Pto speed on mower

[Cowabunga]

540 or 1000 both reached at 2000 engine rpm. Wouldnt think there be any fuel saved.

Quite right. None. Its not about efficiency or fuel saved but about reducing the twisting force, torque, on components in the implement driveline.

 

[oakleaf]

Everything else l have is 540.
Both mowers are on 6 spline shafts.
Probably easier to stick with 540.
Remember years ago when the forager was changed and nobody told us it was 1000 box on the new one.
First hour out it kept blocking and wouldnt blow into trailers. Took us a while to figure out what was going on. Then had to hire a tractor from neighbour as none of ours at the time had 1000 pto.

 

[Bury the Trash]

Saves absolutely zero diesel. What is your attempt at a logic to explain your fantastic hypothesis?

I often feel like it takes more fuel , never really worked it out as a comparison on my older tractors that's using on a p harrow as the only 1000 implement we have bit more torque needed for that than a mower I guess

 

[Cowabunga]

I often feel like it takes more fuel , never really worked it out as a comparison on my older tractors that's using on a p harrow as the only 1000 implement we have bit more torque needed for that than a mower I guess

The only torque and power you need worry about is that consumed by the implement from the tractor's engine. That is the same, all other things being equal, whether the implement primary driveline [the PTO shaft] runs at 540 or 1000 rpm, assuming that the implement is designed for one or the other.

 

[Cowabunga]

Everything else l have is 540.
Both mowers are on 6 spline shafts.
Probably easier to stick with 540.
Remember years ago when the forager was changed and nobody told us it was 1000 box on the new one.
First hour out it kept blocking and wouldnt blow into trailers. Took us a while to figure out what was going on. Then had to hire a tractor from neighbour as none of ours at the time had 1000 pto.

Any implement requiring between 80 and 160 hp running a 540 rpm shaft speed really needs a much heavier duty PTO shaft than one running at 1000rpm. Shaft size and weight gets extreme beyond about 160 at the shaft [or more precisely perhaps, over about 2000Nm through the shaft.] so 1000 rpm is pretty much mandatory.

You might wonder how a tractor that is rated to produce say 650Nm maximum torque produces perhaps in excess of 2000 Nm at the shaft? Well it is because maximum torque is rated at lower revs than maximum power and is typically 30% higher than at rated speed, which needs to be taken account of for overload situations. But more than that and my point being that at 500 rpm at the shaft, the torque at the flywheel is subject to a multiplication factor of four compared to at 1000rpm assuming that the flywheel actually turns at 2000rpm to attain either PTO rated speeds.

If you have not understood the above, I urge you to read it as many times as necessary to do so.

The figures are approximate for illustration purposes only, so nobody get on their high horse and quibble about how much torque their own 160 or 180hp tractor is rated at or that their tractor makes 540 at 1900 but 1000 at 2100. I know all of that and it is the principles involved I am explaining.

 

[Scribus]

1,000 rpm PTO's were introduced to enable more power to be transmitted through a standard diameter shaft and/or implement driveline without having to beef it up and so add to the overall weight. It's all about torque as noted above.

The thing to remember is that when changing from 540 to 1000 all you are doing is changing the gearing between the engine and gearbox, the engine will still turn at 1,800 rpm (or about that) to deliver the the desired PTO speed.

As a general rule the faster an engine turns the more power it makes so fuel savings can be made if the work being done does not require the full power of the engine. You can then have the engine running slower and still have the PTO running at 540 revs via the 1000rpm gearing. This is the principle behind the 'eco' settings.

With reference to a mower then first cut is going to need a lot of power so you will need the engine to be running at 1,800 rpm. If the mower is a 540 model then you will need the 540 setting to ensure the correct tip speed. If you were to use the same mower for a bit of light topping then it would be quite possible to drop the revs and use the 1,000 PTO setting because you don't need as much power.

At the end of the day power is the rate at which energy in the fuel can be turned into mechanical energy to do work. The faster an engine can do this the more powerful it is. By reducing the engine speed you are making it less powerful but more efficient.

 

[Cowabunga]

1,000 rpm PTO's were introduced to enable more power to be transmitted through a standard diameter shaft and/or implement driveline without having to beef it up and so add to the overall weight. It's all about torque as noted above.

The thing to remember is that when changing from 540 to 1000 all you are doing is changing the gearing between the engine and gearbox, the engine will still turn at 1,800 rpm (or about that) to deliver the the desired PTO speed.

As a general rule the faster an engine turns the more power it makes so fuel savings can be made if the work being done does not require the full power of the engine. You can then have the engine running slower and still have the PTO running at 540 revs via the 1000rpm gearing. This is the principle behind the 'eco' settings.

