Finally started on the engine brake gear for Lord President
A pattern in styrene was made to fit on the brake hanger pivots to check the size.
This then needed to be copied eight times in 20 thou nickel silver. To make eight pieces, a strip was tinned, folded up, and then squeezed together in the vice and re-heated to join up the layers.
This block was then drilled with two 0.5mm holes for the hanger and push-pull beam pivots.
This was then filed up in the vice.
And then a lot more filing.
Next stage was to separate them and file in the brake shoes and hangers. Final filing and shaping of the brake blocks and hangers required the use of some nice safe-edged Vallorbe escapement files.
What can’t be seen is the finger nail that would be holding down the brake block.
Each block was made to fit a particular pivot, as my chassis drilling wasn’t that accurate.
They tuck snugly into place on the wheels and definitely fill the space well, helping to hide the overscale flanges. There is no way I could have made this engine with scale size wheels: the brake gear would have been impossible to fit.
The brake cross beam assemblies consist of thin double sided PCB with a brass pin soldered across and gapped. The assembly is gently sprung over the brake hanger pivots: these are a shouldered 16BA steel bolt tapped through the frames.
The cross beam was also strengthened by a piece of shim brass on the other side to span the weakened area of the insulation gap: this will have the push/pull rods soldered to it to allow the brakes to be held in the ‘off’ position.
Before mounting on the engine the whole lot was chemically blacked.
Afraid these photos are desperately cruel. Just need three more and the push pull rods.
Tim