Rotary Cutter PTO Clutch Problem

[gbw]

Hi fellow tractor folk:

I have a JD 4320 CUT with an old, very heavy duty (I think) 5' rotary cutter attached. It gets used a good bit.

The cutter is driven through a 1.5" input shaft, connected to the PTO via the normal shaft, U-joints on both ends.

The 1.5" bore of the U-Joint on the implement end is held in place by a 1/2" shear bolt. Grade 5 is required or they break all the time, and the G5s don't last all that long but I want to protect the tractor PTO system.

I would like to add a slip clutch ahead of the input shaft.

I cannot find a clutch with a 1.5" smooth bore for the cutter input shaft. 1- 3/8" is the closest. Are these borable to 1.5"? Who would do this type of mod?

Or, what is the objection to putting the clutch on the tractor end of the shaft? i.e., attaching it directly to the PTO, then to the shaft?

I know this is not normally done, but I don't know exactly why.

Thanks for your help!

 

[huskerhayman]

I have a 6' JD 606 shredder and have the same problem with the shear bolts. I put a grd 8 in and a slip clutch on the tractor end. People will tell you it is a hazard having it that close to you but at least on my tractors it is far enough down that if it did come apart you would be safe in the seat. I have ran it that way for a couple of years and mow about 20 acres twice a year without issue. Sure beats getting off every time it hits something to replace them darn bolts.

 

[greg_g]

Yeah, that must be a moldy oldy. I'm not sure where to even start looking for 1.5" stuff. It's apparently predates the introduction of SAE standards (1-3/8") to the industry. Pursuing this particular course might actually end up more expensive than simply buying another 5' mower.

//greg//

 

[gbw]

The cutter works well and is in good condition, so I'm not sure whre the expense would come from. I see 2 choices, neither especially costly:

Get a 1-3/8" clutch and have it bored 1/8" over to fit the mower shaft.

Put the clutch on the PTO output shaft ahead of the driveshaft. There is a sort of shielding around that area. Is there some mechanical reason that th clutch must be on the implement end of the shaft?

 

[greg_g]

Put the clutch on the PTO output shaft ahead of the driveshaft.

There I disagree. It's simply an unsafe practice, shield or no shield. Some folks use this method when they have more than one implement that works best with a slip clutch. What they don't understand (or ignore) is that slip clutch adjustment is based upon horsepower requirements. And that can vary between/among implements - on the very same tractor. Safest is one slip clutch per implement.

Then besides the fact that the one-size-fits-all concept doesn't work, there's the safety factor. And trust me, I'm no fan of OSHA. Granted it's less probable, but - if and when a slip clutch comes apart - you want it to happen as far away from the tractor seat as possible

Boring the splines off your 1-3/8" hub reduces the strength of the remaining metal by probably half. Not that I've ever seen it done - but I'll speculate that the remaining cast steel will give up before the shear bolt. Also unsafe.

//greg//