Tell me about 20 series PTO operation

[bam747]

I'm glade to see I'm not the only one who thinks the 4x20 owner's manual recommended PTO engagement and disengagement methodology seems like a pretty big step back. This "come to a stop" recommendation is just nuts for something advertised as an "independent" PTO.

I have a 33 year old JD 1020 small utility AG tractor with a MUCH better fully independent PTO control setup. In this case, there is a lever that controls a separate hydraulic clutch for the PTO. Manually feather the PTO on for a nice smooth engagement regardless of engine speed. Shutting the PTO off just means flipping the lever off.

As for the 4x20 PTO, I did specifically challenge a JD dealer salesman about this apparent PTO engage/disengage issue. His feedback was that they engage/disengage the PTO at pretty much any engine speed, moving or not, and that it does have some amount of modulation built into the system to feather the PTO on and off.

Before I plunk down any money on a 4x20, I'm going to make the dealer put on a 6' rotary mower and have them show me just how "modulated" the PTO engagement is, or isn't.

 

[bam747]

I'm glade to see I'm not the only one who thinks the 4x20 owner's manual recommended PTO engagement and disengagement methodology seems like a pretty big step back. This "come to a stop" recommendation is just nuts for something advertised as an "independent" PTO.

I have a 33 year old JD 1020 small utility AG tractor with a MUCH better fully independent PTO control setup. In this case, there is a lever that controls a separate hydraulic clutch for the PTO. Manually feather the PTO on for a nice smooth engagement regardless of engine speed. Shutting the PTO off just means flipping the lever off.

As for the 4x20 PTO, I did specifically challenge a JD dealer salesman about this apparent PTO engage/disengage issue. His feedback was that they engage/disengage the PTO at pretty much any engine speed, moving or not, and that it does have some amount of modulation built into the system to feather the PTO on and off.

Before I plunk down any money on a 4x20, I'm going to make the dealer put on a 6' rotary mower and have them show me just how "modulated" the PTO engagement is, or isn't.

 

[NoMo]

Forgive my ignorance in this situation, but doesn't "feathering" (better described as slipping) the clutch reduce it's longevity? Wouldn't it be better to leave the cutter running and just raise it while traversing the areas you can't mow?

 

[NoMo]

Forgive my ignorance in this situation, but doesn't "feathering" (better described as slipping) the clutch reduce it's longevity? Wouldn't it be better to leave the cutter running and just raise it while traversing the areas you can't mow?

 

[RogerH]

I have some experience with the 4710 which is essentially the same transmission as the 4120. The sequence for PTO operation in the manual is a recommendation, not a requirement. There is nothing to prevent you from starting and stopping the PTO at any engine speed, nor while the tractor is moving. You do have to be in the seat, though, unless you follow the procedure for out of seat operation.

The recommendation for starting at 1500 rpm is a good balance to prevent stalling the engine when starting up high inertia equipment while lowering the shock through the drive train compared to starting at high idle. The suggestion to idle back to 950 rpm is because the PTO has a brake and idling back will reduce the brake wear. Stopping to engage and disengage is to encourage the safe practice of looking back for proper clearance of people and surroundings before starting PTO driven equipment.

The PTO is actually hydraulically engaged via a solenoid valve and is modulated. I have never had an issue with its aggressiveness, but I think you would be wise to ask your dealer to demonstrate it to you with a rotary mower attached to make sure it meets your satisfaction. When starting a rotary cutter, it can make a big clunk as the blade swings around its pivot.

The clutch and brake are wet disks and are quite durable. I have started an MX8 mower up from high idle and stopped it from high idle with no ill effect. I don't recommend it, but sometimes you get thinking about other stuff and forget.

 

[RogerH]

I have some experience with the 4710 which is essentially the same transmission as the 4120. The sequence for PTO operation in the manual is a recommendation, not a requirement. There is nothing to prevent you from starting and stopping the PTO at any engine speed, nor while the tractor is moving. You do have to be in the seat, though, unless you follow the procedure for out of seat operation.

The recommendation for starting at 1500 rpm is a good balance to prevent stalling the engine when starting up high inertia equipment while lowering the shock through the drive train compared to starting at high idle. The suggestion to idle back to 950 rpm is because the PTO has a brake and idling back will reduce the brake wear. Stopping to engage and disengage is to encourage the safe practice of looking back for proper clearance of people and surroundings before starting PTO driven equipment.

