their inner sides to fit around the boiler. I created these by drawing the end profile and extruding this along the length of the tank. I added the tank fillers by extruding upwards from the top surfaces of the tanks, after drawing their profiles.
     
    The coal bunkers were extruded in two parts: a rectangular base and the (initially) vertical plate behind the bunker. I then used the move tool to tilt the plate to the angle shown on the prototype drawing. After joining the two parts together I moved them into position on top of the relevant tanks (on the Fireman’s side) as shown below:
     

    Coal Bunker on Fireman’s Side
     
    Adding some Coal
     
    As an interesting exercise, I thought that I would try adding a simulated coal load by means of 3D printing. In a previous post I described how I used an extension to Fusion 360 to create a surface texture. This comprised a ‘plug-in’ for 'Fusion 360' called ‘Image2Surface’, which adds the capability for 'Fusion 360' to create a textured surface from a 2D image. Downloading the appropriate software and then getting it to work was not straightforward but, fortunately, I found a 'YouTube' video, which explains the procedures very well.
     
    In my previous post, I created a textured surface based on a photograph of gravel ballast. It occurred to me that the appearance was quite similar to that of small coals in a bunker, so I made a copy of my previously created texture and used the cutting tools in ‘Fusion 360’ to make a rectangular section to fit in the top of my coal bunker. The result is shown below:
     

    ‘Coal’ texture panel above my rectangular Coal Bunker.
     
    With appropriate colouring, I feel that the gravel texture provides a reasonable representation of the top of a filled bunker! There is an important caveat when creating surfaces by this method – they can involve a very large number of facets and vertices, which results in very large file sizes. Even though my model bunker top only measures 4 mm X 17 mm, the .STL file that describes it occupies a staggering 258 MB. Of course, I could easily reduce that size by reducing the level of detail but the act of ‘slicing’ the model for printing reduced the size anyway, to a manageable level.
     
    This is a technique to bear in mind for small applications but not really suitable for creating large areas of ‘facings’ on buildings and other scenery.
     
    The Boilers and Smokeboxes
     
    The two boilers are identical and are simple cylinders, formed in exactly the same way as I have described for many earlier engine models. Similarly, the boiler fittings and smokebox all followed my usual methods. Once I had brought all these parts together within the ‘Fusion 360’ software, my 3D model looked like this:
     

    My 3D Model of a ‘typical’ Double Fairlie
     
     
    Printing my Model
     
    As usual, I printed my model as a set of components, arranged so that each could be built up from a flat surface. With experience I have found that my FDP printer is far more tolerant of overhangs than I had initially thought. I now take more ‘liberties’ in the design and find that quite large openings, such as where the boilers fit into the cab ends, can be printed without any additional supports or ‘helpers’
     
    I have previously printed smokeboxes as open tubes and added the curved front door separately. This time, I tried printing the smokebox as a single item and was surprised to find that my printer bridged the hollow centre behind the curved front without difficulty. I suspect that the ability to bridge gaps during printing depends strongly on the temperature of the filament when it is extruded.
     
    The largest single part was the footplate and I printed this ‘upside down’ on the printer bed, taking advantage of the extensive flat surfaces. Note the opening in the cab side, which is ‘bridged’ without any additional support.
     
     

    Footplate Model on the Printer bed
     
    Next, I printed the cab, which comprises the end and upper side walls, up to the level of the roof. Note that the lower side walls and a plinth for the firebox were included as parts of the footplate component.
     

    3D-printed Cab, mounted on Footplate
     
    The holes in the cab end walls are to accept a brass tube which runs the length of the model and holds the boilers and smokeboxes in alignment. This tube also adds weight to the structure.
     
    I printed several of the smaller parts – sandboxes, domes, and chimneys – together as a group. They all printed surprisingly cleanly and despite the small contact areas remained firmly attached to the printer bed. This set of parts took just 12 minutes to print!
     
     

    3D-printed Small Components
     
    For this model, I set the layer height when printing at the ‘normal’ setting (0.15 mm) rather than the ‘fine’ setting (0.10 mm) , which I use when there are rows of rivet detail or other detailed structures. This does mean that some ‘banding’ is visible in the photographs but is not noticeable at normal viewing distance on a 4 mm scale model.
     
    My complete set of parts after printing is shown below:
     

    3D-printed Components of my Fairlie model
     
    The first step in assembling the parts was to place the twin-firebox unit within the cab. I then inserted the central rod and slid the two boilers and smokeboxes over this, to check the overall alignment – which was good. I used superglue to hold this partial assembly together. I have read in some places that superglue does not work well on PLA plastic but that is not my experience, provided it is given time to polymerise. In fact, I have sometimes found it difficult to separate parts that I have inadvertently not aligned properly!
     
    Adding the tanks came next. It’s important to get each tank in its correct position since they are all different! After a little trial and error, I found that the best method was to glue each tank to the appropriate end of the cab, ensuring that they were aligned correctly with the two boilers and that the tanks and cab all sat flat on a plane surface.
     

     
    3D-printed Model with tanks glued to cab
     
    Once the bonds had hardened, I added the various small details – sandboxes, domes, and chimneys - by means of tiny drops of glue under each, then holding them in position for a few moments until the joint was firm.
     
    Finally, I could glue all this ‘upper’ structure to the footplate, which was rather flexible on its own but gained rigidity once glued to the lower surfaces of the tanks. The complete assembly then looked as below:
     


    My 3D-printed double-Fairlie model
     
    I have thoroughly enjoyed designing and constructing this model. Of course, the issue of the two power bogies remains!
     
    I intend to apply lining and lettering by means of printed vinyl overlays as described in my earlier series of posts about ‘lining and lettering’.
     
    Mike
     
     
  12. MikeOxon

    An Ugly Duckling – 4

    By MikeOxon,


    General
    Now, wake up at the back there, @Mikkel, this is a new post on this subject.
     
    At the end of my previous post, I wrote “Next, I shall turn my attention to designing and constructing a suitable chassis.”, so that’s the subject for today.
     
    Frames
     
    The frames of these early engines were rather unusual in that they stopped short in front of the leading drivers. The front bogie was attached directly to the boiler in traction-engine style. The frames were also quite light, with sizeable cut-outs between the driving wheels.
     
    Following my usual method, I imported a drawing of ‘Aurora’, originally shown in ‘The Locomotive Magazine’, 1896, into ‘Fusion 360’ as a ‘canvas’. I copied over the outlines of the frame, using the sketch mode, and then extruded the enclosed area to a depth of 1 mm, to form the frame. I used the ‘offset’ command to create a rim 0.5 mm in depth along the top edge of the splashers and then extruded this area a further 5 mm, to form the tops of the splashers. Similarly, I made an offset below the outer edge of the extruded splasher tops, to form the front valance.
     
     

    3D extrusion over imported drawing
     
    Experience has shown me that my printer can cope with this amount of valance overhang, when printed with the design laid flat on its back on the printer-bed. There was no need to create a different frame for the opposite side of the engine, as all I had to do was apply the ‘mirror’ command before printing.
     
    Alignment
     
    The next step was to align the pair of frames at the correct separation and create components to represent the buffer beams and footplate. Rather than do this by measurement, I simply used the ‘move’ tool in ‘Fusion 360’ to align the frames with existing boiler and tank components. Once they were in correct alignment, I sketched rectangles to represent the front and back buffer beams and extruded these to create the appropriate ‘spacers’. At the back of the engine, I also extruded the upper part of the buffer beam forward, to represent the footplate for the crew and support for the firebox end of the boiler.
     
    I find it useful to assemble the various parts in the computer, to check that everything aligns correctly, even though I print them individually. The following screen-shots shows how I designed these parts in ‘Fusion 360’:
     
     

    Additional spacers aligned with Frames
     
    Bunker
     
    Once I had set the correct separation of the frames, the next part to consider was that splendidly curvaceous bunker. I tackled this by first sketching the profile over the drawing that I’d imported into ‘Fusion 360’, as shown below:
     
     

    Extruded drawing of bunker side
     
    I then created two duplicate sides and placed them into their correct positions on the 3D model shown above. I sketched a rectangular backplate and extruded this to form another body that I combined with the two sides. Finally, I used the fillet tool to provide the curved corners between the back and sides of the bunker, to create the overall design shown below:
     
     

    Bunker created to fit onto the existing computer model
     
    Boiler Fittings
     
    Three fittings are needed on top of the engine: chimney, sand-box, and safety valve cover. In the past, I have made a bit of a meal of creating such items but it is, in fact, extremely simply to create circularly-symmetrical objects in ‘Fusion 360’
     
    To take the sandbox as an example, the first step is to sketch the half-profile and then to use the ‘Revolve’ command in the ‘Create’ menu to create solid body.
     
     

    Using the Revolve tool in 'Fusion 360'
     
    I used the same method to create the chimney and the safety-valve cover. I added these parts into their correct positions on the computer model, to complete the assembly, as shown below.
     
     

    'Aurora' components assembled in 'Fusion 360'
     
    Having checked that all the parts fit together, I simply transferred the various parts to the 'Cura' slicing software and printed the resulting files. Most parts only take a few minutes to print.
     
    Bogie
     
    One more component is needed to complete the main features of this engine and that is the front bogie.  In the prototype, the bogie pivots on a central ball-and-socket joint attached below the boiler. I feel that this arrangement would not provide sufficient side-swing for a model engine on practical track curvature, so I have decided to adopt the more usual swinging link method of attachment.
     
    Lessons learned (so far)
     
    I feel that I’ve learned a few more useful techniques with ‘Fusion 360’, such as the use of the ‘Revolve’ command.  I’ve also appreciated the various modes of the ‘Pattern on Path’ command.
     
