Engine balancing

[racemo]

I'm rebuilding my 1925 and will be using Aluminum pistons and a Scat crankshaft. I'm familiar with crank balancing and can handle that OK but would really like to balance the flywheel assembly (with magnets) because of it's greater mass. Does anyone have experiences in getting this done? I could turn up a arbor and set it on knife edge rolls but that's pretty envolved. I would appreciate other experiences if there are any.

Thanks...

 

[Erik Barrett]

The scat cranks are balanced right out of the box, you won't need to touch it. On the flywheel, just use two trans main shafts back to back bolted to the flywheel for a mandrel and balance on knife edges. You can get it very close that way. Make sure the blades are level in both directions. I use a machinist's level to do it. I also made mandrels to balance the trans drums, many are badly out of balance. Same for the triple gears.
Erik

 

[John Otis]

I have never seen a T transmission drum that was anywhere near balanced without doing a lot of work to it.

 

[rond]

Triple gears can be a mile apart on balancing as well, even in a set that came from an original transmission

 

[J and M Machine]

Racemo; I would take the flywheel after cleaning and reassembly of the magnets to a reputable machine shop and have them balance it for you.
As you can see in the pictures I spin the flywheel on a mandrel and then the machine would tell me where to make the corrections.
http://www.jandm-machine.com/balancing.html

 

[John Otis]

Yes excellent!. And having the digital runout indicator sure makes it easy.