4010 is back up and running, scared to use it

chliansh · Sep 20, 2005

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I just got it back and after $200 worth of parts and about 4 hours of professional JD labor $$$ I am ready to go. The bad part is I am scared to rototill anymore. Even the techs who worked on it were surprised at how light duty the driveline was to the hydro pump, just a simple roll pin holding back all my mighty 18.5 hp? No splines????
I am no engineer but hope that at the 2-3000 rpms the true force applied to the pin\shaft is much is less than say the twisting force on the rear PTO spinning at 540 RPM?

Disappointed first time JD owner......

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beenthere · Sep 20, 2005

Is there no shear pin or clutch in the PTO drive line of the tiller? Maybe the roll pin is the next weak link to protect something more expensive that could break.
I'd look to get something to protect the roll pin.

chliansh · Sep 20, 2005

What would I get to protect the roll pin?

timb · Sep 20, 2005

Good luck with the shear pin but your intuition is correct - the 'twisting force' is less at higher rpm. Twisting force is torque - and torque, hp, and rpm are all directly related to each other. If you transmit the same hp at 3 times the rpm - you'll encounter just 1/3 the torque. That's why some PTO's on garden tractors turn at 2000 rpm instead of 540 - or why some bigger tractors use 1000 rpm instead of 540. Let's you get the hp through the connection with less actual torque involved.

In your case - 18.5hp @ 3000 rpm = 32.4 lb-ft of torque - but if that same 18.5hp were at the 540rpm PTO - it would equal 179.9 lb-ft of torque.

beenthere · Sep 21, 2005

I would be sure that there is a shear pin or clutch in the PTO shaft going from your tractor PTO output to the PTO drive on your tiller. In that tiller drive line, should be a working clutch or shear pin that would protect the tractor innards.

Maybe I am missing the point, but the tiller should have the failing or slipping part, not the roll pin inside your tractor.

Within your tractor, that roll pin is the weak link that is protecting more serious damage to the gears and castings that would be much more expensive to replace. Otherwise it would be a splined shaft, if it were not meant to be a 'safety' fuse, so to speak.

I would be looking at the tiller that you are using as the contributing factor, or gamble that it won't happen again to the roll pin.

What tiller are you using? and what 'protection' does it now have for your tractor?

Just hoping to help some /forums/images/graemlins/wink.gif

chliansh · Sep 21, 2005

( That's why some PTO's on garden tractors turn at 2000 rpm instead of 540 - or why some bigger tractors use 1000 rpm instead of 540. Let's you get the hp through the connection with less actual torque involved. )

I see, just like higher voltage = less current in the electrical world.

The unit is a JD 647 Tiller (48-inch, commercial-duty)and I cant find anything about a slip clutch or sheer pin in the manual???? I also can not find anything about a shear pin in the tractor manual.

This still seems odd to me for example what if I am pulling a heavy load (box blade ect) and get all 4 of the tires hooked up in the dirt 100% so they dont slip and all of the sudden catch a big rock or something that I cant move? I either get a wheel to slip or bust the roll pin again?

Worst case scenario:
All 4 tires hooked up good
Wheels turned all the way to the side
Tiller working hard

Combine all 3 things and there goes the roll pin?
I would think that even the roll pin would hold strong at 32.4 lb-ft of torque and the engine would die.