Some while ago I acquired a 'Myranda' fan (eg
With the piston and displacer rods disconnected, it was obvious that the engine was far from free running. I first put this down to the somewhat wonky crankshaft with crankpin and main shafts held into the webs by grub screws, but, even after removing the shaft the bearings still felt rather lumpy. I concluded that they had either been fitted too tight (it doesn't take much interference on these small sizes to eat up all the internal clearance) or had been pressed in using the inner ring thus brinelling (denting) the races. I pressed them out (certainly did feel tight) line reamed the standards to a nice sliding fit and fitted another pair, securing with drop of loctite.
Next the crankshaft was remade, soft soldering the existing webs and crankpin to a length of silver steel and then removing the piece between the webs. It sprung slightly when the centre was cut out but was still a deal straighter than 'old wonky'. It is interesting to note that 1/4" silver steel will not slide smoothly into a 1/4" bearing, but a very little work with fine emery cloth soon remedied this and the result was a beautifully free running assembly.
Displacer and piston rods were refitted, everything given a dose of thin oil and a small blow lamp applied to the hot cap. After a few minutes I gave the fan a flick and off it went - hooray! Not quite home and dry though, the running was accompanied by much wheezing and spitting of oil from the piston and would only continue with regular applications of this sealing medium - that's the next job then, and I'll bet the bore is bell mouthed too!
By this time it was around five and I went indoors to make a cup of tea only to find the one I had made at nine in the morning still sitting there stone cold - funny how time flies etc etc!
I don't think I'd ever want to tackle building something like this from scratch, but I do enjoy this sort of 'rectification' of other peoples builds.