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Some time ago I read a story about Murdoch’s and Watt’s sun and planet gear arrangement (1781) to avoid paying a royalty to James Pickard who held the rights to the common crank – connecting rod mechanism. Since it involves gears and is #39 in the book of 507 mechanical movements which I’m working through, why wouldn’t I make it?What I find interesting is that the use of a conventional crankpin – crankshaft mechanism dates back to the 3rd century in the Hieropolis Sawmill so I’m puzzled as to how Pickard could get a patent for this?
An interesting problem is encountered. One cycle of the planet gear (con rod) equals two cycles of the sun gear (crankshaft) when gears of the same size are used. I have my eccentric fastened to the crankshaft. Therefore, when conventional oscillating rotary valve motion is used, the cylinder gets a shot of steam in port #1 just after TDC and again in port #1 just after BDC which is not good.I guess the straightforward fix is to put a 1:2 gear setup off the crankshaft to a jackshaft with the eccentric fixed to it. Then the valve will work OK.Has anyone seen Watts engine with the planet and sun gear arrangement in The Whitbread Engine at the Powerhouse Museum in Sydney, Australia? I would like to know how Mr. Watt dealt with this issue.Cheers,Phil