    Moving separate parts into the correct registration with one other, within my computer, has proved to be very useful for ensuring that everything will fit together when printed.  An overall 'rendered' view of my model 'assembled' in this way within Fusion 360 is shown below:
     

     
    I am now much more aware of the limits set by the fused deposition method of printing. The extruded filament has finite diameter, which sets a limit to the details that can be printed.

    If too small, features are simply ignored by the ‘Cura’ software, so it is essential to check the appearance with the ‘Preview’ option before committing to print. Very tiny adjustments to the computer model can make significant differences to the final appearance.
     
    The software can still tie me up in knots sometimes but I think I’m now better at getting out from them
     
    Printing and Assembly
     
    Now comes the easy bit, once the design has been completed. By printing parts separately, the print times can be very short. I made a list of the ‘Cura’ estimates for print times of the various components:
     
    Tank 1h 2min Firebox 39 min Footplate & Buffer Beam 27 min Smokebox 21 min Frame (each) 19 min Bunker 15 min Chimney, Safety Valve, Sandbox (together) 14 min Backplate 7 min Front of Smokebox 6 min  
    It’s easy to refine the prints, in order to optimise detailing within the limitations of my printer, in view of these short times. Printing individual parts also minimises the need for support structures, by choosing the orientation of individual parts to eliminate these wherever possible.
     
    Printing more at once can be appropriate, once the details are known to be correct, but small print-times encourage ‘trial and error’ improvements.
     
    My current printed set of parts is shown below, after assembly of the individual components. A bogie frame appears in front of the engine itself.


    ‘Aurora’, assembled from 3D-printed components, including bogie frame
     
    The way ahead for this model will now follow conventional lines, adding wire handrails, pipes, and similar details. I have not yet decided about wheels but may consider these in another post. My method for constructing 3D-printed wheels has already been covered in an earlier post.
     
    I expect that here will now be a pause, while I continue through to the painting stage.
     
    Mike
  13. MikeOxon
    I had hoped to have moved a lot further with No.184 but, unfortunately, have made a very elementary mistake! I knew that one of the problems with 00-gauge is that it is, in fact, a narrow gauge, with implications for fitting the boiler, etc., between the wheels. I think this had lulled me into a false sense of security with the outer dimensions, but these do become rather important in the case of an outside-framed locomotive with outside cranks! I 'got away with it' on my earlier scratch-built 'Queen' locomotive, because it didn't have these features.
     

     
    My 'Queen' locomotive in photographic grey, showing excessive clearance outside 00-gauge wheels
     
    My silly mistake was not to allow for the thickness of the metal, when folding the footplate structure. I had marked it out for 7 ft (28 mm) width but, of course, the 10 thou brass sheet is, itself, 0.25 mm thick, which, doubled-up both sides, is another 1/2mm, plus a bit because the fold isn't quite 'tight'. Once the cosmetic outer sides were added, I'd run out of clearance for the outside cranks on 32 mm extended axles (which actually measured at only 31.7mm). Fortunately, my rectangular footplate is simple to re-make to a nominal 26 mm, between the fold lines, but I mention this, in the hope it might save others who may be tempted to follow my very basic approach to model-making.
     
    Another poor aspect of the design was that the large cut-out in the footplate, to accommodate the driving wheels, had weakened the structure very markedly. With my 'Queen' model, there were large areas of flat plate both in front of and behind the single drivers and these provided firm platforms on which to place the cab and smokebox. My solution for No.184 was to design the raised firebox such that it includes strengthening lugs, passing between the drivers to the outside frames. Once fixed to the front of the cab, which is itself soldered to the insides of the rear wheel splasher faces, the 'rear end' of the engine became much more rigid.
     

     
    Underside view (temporary fixings with 'Blu-Tack')
     
    With these 'improvements', the main components of the engine body have fitted together quite well and the overall dimensions lie close to my initial drawing, as shown in the photo below, where I have super-imposed the drawing. There is still a lot of rather 'fiddly' construction to do, including fitting the tops of the splashers and the splasher 'boxes' inside the cab. After that, the tasks change, as it becomes a matter of adding all the components, such as springs, axle boxes, and boiler fittings. Only then will the 'character' of this particular locomotive become apparent.
     

     
    Photo of current stage of model, with drawing super-imposed
     
    One pleasing event is that I think I have found a paint to represent 'Wolverhampton' green. I have been scouring the shelves of various suppliers and recently spotted 20 ml jars of 'Rust-oleum' 'Painter's Touch' enamel in my local 'Homebase' store. Conveniently, this paint is packaged in clear jars, which enabled me to judge that their 'Dark Green' colour had the bluish-green shade that I was looking for.
     

     
     
    I've not tried using this paint yet but I'm looking forward to seeing the effect on my model.
     
    I expect to take a break from modelling over the Christmas period so wish all members of
    RMWeb a Happy Christmas, with the hope that Santa proves to be a railway fan
     
    Mike
     
    Continue to next part
  14. MikeOxon

    Extending my 3D Modelling

    By MikeOxon,


    General
    3D- Printed Track Base
     
    At the beginning of the year, my thoughts turned towards making some track for my Broad Gauge (BG) models. I have already built a short section of track using traditional methods but I decided to see if 3D printing could help.
     
    After some experimentation in the early days of the GWR, the design of prototype broad gauge track settled into the form shown below:
     


    Construction of Broad Gauge Track
     
    The longitudinal baulks were about 30 feet (~ 9 m) long and held at the correct separation by transoms placed at around 8 foot (~ 2.4 m) spacing.
     
    For modelling purposes, I created baulks of 120 mm length, with 4 transoms evenly spaced in each section, so that individual pieces can be butted together, while maintaining constant spacing of the transoms. Creating a 3D model in ‘Fusion 360’ was straightforward, by extruding from a plan-drawing to a depth equivalent to the prototypical 7” (~ 18 cm). I added some surface detail to represent the short packing pieces that were placed immediately below the rails themselves.
     
    Once extruded, the 3D model appeared as below:
     


    My 3-D Model of a section of BG Track
     
    Remembering my old ‘Tri-ang’ track, with its grey plastic base representing the ballast, I thought I would see if it would be possible to 3D-print the ballast. It proved to be far from simple but opened up a whole new aspect of printing with 'Fusion 360'!
     
    Creating Surface Texture in ‘Fusion 360’
     
    I soon found that there appears to be no simple way of adding surface texture in ‘Fusion 360’ – it can be added as a visual effect for on-screen display but not in a way that can be 3D-printed. So, I started researching by means of Google, to see if there were any ‘work arounds’.
     
    I found several references to a ‘plug-in’ for 'Fusion 360' called ‘Image2Surface’. This adds a capability for 'Fusion 360' to create a textured surface from a 2D image. Downloading the appropriate software and then getting it to work was not straightforward but, fortunately, I found a 'YouTube' video, which explains the procedures very well – see: https://www.youtube.com/watch?v=ChdJ8nL7qQA
     
    Warning. The next few paragraphs are rather technical and largely an aide memoire for myself. All the information is in the video above.
     
    At first, I had to keep listening to short sections of the video and then trying one step at a time.  For reference, I have made the following précis:
     
    The first step is to download a zip-file containing the software  Fusion360Image2Surface-master.zip from the Autodesk Knowledge Network. Mine is the Windows 64-bit version but there is a version for Mac as well.
      On my Windows machine, the downloaded zip-file has to be extracted into the ‘Fusion 360 Addins’ folder, where the extracted folder must be re-named to ‘Image2Surface’. The Addins folder is typically located at C:\Users\’user name’\App Data\Roaming\Autodesk\Autodesk Fusion 360\API\Addins
      Within the running 'Fusion 360' application, open the ‘TOOLS’ menu and then open the ‘Addins’ drop-down box to select ’Image2Surface’. There is a check box to open this addin automatically whenever 'Fusion 360' starts.
      Once the addin is running, simply click on its icon and a new window opens in 'Fusion 360'. This allows you to open a standard JPEG image from your computer. There are various adjustments available, to make sure it has an appropriate amount of detail.
     
     
    Once the settings have been made, click on ‘Generate Surface’. The next process may take some time, depending on the complexity of your image, but eventually an image will appear on the main 'Fusion 360' screen.
     
    At this point, there are still several steps to be taken before you have a 3D-printable object.
     
    The surface created by the addin has now to be converted into a ‘body’, which involves several stages, as listed below:
     
    Open the ‘SOLID’ menu and then click on the ‘Create Form’ icon in the ‘CREATE’ section.
      A new series of icons will appear. Click below the ‘UTILITIES’ icon to open a drop-down menu.
      Click on ‘Convert’ in the drop-down menu.
      In the box that appears, select ‘Quad Mesh to T-spline’ in the ‘Convert Type’ selection box, then choose the ‘Select’ button and click on your design. Click ‘OK’ to create a new ‘body’.
      At this stage, there are various clever-looking options in the drop-down ‘MODIFY’ menu but I haven’t explored any of these yet.
      To complete the conversion, click the ‘FINISH FORM’ button. There may be another long wait, at the end of which you have a new body but it is still only a surface and is not yet printable.  
    By now, if you still reading, you are probably feeling ready for a stiff drink but hold out just a little longer!
     
    To make a stand-alone solid object from a surface, create a profile plane below the surface object created by the plug in.  In my example, the subject is rectangular, so I drew a rectangle on the X-Y plane below my object, as shown in the following illustrated steps:
     


    Stages in creating a 3D model of ballasted BG track in 'Fusion 360'
     
    Once I had a solid ‘body’ in 'Fusion 360', I could add this to my model of Broad Gauge track, shown above. It does indeed look quite like the old Tri-ang track!
     
