An Idea Whose Time Has Come

[OkieDave]

Fixed-speed PTO.

Think about it--a PTO that always turns 540 RPM, regardless of throttle setting. Could be a hydrostatic drive, could be CVT, could be lots of things, but it always gives you the proper speed, regardless of how much power you're actually delivering.

The multi-speed PTO guys know what I'm talking about: with a 540/1000 RPM PTO, you can select 1000 RPM and run a half-throttle to get the same 540-ish, but burn half the fuel on jobs that don't need the extra power. JD is even advertising this feature under the name "Economy PTO." We all know what it really is--a two-speed PTO, with a second marking on the tach to tell you where to get 540 RPM when set to high-speed.

So why not? Why not a system that will maintain 540 regardless of input power? I mow my lawn with a brush hog; the hog will happily cut 3" saplings, but I do that once, maybe twice a year--most of the time, it's 3" tall grass. I don't need the full 25 HP my PTO delivers at 540; frankly, I suspect 5 HP would be enough as long as it was delivered at appropriate speed. Give me that, and I'll be at the Diesel pump twice a year instead of once a month.

What do y'all think? Am I just crazy, or am I on to something?

 

[oldnslo]

I can think of one application where this technology is being used today and that is truck mounted cement mixers. As they drive down the road and the engine RPM varies the drum turns at the same speed. These are Hydrostatic drive systems.

I suspect the cost of this feature would probably make it prohibitive on small tractors.

Roy

 

[blueriver]

I quess I just don't understand PTO's ... take for example all my equipment is 540 rated .. so what your saying is when I hook up for example my disc mower and go to cutting hay I can set the PTO lever to 1000 and run my tractor at half rpm's? At half throttle would I not be lugging the diesel engine?

I was under the imression that some of the equipment you buy may be 1000 rated not 540 and that would be the only time I'd use the 1000 but I would still run the tractor at the PTO rpm's.

 

[leonz]

I quess I just don't understand PTO's ... take for example all my equipment is 540 rated .. so what your saying is when I hook up for example my disc mower and go to cutting hay I can set the PTO lever to 1000 and run my tractor at half rpm's? At half throttle would I not be lugging the diesel engine?

I was under the imression that some of the equipment you buy may be 1000 rated not 540 and that would be the only time I'd use the 1000 but I would still run the tractor at the PTO rpm's.

No, you need to buy the 1000 to 540 adapter
stub to install over your 1000 R.P.M., shaft stub assuming it is the
20 plus spline stub intended for 1,000 R.P.M., implement use.

 

[Duffster]

I suspect the cost of this feature would probably make it prohibitive on small tractors.

Bingo.

I can't think of to many things I do were I would want to run the tractor at less RPM any way.

Also when concrete mixers want max barrel rpm they have to have max engine rpm as well.

 

[blueriver]

No, you need to buy the 1000 to 540 adapter
stub to install over your 1000 R.P.M., shaft stub assuming it is the
20 plus spline stub intended for 1,000 R.P.M., implement use.

My tractor has the standard 6 spline 540 PTO ... I do have a lever in the cab to change to 1000 ... so as I asked when I hook up the disc mower to the pto 540 shaft and then shift the lever to 1000 I would run at 1/2 throttle?

 

[wny770]

What about a post hole digger?

 

[OkieDave]

My tractor has the standard 6 spline 540 PTO ... I do have a lever in the cab to change to 1000 ... so as I asked when I hook up the disc mower to the pto 540 shaft and then shift the lever to 1000 I would run at 1/2 throttle?

Yes. It's just like the gears in a manual transmission: if you shift from 1st to 2nd, your engine RPM goes down, but the tires turn at the same speed. The downside is that, even though you're going just as fast, you're delivering less power to the wheels, which you notice when you step on the gas and the car grumbles at you instead of leaping to action. If you need the power, you stay in low gear; if you're cruising on the highway, you go to high gear and trade the responsiveness for lower fuel consumption.

Now, if you're doing something that requires the full power output of your tractor, and you try to run it at half-power, it's going to bog down. If you're doing light work, though--such as mowing short grass with a brush hog capable of cutting small trees--you're nowhere near needing that full power.

 

[Hooked_on_HP]

I can think of one application where this technology is being used today and that is truck mounted cement mixers. As they drive down the road and the engine RPM varies the drum turns at the same speed. These are Hydrostatic drive systems.

I suspect the cost of this feature would probably make it prohibitive on small tractors.

Roy

On mixers drum speed does change with engine RPM's. You control drum speed with the amount of hydraulic pressure coming out of the variable displacement hydrostatic pump. This is manually controlled by the driver.
Bill

 

[leonz]

My tractor has the standard 6 spline 540 PTO ... I do have a lever in the cab to change to 1000 ... so as I asked when I hook up the disc mower to the pto 540 shaft and then shift the lever to 1000 I would run at 1/2 throttle?

If that is the case with your mule you should have a set engine speed marker on the dash boards tachometer that gives you the proper engine speed setting for the conversion speed for the towed implement

 

[David Devuono]

Heck I just mow twice as fast. If its a light cut I move to a higher gear. Neigbour (real farmer) must have had a chuckle as I bounced across the field at 20MPH. Got the job done though.

