540 RPM -MAX SHP?

[401FordManNZ]

Righto, somewhere I have heard that 540rpm pto is only good for implements requiring up to 70 odd shaft horsepower? Is the additional torque above this liable to shear the shaft off, as opposed to 1000rpm? Just had me wondering as over here we have a particular brand of hay/silage mower(drum,with wilter/scatter rake) that,in the bigger models will hog a good 100pto Hp

 

[SPYDERLK]

Good point. A 70 hp limit would allow for an ample safety factor.
larry

 

[RickB]

What really causes problems is operating near the upper limit of the torque level that can reliably be transmitted, then adding random shock loads. I have seen 540 output shafts twisted off of just about every color tractor made by whatever brand 15' batwing R/C you choose. I always recommend folks buying 1000 RPM drivelines on batwings regardless of tractor size if they have the capability of running them.

 

[SPYDERLK]

What really causes problems is operating near the upper limit of the torque level that can reliably be transmitted, then adding random shock loads. I have seen 540 output shafts twisted off of just about every color tractor made by whatever brand 15' batwing R/C you choose. I always recommend folks buying 1000 RPM drivelines on batwings regardless of tractor size if they have the capability of running them.

Yeah ... 1000ft-lbs torque would be quite comfortable on a 1.1" hi strength shaft. [That is the root dia of the 1-3/8 6 spline.] 1000 ft-lb equates to a hair over 100hp @ 540. The twist off strength of that shaft is well above 2000ft-lb but 100+hp with even a good non nuisance adjusted slip clutch would put shock loads near the danger zone. Too close considering tendency for neglect.
larry