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| We'll Call it Metisse........ |
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| Stilldrillin:
Well. It's next week, now..... Not such a happy chappie, today. ::) I've got a big (ish) day tomorrow. So, I assembled the finished engine. Hoping to have a new toy....... :) Put a temporary light under....... And NOWT happened! :scratch: After 20 mins, the whole engine was hot. No attempt at running. Just a couple more rotations, in the correct direction. Compared to the wrong direction. So, I let it cool, and fitted a temporary heat shield......... That made no difference! The assembly was "neat", rather than sloppy. Probably needs some slop. So, I pushed out the double bearings. Replaced with single, to allow some crankshaft wriggle........ Faced all square. Polished the cylinder bore.......... No difference! :( Detaching the power piston big end, proves the displacer section will spin freely........ So...... The problem is with the power piston. I eased the piston o/d. Twice. No difference! :bang: So...... I hit it with my little blowlamp!!! THAT, made it run, for a few seconds. Then it stopped......... Again! Thinking calmly....... :med: Who in their right mind, makes a cylinder from a section of copper pipe. And fits an alloy piston? :loco: Unless, someone knows differently? :scratch: David D |
| vtsteam:
David, is that because they don't run together well or because the coefficient of expansion is different? Well the difference in expansion of aluminum and cast iron is worse, yet they are used together. But maybe you need more clearance to compensate for heating up. Other thoughts -- Is the compression good when you flip it over? That vertical line it the pipe/cylinder -- is that a seam? A leak somewhere in compression is a real killer for hot air engines. Should be strong compression when rotated by hand. |
| Stilldrillin:
VT. I don't know how they "officially" run together. But, I have never seen a copper cylinder before. :scratch: The original bore was, "as extruded water pipe", with fine polish/ scuff marks from the piston, in places. The piston had a ground finish, with matching polish/ scuff marks. There is now more clearance between the components. I think the two materials are galling together, but there is not enough power to cause obvious damage. Trying the piston fit in the bore, immediately after stoppage, feels a really nice fit. But the engine's power forces are much less than a "nice sliding fit". The engine feels all it should be. Just doesn't want to run. I think it's the copper cylinder at fault. Will see if I can sleeve it with a steel liner. David D |
| sbwhart:
I think you are getting to grips with this one Dave :whip: the copper doesn't seem right as you said its probably expanding with heat and making things to go a little to tight. Stew |
| vtsteam:
I'm sure you'll work it out David. :thumbup: |
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