Belt Slippage

[KenSandyEggo]

I've been wondering if the prerotator belt could slip under high loads on the RAF or Sparrowhawk and how to determine this. If I make a paint mark on the small pulley and a mark on the belt, both at the same locations, should those marks always line up after running the engine if there is no slippage? I know that this is basic physics, but it's been a long time. I don't know if the reduction ratio changes that. :confused:

[Mike Hook]

Yes Ken they will not line up you have a ratio there with two different sizes of pulleys.

Example if you have a 2 in pulley the circumference = (3.14)Pi.x dia. so if the dia was 2 the cur would be 6.28 inches
if you have a belt of say 20 inch dia. cir is dia x (3.14) PI. =cir of 62.8 in you have a ratio of 10 to 1 so the belt would line up only every ten revolutions of the pulley. Now the pulley is measured at the point of pitch and the belt is measured on the inside so you see it is a hard thing to get to work accurate.

Mike

[KenSandyEggo]

Thanks, Mike. Guess I'll have to figure some other way to see if there's any slippage. When I stop prerotating after a 1/2 hour or so of testing, the belt is not hot at all. I'd think that if it were slipping, it would be hot or quickly shred, but I'd like to find out for sure.