    Of course, I realise that, in most cases, 3D printing is not a very sensible way to create ballast and traditional methods are more effective and probably easier to create.
     
    Potential Applications for Surface Modelling
     
    I believe that the real significance of having found this method of creating a 3D surface textures in ‘Fusion 360’ is that it opens up all sorts of new possibilities for model-making.  Ideas that spring to mind immediately are surface finishes, such as stone or brickwork on buildings – these could easily be derived from photographs of real buildings. A search on the web for ‘greyscale depth map images’ shows plenty of examples, many of which could be applied as architectural features:
     


    Examples of Depth Map Images from Google
     
    Another possibility is to create 3D nameplates. I found that, by starting from a photo of ‘Rob Roy’ (an engine I have previously modelled), I could convert the actual name plate into a 3D printed model, as shown below:
     
     

    My 3D-printed nameplate on the printer bed.
     
    Unfortunately, the resolution of my basic FDM printer is insufficient to reduce this to 4 mm scale; the example shown is around 7 mm scale and the detail becomes blurred if I make it smaller. Nevertheless, even with a simple printer like mine, station name plates, shop signs, and the like should all be realisable in 4 mm scale.
     
    For fun, and in anticipation of a more cheerful year in 2022 , I copied an image of the frieze high above the entrance to the Paddington Station hotel!
     


    Paddington Hotel Entrance (created from Google Streetview)
     
    There are good detailed illustrations of the frieze on this website: http://www.speel.me.uk/sculptlondon/paddingtonstation.htm , including an engraving of the pediment, designed by John Thomas in 1854. According to the website: “John Thomas, a now little known but extremely good sculptor, shows his skill at composition in this work. There are 10 full sized figures in the pediment, of which two are seated on one side, one on the other, and three large animals, and yet a perfect balance between the two sides is maintained.”
     
    Of course, it was a very ambitious subject to attempt but I simply copied the engraving shown on the above website, increased the contrast a little, and read it into the ‘Image2Surface’ software. Since the original was not a ‘depth map’ image, I could not expect a highly accurate rendering. The depth of the relief depends on the brightness of the image, so some work to bring forward selected parts of the image, by making them lighter, and to recess others, by making them darker, could help to improve the result.
     
    I converted the image into a sold body, using ‘Fusion 360’ exactly as described above. I then transferred the file to my ‘Cura’ slicing software and prepared it for printing. This resulted in a rather large file and, at first, it seemed to give my printer ‘indigestion’, as it didn’t want to start on my first attempt. After a re-set, it started up, although it initially indicated a print time of 15 hours!  Fortunately, this proved to be a dramatic over-estimate and the print actually took about 50 minutes, to produce the following result:
     
     

    My 3-D printed model of the Paddington Station Frieze
     
    It’s not exactly Hi-Fi, partly due to the limitations of the original image, which was not intended for this purpose, but it would make an interesting addition to a model building.
     
    I think there is plenty of food for thought here, to influence my modelling in 2022.
     
    Mike
  15. MikeOxon

    Back in Time - 517 class

    By MikeOxon,


    general
    In my very first post in this blog, I mentioned converting an old K's 14xx to a fair representation of a 517 class. Since the 517 was a very variable class, it's impossible to select a 'typical' version - they vary from the earliest tiny saddle tanks, with a short wheelbase, to the final re-builds, which were very similar to Collett's 14xx series. Nevertheless, there were significant differences between even the latest of these engines and the 14xx - most obviously in the cab but also the 14xx has a higher-pitched boiler and longer smokebox. That's why I said a 'fair' representation, since an accurate model would require a complete re-build!
     
    Superimposing drawings of a late 517 and a 14xx, shows both the similarities and differences. In fact, if you 'scale up' the 517 drawing by about 6%, then they become very close indeed, so I comforted myself by thinking that a small difference of scale is hardly noticeable in a model!
     

     
    The K's model is a simple white-metal body casting, which includes plates below the footplate, to carry dummy outside-bearings for the trailing wheels. As I wanted an inside-bearing model, it was simply a matter of removing these parts. The next 'removal' was more difficult, since the front toolboxes on the 14xx model are cast integrally with the front splashers. It needed careful work with a saw to separate these without damaging other parts of the model. Cutting away the cab was relatively simple, leading to the stage shown below.
     

     
    I then made a new spectacle plate from styrene sheet and rear extensions to the tops of the side tanks, in the same way. I cut out part of the original cab sides and fixed them to the new tank tops and spectacle plates with superglue. A new cabroof completed the model -a pretty quick and easy conversion.
     

    Since the original model had a Belpaire firebox, I needed to find a prototype 517 with both this type of firebox and inside-bearings on the trailing wheels. Fortunately, Russell's 'GW locomotives' contains a photo of No. 835 with these key features, so I numbered mine accordingly. With modeller's licence, I decided I also wanted smokebox 'wing plates', since these are a nice 'Victorian' feature and also disguised the drum-type smokebox. To shape these, I took a head-on photo of my model and then scaled and printed this as a template for cutting out styrene sheet.
     

     
    I also needed new sand boxes so, as I have mentioned in another forum, I made these out of the ends of a couple of nylon cable-ties:
     

     
    As I pointed out at the outset, there are plenty of detail errors but I think No.835 takes its place very well alongside my 'Stella' conversion.
     

     
    Mike
     
    addendum - since writing this post, I have started a thread covering the variations within the '517 class' at http://www.rmweb.co.uk/community/index.php?/topic/92797-george-armstrongs-masterpiece/&do=findComment&comment=1668654
  16. MikeOxon

    A Hat Box for Blanche

    By MikeOxon,


    general
    In an earlier post in my blog, I described construction of a GWR Tilt Wagon, based on a photograph in a Forum Post by Wagonman. I also reported that, when Sir John saw it in North Leigh station, he commented that it might just hold all his daughter's hat boxes. So, I now call it my 'Hat Box'.
     
    At the time of my earlier entry, I had designed and built the basic body and started adding some of the detail. Completing the rest has been a very fiddly task, using lots of rivet strip (from Mainly Trains) and wire for the various rails.
     
    I had just decided that I was going to have to scratch-build the chassis, when the GWR/RCH underframes re-appeared in the MJT catalogue (Dart Castings), after having been 'temporarily out of stock' since the end of last year. After a previous experience of slow delivery, I was expecting a long wait but they arrived by return post - excellent service from Dart Castings!
     
    The W-irons have a rather spindly look, which suits the model very well and conveys the look of the prototype. As a finishing touch, I added some lengths of very fine chain (32 links per inch) from Scale Link.to make the door keeps.
     
    My method for attaching the chain was to cut a short length, dip it in a dilute PVA solution and then tease it into place on the side of the wagon (laid on its side), using a cocktail stick.
     

     
     
    The PVA dries completely clear and seems to hold adequately - though I would not try rough handling! Once it had dried, I set the wagon in front of a line of clerestory coaches, similar to the position of the prototype in the heading photo:
     

     
     
    It can be seen to be quite a large wagon, especially when compared with the adjacent Iron Mink (V6) van. I still have lettering and numbering to do, but this can wait until I do an overall job on my fleet of back-dated 'red' wagons.
     
    With the Winter modelling season approaching, I feel that I need to turn my attention from building stock to developing the scenery on my layout. As I have mentioned in earlier posts, my layout is derived from a simple Hornby-Dublo track plan, with the addition of a narrow gauge feeder (009) on an upper level.
     
    I intend to tackle the development of the scenery as a series of 'vignettes', as indicated on the following diagram.
     

     
     
    Working on each element in turn will allow me to follow Mikkel's dictum of eating an elephant in small portions! Even with my tiny layout, I think it could take quite a long time
     
    Mike
  17. MikeOxon

    A Change of Gear

    By MikeOxon,


    General
    The ‘gear’ I’m referring to in the title is my 3D-printer, which I have just replaced.
     
    As I mentioned in my previous post, my Geeetech E180 is no longer supported, with essential items like replacement print-heads not available. I have therefore bought a Prusa Mini+ as its replacement. The E180 was cheap and took me some time to optimise, following a rather shaky start, but eventually performed very well, until key components started wearing out.
     
    My choice of the Prusa machine was a deliberate move to choose a European product and one that has gained a good reputation amongst the 3D printing community. Unlike the E180, which was smartly styled, the design of the Prusa is strictly functional, with most of its working parts fully exposed. I have stayed with a ‘fused deposition’ type of printer (FDP), because it does not not use liquid resins and other materials that require careful handling and disposal. I recognise that FDP cannot provide as good a surface finish as some other methods but I have found it adequate for my interests in historical modelling.
     
    The Prusa Mini+ is supplied either as a kit or partly assembled; I chose the latter course, since my eyesight and general dexterity are no longer what they once were. The packaging and overall presentation of the machine as delivered was excellent, with all the parts firmly secured within the cardboard packaging and all the small parts in individual, labelled, re-sealable plastic bags. There is also a substantial printed manual, covering both the assembly instructions and operation of the printer.
     

    Prusa Mini+ Components after Unpacking from Box
     
    Assembly
     
    Unfortunately, the photographic illustrations in the manual are small and, because most of the printer parts are coloured black, it is difficult to make out many of the details. My troubles started with fixing the soft feet (foam pads). These do not fix onto the obvious flat areas under the plastic end-pieces of the base section but under the aluminium channel sections. The illustrations are far from clear and caused me some hesitation. Fortunately, I found a helpful video on YouTube at https://www.youtube.com/watch?v=xYGaWYKzvsM  This video presentation is rather too rapid to follow on its own, but is very useful to check on any points of doubt.
     
