Re: Conrod force/acceleration

[James Marriott <marriott@micron.net>]

Graydon D. Stuckey wrote:
> 
> Hi guys,
> 
>         I'm still not able to receive email, but I can send email out.
> SO, I've been monitoring the Q-list by reading the archives.

Sorry to have to pinch Graydon when he can't easily respond . . .

>         I thought I'd try to clear up Glen's misunderstanding of the
> piston/conrod acceleration/force.
snip

> Glen, your assumptions are correct, as you write them.
> _Acceleration_ of the piston is zero at TDC as is velocity, relative to
> the engine block.

Glen was indeed correct in believing his (what-he-thought-was-wrong)
intuition:

Assume TDC = 0 deg
Assume BDC = 180 deg

factor             Min (deg)       Max (deg)
Position           TDC             BDC
Velocity           TDC, BDC        ~90, ~270
Accel              ~90, ~270       TDC, (nearly max again at BDC)

The reason for the "approx" 90 and 270 is because of the relationship
between rod length, piston stroke, and piston-travel centerline (ie,
does the centerline of piston travel pass through the centerline of the
crank rotation).

If anyone is interested in the "maths" or some graphs (I can scan from
reference work or send self-generated spreadsheets), e-mail in private.

hth,
James