 

[wcampbell47]

Recently I used my PTO tiller to make a new garden in extremely hard dry soil. I needed the power delivered at full rpm's to get the job done.

My own garden has multiple truck loads of bank sand that I have tilled into the south texas gumbo. I run the engine at something between 1600 and 2000 rpms which delivers more than enough power to turn the tiller.

Mowing ... obviously I get a better cut when the blades are spinning at the rated rpms. I could see the benefits of a multi speed PTO.

Now comes the kicker. On my B7510 shifting the PTO into 540 turns the rear pto shaft. It has a mid pto that runs at 9600. When shifted into the 9600 both shafts (rear and mid) turn. Just for grins I have shifted into the 9600 while attached to my land pride finish mower. The engine lugged and strained when I tried to mow. I stick to the 540 shaft speed and run at about 2000 rpms for light duty mowing.

 

[Redneck in training]

You don't save half fuel running on half throttle while moving. In fact you might use more fuel. There is a balance between engine power and power required to turn your mower. If you look at the power, torque and efficiency curves for your particular engine you will see that most engines are geared such a way that they deliver maximum torque and have the lowest specific fuel consumption (oz/HP) at or in vicinity of the PTO speed.
If your mover requires 15 HP to cut your grass the speed governor will adjust the fuel delivery so the engine will deliver exactly the power required.
Running at too low speed while the engine is loaded might be bad for bearing. There is certain minimum linear speed of the shaft relative to bearing that will provide separation of the shaft and the bearing by oil film. The higher speed the higher is the load the bearing can handle. Think about aquaplaning. At low speed and high load the oil film might be penetrated and the shaft touches the bearing causing wear. Think about lugging the engine.

The conclusion is that the fuel delivery is proportional to the power required to run your load (mower) adjusted for efficiency at particular speed. I would bet that you will use less fuel at normal PTO speed.

 

[CalG]

I can see some reasoning behind a variable output speed PTO.

'Would be handi for the "suburbanite".to run things at a "comfortable pace".

But many owners look at the PTO Horse Power as a means of assessing the unit's potential to do the task required.
A Variable speed drive, Especially a Hydro Static unit SUCKS HP and turns it in to heat. I'm not paying a premium for that! What would you say if you bought a 100 HP tractor that only put 55 HP to the PTO? Not much I bet.

A multi SPEED gearbox for the PTO might be a good deal. (Some makers offer at least three) But then, would some fool blow up his baler or throw a blade into the next county??

The 540 and 1000 "standards" ( I know, there is everything between) seem to answer most needs.

You could whip up your own if you really needed too. Vickers makes some nice units.

 

[blueriver]

If that is the case with your mule you should have a set engine speed marker on the dash boards tachometer that gives you the proper engine speed setting for the conversion speed for the towed implement

Thus therefore my confussion. I have one tach mark at the 2600 rpm for the 540 ... nothing for the 1000. This thread is bothering me so last evening I went and visited my old retired neighbor farmer and we talked about this.

He stated that equipment has been designed for either 540 or 1000 not both ... he had a no-till drill that was 1000 and on his JD tractor his pto shaft was 2 shafts ... one for 6 spline 540 and the other for the 1000 ... a 1000 gearbox is geared to match the equipment and the tractor to run at rated rpm ... thus you run a 1000 at the same engine rpm to avoid lugging the engine and run the gearbox ... also stated if you like go ahead and just run your 540 equipment at 1000 with half throttle and lug the engine and burn up bearings.

Just saying what he was saying ... and sometimes we can learn from the old timers. So ... I' think I'll run 540 at 2600 for the equipment I have ... If I ever get a 1000 piece I'll use that.

 

[Mark Page]

Sounds like a good idea if you have sufficient power. I'm pretty sure my 45 horse Massey would do it if all I'm doing is mowing with a 7ft finish mower.
The old farmers say gear up and throttle down.

 

[oldnslo]

Thus therefore my confussion. I have one tach mark at the 2600 rpm for the 540 ... nothing for the 1000. This thread is bothering me so last evening I went and visited my old retired neighbor farmer and we talked about this.

He stated that equipment has been designed for either 540 or 1000 not both ... he had a no-till drill that was 1000 and on his JD tractor his pto shaft was 2 shafts ... one for 6 spline 540 and the other for the 1000 ... a 1000 gearbox is geared to match the equipment and the tractor to run at rated rpm ... thus you run a 1000 at the same engine rpm to avoid lugging the engine and run the gearbox ... also stated if you like go ahead and just run your 540 equipment at 1000 with half throttle and lug the engine and burn up bearings.

Just saying what he was saying ... and sometimes we can learn from the old timers. So ... I' think I'll run 540 at 2600 for the equipment I have ... If I ever get a 1000 piece I'll use that.

The Old Timer is correct. All Ag equipment I have seen and used is either 540 or 1000 RPM. On every tractor I have driven the Engine RPM to achieve these speeds was the same position on the tach. Some equipment like a hay elevator I never ran at rated speed while a forage harvestor/chopper I ran the engine full throttle since I wanted max power to the PTO.

Yes IF you have enough HP you can buy shaft adapters to convert from 1000 RPM spline down to 540 RPM spline and run your engine at half throttle to obtain the 540 RPM on your PTO.

Example: 200 HP tractor running a conventional small square baler that a 50 HP tractor could operate.

Roy