    N.B. There are also some, to my mind, dreadful American ‘live’ videos about assembling this printer, where the facts are submerged in peripheral chat.
     
    The same problem of poor illustrations applied to many other parts of the assembly task. I still don’t understand the statement from the instructions: "try fitting the “clamp” (XZ assembly) directly on the M3nE nut which you have moved to the centre of the extrusion.”. It took some time for me to work out that the long screw passed through a ‘tunnel’ within the electronics module to reach the nut in the base unit. A diagram like that I made below might have helped a lot!
     

    Screws connecting main units
     
    It’s actually quite simple, once one has interpreted the instructions, with three screws connecting to nuts that slide along aluminium channels in the base unit. These screws hold the two major components together.
     
    There are then several cables to be connected between the two major components. The ‘electronics module’ is very compact, with a high density of sockets and wiring. If you are familiar with the small connectors that are widely used within computers, then it is not too difficult but, once again, the instructions are minimal and more guidance would be very helpful to many people.
     
    The first cable to be connected is the ribbon cable that will eventually attach to the display unit. This has to be orientated correctly in its socket. The most obvious guide to alignment is that one side of the ribbon is coloured red but this fact is not mentioned in the instructions, which are therefore hard to follow.
     
    The circuit board is referred to as the ‘Buddy Board’. There is no diagram that shows the various sockets on this ‘Buddy Board’ in the electronics box, nor is there any very clear indication as to which connector goes where. Again, I suggest that a diagram like that I made below would help a lot:
     

    Electrical connectors on circuit board
     
    Finally the lid has to be re-fitted to the electronics box, which is quite tricky, since all the cables have to be squeezed inside. There is a dire warning that ‘The nut must not fall out’. I never saw this nut, so sincerely hope it is safe!
     
    That completes the main assembly. There is also a spool holder. The instructions start by stating “Take the two BASE parts”. Actually there are four parts in two pairs, which confused me at first. Note that there is just one hexagonal recess in each part to take a nut. In my experience, it is essential to use one of the screws to draw the nut down to the bottom of its recess, otherwise the screw will not reach the nut when attempting to join the paired parts together.
     
    As I stated at the outset, the design of this printer is strictly functional. All the moving and heated parts are completely exposed and there is no back to the display unit, nor is its ribbon cable enclosed.
     
    Unlike my previous E180 printer, this machine has a heated print bed and the ‘hot end’ is also completely exposed, so any children need close supervision, if allowed nearby when it is operating.
     

    Prusa Mini+ after assembly
     
     
    First Start
     
    Now it was time to switch ‘on’. The LCD screen lit up and the ‘Calibration Wizard’ started to run; the first stage being a series of ‘self tests’, which were all cleared successfully.
     

    Switched ‘on’ and Ready to Print
     
    After this, it’s time to load some filament. I pushed it into the PTFE tube and the system recognised it as ‘loaded’. It then carries out ‘Mesh Bed Levelling’, and finally ‘First Layer Calibration’. For this process, the printer is supposed to lay down a zig-zag course of filament across the printer bed, so that the user can make any necessary fine adjustments to the vertical (Z)-axis to optimise first layer adhesion.
     
    The calibration proved to be so far out that I could see the filament extruding from the nozzle while it was at least 2mm above the print bed. There is a knob on the controller to adjust the height but the range was insufficient to close the gap. The manual claims that “the ‘SuperPINDA’ sensor height is set from the factory, no need to adjust it now”. Disappointingly, this did not seem to be the case, so I turned to the ‘Help’ pages on the Prusa website, which included instructions for setting the sensor height. I followed the procedure given on the website and did manage to achieve reasonable adhesion within the range of the control knob – just.
     
    I suppose one should always expect some teething problems but because this was a relatively expensive machine, compared to the many ‘clones’ that are available, I was not feeling very happy about these irritations.
     
    Printing
     
    The real proof, however, lies with the performance, so I had prepared a 3D model of a GWR Tilt Wagon in ‘Fusion 360’, to see how it would go. I used the Prusa slicer software, in my 'Windows 10' computer, to prepare the ‘gcode’ file for printing and copied it onto the USB memory stick supplied with the printer.
     

    My 3D model of GWR Broad Gauge Tilt Wagon in 'Fusion 360'
     
    As soon as the memory stick was plugged in to the socket on the side of the printer, the LCD screen on the printer helpfully showed a colour image of the job to be printed, which I think is a good feature. The printer then set itself up automatically, first checking the printer bed height at several points across the entire surface.
     

    Completed ‘First Test’ on Printer bed
     
    For this ‘first test’, I printed the central section of the wagon, comprising the floor and side walls. First impressions were good: the rivet detail is clear and the sides have printed very smoothly. There is a little ‘over-print’ in a few places and some fine gossamer-like excess that I had not seen with the old printer.
     
    What was most impressive was the quietness and smoothness of the printer, as it carried out its task. When I left it for a while, I thought it must have stopped, because I couldn’t hear it all from outside my work-room, but the job was progressing well and somewhat quicker, I thought, than when using the E180 printer. This job took just 43 minutes to complete, as recorded on the display screen.
     
    My impression was of a well-engineered machine that performed its task with a minimum of fuss.
     
    This was a considerably better ‘first test’ than when I first started with the E180, just over four years ago, and I have made no attempt to optimise any of the settings as yet.
     
    It will probably take me a while to familiarise myself with this machine and its associated software but, apart from the teething problems referred to above, it’s smoothness of operation indicates a good quality product.
     
    Mike
  18. MikeOxon

    ‘Rob Roy’ Re-Framed

    By MikeOxon,


    General
    Six years ago, in June 2017, I embarked on scratch-building a model of the Broad Gauge ‘Waverley class’ engine ‘Rob Roy’. The prototype was involved in an accident near Bullo Pill, where some of my wife’s ancestors were working for the GWR at the time.
     

    ‘Rob Roy’ – Accident near Bullo Pill, 1868
     
    I took advantage of the fact that the boiler used for the Waverley-class was the same as that on the Gooch Standard Goods engines, for which the Broad Gauge Society (BGS) provide an etched-brass kit.. My old series of posts described in sometimes graphic detail how I constructed the kit, which involved rolling a boiler from rather thin brass sheet.
     
    After completing the boiler from the kit, I was then faced with scratch building the chassis, which I also constructed from brass sheet.. The process was not without its problems, especially when fabricating the bicycle-style splashers over the large driving wheels but, after much trial and error, I ended up with a passable model.
     
    One major compromise, however, was that I used wheels supplied by Hornby for their ‘Lord of the Isles’ model.  I chose these because they have the required 24 spokes and these exposed driving wheels create a large part of the ‘character’ of the Waverley-class engines. Unfortunately, the wheels are over-size and this not only means they stand a little too tall but also that they had to be more widely spaced than on the prototype. At the time, I felt I had to live with the compromise but now that I have the means to print my own wheels, I felt I should try something better.
     

    My first scratch built model of Rob Roy, with Hornby driving wheels
     
     
    Enter my 3D-Printer
     
    The advent of 3D printing completely changed my approach to model building and I realise that there’s now no need to undertake the tricky fabrication of splashers from brass sheet and nor do I have to cut out the profiles of the sandwich frames by hand.
     
    All I had to do was find a suitable drawing – I chose the one by E.W. Twining – and trace over it in ‘Fusion 360’ before extruding the drawings into 3D structures. My methods have been amply described in earlier blog posts but one of the important lessons I have learned is that it is possible to extrude the valances around the outer rim of the splashers without the need for any additional support during printing. This method worked successfully on my ‘Firefly’ model  and I applied it again here.
     

    Extruded Frame over Twining 'Canvas' in Fusion 360
     
    I then created a mirror image of this first frame and separated the frames at the appropriate distance, linking them be means of a buffer beam and drag bar, as shown below (rendered in Fusion 360):
     

    3D model of chassis, rendered in Fusion 360
     
    As on my previous model, I filled the open space under the front of the boiler by adding a motion plate and ‘suggesting’ part of the motion. Further back, any underpinnings are hidden by the sandboxes and splashers.
     
     

    3D model of chassis with motion plate added
     
     
    Printing the Components
     
    The next step was to pass the various components to the Cura slicing software and then to my 3D printer, which created the following components:
     

    3D printed chassis components, together with my boiler assembly,
    constructed from a BGS etched-brass kit
     
    Once assembled, the chassis looks as shown below, with the boiler supported by the curved motion plate. An advantage of designing the model in ‘Fusion 360’ is that the ‘fit’ of all the parts can be tested before committing them to print. This was especially valuable for this model, in view of the tight tolerances between the splashers and the driving wheels. Note that, as in the prototype, the hind wheels are flanged but the forward pair of drivers are not.
     

    3D-printed Chassis and Wheels after assembly
     
    Although I had felt reasonably content with my original fabricated chassis, mainly because I was unable to improve on the over-size wheels at the time, I realise now how ‘wrong’ it looks, when placed together with the 3D printed version!
     
     

    My original chassis in front of the 3D printed version,
    carrying my original brass boiler assembly
     
    Overall, 3D-printing this chassis was a lot easier than using traditional methods, now that I am reasonably familiar with the ‘Fusion 360’ software. Of course, it is an option that was simply not available to me when I built my first model.
     
    Now I have to add the brass finishing to the splashers and valances.
     
    End of an era
     
    This is probably the last model that I shall print with my ‘Geeetech’ E180 printer. It has given a few problems recently, first with the feed mechanism and now the hot-end temperature has become erratic. This printer uses a modular print-head, specific to this model, and Geeetech have informed me that replacements are no longer available.
     
