geared tractor operation question

[ericm979]

This property I bought came with a Deere 5105, which has a pretty basic gear transmission- sycnros only between low range and reverse. I'm going to do some mowing with a rotary cutter. I've driven manual transmission motorcycles, cars and trucks quite a bit but my tractors have been HST. So I have a question:

when you're running a PTO implement do you 1. raise the rpms to PTO speed 2. slip the clutch to get the tractor moving. Or do you use the foot throttle to get just enough rpms to get in motion, like you would with a manual transmission car or truck, and then raise the rpms to PTO speed as you're moving?

 

[Sawyer Rob]

I use option two, with all of my gear drive tractors.

SR

 

[rangerfredbob]

I wing it, mine has a single clutch but I usually engage everything low rpm and up it afterward... mine isn't synchronized but I have the timing figured out where I can shift in motion anyway... just not reverse but I do go up and down gears occasionally...

 

[rScotty]

This property I bought came with a Deere 5105, which has a pretty basic gear transmission- sycnros only between low range and reverse. I'm going to do some mowing with a rotary cutter. I've driven manual transmission motorcycles, cars and trucks quite a bit but my tractors have been HST. So I have a question:

when you're running a PTO implement do you 1. raise the rpms to PTO speed 2. slip the clutch to get the tractor moving. Or do you use the foot throttle to get just enough rpms to get in motion, like you would with a manual transmission car or truck, and then raise the rpms to PTO speed as you're moving?

For mowing or tilliing, It depends a bit on if you have a fully independent PTO with its own clutch, and whether the implement needs to start cutting immediately or if you can accept a partial cut for the first ten feet. And it also depends on how hard the blades are going to have to work to cut whatever it is that you are cutting. There's no way to know all that until you begin to cut. Then you will know very quickly.

Our PTO tractor is a 1957 two-cylinder 30 hp model 530 John Deere. Not as modern as your 5105, but proabably not all that different either. Even those old JDs had some surprisingly modern features - power steering, fully independent PTO, good lights, comfortable seat suspension...and such. Like most Ag tractors, It has separate independent engagement for the PTO. What I'm saying is that the PTO clutch and the transmission clutch are completely separate and either can work independently of the other. Usually I will engage the implement at low RPM and bring it and the engine up to speed while also slipping the PTO clutch. Once the implement is spinning well I will lower it and then begin to engage the transmission clutch so that we can move off doing work right from the start.

Suppose I am bush-hogging saplings, and tall grass, and for some reason need to start was close as I can get backed up against a fence line. Since I want the PTO to be up to speed when it starts to cut the thick stuff, I'll engage the PTO while using the 3pt to hold the bush hog a little bit above the height I plan to cut. Then I'll engage the PTO clutch, rev up engine and the implement's slasher blade, and lower the hog down to operating height. I wait a moment for the dust and cuttings to clear and to make sure that all is working well...which means I didn't hit any rocks or old fence posts that might have been there. If all is good, I'll leave the PTO spinning at full speed, engage the transmission clutch, and move off making a nice even cut right from the beginning.

Every time is different. I like to have the PTO spinning right from the start.

REMEMBER: The PTO drive shaft MUST HAVE either shear pins or a slip clutch in the PTO drive line.
And the PTO also MUST HAVE an over-running clutch. It simply isn't worth risking your tractor and implement to operate without those things.

Like plowing, PTO work is very satisfying. It's what tractors were made to do.
rScotty

 

[ptsg]

Foot throttle is your friend. No reason to slip the clutch to death at high RPMs.

Turn the PTO on, select your preferred gear, release the clutch and increase RPMs with foot throttle. At the end of the run, if you need to change directions, simply let it coast down, change from forward to reverse and vice versa as needed and increase the RPMs again with the foot throttle. This if you're doing short runs.

For long runs, start at idle and just increase RPMs with the hand throttle and at the end just do the foot throttle thing to change directions and you're good to go with minimal clutch slippage.

EDIT: Added a little example of how I do in constant direction changes.

 

[LouNY]

Depending upon what I'm doing if I need the pto at rpm I'll bring the engine speed up after engaging the pto then engage the clutch. It will slip slightly but I'm engaging it rapidly after it starts to pull so it has minimal slippage.
I very seldom use the foot feed throttle, I prefer the hand throttle and leave it set were I need it if, if for some reason I need or want more speed for just a bit I may over ride with the foot feed.

