Well, technically, you are correct. The larger wheel will have greater frictional losses (bearings and air resistance). So a small motor may have trouble keeping up with those losses. (if there were no friction, though, the final speed would be exactly the same, no matter what the difference in wheel mass/size)
Originally Posted by vpt
And, I wouldn't expect the effect going from a 9" to a 14" wheel to be noticeable, or even measurable. Remember, these motors have way more power than needed to get over the frictional losses. If they didn't, you wouldn't be able to do much cutting/grinding with them.
Originally Posted by andywander
That is true but it would also depend on the make of the grinder and its condition. I have a Bosch grinder that can't reach full speed with nothing on the arbor. My Milwaukee spins slower than my porter cable.
I think it would be interesting to test rpm's of a single grinder with different sized wheels on it. Yes they should have the power to overcome but the results may be surprising.
Hoping that it does not have enough balls to reach destruction speed is like playing Russian Roulette
The fact that the thing was out of balance and bouncing around could have been his saving grace as this eats horsepower too and therefor max RPM's
Mr. Hosie is extremely fortunate, this is how people end up dead or missing things like their face and stuff...