MTFCA Forum

Is there any reason to not use brass spools to balance a flywheel?

Bob, Too damn simple, please drill holes like the rest of us idiots!

LMAO!

All the Best,

Hank

Hank, don’t your little plates look pretty, Thanks again. It is very simple and is done while on the balancer. Very easy to cut different weights beforehand and takes only a minute or two to change them out. Of course balancing done before height rechecked and the screws peened.

Bob

pre-weighing the magnets and marking N/S on them, and then placing them in an advantageous location, can overcome a significant amount of unbalance in the bare flywheel.

Two-plane spin-balance is better than what I do, but I'm a bit out in the boonies and with careful manipulation of magnets and a bit of drilling on the flywheel, can static balance down to where the weight of a 6-32 nut can be detected out on the rim...a darn bit better than the factory and gives a considerably smoother engine than stock.

FWIW

Bob, I presume you are substituting brass spools for alloy ones, thus adding weight to the light side. How many substitutions have you had to make at any given time? Some of the flywheels I have static balanced have had considerable drilling done to bring them up to snuff. Do you still drill to fine tune the balance once you get close?

Allan from down under.

OK, here’s the dill pickle. When the triple gears were added, everything went South. The gears are with in 8 grams of each other, but made a big difference in the balance no matter how I placed them. The balance improved by changing their location, but was still not acceptable. I’m thinking the gears and flywheel must be balanced as an assembly. And if you really wanted to do it right, Mike Bender’s set up which includes the crank and tail shaft is probably the best.
Back to the story, by cutting several different weight spools, the height being the only constant, it’s very simple to achieve balance and can be done on the balancer with no drilling. Next time I’ll balance first and then set the height and torque. Ended up using 2 brass spools.

Bob, just for my general knowledge how are you determining acceptable and unacceptable balance?

When the flywheel stops at any position after a gentle turn and doesn’t move on it’s own.

Bob, 8 gm difference in the triple gears is not inconsequential. That difference is magnified further from the centre of the assembly. With one piece triple gears as you show it is easier to get them exactly the same than it is with the three piece riveted gears. In an ideal world, each gear could be balanced within itself AND match weighted withe the other two.

I don't know about progressively balancing the assembly each time you add a component. Because there are components which revolve within the assembly, there are going to be changes in balance. The flywheel, crankshaft, transmission shaft, fan pullet etc which make up a fixed assembly, can be balanced together as a unit, but about the best you can do with the rest is to get each component as close to balanced as possible before they are assembled. This is how it was explained to me by the operators of a precision machine shop owner who balances some really high end racing engines and aircraft components.

Allan from down under.