 

[SPYDERLK]

...Snip...

Every time is different. I like to have the PTO spinning right from the start.

REMEMBER: The PTO drive shaft MUST HAVE either shear pins or a slip clutch in the PTO drive line.
And the PTO also MUST HAVE an over-running clutch. It simply isn't worth risking your tractor and implement to operate without those things.

Like plowing, PTO work is very satisfying. It's what tractors were made to do.
rScotty

Hi! Could you develop your thinking as to why a PTO MUST have an overunning clutch? There are some old platforms where load inertia can drive the wheels that I understand "must" would apply, but otherwise?

 

[rScotty]

Hi! Could you develop your thinking as to why a PTO MUST have an overunning clutch? There are some old platforms where load inertia can drive the wheels that I understand "must" would apply, but otherwise?

Sure. Just like you say, it's all about inertia/momentum... or spinning anything heavy and fast.

When the PTO is powered up and doing it's normal job of spinning the implement, all the forces in the PTO transmission are pushing in one direction. The dogs of the overrunning clutch is fully engaged & everything is sweet.

But when the power to the PTO is suddenly reduced for any reason, the stored momentum in the spinning implement tries to turn the PTO transmission shafts in the opposite direction. Like you say, that can drive the tractor wheels and cause an exciting ride for a few feet. But also, reversing the forces like that puts a twist into the PTO shafts as it reverses the loads on the gears.
When you add an over-running clutch into the drive line all this is prevented. The over-running clutch just disengages in that direction and the momentum of the implement cannot drive the PTO transmission backwards.

So what happens without an over-running clutch? Well, without one it's probably better to slow down gradually, and even let the momentum drive the wheels to soak up some of the forces that way. All of that is better than chopping the throttle and then riding the brakes. That risks the twisting forces breaking a shaft or gear.

Either way works. But best way is to just lift the implement while reducing the throttle, and let the over-running clutch do whatever it needs to do while the implement spins down.
Hope this Helps.
rScotty

 

[LouNY]

Sure. Just like you say, it's all about inertia/momentum... or spinning anything heavy and fast.

When the PTO is powered up and doing it's normal job of spinning the implement, all the forces in the PTO transmission are pushing in one direction. The dogs of the overrunning clutch is fully engaged & everything is sweet.

But when the power to the PTO is suddenly reduced for any reason, the stored momentum in the spinning implement tries to turn the PTO transmission shafts in the opposite direction. Like you say, that can drive the tractor wheels and cause an exciting ride for a few feet. But also, reversing the forces like that puts a twist into the PTO shafts as it reverses the loads on the gears.
When you add an over-running clutch into the drive line all this is prevented. The over-running clutch just disengages in that direction and the momentum of the implement cannot drive the PTO transmission backwards.

So what happens without an over-running clutch? Well, without one it's probably better to slow down gradually, and even let the momentum drive the wheels to soak up some of the forces that way. All of that is better than chopping the throttle and then riding the brakes. That risks the twisting forces breaking a shaft or gear.

Either way works. But best way is to just lift the implement while reducing the throttle, and let the over-running clutch do whatever it needs to do while the implement spins down.
Hope this Helps.
rScotty

Good answer but you missed one very important fact.
With an over running clutch installed on pto implements that have a lot of stored momentum these tractors with independent pto are using the built in pto brake to stop the pto turning. Those brakes can be very expensive to repair/replace. Many implements may have one built in, except one of the more common ones used here the brush hog.

 

[rScotty]

Good answer but you missed one very important fact.
With an over running clutch installed on pto implements that have a lot of stored momentum these tractors with independent pto are using the built in pto brake to stop the pto turning. Those brakes can be very expensive to repair/replace. Many implements may have one built in, except one of the more common ones used here the brush hog.

Well, about we can do with PTOs is offer some general principles. There is no standard for how they are designed and controlled. Tractors are individualistic that way.

For the PTO, some tractors have an over-running clutch, with or without a slip clutch or brakes built into the tractor. Many makes rely on some of these being added into the PTO driveshaft. I assume the operator has an idea, or if not we try to tell him what we look for ourselves.

There are also different types of PTOs - like the transmission driven versus a couple of different types of independent ones... Two stage clutches are in some and independent clutches in others. So not all have the same sort of engagement or clutching.

But they all do the same job and have the same things that a person just starting out should look for.
rScotty