The Rider-Ericsson pumping engine has always been popular with model engine builders and casting kits are available for 1ins 2ins & 3ins models. I do not build from kits myself preferring to scratch build from plate and bar stock and have built one 1 1/2ins bore and one 1ins bore and both worked out well. Last year I built the "Vickie" stirling engine from plans with a .60 ins bore cylinder which required the making of a .60 ins lap to finish the bore. When the engine was finished rather than discard the lap never to be used again, I decided to build a further engine to use this lap and so scaled down my 1ins Rider-Ericsson by a factor of .6. When scaling down the screw fixing soon become very small and were only 8ba &10ba. When I was a draughtsman working on instrumentation work I never had any hesitation in calling up 12 ba tapped holes in stainless steel much to the protests from the machine shop, but I just used to say no bother, but now in my own workshop I never go down below 10ba in mild steel and its funny how one views change.
The little engine worked out well and pumped a fair bit of water, the only problem being that water leaked around the pump rod and I wished I had enough room to fit a pump gland with soft packing but there is not room, I wish I had lowered the pump a little but it is too late now, may be on the next one.
Hugh
