I have lightened many flywheels for race cars and never had a problem. It never occurred to me to try it on a rotary. The rotary has no reversals like a 4 cylinder piston engines, but has two powerful accelerations per revolution. There is no aircraft application for the stock flywheel lightened or otherwise. First of course is the unbelievable weight of the stock unit.

The counterweight is cast into it and it would take a month of machine time to reduce it nearly any amount. In racing there is no need at all for a flywheel. Just a low ground clearance Chevy button flywheel and a 5 1/2" Tilton 2 disc clutch. Under 5 pounds for everything. Many flyers have notice that awful rattling sound when the idle is reduced too far.

Those are the sounds of the gear box loaded in acceleration then when the crank slows as the next rotor goes into compression, the crank slows and the gear lash stacks up in opposition. Makes you jump the first (every) time you hear it. The race car does it to the big strong road racing transmission. There are many gears involved, and it is loud. The driver always thought it was some terminal sound, and the weekend was over. Just bump the idle speed up a bit and it is gone. You might get a taste on shutdown.

The amount of energy you can store in a flywheel is a function of its mass among other things. Once at Indianapolis Racway park a bunch of RX-3s were coming onto the long straight when a big chunk of car went straight up in the air. The cowl, windshield, part of the rugs and floor board, and the transmission. All on the track. Half of the flywheel was stuck into the track. Trans oil everywhere. So there was a long cleanup. The car was toast. Lots of damage. Too many revs before a shift.

Then there were few aftermarket flywheels available, and some people actually lightened the stock wheel. The drivers feet are behind the bellhousing so rotaries need not run a scatter-shield. I don't have one on the new car. But the flywheel and clutch are so small in diameter and lack the mass to store much energy. Plus, the rev limiter stops it at 9,600 RPM.

A rotary with no load can attain astounding RPM in the flick of a throttle cable. Never stand in the plane of the flywheel. A automatic counterweight and a flex plate are just fine.

A single rotor is a different deal. The more mass the better.

Lynn E. Hanover



Thanks Lynn.
Interesting stories as always.
Do you know any sources for 7.25'' (or 5.5") ring gears and lightweight starters that will mesh?

Cheers
Cary