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Splashers!


MikeOxon

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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.

 

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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.)

 

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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.

 

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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.

 

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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.)

 

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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.

 

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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.

 

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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!)

 

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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.

 

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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.

 

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Mike

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Well done, you got there in the end, they are an extremely trying item to fit and get looking slim, covering the tyres, and not touching the flanges.

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Many thanks, Northroader.  It was, indeed, very trying!  I'd like to make the tops a little narrower, so I shall have a good look at the tolerances, when I do the other side, and see if I can get things a bit finer.

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A very useful post, nicely done. 

 

Using the silhouette to make templates from direct scans of the loco for sheet metal work really is a good idea. Marking those out by scribing would be difficult; your technique allows a bit of leeway for the real life problems of making parts to suit the tolerances of a model. 

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Glad you found it useful, Dave John.  I have used scribing but the lines aren't so easy to follow as printed ones - make sure that the paper is stuck down firmly, though!

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You did it! As we knew you would :-)

 

As Dave says, some useful ideas for the Silhouette too. I haven't actually used the Studio software much so far, other than to convert Inkscape files for cutting. Must explore those opportunities.

 

BTW I know what you mean about writing up these notes for your own later use also. We tend to forget these things over time. I recently Googled something and found the answer in a three year old post on RMweb. It was my own post!

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"and found the answer in a three year old post on RMweb. It was my own post!" - you're still young, Mikkel.  Wait a few years and you'll find yourself staring at yesterday's post with no recollection :)

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I had completed forgotten your post about the splashers on your Dean Goods, 3 months ago, Mikkel 

 

Your method was not that different from mine, although I like to cut metal!  If you need shiny brass, then adding foil to card or plasticard could provide it and I have shown that the Silhouette cutter works on the material, after the foil has been added. 

 

I'm not sure how it will 'weather' - probably better than real brass, since I think the foil is actually anodised aluminium.

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