G'day

On APC's website they suggest -

Glow Props Max rpm = 190,000 / prop diameter in inches

Therefore a 10 x 6 prop has a max rpm rating of 19,000 rpm

Thin Electric and Folding Electric = 145,000 / diameter in inches

Therefore a 10 x 6 prop has a max rpm rating of 14,500 rpm

Slow fly props Max rpm = 65,000 / prop diameter in inches

Therefore a 10 x 6 prop has a max rating of 6,500 rpm.

If you are using 10 or 11 inch slow fly props, you are well outside the max rating suggested by these calcs with a 1250 kv motor which is going to try to turn the prop at about 12,500 rpm.

Cheers

Mike in Oz