Over two months have passed since I last wrote about my attempts to build a model of a Waverley-class 4-4-0. To re-cap, I have built a boiler, by using the Broad Gauge Society (BGS) kit for a Gooch Standard Goods, and have cut out some inside frames from card, to carry 24-spoke driving wheels taken from a Tri-ang ‘Lord of the Isles’ model. After putting these parts together, rather roughly, I felt that I had achieved an approximation to the appearance of the prototype.
As I continued to look at this basic outline, however, I began to feel less and less satisfied with the appearance, which made me reluctant to press on with the difficult job of cutting out real frames in brass sheet. As a distraction, while waiting for inspiration on how to move things on again, I built a couple of broad gauge carriages and a luggage van, to make up the rest of my planned mail train.
During this fallow period, I was contacted by another BGS member, who has also been constructing a model of a Waverley-class locomotive, and he has provided me with several useful tips.
This is a post about the difficulties and compromises that are involved in constructing a model that captures the appearance of the prototype, while using commercially available parts and minimal engineering skills.
The first area to consider was the boiler, which came from the BGS Standard Goods kit.
Although the boiler of the Waverley class was the same as that used for the first three lots of the Standard Goods, the information provided in the RCTS volume covering the Broad Gauge shows that it was pitched considerably higher. Whereas the Goods boiler was pitched at 6’ 4¾”, that of the Waverley was at 7’ 1½”. This difference in heights could be expected to alter the relationship between the boiler and the cylinders and, hence, raises questions about the suitability of the smokebox components provided in the BGS kit.
Photographs of the front end of Waverley-class locomotives indicate that the cylinders were horizontal so, with 7’ diameter driving wheels, the centre-line of the cylinders is expected to be 3’ 6” above the rail tops. On the other hand, the cylinders of the Goods engines were angled, to enable the connecting rods to clear the leading axle. Because of this upward slope from the centre axle, the fronts of the cylinders are considerable higher than might be expected for driving wheels of only 5’ diameter.
The actual distance between the centre line of the boiler and the centre lines of the cylinders on the prototype Waverley-class locomotives is expected to be 7’ 1½” minus 3’ 6”, which is 3’ 7½“, or 12.5 mm in 4mm/ft scale. Fortuitously, my measurement of this distance on the front plate of the smokebox in the BGS kit was also 12.5 mm !
So, by sheer coincidence, it seems that the smokebox front of the BGS kit for the Standard Goods has the correct separation between boiler and cylinders for the Waverley class!
The next areas to consider are the frames and wheels.
I chose to use driving wheels from the Tri-ang ‘Lord of the Isles’ because these appear to be the only commercially available wheels with the required 24 spokes. I admit that I had hoped that, like most ‘toy’ models, the Tri-ang wheels would have been considerably under-size but, alas, thy are not. Even after turning down the tyres as much as possible, they were still about 1 mm over-size for my model.
So, as so often happens in modelling, I was faced with a compromise! After careful measurements, I decided that the minimum wheelbase I could set between the pairs of driving wheels was 31 mm, compared with the prototype’s 7’ 5” (29.7 mm). Initially, I compromised by spreading out the wheels symmetrically, around the mid-point, but this had the knock-on effect that the rear pair of leading wheels had also to be moved forward slightly to maintain clearance.
Whereas the change to the driving wheels was barely noticeable, the resulting ‘crowding’ of the leading wheels was all too obvious and changed the ‘character’ of the locomotive, giving a ‘front-end’ appearance more like the 4-2-2 ‘singles’. In fact, this is an example of where the ‘eye’ can be more important than the measurements, since the leading wheelbases for the two classes are actually the same but the leading wheels of the ‘singles’ are of larger diameter.
I used the technique of laying my model on its side in my scanner, to get a direct visual impression of the relationships between the wheels. One advantage of making a scanned (scale) image was that I could make a direct comparison with published drawings of the prototype, by overlaying a drawing (blue) over my scan, by means of ‘Photoshop’, as shown below:
This comparison shows very clearly the ‘crowding’ of my front wheels. Incidentally, I had also glued the frame rather too high onto the side of the smokebox but I laid the front wheels on the scanner in their correct locations, relative to my frames. . Although I had only ‘tacked’ the frames in place, with dabs of ‘Uhu’ adhesive, I found them surprisingly difficult to remove, when I came to replace them with revised versions!
I decided that the ‘visual impression’ would be improved, if I moved all the driving wheels, and the rear pair of the leading wheels back a little, to achieve the correct spacing between the leading wheels. This meant the the rear footplate would be a little longer than on the prototype (perhaps to the delight of the model drivers).
This change was very simple to implement by lengthening the frames on my drawing, between the leading wheel pairs, and re-cutting on my Silhouette cutter.
The revised model now looks like this and I feel that it is a fairer representation of the prototype:
Although it is far from finished, I feel sufficiently confident to proceed to the difficult task of cutting out splashers and frames from brass sheet. My fellow BGS member has already warned me that “The splasher top / running boards are a real pig, there is no other way to describe the making of them.” Oh well, something to look forward to