E.T.W. Phoenix

[John PurdyParticipant @johnpurdy78347]

Twenty five or so years ago I acquired a part finished Phoeinix IC engine by E T Westbury and have been working on it off and on since. It’s almost finished and I have a question for the IC grus. In his description, he states that the driving coupling can be fitted to either end of the crankshaft provided that the engine is arranged for the appropriate direction of rotation, which should always be with the crank pin moving upwards on the transfer port side. My question is why is this?

The only reason I can think of is for an unimpeded flow of crankcase charge through the transfer port up into the cylinder, as if rotation is the other way the con rod would be moving down through the transfer port as the piston descends pushing the crankcase charge up through the transfer port into the cylinder. Any ideas?

[JasonBModerator @jasonb]

I thought it was so that the coupling is not unscrewed by the crankshaft rotation so engine rotation needs to be arranged so crankshaft is always being screwed into the coupling when under load.

[Perko7Participant @perko7]

It could be to do with the way the centreline of the cylinder is offset from the crankshaft (the Desaxe Principle) which I understand helps with improved efficiency and operation of 2-stroke engines. To run the engine in the opposite direction without a corresponding alteration to the crankshaft location would negate these benefits.

[bernard towersParticipant @bernardtowers37738]

Exactly, well done Perko you beat me to it!

[John PurdyParticipant @johnpurdy78347]

I just realized I think it is as, Perko says, because the cylinder is offset away from the transfer port. But I think the reason might be more to do with the angularity of the con rod to crank pin being less on the downward power stroke with the crank pin going down opposite the transfer port as opposed to going down on the transfer port side. Thus less stress on the con rod and crank pin.

John

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