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

Oh My! Jaxie hasn't posted here in over 2 years and he's still
catching people with this one!

The geometry is clearly not the same for the top and bottom parts of
the cycle. Draw it out - its just a matter of trig. The piston moves
slightly more than half its travel going from 0 (TDC) to 90 degrees.

As an interesting degenerate case, consider when the connecting rod is
the same length as the crank offset (I forget what that is really
called). In that case, the piston will reach the center of the crank
at 90 degrees and stay stationary for the entire bottom half of the cycle.

That is a situation impossible in practice.
If you just draw it out with lines on paper you will find that the piston
does not move at all once it is at the centre since everything would just
revolve around it.
I am beginning to think that you invented Jaxx just to have a bit of fun
with us...