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Pto over run clutch question

W

wilson ind

Well-known Member
Is it possible to put the sprag clutch in backward? Thinking might be a good way to make a starter for older tractors. Unit would be easily moved to different tractors . Your experiences please. I have experience with sprages , just not with over running pto units.
 
Driving a PTO based starter requires a substantial gear reduction. Considering that a 540 PTO spins at about a 3.33 to one ratio slower than engine speed, the driver needs to be geared maybe 3 times the ratio of a flywheel ring gear to starter pinion which is in the relm of 10 to one reduction. Thus a 30:1 ratio is about right if a starter motor was used on the device. A shaft from tractor to tractor would require a reverser gear set to turn the engine correctly CW looking at the radiator. Turning a standard overrunning clutch end for end, or flipping the sprag internally would allow the motion to be controlled, but the reverser would be the difficult issue. There are torque reaction issues that need to be addressed as well. The reverser housing will need to be held from turning by being anchored to the ground, or the driving or receiving tractor frame. Jim
 
There was a very talented old shade tree mechanic that used to bring a lot of stuff to my hometown Pioneer days. He once brought an early Farmall that had the exposed shaft between the clutch and transmission, and he had mounted an automotive flex-plate and starter. it seemed to work real well, like everything he designed and built, unfortunately he is no longer with us.
 
Built one like that years ago. Worked well, however I have several tractors I would like to start without hand cranking. Please refer to my reply below on what I am thinking for multiple tractors.
 
With all due respect possibly you are overthinking what I have in mind. Plan on a hydraulic motor , of which I have several, with a six spline pto adapted to hydraulic motor. Several tractors I have would provide a reliable source of hydraulic power with the greater expense being the overrunning pto. Have already extension hydraulic hoses which would work well. Your ideas welcome.
 
I once saw a 10 20 McCormick with a flexplate attached to the belt pulley and a bracket for a starter. I think the reduction is less for the pulley than the PTO shaft.
 
Take a torque wrench to the PTO spline on the tractor (maybe fab up a socket to fit). Turn the PTO in the correct direction noting the Ft/Lbs needed to get it past a compression stroke (sample 5 or 6 strokes) look at the torque rating of the Hydraulic motor you intend to use. I imagine 200 to 250 Ft/Lbs. Gearing it appropriately will work. you still need to worry about torque reaction as the hydraulic motor will spin the opposite direction. Jim
 
(quoted from post at 12:11:59 12/23/17) Is it possible to put the sprag clutch in backward? Thinking might be a good way to make a starter for older tractors. Unit would be easily moved to different tractors . Your experiences please. I have experience with sprages , just not with over running pto units.
Click to expand...
do not know if that is how one gets reversed, but I have one that is backwards that I keep intending to take apart and see if that is all it takes to put it right again.
 
I guess I'm going to have to go out and play with one. It seems to me if you just turn it around it will operate the same way. I think you'd have to cut the male spline off the end and weld it to the other end of the housing to get the operation reversed. Looking at an implement from the tractor only counterclockwise drives the output. Looking at the tractor from the implement counterclockwise of the output still drives the input so reversing the whole unit does nothing except change where the male and female ends are. I think you have to reverse the unit but still have the insides connected to the rear.

I bet yours was welded together backwards.

Am I missing something?
 
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