"Jeff" wrote in message
...
Edgar wrote:

I particularly enjoyed his efforts to convince us that he could prove by
trigonometry that a piston travelled further on the upstroke than the
downstroke (or maybe it was vice versa)


Edgar, sorry to burst your bubble, but this was one case where jaxie
was right! The piston travel from 90 degrees to 270 degrees is
different from 270 to 90 degrees. This is one of the "bar puzzles"
that is counter-intuitive, since we would normally think in terms of
upstroke versus downstroke, or 0-180 versus 180-0, which is quite
different from "top of cycle" versus "bottom of cycle." (I suppose it
depends on which bar you hang out in...)

At the risk of starting this thread again I do not think you are correct.
The geometry of 90-270 is identical to that of 270-90 and so is 0-180 and
180-0.