    After some thought, I’ve decided to buy a Prusa Mini+, partly because I prefer to buy a European product (although I have no complaints about the Geeetech company). I shall report my impressions once I receive the new printer.
     
    Mike
  19. MikeOxon

    Broad-brush Planning

    By MikeOxon,


    General
    One thing leads to another ... back in 2013, I started a blog to cover my growing interest in 19th -century railway models. Since I chose to model the GWR, this inevitably brought me onto a collision course with the Broad Gauge. At first, I thought of this system as something that was only associated with the 'primitive' stage of railway development. It was something of a surprise to realise that broad-gauge trains ran almost until the end of the century: the 'last gasp' being in 1892. As I have already observed in my other blog, the Broad Gauge was a 'different type of railway'.
     
    Although my existing model of North Leigh has a broad-gauge 'history', visible in the wide spacing of the tracks through the station, there is no realistic way in which I could adapt this model. My model is already shoe-horned into too small a space for a 'proper' 00-gauge layout and broad gauge track would be far more demanding, so there is no option but to make a completely new start.
     
    For some time, when looking at carriage designs for potential models on my existing railway, I have found myself having to keep checking whether a photo was actually of a broad-gauge vehicle ... and some of those looked rather interesting!
     

    Assorted Broad Gauge Carriages at Swindon in 1892
     
    So, where to begin?
     
    It happens that my wife's family has a long history of Great Western associations, starting in Reading and then following the line as it spread westwards, through the Forest of Dean towards South Wales. One ancestor was located at Bullo Pill, on the Severn Estuary, when a serious accident happened, about a mile to the south of the station in 1868. There are several photographs of the post-accident scene, one of which shows the derailed locomotive 'Rob Roy' surrounded by railway staff and 'sightseers' on the bank in the background. Perhaps, our family ancestor is among these people.
     

    Aftermath of the Bullo Pill accident, 1868
     
    This scene, taken together with the detailed description of the make-up of the two trains that is contained in the official accident report, provided me with inspiration for a new project. I intend to use the train descriptions as a 'recipe' for models, which I shall build and place within a small diorama based on the location.
     
    The accident site was in a shallow cutting about 150 metres north of Cockshoot Bridge [SO 695086], which now carries a minor road to the village of Awre from the main A48. The railway was the double-track main line to South Wales, via Gloucester,
     


    View North from Cockshoot Bridge, 1951 (Creative Commons Licence)
     
    The above photo shows that the cutting sides look much more overgrown in 1951 than in the 19th century photograph and, of course, the track bed has been changed to standard gauge. Another photo,which I took myself, shows the shape of the arch of Cockshoot Bridge in 2016:
     

    Cockshoot Bridge from the South, 2016
     
    In order to start planning my model, I needed to learn how the original broad-gauge track might have looked. For this, I used the construction details provided in the book 'Great Western Way' and, from these, I made a 4 mm scale drawing of the track bed, as a basis for future construction. This 'paper template', set in context by my old 'K's Milestones' model of a Gooch 'Single' locomotive, is shown below.
     

    Broad Gauge Track Template
     
    This shows how the 'look' of the trackbed is very different from the familiar cross-sleepered track, so I shall place this key feature across the front of my diorama. I have yet to decide exactly how I shall construct the framework of baulks and cross-ties, on which the rails are laid. The first step will be to build a length of straight track, before venturing into how to make a curve!
     
    My diorama will be housed in an open-fronted box, rather along the lines of the APA boxes that are, unfortunately, no longer available from Ikea, so I shall have to construct my own version. I like the idea of building an open frame, with separately attached panels, since this will provide ease of access during construction and also facilitate painting a 'backscene'.
     
    My plan is that the broad-gauge railway will run across the front, backed by the bank seen in the accident photo. At one end, the scene will be 'closed' by the Cockshoot Bridge. I shall have to think about how to provide a 'scenic break' at the other end but I expect that I shall include a few other line-side structures, to add interest.
     
    My initial sketches are shown below.
     

    Plan and Elevations of Proposed Diorama
     
    So, I now have a simple plan of action.
     
    In addition to the plan, I have bought some lengths of 'bridge rail' from the Broad Gauge Society and kits to build a locomotive and a mail carriage. Now, all I have to do is start building
     
    EDIT : new photo of Cockshoot Bridge added
     
    Mike
  20. MikeOxon

    3D-printed Modelling Tool

    By MikeOxon,


    General
    For some time, I have been feeling dissatisfied with the shaping of the frames on my model of the broad gauge engine ‘Rob Roy’ but couldn’t think of any ways to improve them, with the limited tools that I have.  The construction of my model is described earlier in my blog.
     

     
     
    Recently I started to think about whether my 3D-printer might be able to help. I do like engines to be made of metal, so a complete plastic print wasn’t my favourite option, although I did find it a useful exercise for testing my modelling skills.
     
    I had the idea that it might be possible to make a tool or template, to help in forming brass sheet to the correct curved shapes. I couldn’t work from published drawings because I have modified the frames to suit some slightly over-size Tri-ang wheels, which I chose because they have the correct number of spokes for the GWR ‘Waverley’ class. These wheels are a very prominent feature of the prototype.
     
    My starting point was a JPEG image of the frames that I made for my model, which has some compromises in dimensions, to accommodate the wheels. It proved quite difficult to turn this into something that I could ‘extrude’ into a ‘solid’ model by using my 'Fusion 360' software.
     


    Rob Roy Frames (modified) – JPEG image
     
    Different software packages have their strengths and weaknesses. For this application, ‘Silhouette Studio’ has an excellent ‘trace’ function but has very limited export capability.
     
    My first step was, therefore, to open the JPEG image in ‘Studio’. One pitfall is that the image had be scaled to 72px/inch, which caught me out because I usually use 300 for printing. I was initially puzzled because the image appeared 4.2 times too big!
     
    Once I had a correctly-sized background image, I use the ‘trace tool’, with the various filters turned off. The result was an outline drawing, which I saved in ‘Studio3’ format.
     

     
     
    To get this drawing into ‘Fusion 360’, it needs to be converted to SVG, which proved tricky.There is, however, a website  that will do an on-line conversion of ‘Studio’ files to SVG format, so, by using this, I now had the drawing in a format that I could insert into ‘Fusion 360’. 
     
    In principle, the extrude tools in ‘Fusion 360’ can be used to transform an imported drawing into a solid object. In practice, however, my drawing turned out to have tiny gaps in the lines, which did not create the closed areas that are needed for extrusion to work.  There is an ‘inspect’ tool, which identified a very large number of places where such gaps occurred but I don’t know of any easy way to close gaps in ‘Fusion 360’, other than on a point-by-point basis. Since the gaps are very tiny, it is difficult to find where to apply the editing tools such as ‘extend’ and ‘join’ and, in some places, they did not seem to work on the imported drawing. Failures seemed to occur where lines met some types of curves and would not connect .
     
    I needed another piece of software, to try and resolve the problem. So, I opened my SVG drawing in ‘Inkscape’ and explored the various ‘repair’ tools in that software. The ‘edit paths by nodes’ tool revealed that there was a very large number of nodes in the traced drawing. The ‘simplify’ command on the ‘path’ menu did a good job in reducing these to a more manageable number. By zooming in on the drawing to look at the detail of the nodes, it was easy to see where some nodes did not link up and it was easy to move node points so that they ‘fused’.
     
    I re-saved the drawing and inserted the new version into ‘Fusion 360’. Overall, the situation was now much better in that the main area could now be selected as a closed object. The ‘inspect’ tool revealed just a few problem areas and it was now feasible to give these points individual attention. In some cases, it was quicker simply to delete a short section and replace it with new lines. This method was sufficient to ‘close’ all the separate areas.
     
    It was only when I came to transfer the design to my slicing software, ‘Cura’, for printing that I realised that the scale had somehow changed during the transfer from ‘Inkscape’ to ‘Fusion 360’.  In my previous work, I had always used DXF files from ‘Autosketch’ and these transferred correctly to scale. As a check, I tried saving the file in DXF format from ‘Inkscape’, which solved the scale problem, but the other problems of ‘loose ends’ appeared again and, in the end, I found it easier to re-scale the printer file within my ‘Cura’ software, before finally converting the model to ‘gcode’ for my E180 printer. The printed tool is shown below.
     

     
     
    For my purpose, the most important part is the curved top surface, which provides a firm base on which to construct my curved splashers.
     
    My first step was to glue a sheet of 10 thou (0.25 mm) brass sheet to one face of the tool. I used ‘UHU’ adhesive so that, after processing, the brass could easily be removed by immersion in hot water.  I then used my Dremel ‘Moto-Saw’ to make a rough cut around the main features. This wasn’t as easy as I had hoped, since the saw operates with a vibrating motion and tended to pull at the thin brass sheet. It was, however, adequate for making a rough outline, which I could then refine by means of jewellers’ snips..
     

     
     
    I found it easy to use the snips, now that the brass sheet was firmly attached to the tool, which I could hold comfortably during cutting.
     

     
     
    For the final trimming, to match the edges of the tool, I used a selection of needle files. Although the tool is, obviously, very soft, it was sufficiently firm to provide feedback when the brass edges had matched the tool surfaces.
     

