Petter PH2 "timing"

PeterK 20 years ago

Whilst I appreciate a PH2 is not a "classic" stationary engine I think this is the group that can give me the answer.

Assuming a PH2 hasn't a two piece camshaft and its assembled wrongly - can anyone explain why the engine over 2 turns has both pistons on their compression stoke (180 deg apart) on one turn and obviously then a turn with no compression? I think that's explained it but trying another way - turning the crankshaft through 720 degs the results in:

0 compression started
90compression "lost"
180 compression started
270 compression "lost"
720 - back to 0

I hope this is not egg on face time but it just offends me.

Thanks

PeterK

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Peter A Forbes 20 years ago

Unlike most British motorcycle engines, most industrials are/were 180 degree cranks, so you get 'bang bang nothing nothing' when running rather than 'bang nothing bang nothing'.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Dave Carter 20 years ago

It is all to do with vibration and torque reaction of the engine. By making the cylinders fire closer together than 360 degrees makes for less vibration. IIRC the drawn shape for the vibration of an engine with cylinders firing as you describe over 720 degrees is a smoothed out "heart" shape rotating about its centroid rather than an (almost) elipse. Some Japanese motor cycle engines in the late sixties and seventies built their twins like this and probably still do today. Lister LR2 the same I think.

Regards, Dave Carter.

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