Fwd: <VV> Piston weights

[Tony Underwood]

At 03:17 hours 12/12/2005, klingaman at tellurian.com wrote:

>while the piston and small end weight may be balalnced as
>opposing pairs, the imbalance of the big ends may give a
>rocking couple to the engine. I think?
>Ken



I wouldn't think so, as long as the big ends of each opposing pair 
were balanced as per normal procedure.   Since they're not both on 
the same journal and in fact are 180 degrees apart from one another, 
as long as they both weigh the same they should simply cancel one 
another out, and since they're not on the same plane as the other 
rods, they'd have no "wobble" interaction on the crank that wouldn't 
be countered by the same wobble from the other rod pairs as well as 
the gyro effect of the spinning crank and flywheel.    Evidently GM 
thought that there wasn't enough of a wobble problem from such a 
configuration to justify a counterweighted crankshaft for this 
application.    And the typical Vair engine runs pretty smoothly with 
no counterweights on the crank at all, and oft times in spite of 
having rods that were rather embarrassingly out of balance with one 
another straight from GM.     (hence a Vair engine article I read a 
while back that showed its connecting rods with lots of material 
carved off the big ends of several of them to get them to match up 
with their mates)

At least this is how I see it...   ;)    However, I'm not an 
automotive engineer.    Perhaps someone else has a better explanation 
that makes more sense...?


tony..