In my previous post in this blog, I described my chance discovery of the former narrow-gauge system that linked the farms on the Buscot Park estate to a distillery and other works, located at a wharf on the upper River Thames.

 

This was especially interesting to me because I had introduced an imaginary narrow-gauge (NG) line on my ‘North Leigh’ layout, to serve the local quarries for Cotswold stone and the sawmills around Wychwood Forest, by connecting them to a railhead at North Leigh – itself never actually served by railway, although a branch to Witney had been proposed in 1849.

 

My model NG railway is worked by two aged ‘Peco’ NG locomotive body kits, mounted on ‘Arnold’ 0-6-0 and 0-4-0 chassis.  Although I still like the saddle tank version (known as ‘James’ in the Peco catalogue), I’ve never liked his side-tank sibling, known as ‘Jeanette’, very much – something about the proportions never felt ‘right’ to me.

 

NG engines at North Leigh NG engine shed

 

So, having discovered ‘Edith’ on the Buscot railway, I thought I might design a body based on her, to fit onto my existing Arnold 0-4-0 chassis. There are going to have to be a few compromises, to make the ‘Edith’ body fit over this chassis, so it may not be an accurate model but it will provide a ‘memorial’ to a long-lost prototype, which did in fact operate for a short period in this area of the Country.

 

 

 

In order to create my model, I needed more prototype information than the illustration that I found in Lowe’s book called: ‘‘British Steam Locomotive Builders’.  Fortunately, I found a reference to an article in ‘Engineering’, 20th January 1871. This can be downloaded from 'Grace’s Guide', now behind a paywall but still an excellent source of information about locomotives and engineering in general, during the 19th century.

 

The ‘Engineering’ article includes drawings and several views of the engine ‘Edith’, together with a detailed description, providing all the main dimensions. There are some inconsistencies between the various illustrations but I now had sufficient dimensional information to start to create a model.

 

I gather that some of my readers like to read my ‘blow by blow’ accounts of how I build my models, so I shall record my progress in ‘diary’ form.

 

My first step was to copy a couple of drawings from the ‘Engineering’ article and insert them as ‘canvasses’ into my ‘Fusion 360’ 3D-modelling software. This article also provided some key dimensions, including wheelbase of 5 feet and overall length of 12’ 11”.  I used the overall length, plus the width of 5’ 3”, to ‘calibrate’ the images in ‘Fusion 360’.

 

My next step was to use the ‘sketch’ mode in ‘Fusion 360’ to create a rectangle over the entire outside valance. I followed this by using the line and arc drawing tools to mark out the shape of the valance, where it curves over the wheels, and selected the enclosed area of the valance, after which I used the ‘push-pull’ tool (press ‘Q’), to extrude this by 1 mm above the canvas plane. The result of these operations is shown below:

 

Creating valances in Fusion 360 from a ‘canvas’

 

I created a buffer beam in exactly he same way, by drawing a rectangle over the head-on image of the engine. I rounded off the corners of the buffer beam by using the ‘Fillet’ tool to reproduce the appearance of the prototype.  After extruding the drawing by 1 mm, I now had all the parts necessary to create the outside members of the chassis.

 

To do this, I used the 'Move' tool to rotate the parts into the appropriate orientations, followed by the 'Copy' tool (which is an option within the 'Move' tool) to provide duplicate frames for both sides and buffer beams for both ends, as shown below:

 

Creating the Frame in Fusion 360

 

I like to keep all the parts as separate bodies at this stage, so that I can easily re-position them later if necessary. I think this approach is analogous to using ‘layers’ in Photoshop, to keep options open for making alterations later.

 

The article in ‘Engineering’ gives the boiler diameter (inside) as 2’ 8” and the length from smoke-box tube-plate to back plate of the firebox casing as 7’ 6”. I checked these dimension on the drawing (they were correct) and drew circles over the drawing to represent the inside and outside diameters of the boiler and then extruded this to a length of 30 mm, to create my model boiler.

 

On the prototype, the firebox can be seen to be located within the back end of the boiler. I added lines to my boiler sketch to represent the outer faces of the firebox and extruded these to a length of 14 mm (equivalent to 3’ 6” on the prototype). Since the grate slopes down towards the front of the firebox, I drew a triangle on one side of the box and then used the push-pull tool to Cut the lower part to the correct profile, as shown below.

 

Creating the Boiler and Firebox in Fusion 360

 

None of the illustrations that I have of ‘Edith’ shows the front of the smokebox, so I had had to make informed guesses. I simply extruded another body from the front end of the boiler, to create a cylindrical smoke box of length 4.67 mm, in accordance with the drawing and equivalent to a prototype length of 1’ 2”.

 

The ‘Engineering’ article describes the cylinders as: “outside cylinders 8 in. in diameter with 15 in. stroke, these cylinders being placed at an inclination of 1 in 5, and being situated at a distance apart transversely of 4ft. 2 in. from centre to centre.”  I decided to create these cylinders as separate components, so that they can be positioned on my model as required.  I started by creating a simple ‘box’, then drew a circle on one end face, which I extruded to represent the cylinder end-plate.. In exactly the same way as I did for the firebox, I cut away part of the side of the box so that it would fit against the outside frame at the desired 20° (1 in 5) angle.

 

(as a note to self: it’s good to write up like this, because I suddenly realised, while writing, that I had wrongly set the angle to 5° through a hasty mis-reading of the above description)

 

After placing these various bodies in their appropriate locations on the overall model, the assembly now looked as below. Note that I have still kept all the parts as separate bodies, so that I can re-adjust them if necessary and also so that I can print them individually.

 

Creating the Smokebox and Cylinders in Fusion 360

 

The remaining, most obvious parts are the two coal bins at the sides and the back-tank, so I drew these next, following my standard method of extruding from the drawings. These are simply extruded rectangles, with a few radiussed corners. The outline of the side bunkers was marked by a very faint dotted line on the ‘canvas’ but the main body of the back-tank was obvious.

 

I initially extruded these parts as simple cuboids and then rounded the vertical corners of the back-tank by using the ‘Fillet’ tool to create the rounded appearance shown in the illustrations of the engine.  I placed the three items in their locations on the frame and then tackled adding the flare around the top of the back-tank.

 

I’ve tried various methods for creating such flares, of varying degrees of complexity, but since I found the ‘Sweep’ tool in the ‘Create’ menu of Fusion 360, it’s become very simple!  I simply sketch the end profile of the flange and then click on the ‘path’, which is the line around the top of the tank body. The profile is then automatically turned into a solid body, as shown below:

 

Creating the flange around the Back Tank in Fusion 360

 

With a few minor additions, such as the tank filler, the assembly was now beginning to look very much more like a locomotive!

 

My 3D-model assembly in Fusion 360

 

I have now reached the point of adding the boiler fittings, where I can adopt my tried and tested method of using the ‘Rotate’ command on a profile sketch. I made the chimney and dome in two parts, the lower of which I ‘Joined’ to the top of the boiler, leaving a flat surface on which to attach the upper part, after printing.

 

Normally, I would now start on the design of the chassis but, since I want this to be a working replacement for ‘Jeanette’ on my layout, I shall have to make some modifications, to enable the body to fit onto my Arnold chassis. I shall keep the parts designed so far, so as to leave open the option to create a true scale model but shall now take a break , to consider what ‘distortions’ I shall have to make.

 

Meanwhile, a colourised view of model ‘Edith’ so far:

 

 

 

 

Mike