MTFCA Forum

My flywheel has .004" of runout in one small portion of the rim, about 4" long, which I discovered when I put it on a mandrel in the lathe. I placed a dial indicator on the FACE of the rim....on the edge it's fine. How could that be you ask? Well, the machining looks good and upon very close inspection I realized the casting itself was off...warped, whatever...yet it was sent through the machining process anyway and installed in an engine! Personally, I don't think it's much of a problem as the flywheel balances quite well, but I'd like opinions from the group.

By the way, it has the letters "DS" embossed in the cast iron. Was this a Dodge Brothers product? The engine is a crank start 1918. Thanks!

Here’s my take on your question. Rotating unbalance is the uneven distribution of mass around an axis of rotation. A Model T transmission weighs approx. 75 lbs. (1200 oz.). The uneven distribution .004” x 1200 oz. = 4.8 oz.in. or 5.36 g/mm unbalance. 5.36 g/mm is better than a Balance Quality Grade of G 6.3 (Balance Quality of Rigid Rotors ISO 1940/1) for flywheels. Run it!

LOL...........I actually had to read that TWICE, but finally got it! Thank you.

If you mean .004” indicator runout, then that area is only .002” off center.

What you have is probably fine.

If you want something a little better to start with, get a ‘26-‘27 flywheel. They are machined all over and sometimes are a bit better in balance.