It’s some time since I’ve scratch-built a standard gauge locomotive, having been spending my time recently on Broad Gauge models. I learned several lessons, however, during the construction of my previous 00-gauge models, the most important of which was to remember that 00-gauge is actually a narrow gauge – closer to 4’ than 4’ 8 ½”, when scaled.
My first scratch-build, described in 'Railway Modeller', July 2014, was of a 2-2-2 ‘Queen’ class engine, which was a simple choice because single-drivers create no problems of coupling rods and their alignment. As I commented at the time, building a ‘single’ is little different from building a wagon, especially if tender-drive is used for the model.
My ‘Queen’-class model
The problem of ‘narrow gauge’ raised its ugly head when trying to fit the large driving wheels since, in 00 gauge, they intercepted space occupied by the boiler! The solution was to cut oval apertures in the sides of the boiler, where they are hidden behind the splashers. It’s a good job I didn’t attempt an earlier version, with ‘open’ splashers. A rather wide gap between the wheels and the outside frames remains obvious at some angles.
Later, I built a model of one of the former West Midland Rly. Engines, which was absorbed by the GWR as No. 184, where it retained the ‘Wolverhampton’ livery.
My model of GWR No.184, with ‘517’ class
In this second case, the ‘narrow gauge problem’ appeared when attempting to fit the outside coupling rods. I found that I had been over-generous in my frame spacing and couldn’t prevent the outside cranks from rubbing on the frames. Because of the way I had constructed this model, it was not simple to reduce the separation of the frames, I had formed the frames by folding down the edges of the rectangular plate that represented the footplate. Part of the problem was that I had forgotten to take account of the thickness of the folded edges, which made the outside dimensions wider than I had intended. Another ‘lesson learned’.
With these ‘lessons’ firmly in mind, I began to prepare drawings of my new engine, taking account of 00-gauge constraints.
As noted in my previous post, I have a side-on photo of No.31 and a drawing of Armstrong’s earlier No.361, which differed in the style of the frames. By merging information from these two sources, I prepared outline drawings to form a basis for my model, as shown below:
My Interpretation of an Armstrong Standard Goods with Original Boiler - derived from various sources
In the head-on view, I have marked in red the positions of 00-gauge wheels. Although they will just be clear of the boiler (including an allowance for cladding), they will interfere with the smokebox cladding and the lower sides of the firebox, so I shall need to make allowance for these intrusions. In both cases, the necessary openings will be concealed by the splashers, which I shall maintain close to their ‘true’ locations.
I have examined several different early photos of the prototypes and it is clear that some fittings, such as the location of the injectors on the sides of the boiler barrel, varied quite widely. I decided to add a cab, since these were adopted quite soon after the introduction for these engines although initially in a more truncated form.
My plan for the actual ‘build’ is to adapt techniques I developed when making broad-gauge engines, such as my Gooch Goods, in that I intend to use a combination of brass components and 3D-printed overlays. This is the first time I have adopted this approach for a standard gauge model engine. It follows my tradition of trying out new techniques with every model I build
My starting point, therefore, was to construct a set of outside frames, For strength, I decided to make these from lengths of 6 mm x 1 mm brass strip. In fact, I took a single length of strip, marked off the lengths of the sides at 95 mm and marked the width to give clearance to the ‘narrow gauge’ 00 wheels.
I then used a square-section needle file to make vee-shaped grooves in the brass strips at the appropriate positions to fold the strip into a 95 mm x 21.5 mm (inside) rectangle.
Cutting groove and folding into rectangle
I ‘squared up’ the resulting box form over a sheet of graph paper. Once the assembly was ‘square’, I soldered the final joint and trimmed off the excess strip by using a diamond cutting wheel in my mini-drill. Careful trimming with needle files removed any remaining rough edges.
The main boiler assembly was even simpler. I bought a length of 21/32” (16.7 mm) brass tube from ‘Cornwall Model Boats’, which provides an outside boiler diameter equivalent to the prototype’s 4’ 2”. I shall add cladding by means of a 3D-printed sleeve, as I have done previously for my model of a Gooch goods.
Brass skeleton of my planned model
These brass components will form the ‘hard’ skeleton of my planned model and, in the next stage, I shall add 3D-printed parts to carry the details of the outside frames and of the boiler cladding, smoke-box, and firebox.
I intend to use ‘Alan Gibson’ wheels on extended (32 mm) axles, to carry the outside cranks and coupling rods.
I hope that my next post will show something that looks more like a locomotive