After a few months of doing other things, I have once again started work on my 3rd loco. Previously, I had formed the saddle tank (http://www.rmweb.co.uk/community/index.php?/blog/1009/entry-16413-gwr-buffalo-1076-class-in-2fs/) and there the project had stalled for no other reason than I wanted to progress Modbury for the 2mm Association's Supermeet last month.
Picking up the reigns again, I have made a start on the chassis. Once again I have decided to provide the engine with a milled solid brass (albeit split framed) chassis. To achieve this, a length of 1mm thick brass is bolted to a main chassis block some 6mm thick the bolts being secured in insulating material in the main block. Once the pair are united at their extremities (outside the finished size of the chassis), the various holes for fixing bolts, axles and gear shafts are drilled through before the shape of the chassis is milled away.
For this loco, I will be using some etched coupling rods of 14.5mm x 16.5mm wheelbase that I have done my own artwork for (they are of the "fish bellied" profile which unfortunately the Association do not provide). Until my own rods are ready I will be using Association ones as a jig to drill the axle holes and to test the final chassis build.
Because the Buffalo class had outside frames, Association wheels with extended axles were purchased, unfortunately the wheels do not come with Fly Cranks so these had to be manufactured. A sheet of 0.018" nickel silver was used to fabricate the cranks, a 0.7mm hole drilled in a piece of the material for the spigot on the extended axle, and a 0.5mm hole was drilled 0.080" (about 2mm) from that hole. A little jig was made with a 0.7mm peg in it onto which the piece of nickel silver sheet was hung and the 0.5mm hole drilled 0.080" away from it. The crank was then filed around these two holes.
Completed chassis, albeit with the extensions still in place - these will be cut off once all of the machining has been complete (the worm housing still needs to be made and bolt holes drilled and tapped)
Finally a short video of the chassis being pushed along
There is still a bit to do, not least of which will be a full strip down so that it can be painted!