The Stovebolt Site Forums The Shop Area Engine Shop wow! hi-tech crank balancing

i went up to the mach shop today to sit in on balancing my crank. one rod was off too much on weight so we did a little grinding. the down-side to these old rods is that they don't have a 'pad' for grinding. punched in the figures in this $35K machine, spun it, and voila. 1/2" bit @ .43 depth off of the front counter- weight. that got it to a street balance of .5. so for the heck of it, we spun it again for a nascar balance, and power sanded off, what would have been next to nothing with a 1/2" bit, of the rear counter-weight. .2 nascar

Well, now you're all set to run her up to 9,500 rpm all day long, right?
DG

9500 rpm? sorta - but there are even more advanced balancing levels, tiered by 1k increments up to 8k. but in consideration of practcality, we didn't go that far. that's, paint the interior of the engine level, blueprint building. there's even an add weight option where-by standardized, cylindrical weights are added to the crank
and prior to this, i thought ya just layed a rod on a good scale and weighed it. nope. if you're not aware; they're weighed on a scale whereby the crank end is resting on the scale, and the pin end is horzontally supported by a 'mini' trapeze. then the weight of the rod is put into the data log, where-by the individual crank end and pin end weights are calculated, and introduced into the balancing 'equation'
pretty far out dude

rednate-

I posted this about a week ago, i think...

Really good stuff here, after reading this I might consider tackling some rod balancing when my engine get rebuilt.

I learned alot!

http://www.eatonbalancing.com/blog/category/balancing/

good article - thanks
def fills in the blanks

Yup, I think those slugs they put in em are called mallory....

Mallory metal is used when a LOT of weight needs to be added to a counterweight. It's actually heavier than lead. I static-balance my round track engine rods to 1/10 gram or less by using a triple-beam scale and one of those ball bearing rod hangers. Since a dollar bill weighs one gram, that's a pretty close weight-match. Ditto for weight matching piston/pin/ring assemblies. There's even a fudge factor on the dynamic (spin) balance procedure for figuring how much oil weight is retained by the spinning piston/rod assembly.
Jerry

yeah, i have a t-beam here at the house, but the shop has a digital. and yep, the computer accounts for the weight of the oil