DIYbanter - View Single Post - Bursting speed of flywheels (and overspun ball bearings)

In article ,
says...
In article ,
Ned Simmons wrote:

I have no interest in exploding a bearing g. I just wanted to get it
spinning fast enough to run the tests described.

How fast did you get it to go?

About 6500 RPM. I didn't have the needle valve opened all the way, but I
don't think it would have gone much faster with the small tube.

I bet your Son can test your hearing limit.

He tests many limits.

I agree that higher speeds than 20 KRPM should be attainable, but the
deterioration will limit the speed, and that may be why he couldn't go
faster. As the bearing gets beat up it'll take more power to keep it
spinning at a given rate.

Will deterioration really be that much of a limit on an unloaded
bearing, especially if it isn't in contact with the inner race all that
much? And, the airjet has plenty of power.

There's lots of power in the compressed air - transferring it to the
bearing is another matter. Even air motors are notoriously inefficient.

Based on the numbers, and 25 years of machine design experience, I'm
very confident that the bearings did not explode from centrifugal force
alone. The reports of the noise going ultrasonic do give me pause, but
not enough to make me believe that the bearings were spinning at 1300
FPM. I guess someone needs to volunteer to explode a few properly
instrumented bearings. Not me, I'm off to Boston for college visits with
the boy tomorrow.

Ned Simmons