     
     
    Once the frames had been shaped to my satisfaction, I started to add the curved top surface to form the splashers. For this, I used lengths of 5 thou (0.125 mm) brass shim. I used separate lengths for each section of the splashers, as I had done in my original model, but I feel it would be possible, with care, to fold the whole top as a single sheet. I provided a series of tabs along the back of the splashers that I folded down for attachment to the frame. Because the  tool is plastic that melts easily, I could not solder these tabs in situ but, once everything was correctly shaped, I could remove the components from the tool, by immersion in hot water, and solder the parts together subsequently.
     

     
     
    I treated this as a ‘practice run’ and propose to try it ‘for real’ on some future engine builds that are in the pipeline. In fact, having looked at my ‘Rob Roy’ again, it doesn’t look nearly as bad as I thought and I shall finish it in its present form, while using the new techniques to build different designs.
     
    Having got this far, I decided to see how much extra work was needed to create a complete 3D-printed frame. The answer was not a great deal and, as a training exercise, I made a complete set of frames and splashers with ‘Fusion 360’, as shown below.  It was necessary to extrude selected parts of the drawing by different amounts to create the 3D structure.
     

     
     
    I took the opportunity to add sand-boxes and rudimentary springs to my original drawing. One advantage of using computer-aided design is that producing a pair of right and left handed frames is simply a matter of pressing a ‘mirror’ button! So, here’s a pair of frames, straight from the 3D-printer, with Tri-ang driving wheels in place on one side.
     

     
     
    Although the splasher tops are rather ‘thick’, to allow successful printing, they are also surprisingly robust and this would be a feasible method to use … providing you are content with plastic engines.  I intend to continue with brass construction but with the assistance of 3D-printed tools, to help in forming complex shapes.
     
    Mike
     
     
     
     
     
     
  21. MikeOxon

    Waverley - Between the Frames

    By MikeOxon,


    General
    Looking at the frames of my ‘Rob Roy’ model, I realised that there is a very visible ‘yawning gap’ between the frames, which really needs to be filled with something. It never bothered me with ‘narrow’ gauge ‘double-0’ models but a 28 mm gap is a different matter altogether.
     
    The instructions for the Broad Gauge Society (BGS) kit of the Gooch Goods, on which I have based my model, contain very little information beyond: “note: the kit provides for two slidebars per cylinder but it was probably a four-bar arrangement”
     
    It soon proved much more difficult than I had anticipated, to find out, with any certainty, what should be there. Drawings of these early engines are few and far between and, where they do exist, tend to be in rather poor condition and difficult to ‘read’.
     
    Fortunately, several fellow members of the BGS came to my aid and I was directed towards a ‘general assembly’ drawing from the National Railway Museum (NRM), which certainly met those criteria of difficulty mentioned above. It did, however, start me off on a line of enquiry, which answered many questions.
     

    NRM dwg 4742 – a full-size copy can be obtained from the museum
     
    My initial examination of this drawing revealed that the leading pair of driving wheels were flange-less, which I had already anticipated in my model, since it was needed to provide sufficient clearance between the pairs of wheels. On the prototype, it was doubtless desirable, to enable these locomotives to negotiate even moderate curves.
     
    More surprising is that the centre line of the cylinders appears to be above the centre line of the driving wheels but the cylinders do not appear to be inclined. This may be down to the rather poor quality of the drawing and the inclination would only need to be about 3°. On balance, this small inclination seems to be the more likely arrangement.
     
    Being a general arrangement drawing, the detail of the motion is difficult to discern from the NRM drawing, because there are many overlapping details. The Waverleys, however, were built around the same time as many of the Gooch Goods locomotives, so it seemed reasonable to me that the arrangement of the motion should share many features with those engines.
     
    Locomotive design at that period was still heavily influenced by Stephenson’s ‘Patentee’ locomotive, which set the pattern for design throughout much of the Victorian period. Here was the prototype of the classic British ‘Victorian’ locomotive, with two inside cylinders mounted between the frames. There is a very detailed description of the components of Stephenson’s engine in G Drysdale Dempsey’s book “A Rudimentary Treatise on the Locomotive Engine” (download from the Internet Archive)
    I found this book very useful in helping me to understand many of the construction details of the early engines. For example, there are detailed drawings of the cross-heads and many other parts of the motion, accompanied by information about the four slide-bars that were used.
     


    Cross-heads Stephenson’s ‘Planet’ type
     
    Gradually, I began to build up a detailed ‘picture’ of how the motion of the Waverley class was probably put together. This was helped further by detailed drawings of a Gooch Goods engine ‘Pyracmon’, in the Atlas of Plates, by Dempsey.
     
    ‘Pyracmon’ had a layout of the valve gear that was superficially similar to the more familiar Stephenson-Howe motion but with the important difference that the expansion link was mounted on a fixed pivot, while a radius rod attached to the piston rod could be raised or lowered to reverse the gear. This arrangement is attributed to the Gooch brothers and was applied to many of the Gooch locomotive designs for the GWR.
     


    ‘Pyracmon’, showing layout of Gooch valve gear
     
    Taken together, these various sources of information allowed me to attempt a rough sketch of how the motion of the Waverley class engines was probably laid out. By overlaying details from the ‘Pyracmon’ drawing onto the NRM drawing, I established that the overall layout of the components was very similar in the two designs.
     
    One notable difference was that, whereas the feed pumps for the boiler were driven by eccentrics on the driving axle in ‘Pyracmon’, they were driven from the cross-head on the Waverleys.
     
    My very basic sketch, below, shows the overall layout of the motion between the frames of the Waverley-class locomotives. A centre stay ran the length of the engine, between the back of the smokebox and the front of the firebox. My sketch shows the components on one side of this stay, which were mirrored on the opposite side.
     
    The four slide bars are shown in red. These were attached to the back of the cylinders and to angle brackets that were fixed to the motion plate, running across the engine.
     
    The Gooch valve gear components are shown in blue. The reversing action is conveyed to the valve rods via a rotating shaft running across the engine and operated by the reversing control lever, which ran along the side of the locomotive to the footplate.
     
    Moving parts are shown in grey and the fixed mounts for the reversing link and the reversing shaft are black. The reversing shaft was also attached by trunnions to the slide bars.
     


    Simple Sketch of Gooch Motion (LHS only)
    NB I now think that the reversing shaft should be above the motion in the Waverley class, not below, as shown in this sketch, which is based on the Gooch Goods.
    More information to follow in my next post
     
    I must emphasise that this is my own interpretation of the references quoted above, so there may well be points of detail that I have missed. I intend to use it as a basis for producing a few simplified components, to fill in some of that yawning gap between the frames of my model.
     
    EDIT (5th Jan) - I have re-assessed the possibility of a small inclination of the cylinders since first posting.
     
    Mike
  22. MikeOxon

    Splashers!

    By MikeOxon,


    General
    This is a lengthy post, containing a lot of detail about the methods I devised. When I started to write it, I realised that I had already forgotten some of the steps, so I have made this detailed description as a support to my own memory!
     
    From the very start of my plan to construct a model of a Broad Gauge ‘Waverley’ class locomotive, I realised that those bicycle-like splashers were going to be difficult! They are a very prominent part of the locomotive and fit closely around the rims of the large exposed driving wheels.
     

     
    On the positive side, these engines, like most steam locomotives, were built up from metal sheets that were either flat or curved in only one dimension. This makes it possible to construct models from metal sheet with simple tools and without any specialist techniques for metal-forming. The difficulties are, therefore, confined to marking out and then cutting sheet metal components that will fit together accurately with all the other parts of the complete locomotive.
     
    This is a problem that also faced ‘real’ locomotive engineers. So, for example, when Daniel Gooch had the foresight to realise the advantages of having parts that would be interchangeable between engines built by different contractors, he adopted the method of supplying templates or ‘jigs’ to the manufacturers. The ‘Firefly’ class, built using such methods, were amongst the most successful of early locomotive classes at a time when ‘standardisation’ had hardly been thought of by other designers.
     
    I have taken a similar approach and, instead of trying to produce accurate drawings of each component, I have use my computer scanner to produce two-dimensional templates, which could then be applied to the parts that I needed to cut from brass sheet.
     
    By the end of my previous post, I had produces a set of card templates for the inside frames, which could hold the wheels in positions that corresponded fairly closely to the prototype, after taking account of compromises needed to allow the use of commercially-available wheels.
     
    In this post, I address the problem of making splasher tops that are aligned accurately with the wheels and held securely in position, to form a reasonably robust model.
     
    On the prototypes, the backs of the splashers were attached to the inside frames and the curved edges of these supported the polished-brass splasher tops, which fitted closely around the wheels. So, my first step was to produce splasher backs that were profiled accurately enough to fit closely around the revolving wheels. To do this I attached the wheels by means of nuts and bolts to the card frames that I had already cut out and then laid the assembly on its side in my scanner.
     
    Once the scan had been transferred to my computer, I had an accurate, 1 : 1 scale, 2-dimensional digital representation of the ‘elevation’ (side view) of my model. I then used the following procedure to turn this ‘elevation’ into a template that I could print out and apply to brass sheet.
     
    Step 1
     
    I displayed the scan of the locomotive side in my photo editing software (I use Photoshop Elements but there are many alternatives.)
     

     
     
    Step 2
     
    I displayed a drawing of the prototype engine (drawing from Mike Sharman’s ‘The Broad Gauge of the GWR’, originally from ‘The Locomotive Magazine’, 1902), also in Photoshop Elements.
     

     
     
    I then used the ‘Magic Wand’ tool in Photoshop, to select the splasher fronts on the drawing, and used the ‘Fill’ tool to colour these valances bright red. Note that the top line of the valance corresponds to the top of the splasher backs, which are attached to the inside frames.
     
