rbargeron
Elite Member
Mathey, I added a 2-speed pto to my Kubota for the same reasons you describe at the top of this thread. Here's the story - pics start on 2nd page
http://www.tractorbynet.com/forums/showthread.php?t=9488
Personally, as a part-time gearbox engineer, I'm not be concerned about running a rotary mower at 636 rpm - 17% faster than the nominal 540 rpm it is "designed" for. What the mower manufacturer tries to do is get the tip speed up to a decent minimum velocity for cutting grass. If it spins a little faster it isn't a big deal. Inertia loads, etc., go up with the square of velocity so at 17% over, the loading is maybe 36% higher - well within the design margins for ag machinery. If you were running 50% over, that might be another story - the forces are 225% (more than doubled) - that would be pushing things and would increase the wear. Of course, if you ran at twice speed, the forces are up by factor of 4 !! That can get dangerous and may be why Kubota and other tractor manufacturers have been getting away from 2-speed pto's on tractors sold in the U.S. As always, prompt cheerful refund if info is bogus. Dick B
http://www.tractorbynet.com/forums/showthread.php?t=9488
Personally, as a part-time gearbox engineer, I'm not be concerned about running a rotary mower at 636 rpm - 17% faster than the nominal 540 rpm it is "designed" for. What the mower manufacturer tries to do is get the tip speed up to a decent minimum velocity for cutting grass. If it spins a little faster it isn't a big deal. Inertia loads, etc., go up with the square of velocity so at 17% over, the loading is maybe 36% higher - well within the design margins for ag machinery. If you were running 50% over, that might be another story - the forces are 225% (more than doubled) - that would be pushing things and would increase the wear. Of course, if you ran at twice speed, the forces are up by factor of 4 !! That can get dangerous and may be why Kubota and other tractor manufacturers have been getting away from 2-speed pto's on tractors sold in the U.S. As always, prompt cheerful refund if info is bogus. Dick B
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