The PTO is actually hydraulically engaged via a solenoid valve and is modulated. I have never had an issue with its aggressiveness, but I think you would be wise to ask your dealer to demonstrate it to you with a rotary mower attached to make sure it meets your satisfaction. When starting a rotary cutter, it can make a big clunk as the blade swings around its pivot.

The clutch and brake are wet disks and are quite durable. I have started an MX8 mower up from high idle and stopped it from high idle with no ill effect. I don't recommend it, but sometimes you get thinking about other stuff and forget.

 

[browns40]

Hi cargun,

In real life it is not so complex as the manual makes it sound;

What I think the goal is is to reduce shock load on the system while engaging and disengaging--as mentioned earlier, a bushhog gearbox is big & heavy enough to damage your tractor (i.e. shear pins & slip clutches)... so engage with enough power that the engine doesn't lug... disengage when PTO is slowing down it's rotation.

The only time I stop the PTO is if the work is done (or have to move a ways to start again), or the cutter becomes unbalanced, in which case the darn thing needs to stop turning itself before you can start it up again.

With a spreader I engage & run at lower RPM, as 1500 would be too fast for the task (sanding driveway), and the gearbox is tiny.

With a winch engage it at 12-1500, but still don't run at 2600 unless I need every bit I can get out of the winch.

Disengaging all implements I usually do the same: pull throttle back to idle & then disengage--now that engine RPM is still way above 950, but it's slowing down, so I figure the intent is met anyway.

Real world I have turned the PTO off at 2600 which a rock is bouncing around up in the cutter... turned it on lower than recommended too... never had problems with it.

No troubles to date with tractor or implements operating in this train of thought... high enough torque to start things turning, low torque on parts to disengage... it's rotating shafts & variable torque... of course you have to assign something concrete (like specific engine RPM's) to things or people get all wound up. /forums/images/graemlins/blush.gif

Don't let the manual scare you--take one out & see. /forums/images/graemlins/wink.gif

 

[browns40]

Hi cargun,

In real life it is not so complex as the manual makes it sound;

What I think the goal is is to reduce shock load on the system while engaging and disengaging--as mentioned earlier, a bushhog gearbox is big & heavy enough to damage your tractor (i.e. shear pins & slip clutches)... so engage with enough power that the engine doesn't lug... disengage when PTO is slowing down it's rotation.

The only time I stop the PTO is if the work is done (or have to move a ways to start again), or the cutter becomes unbalanced, in which case the darn thing needs to stop turning itself before you can start it up again.

With a spreader I engage & run at lower RPM, as 1500 would be too fast for the task (sanding driveway), and the gearbox is tiny.

With a winch engage it at 12-1500, but still don't run at 2600 unless I need every bit I can get out of the winch.

Disengaging all implements I usually do the same: pull throttle back to idle & then disengage--now that engine RPM is still way above 950, but it's slowing down, so I figure the intent is met anyway.

Real world I have turned the PTO off at 2600 which a rock is bouncing around up in the cutter... turned it on lower than recommended too... never had problems with it.

No troubles to date with tractor or implements operating in this train of thought... high enough torque to start things turning, low torque on parts to disengage... it's rotating shafts & variable torque... of course you have to assign something concrete (like specific engine RPM's) to things or people get all wound up. /forums/images/graemlins/blush.gif

Don't let the manual scare you--take one out & see. /forums/images/graemlins/wink.gif

 

[Cargun]

Ok, that makes me feel better that the manual may have too much nannying... but it still worries me. It would be more appropriately worded "You can engage/disengage whenever you want regardless of RPM or speed, but to minimize wear and tear we recommend...." The fact that it simply states "This is how to do it" makes me think they don't believe the PTO will last it's intended service life unless that procedure is followed.

NoMo... when you drive a manual tranny vehicle do you sidestep the clutch when starting out? Of course not. Clutches are meant to slip some... as long as you don't build up excessive heat in them they'll be ok. I'd even venture to say sidesteppping a clutch is harder on it than feathering it in like normal.

 

[Cargun]

Ok, that makes me feel better that the manual may have too much nannying... but it still worries me. It would be more appropriately worded "You can engage/disengage whenever you want regardless of RPM or speed, but to minimize wear and tear we recommend...." The fact that it simply states "This is how to do it" makes me think they don't believe the PTO will last it's intended service life unless that procedure is followed.

NoMo... when you drive a manual tranny vehicle do you sidestep the clutch when starting out? Of course not. Clutches are meant to slip some... as long as you don't build up excessive heat in them they'll be ok. I'd even venture to say sidesteppping a clutch is harder on it than feathering it in like normal.