PTO engagement with bush hog rough

[PeteN]

Got an LS MT357 and when I use PTO implements the engagement is relatively sudden which creates a huge load on the drivetrain. This is very noticeable with the bush hog but I also note the sudden engagement when I use a wood chipper. I'm engaging the PTO at low engine speed. I assume this PTO is engaged with hydraulics but is there some type of clutch that is supposed to engage the PTO more smoothly? It doesn't appear that the speed you move the knob to engage the PTO has any effect on how instantaneous the engagement is. The bush hog blades are free to move and once it is engaged it is smooth with no shaking. On my ag tractor I have a mechanical lever that mush have some type of clutch behind it since I can slowly ramp up the speed of the bush hog without the instantaneous engagement I see with the LS. The LS has been this way since new.

 

[ptsg]

So, most of these compact tractors these days, use a wet clutch for the PTO. Then, a PTO valve is used to control this clutch.

The PTO switch only turns a solenoid on this valve that turns the PTO On or Off. There is no feathering from the switch, just On or Off.

The PTO valve block has a couple cartridge valves. One is a relief valve that sets the clamping pressure of the wet clutch pack. The other is a sequence valve that, in conjunction with a 1.3 mm restrictor, sets how harsh or softer the PTO engages. Adjusting this sequence valve, should make it possible to have a less harsh PTO engagement.

Of all the manuals I've went through, for various manufacturers, TYM, LS, Kioti and more, none did really cover any adjustments, only how it works. So I advise you to let a dealer that knows the system to handle any adjustments.

EDIT: There is also a spring loaded brake. Meaning, when the PTO is Off, a spring push a brake disc that prevents the PTO from turning. This is also the reason why having lever to put the PTO in Neutral is a great advantage, since you can then free spin the shaft by hand when attaching PTO implements.

 

[Mtsoxfan]

I can't speak of your tractor, whenever I engage a PTO, be it on tractor or lawnmower, I always engage at a low speed. With my tractor, I engage at low speed and release clutch slowly.

 

[CloverKnollFarms]

My Branson has a soft engagement. It's electronic, just a solenoid switch, but it feathers in. I wonder what the difference is

 

[PeteN]

My tractor has an HST trans so no clutch. I did look in the service manual and found this.

Wonder if there is an issue with the orifice (3) that is supposed to "limit hydraulic shock"?

 

[oldnslo]

Item 6 is the valve that is supposed to provide the delayed soft start of the PTO. In looking at the schematic it is not drawn as an adjustable valve. Not sure if the orifice can be tweaked in valve 6 since that would affect engagement speed. Spring rate on valve 6 may also affect engagement speed.

The sequence valve is in the system to supply a continuous pressure to the reducing valve and should not be adjusted below the recommended setting pressure.

The 1.3 mm orifice can affect engagement speed in conjunction with valve 6.

 

[5030]

My Branson has a soft engagement. It's electronic, just a solenoid switch, but it feathers in. I wonder what the difference is

The difference is actuation pressure and that engagement pressure is contrilled by the hydraulic valve (usually located on the back lower side of the gearcase). On Kubota's, it's adjustable and the shop manual calls out the engagement pressure as the pto clutch is hydraulic actuated.

Other thing to keep in mind and that is the pto brake on most hydraulically actuated units is a single wet disc so when disengaging the pto, always either do it at an idle or install an over running coupler that will allow the stub shaft to cease turning as the implement freewheels. Driving the pto with implement inertia will quickly destroy the pto brake. You can easily tell if the pto brake disc is shot by obesrving the stub with the tractor running in neutral. If it is, the stub will rotate continuously from parasitic drive which the brake negates if it's operating correctly.

 

[ptsg]

My tractor has an HST trans so no clutch. I did look in the service manual and found this.View attachment 3618490
Wonder if there is an issue with the orifice (3) that is supposed to "limit hydraulic shock"?

Yes, it does have a PTO wet clutch. Number 5 in that schematic you shared.

 

[5030]

No builder that I'm aware of, has used a dry pto clutch in years. Reason bring is that a wet plate pto clutch is much more tolerant of engagement and disengagement than any dry pto cutch could ever attain.

Having said that again, freewheeling a wet clutch by driving it with a spinning implement (inertia driving the pto) will destroy it in pretty short order and why I ALWAYS run an over running adapter when I run my slasher. All my other driven implements have built in over running clutches as part of their drivelines.

 

[spruce Deere]

The pto brake in the xr3140 is a pta... pain in the a$$.

When using my cannon sprayer I idle the engine all the way down then kill the pto. When hooking up the cannon sprayer I have to use a pry bar to turn the drive shaft of the sprayer... no way to turn the tractor end.