The news story above was found in the June 3, 1921, Lowell Sun newspaper (MA) while doing some racing research in New England. I decided to post this for individuals who have speedsters or racing cars with modified engines and run them today at high RPMs and are unaware of the fact that Ford cast iron flywheels as well as those made by other automakers at the time can explode under these type of conditions.
In the period, racers would turn down a Ford flywheel in a lathe to about 10" in diameter to prevent this. It also allows the engine to rev up quicker and improves acceleration. To run safely at engine speeds above 3500 to 4,000 RPM, the "speed merchants," Fronty, Green Engineering, Roof, and others sold small diameter racing flywheels machined from chrome-nickel steel.
Flywheel offered by Green Engineering.
It was common knowledge among racers in the past that cast iron flywheels can and do explode at higher RPMs than they were designed to operate at. A standard Model T flywheel IS SAFE AT NORMAL ROAD SPEEDS but can 'blow" while traveling at high rates of speed of 65 to 70 plus mph or while racing IF IT has a flaw.
If it runs out, is warped, cracked, or has issues with the triple pins or cracks around the holes the pins sit in, there is a good chance that it will explode at some point. If it happens at high engine RPM, the resulting shrapnel can literally cut a T in half and injure or kill the driver and passengers.
At higher road speeds, even magneto magnets that crack and come loose from the flywheel usually break and exit through the top of the hogshead. The broken pieces then usually travel thru the upper floorboard and have been known to tear holes in a sheet metal cowl and exit thru them. Scroll down to view the damage caused by broken magnets at 55 mph @ http://www.mtfca.com/discus/messages/70 ... 1505838216