    Step 3
     
    I used the ‘Copy’ command in Photoshop to copy the selected valance detail and then ‘Pasted’ this as a new layer over the scanned image of my model. I then used the ‘Move’ and ‘Re-size’ tools, to adjust both the size and position of the pasted layer, until it coincided with the positions of the wheels, shown in my scanned image. I had to select parts of the pasted layer and move these separately, to allow for the small changes in the wheelbase of my model, compared with the prototype.
     

     
     
    This process provided me with a scale image of the valance, ready for use as a template on which the construct the splashers for my model. I could, of course, have drawn the valances ‘freehand’ over the scanned image but the method I used ensured that the curvature over the wheels corresponded to the prototype.
     
    In order to make use of this template, I again ‘Selected’ the red valance image and used it to create a new image, just containing these details (‘Paste as New Image’ in Photoshop).
     
    Next I opened this image in the Silhouette Studio software that drives my ‘Portrait’ cutter. I then used the ‘Trace’ command in studio to produce a cutting outline of the valance. In addition, I opened the drawing of the inside frames, which I had made previously and ‘added’ the curves corresponding to the top of the valance above the existing inside frame, so providing an inside frame which would support the splasher tops. Below, I show a screenshot of the cutting outlines as they appear in my Studio software. (I made two copies each of the valance and the inside splasher supports, to provide parts for both sides of my model.)
     

     
     
    Before committing to cutting metal (which the Silhouette, sadly, cannot do!), I cut out a set of the components from card to check the fit on my model. The result indicated that there was no need for any further adjustments around the driving wheels but I decided to lower the frames over the leading wheels by 1 mm, to allow for the low-set of these wheels, relative to the slightly over-size drivers.
     

     
     
    I made the final modifications in the Studio software and then printed the component outlines on plain paper. I cut out each component separately and stuck these templates to 10 thou (0.25 mm) brass sheet, which I then cut with jewellers’ snips, carefully following the outlines of the template.
     
    When cutting out parts in this way, I find that it is best to do a ‘rough cut’ first, to remove most of the surplus metal. I then follow the more delicate paths around the template outline, using a mix of straight and curved snips. Where there are inset curves, I do not attempt to follow the line precisely but work slightly outside them and use a selection of needle files to trim to the exact shape of the template For the cut-outs within the frames, I initially drilled round holes and then used a triangular needle file, to create the correct shapes for these openings.
     

     
     
    So far, so good but there was still the problem of those ‘curvy’ splasher tops, with a particular problem arising at the ‘valley’ between the driving wheels!
     
    My first attempts was not very successful, since I tried to make the entire top from a single brass strip. Because of the extreme curvature between the wheels, I knew that I would have to use very thin sheet – almost foil. (I used 3 thou (0.08 mm) sheet from ‘Cornwall Model Boats’). Trying to hold the sheet against the edge of the splasher tops proved almost impossible. I made some L-shaped brackets from snips of brass, to help provide some firm points of attachment, but the very thin sheet was too thin to hold the curved shape and I ended up with a distinctly wavy outline. It was all part of the learning curve for my next attempt.
     
    I decided to use thicker brass sheet and to divide the task into sections. I also decided to include tabs on the individual parts to provide firm fixing point to the splasher backs. Initial tests showed that the brass sheet forms a ‘natural curve’ above the wheels, so that a continuous seam was unnecessary. (N.B. a lot of the excess solder, seen in the photo below, was left from earlier unsuccessful attempts at fixing the tops!)
     

     
     
    This matter of providing ‘tabs’ is one that could make many kits easier to build, if only they were provided!
     
    Now, last but by no means least, is the matter of the valances, which are fully on show, right at the front.
     
    I thought about whether I cut out, by hand, narrow strips of brass with accurately-shaped edges less than a couple of millimetres apart. Then, whether I could attach them inside the outer edge of the top splashers, perhaps using low-melt solder, to avoid releasing all the other joints I have made. After a fair bit of thought, realism set in and I decided I could not do it, with any real hope of success.
     
    So, true to form, I looked for a ‘cheat ‘method. The solution appeared in the form of a roll of sticky-back, brass-coloured foil on a backing sheet. I could stick a strip of foil onto a stiff card backing and then put the assembly into my Portrait cutter. I already had the cutting pattern from the work I described earlier in this post. The advantage of using card rather than plastic card is that I have already demonstrated that it can withstand the heat of any subsequent soldering, when I constructed sandwich frames.
     
    To attach these valances, I put a thin smear of book-binders’ adhesive inside the rim of the splasher and gently teased the ‘brassed’ strip into place, with the aid of cocktail sticks. I put the whole splasher assembly upside down on my work-table and used a small strip of brass, as a small weight to keep the valance in place while the adhesive hardened.
     

     
     
    So, another step along the path to build my model of ‘Rob Roy’ but there’s still a long way to go – not least to repeat all the above for the other side of the locomotive! As the photo below shows, there’s still a lot fettling to do, while the buffer beam is a Photoshop artefact to hide an untidy mess underneath.
     

     
     
    Mike
  23. MikeOxon

    Next Stage – Making Rolls

    By MikeOxon,


    General
    In the previous entry, I described my approach to making sandwich frames. While that was only a small part of building a chassis, I decided to change tack and have a look at how the ‘super-structure’ of the Broad Gauge kit goes together. As I have mentioned before, I am considering how the boiler in this BGS kit for the Gooch Standard Goods might be used to create a model of the ‘Waverley’ class 4-4-0.
     
    To put it mildly, the instructions with the kit are somewhat terse in their description of this part of the construction – just three lines: “The boiler is straightforward. Press out all the rivets in the firebox, roll up the boiler (or use tube) and put the smokebox together. Again, these vary depending on the prototype as they were changed over the years.”
     
    Those few words actually cover quite a lot of work! For a start, the firebox has an awful lot of rivets! So, “all the rivets” actually translates into “242 rivets”. Yes, I counted them! When I pressed out the rivets on the frames, I used a centre punch but it was a bit too coarse for the job so, this time, I used an old school compass point, which provided a much crisper result. Since the boiler was half-etched to ‘raise’ the boiler bands, it’s a pity the kit designers hadn’t used the same method for the firebox.
     

     
     
    From what I have read, many builders quail at the idea of rolling boilers but this one went quite easily, once I had plucked up courage. The rectangular sheet of brass on the fret is already half-etched, with the boiler bands standing proud, so it’s easy to see which way to start rolling. Because of the half-etch, the sheet is thin and flexible and responds well to being rolled. Also, there are no holes or other obstacles in this sheet, to cause difficulty, and I soon had a round-looking tube.
     
    My method is to place the sheet, outer side downwards, on the back of a mouse-mat, which provides a suitable resilient surface. I then use a steel rod as a rolling pin, gently teasing the brass into a smooth curve while rolling back and forth.
     
    The next step, which, also from what I have read, puts a lot of people off building metal kits, is to solder the seam of the boiler tube. I believe that the key points to understand when soldering are that a good dose of flux along the whole area to be joined is essential and that the iron must supply sufficient heat to produce rapid melting, as soon as the iron touches down. The aim is for the soldering iron to heat up the joint enough for the brass to melt the solder - not the iron. I use phosphoric acid flux at about 10% dilution and a 65w temperature controlled iron, set to a nominal 285°C with 60:40 tin/lead solder. It’s also important to remember that the brass holds the heat for some time after removing the iron, so allow several seconds for the solder to solidify, before moving anything.
     
    In the following paragraphs, I set out a detailed description of how I tackled the various stages of construction. For much of the time, I was ‘feeling my way’ and, quite often, I felt unsure of how to proceed. Fortunately, I managed to get through the various challenges, so I hope that my description will prove helpful and will, perhaps, give some encouragement to others.
     
    I use an elastic band, near the centre of the tube, to hold the cylindrical shape and then concentrate on making sure that one end is aligned correctly, before applying heat briefly to that end to make a firm local joint. I then repeat at the other end, before running the tip of the iron along the inside of the joint, to ensure that the solder runs along the full length of the tube. After the ends have been fixed, I prefer to use my fingers to hold the tube and keep the seam straight, with a wad of tissue to protect my fingers from the heat.
     
    Once satisfied that the joint is firm, I immerse the components in water, to remove any residual flux. I also like to clean up the brass with some toothpaste and an old brush. The end result looked like this:
     

     
     
    In the absence of any further guidance from the instructions, I now had to make my own plans for the way ahead. Having pressed out all those rivets on the firebox, I decided to continue working at that end of the boiler. There are several parts, identified in the instructions by the labels shown in the following photo:
     

     
     
    As well as the brief instructions, there is also an ‘assembly diagram’ of the boiler, smokebox, and firebox but it gives no indication of where to begin or the order of assembly. After inspecting the various firebox parts, shown above, I decided that the two hoop-shaped items labelled as ‘firebox rings’, which have half-etched detail, are intended as cosmetic overlays for the ends of the firebox. So, I decided to start by fixing the item labelled ‘firebox ring to boiler’ onto the end of the boiler tube. There is a half-etched recess in the ring, which fits over the end of the boiler. After some thought, I placed the ring on top of the boiler tube while it was standing vertically on my soldering mat. I then used a cocktail stick to hold the top of the ring firmly against the boiler, while I applied flux and then made a local soldered joint at this point.
     
    After checking that the alignment looked good, I moved to the bottom side of the boiler and ran the solder around the inside circumference, using the cocktail stick to keep the parts pressed together. I was pleased to find that the parts fitted together very well, with just a narrow fillet of solder appearing on the outside rim of the boiler, as shown below
     

     
     
    I now had to decide how to roll the firebox wrapper, which is not a simple shape but needs to fit around the profile of the firebox back. There is no etched detail on this wrapper but there are holes for mounting the safety valve cover and whistles. These openings imply a need for extra care when rolling the wrapper, to avoid any kinks at these points of weakness. Because the wrapper is of thicker brass than the (etched) boiler, it proved more difficult to start forming a smooth curve.
     
