Pros and cons of using an over run clutch/coupler on pto??

[ericm979]

Even bringing the engine rpm down to idle some implements have considerable inertia stored to be dissipated some how.

Engine braking is pretty strong, especially with diesels. With both the engine and the PTO brake the energy from the implement gets turned into heat. The engine has a cooling system which is designed to handle the heat from full throttle operation. That's a lot more than the intertia from an implement. The PTO brake is cooled by whatever transmission oil flows past it, probably not much.

 

[5030]

Engine braking is pretty strong, especially with diesels. With both the engine and the PTO brake the energy from the implement gets turned into heat. The engine has a cooling system which is designed to handle the heat from full throttle operation. That's a lot more than the intertia from an implement. The PTO brake is cooled by whatever transmission oil flows past it, probably not much.

Not correct. engine braking with a diesel is much less than a gasoline motor of the same displacement, unless that engine is equipped with a compression (Jacobs) brake.

..and pto brakes usually are wet multi plate units, immersed in gearbox oil. Plenty of oil at all times.

 

[super55]

It's kind of amazing the heavier duty and more expensive equipment comes with built in over running clutches.
So must be they are good in those cases. PTO brakes can be extremely expensive to repair or replace, I've heard of some that were well north of $9000. Plus they put a ton of grit and garbage into your hydraulic system.
Even bringing the engine rpm down to idle some implements have considerable inertia stored to be dissipated some how.

I was about to say the same thing. My hay mower and baler both have overrun built in. If they didn't my tractor PTO driveline would blow apart the first time I tried to stop them. With that point in mind, I still hook up and additional overrun just incase the built in has a failure. With my old bush hog that is only shear bolt I welded it directly to the PTO shaft so that it could not be used without one.

The blades take some time to spin down but the PTO brake isn't adjustable so it really shocks the driveline even at an idle at times even shearing a 7/16 diameter grade 1 shear bolt. It's easy to verify when the blades stop spinning because there is no plastic safety casing on the PTO shaft (which I am not a fan of either). To me it creates a false sense of safety. I can quickly glance at it and if I see it spinning I know to stay away the same way that if I hear an overrun clicking I know something is still moving.

One thing to look out for when adding an overrun extender is to make sure the PTO shaft doesn't bottom out when in the fully raise position so if you have a PTO shaft that is at max compression when lifted without one you will need to shorten the shaft.

 

[5030]

The PTO brake is there for a reason. It's a safety feature in case you need to stop the implement ASAP. I've not needed it yet but I've also not needed my chainsaw chaps in 35 years and I still wear them.

You can save wear on the PTO brake in normal use by throttling down and then once the engine is at idle, turn off the PTO. Even with my chipper which has a 200 lb flywheel that's geared up to turn 2x pto speed, it takes only a couple seconds for the engine to come down to idle.

Not exactly correct either...It's there to prevent freewheeling of the pto stub so you can nook up a pto driven implement. Classic description of a worn out pto brake is the stub shaft turns constantly.

You can idle down to save stress wear on the brake but a better and easier to deal with idea is an ORC.

 

[npalen]

Not exactly correct either...It's there to prevent freewheeling of the pto stub so you can nook up a pto driven implement. Classic description of a worn out pto brake is the stub shaft turns constantly.

You can idle down to save stress wear on the brake but a better and easier to deal with idea is an ORC.

Both of my tractors have internal over running clutches in the PTO driveline. It would be interesting to know what tractors do and do not have internal clutches.

Safe to say that any electric PTO does not?

 

[npalen]

A check to determine whether a tractor has an internal over running clutch would be to try turning the (non electric) PTO counterclockwise with the engine off but with the PTO engaged. A clicking/ratcheting sound should verify an internal over running PTO clutch assuming the PTO shaft can be turned manually.

 

[Smokeydog]

Needed a few extra inches of pto shaft on 6’ rototiller because of Pat’s quick hitch. 70hp overriding clutch was the easy answer. Also makes connecting pto shaft easier to reach. Also like using the rotary cutter with the overriding clutch. Win win.

 

[5030]

Both of my tractors have internal over running clutches in the PTO driveline. It would be interesting to know what tractors do and do not have internal clutches.

Safe to say that any electric PTO does not?

Cannot speak for a Mahindra as I know nothing about them but I can for Kubota and Kubota's have notoriously weak PTO clutch (brake) packs as in not enough discs on the brake section of the pack, the main reason why I use an over running clutch with any implement that don't have one in it's driveline already.

 

[workinonit]

I think you mean lengthen not shorten. The ORC will increase the pto end stickout about 5".

Nope. I said exactly what I meant to. As you increase the length of the PTO drive you decrease the length of the PTO implement shaft. That shaft is obviously adjustable and can be altered or cut/trimmed to compensate for this.

 

[5030]

I understand now. I was looking at it from the opposite end.