How I created my Drawings

My sketches, as reproduced here and elsewhere, are my reinterpretations of the work of others. The majority are based on original GWR weight diagrams, ranging from Russell's "A Pictorial Record of Great Western Engines" volumes 1 and 2 to originals gifted me by a former Swindon Drawing Office staff member. Where budget permits and they are available I have referred to genuine engineering drawings, normally general arrangements or frame plans. Didcot Railway Centre and the National Railway Museum are excellent sources for these. Photographs old and new are of course also vital, especially when trying to puzzle out what a particular line actually means. Dimensioned engineering drawings are always the gold standard though. I've also made use of third party drawings. At one end those of Trefor Jones and Mike Lloyd, available through the Welsh Railway Research Circle, seem to me excellent, and the work of E.L. Ahrons and J.N. Maskelyne at the end of the 19thC and first half of the 20thC vital. Others may be less certain though. I hope none of my errors are as bad as some of the ones I have detected!

I also have doubts about the accuracy of the original sketches. As I understand it weight diagrams and the like were not used for construction or maintenance. Thus I don't think a sometimes hard pressed drawing office would always have drawn them to the limits of accuracy. I sometimes see what seem to me to be obvious errors. For instance to my eyes the diagram B74 drawing of the 5700 (fig 272, Russell Vol 1) shows a dome that is taller than the chimney, but the diagram B70 of the 8750 (fig 463, Russell Vol 2) shows one that is shorter than the chimney. In both the chimney is dimensioned at the same height and I doubt that the domes were different.
This seems to have significant implications for the fine scale modeller. I do not believe that the locomotive diagrams are of great use to you: it seems to me it would be quite unwise to scale dimensions from them. I fear that what you need are the full engineering diagrams made by the drawing office for the factory to use in manufacturing, which I suppose isn't really a surprise.
I must also repeat the advice given by J.H. Russell in his introduction to the books. He quotes J.N. Maskeleyne who said in 1935, "If a model or drawing is to be made, be careful to have at hand a photograph showing the particular engine concerned, and of the period in time desired, as every engine seemed to differ in some way." and continues with his own advice "...watch out for the small details. Boiler fittings are always suspect, chimneys in particular, ao always try and make the fittings please the eye and look like the photograph... Also use the drawings with caution... a drawn line does not prove authenticity."

Most of all do not rely on these sketches to be accurate. I do my best, but they are my interpretation of drawings made at least 70 years ago for a different purpose by men and women (there were women working in the drawing office) whose training I entirely lack, and whose work I don't altogether understand. I also frequently run into the problem that I simply don't have the information. Historical photographs often turn into mud below the footplate where one is desperately seeking detail of brake gear which is normally absent from a weight diagram. Because these sketches are intended as illustrations rather than plans I do sometimes invent what I trust is a credible guess where nothing better is available. Always remember, when it comes to IT generated material, that a wrong line, or a wrong total for that matter, looks just as convincing as a correct one.
The actual process is to scan the drawings from the source and then use a vector graphics program to completely redraw them. Even if the drawings had been reproduced perfectly in a book then when I scan them I probably introduce distortions because I haven't destroyed my book so as to lay each page perfectly flat on the scanner. What I do is to lay out a grid on the screen which matches the measured distances on the drawing, and then juggle the aspect ratio of the sketch to get the closest possible fit. The actual accuracy is going to be variable from sketch to sketch, but its certainly no better than the nearest scale inch and often will be several inches out. Hopefully this illustration gives an idea of my procedure.

On the other hand I can thoroughly recommend this exercise to new modellers. Redrawing the item you are planning to model with a vector graphics program is an excellent way to gain a much improved understanding of how the item is put together and how the parts relate to each other, and is a quicker exercise than you might think: certainly far faster than doing it with pen and paper as our grandfathers did. Its a continual surprise to me how much you learn from drawing something. Of course you learn even more by making the model, but it can be a bit late by then!
If you can look at these drawings and gain a greater understanding of how these locomotives evolved over the years then I will have achieved my aims with these sketches, but if you use them as the main source for anything beyond the simplest "plastic bashing" representational modelling then I have done you a disfavour by creating them.