    Once I had an amount of curvature that was approaching the profile of the firebox back, I had to decide how to create the complex shape of the firebox sides. The lower sides appear flat, so I marked lines on the wrapper to mark the transitions between the curved top-part and the flat lower-parts. I then folded out the lower-sides at an appropriate angle from the upper part.
     
    Next, I decided to place the firebox end flat on my soldering mat and then held the wrapper with its rear end also against the mat. I then pressed the two parts firmly together, ensuring that the wrapper was tight against the top of the back plate. At this stage, I did not attempt to bring the open ends of the wrapper close together but identified two points, either side of the top, where it was still in good contact with the back. I applied flux and soldered these two points. I then continued to make a continuous seam around the top of the firebox.
     
    Once the top was secured, I used the tips of my pliers to press the wrapper firmly against the profile of the back and started to solder around first one side and then the other. While doing this, I also adjusted the angles of the flat sections to ensure they fitted the lower part of the profile. As with the boiler, I used my fingers to hold the wrapper at critical points, with a wad of tissue for protection. It was essential to work quickly, both to avoid re-melting previously joined regions and to avoid burnt fingers! The end result is shown below:
     

     
     
    Now that the shape of the wrapper was defined by the back-plate profile, it was relative easy to attach the firebox assembly to the ring that I had already fitted to the boiler. The only difficulty lay in ensuring that the parts were aligned correctly, before completing the soldering. I started with a local attachment close to the top of the boiler and then worked around the edge of the wrapper, from below, using my fine-nose pliers to keep the firebox sides pressed firmly against the ring.
     

     
     
    The end result of this stage is shown below. I was very relieved to find that the folded grate and ash-pan component fitted neatly into the open bottom of the firebox!
     

     
     
    I readily admit to having had some difficult moments during this assembly. There may well be better ways of building this part of the kit but, at least, my approach has provided a result that pleases me
     
    Next step will be to look at the smokebox end of the boiler.
     
    Mike
  24. MikeOxon

    North Leigh Blanket Traffic

    By MikeOxon,


    general
    For the last couple of weeks, I have been dealing with various track issues and tidying up bits of scenery, none of which makes for very interesting blog writing! I noticed, however, in Mikkel's workshop thread some comments about Witney blanket trains, which reminded me of a photo that I had seen of a GWR 'Queen' class 2-2-2 heading such a train. This seems a rather unlikely combination but I eventually tracked the photo down to Colin Maggs' book "The Branch Lines of Oxfordshire" (Amberley, 2010).
     
    Spurred on by this revelation, I have been searching through the North Leigh archives and found the following photo of No. 1124 heading just such a train out of Witney. The stock is a typical mix of wooden 'Mink' vans in varying heights, which gives 'character' to the train. It is possible that this train might be heading towards Farthing, carrying a load of blankets for the military garrison there. (I'm not sure if Mikkel has ever mentioned that feature but it could be an interesting source of traffic and personnel). If not Farthing, it might have been Devizes, or one of the other Army towns clustered around Salisbury Plain.

     
     
    In a previous post, I showed a 'mock-up' of my then-proposed model of GWR No.184, next to a Dean 'Stella' class 2-4-0. I'm now able to show a photograph of the actual models, although No.184 still needs a lot of work to turn it into a fully-working model. At the moment, it can be pushed along by a motorised Dean 2,500 gal. tender. I'm also not satisfied with the paint finish. I have not been able to tone down the excessively glossy finish - matt varnish made it look 'blotchy' and the current, supposedly 'satin' finish is still too glossy for my taste.

     
     
    I think the comparison makes the Dean design look very 'pugnacious' against the older (1853) low-slung and lightly-built E.B.Wilson engine. For me, there is so much character in these old engines, and they have the advantage for modellers that they are (usually) of quite simple design.
     
    Mike
  25. MikeOxon

    1837 Carriage

    By MikeOxon,


    General
    I.K. Brunel wrote the following, in a letter to T. E. Harrison on 5th March 1838: “... let me call your attention to the appearance - we have a splendid engine of Stephenson's, it would be a beautiful ornament in the most elegant drawing room and we have another of Quaker-like simplicity carried even to shabbyness but very possibly as good as engine, but the difference in the care bestowed by the engine man, the favour in which it is held by others and even oneself, not to mention the public, is striking.”
     
    My own models of early GWR engines are no more than ‘ornaments’ but, as such, have given me a great deal of pleasure. They have led me to take a greater interest in those very early days of the railway and its hesitant progress through the many set-backs experienced at the time. Members of the Broad Gauge Society (BGS) may have read my brief accounts in that society’s recent Newsletters.
     

    Four ‘early’ GWR Engine Models
     
    The GWR was conceived initially as primarily a passenger-carrying enterprise so, after the engines, the first vehicles needed were carriages for first and second class passengers. At that time, there was no concept that ‘ordinary’ people had any need to travel any distance from their own towns or villages. The model for these early carriages was the road-coaches of the time and, indeed, one of Brunel’s justifications for his ‘broad gauge’ was that it would allow large wheels to be placed outside the main body of the coach, as in the case of contemporary stage coaches. This was quickly found to be impractical, since large wheels blocked the entrances to the compartments, but the overall construction methods initially followed road vehicle principles.
     
    I decided to make a model of one of the earliest types of 2nd-class carriage, to help me appreciate the differences between it and later designs. The most obvious distinction is, of course, size but it is clear that the dynamics of railway vehicles was not understood at the time and the choice of a 6 foot wheel base for a vehicle intended to run at speed on 7 foot gauge track seems unfortunate, to say the least! It is hardly surprising that the rough riding of these carriages caused sufficient concern for them to be ‘ordered off the line’ following a Board Meeting on 12th July 1838.
     
    In creating my model, I followed my usual practice of extruding the various components from a reference drawing – in this case, Data Sheet 102 from the BGS.
     

    Creating my 3D model in ‘Fusion 360’
     
    I have often advocated breaking a model down into smaller parts, to reduce the time needed to print each part so that any necessary corrections can be applied quickly. As in most things, it is best not to be dogmatic about this, especially in the case of a small model like this carriage, where the overall printing time is quite short anyway.
     
    In fact, I discovered with this model that printing the body in one piece produced a better surface finish than was obtained by printing the sides and ends separately. This may be down to the settings I use with my printer but the sides that I printed flat on the printer bed showed much more surface grain than those printed upright, as shown in the examples below:
     

    Sides and Ends printed flat on Printer Bed
     
    The time taken to print the above set of parts was 56min.
     
    For comparison, the time taken to print the complete body was only 1h 32min, including internal partitions between the compartments, which resulted in a rigid structure with a fine surface finish. I printed the chassis separately as shown below:
     

    Body Printed in One Piece above Separate Chassis
     
    In this case, printing the sides separately would be a poor decision, as the time saved is insignificant and the surface finish is poorer – and there is the additional need to align and assemble the various components after printing.
     
    Early Carriages in Context
     
    Another member of the BGS brought to my attention the historical engineering collection held in the National NetworkRail Archives  Amongst them, I found a rather perplexing set of drawings of Maidenhead Depot. When the first section of line opened to the public from Paddington, the original terminus was on the East bank of the River Thames near Taplow, where the bridge across to Maidenhead had not yet been completed. According to James Wyld’s ‘Great Western Railway Guide’ of 1839:
     
    “The Great Western Railway Company have a considerable station here, 42 feet above the level of the London depot, with engine-house, police station, and the usual offices. There is a jail for debtors and felons. The principal trade is in malt, meal, and timber, and the passing traffic derived from the Great Western road and the railway”
     
    All this seems to have disappeared, once the bridge across the Thames was completed, but the Archive drawings include one of foundations for what appears to be a carriage shed, with a central traverser to serve several bays. There is also a base for a small turntable, with a note on the drawing stating “This Turnplate to be carried as far West as the Solid Ground will allow”. I assume that this refers to the embankment leading to the yet-to-be-built bridge across the River Thames.
     
    Out of interest, I took this drawing (Ref.NRCA161489) and used ‘Fusion 360’ to create a 3D rendering, as shown below. I added some of my 1837 carriage models, to show how well they would have fitted within the planned structure.
     

    3D Model of Carriage Shed Foundations with 3 Carriages
     
    Whether this shed was ever built is open to conjecture since these early carriages did not last very long.
     
    Rapid Carriage Development
     
    One of the reasons why I like to build these early vehicles is so that I can use them to demonstrate how rapidly the designs evolved as they began to move away from their road-coach origins.
     
    Sometimes, there seem to have been backward steps before ideas moved on towards our modern concepts. For example, according to Whishaw ‘The Railways of Great Britain and Ireland’, 1842, the GWR rapidly abandoned the use of closed 2nd-class carriages, in favour of open sides, because they were thought to detract from the numbers paying for 1st class!
     
    Here are my models of the 1837 carriage next to the slightly later ‘open’ 2nd, showing the overall increase in dimensions, together with the use of six wheels.
     

    My models of ‘closed’ and ‘open’ 2nd class carriages
     
    The difference in scale, when compared with more ‘modern’ practice (in my context, the late 19th century!), was really brought home when I placed my model 1837 carriage alongside one of the well-known Tri-ang GWR clerestory models!
     

    My 1837 model against a ‘00’ Tri-ang Clerestory coach.
     
    Mike
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