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

[JWR]

A diesel has no butterfly on the air inlet, hence no restriction to create a vacuum.

Not exactly... agree, the lack of the butterfly valve on the intake side prevents higher vacuum (that would be there in the intake port if the intake path was more closed by the butterfly) but the intake stroke still creates a lot of vacuum and pulls in the air on a diesel.

 

[Smokeydog]

The difference in vacuum is exactly why gas engines have better engine braking than diesels.

Closing the throttle plate essentially makes a gas engine a vacuum pump. Increasing the energy to turn the engine giving engine braking against a load. Diesel engines have no throttle plate.

Diesels can have the optional “Jake Brake” or like my truck an exhaust brake to increase engine braking. The exhaust brake is essentially a potato in the tailpipe valve. Makes a compressor load on the engine for braking.

PTO
Enjoying the benefits of an add on over riding clutch over the internal braking clutch on the Kubota M59.

 

[npalen]

Deleted--Already discussed

 

[JWR]

The difference in vacuum is exactly why gas engines have better engine braking than diesels.

Closing the throttle plate essentially makes a gas engine a vacuum pump. Increasing the energy to turn the engine giving engine braking against a load. Diesel engines have no throttle plate.

Diesels can have the optional “Jake Brake” or like my truck an exhaust brake to increase engine braking. The exhaust brake is essentially a potato in the tailpipe valve. Makes a compressor load on the engine for braking.

PTO
Enjoying the benefits of an add on over riding clutch over the internal braking clutch on the Kubota M59.

Jake brakes makes a very large air compressor out of the engine. Some diesel Jake brake systems are augmented by a butterfly in the exhaust which increases back pressure for greater braking. One thing NOT clear to me is whether fuel is still being injected while Jake braking is used. It would not ignite (because of the reduced compression) but would be wasteful of fuel and increase crud in the exhaust I would think.

 

[ParkWhite]

My old Ford 641 does not have live power. Without an overrunning clutch you will find yourself pushed through a fence when using a rotary cutter, or even worse, over a cliff.

 

[Smokeydog]

Jake brakes makes a very large air compressor out of the engine. Some diesel Jake brake systems are augmented by a butterfly in the exhaust which increases back pressure for greater braking. One thing NOT clear to me is whether fuel is still being injected while Jake braking is used. It would not ignite (because of the reduced compression) but would be wasteful of fuel and increase crud in the exhaust I would think.

I maybe wrong and decades out of date. Jake brakes simply change the cylinder exhaust valve timing to stay close on the exhaust cycle longer and build pressure to engine brake then release pressure suddenly causing the popping noise. Fueling is at idle level same for exhaust brake. Both turn off if any throttle is given.

I’m sure there are different kinds. For the exhaust brakes there are spring valve release and orifice plate flavors. I had to change exhaust valve springs from 45 to 60# for a spring release BD exhaust brake. Works good at low rpm. Big difference towing heavy loads.

I too used overriding clutches on non- live pto early tractors. Thought they were relics of the past till I had to buy one again for 2014 model.

 

[CobyRupert]

My old Ford 641 does not have live power. Without an overrunning clutch you will find yourself pushed through a fence when using a rotary cutter, or even worse, over a cliff.

Yes, that’s a lesson that has come as a surprise for many, but once known, you can predict and control the outcome of turning off the PTO, or pushing in the clutch, without damage.
Modern tractors with PTO brakes don’t give you the option of not destroying internal parts when you turn off the PTO…unless you buy aftermarket additions.
That should be totally unacceptable.

 

[DK35vince]

Modern tractors with PTO brakes don’t give you the option of not destroying internal parts when you turn off the PTO…unless you buy aftermarket additions.
That should be totally unacceptable.

I think I paid $60 for an over run clutch to save on my PTO brake.
Its been on there for 21 years.

 

[jjeff]

In my hurried arrogance I ruined my overrun coupler it failed before the sheer pins on my rotary cutter. Which I replaced previously with bolts that were not grade 2. It basically twisted the splines and trew the pto shaft to the cutter gear box off, So I told myself I guess my overrun coupler saved the internal pto components on tractor and gear case on cutter thankfully. Ive used pto on tractor afterward without a overrun coupler and everything appears to work as it should.

 

[5030]

Don't much care for that style (I believe it's a Weasler)... I prefer the the over the stub shaft lock on style with external grease fittings. Whatever you do, don't allow the cutter to freewheel the stub shaft (no over run coupler installed) because it will eat up the internal PTO brake. Reduce the PTO rpm gradually, don't just disengage the PTO at rated speed. which is something I do even with the over run coupler installed.

O never want to replace the driven pack or the brake plates. Both require a split and dissection of the gearbox.

Once the internal brake is shot, the PTO stub will rotate constantly whether the PTO is engaged or not. That occurs from the parasitic motion imparted to the PTO wet clutch.

Kubota designed the PTO brake to have a 1/4 rotational free turn to allow you to engage a driven implement easier.