With reference to a mower then first cut is going to need a lot of power so you will need the engine to be running at 1,800 rpm. If the mower is a 540 model then you will need the 540 setting to ensure the correct tip speed. If you were to use the same mower for a bit of light topping then it would be quite possible to drop the revs and use the 1,000 PTO setting because you don't need as much power.

At the end of the day power is the rate at which energy in the fuel can be turned into mechanical energy to do work. The faster an engine can do this the more powerful it is. By reducing the engine speed you are making it less powerful but more efficient.

Obviously if 1000 PTO rpm is at 2000 engine revs then 540 using the same gearing will require the engine to be de-revved to 1080 rpm, which is usually too slow and lacking in power for many jobs. Specifically it will be below the speed at which the engine produces peak torque and in the rapidly declining part of the torque curve, leaving no reserve whatsoever for any overload situation.
This is the reason many tractors have 540 ECO setting as an option to use. This is actually a 750 PTO rpm gearing but provides 540 at around 1500 rpm, which ideally gives a bit of torque rise as overload causes revs to drop slightly further. A reserve against sudden stalling in other words.

If using a front rear combination of PTO driven implements, obviously their speeds need to be matched and there is unlikely to be scope to reduce engine revs below where either conventional 540 or 1000 shaft speeds are rated.

One issue regarding the use of a topper or mower rated to work at 540 but using the 1000 rpm gearing on the tractor at reduced engine revs, typically at around 1100 at the engine, is that the implement will accelerate from a stop much faster than it is designed to. This may or may not be a problem, depending on the inertia of the implement, how sharp the PTO clutch engages, and the strength of the implement driveline. Believe me it can twist topper shafts and gearbox splines etc.

 

[Funnyfarm]

Saves absolutely zero diesel. What is your attempt at a logic to explain your fantastic hypothesis?

I think he means running a 540 rpm machine in light conditions in 1000rpm selected gear on the tractor, running the engine at about 1200 revs instead of the 2000 revs normally required.

 

[Funnyfarm]

Is there any benefit in choosing a 21 spline pto shaft to run 1000rpm machinery instead of a 6 spline which is now quite commonly available?

 

[Cowabunga]

Back in the day, it was recommended when using 100hp tractors on power hungry implements like 3m mowers / power harrows to use 1000rpm PTO.
But these days we use 250hp on 3m mowers / power harrows, so not quite so important.

On the contrary, it is absolutely essential. Indeed at that power level the driveline needs to be fairly massive even when using 1000 rpm and would be unworkable if the machine was designed for 540 shaft speed. In fact at above 200 hp it is very much to be advised to use a 1 ¾" 20 spline heavy duty stub on the tractor rather than a 1 ⅜" 21 spline shaft unless the power output is shared between more than one PTO shaft [front and rear split].

 

[Cowabunga]

Is there any benefit in choosing a 21 spline pto shaft to run 1000rpm machinery instead of a 6 spline which is now quite commonly available?

Not critical but it does help identify which speed the PTO should be running at. 'Standards' are drafted for a purpose but it is now quite common for this convention to be ignored for the sake of convenience.

 

[ollie989898]

I always thought that generally, if 1000 rpm was selected, the tractor would need to be wound up a bit higher to get the required PTO speed than if running at 540 rpm?

I would be loathe to try and run many implements at 540 using the 1000 speed- as the Duck says, it can bring them into gear pretty damned sharpish so best not done with anything that might have a significant load attached to it, 540e is plenty enough but I would be dead careful using that as well.

 

[Green&Steam]

If engine is running at approximately 2000 Reves for 540 – thousand what speed is the mower blades running at what's the point in reducing engine revs down to 540 then gearing back up to run the blades ?

 

[C.J]

I always thought that generally, if 1000 rpm was selected, the tractor would need to be wound up a bit higher to get the required PTO speed than if running at 540.

My Deere is 540 at about 2000 and 1000 at about 2200.

The extra power might allow cutting in a higher gear , for a heavy crop or going up hill , but I'd rather be able to use 540E(1700 engine rpm) for lighter cuts.

1000 @ 2200 gives 540 @ 1200 which is perfectly fine for Hedge cutting and the rotorspreader.

 

[ollie989898]

My Deere is 540 at about 2000 and 1000 at about 2200.

The extra power might allow cutting in a higher gear , for a heavy crop or going up hill , but I'd rather be able to use 540E(1700 engine rpm) for lighter cuts.

1000 @ 2200 gives 540 @ 1200 which is perfectly fine for Hedge cutting and the rotorspreader.

This is what I understood to be the case, if the tractor engine is running at a higher speed, there is more of a 'cushion' if the load does increase dynamically- I presume maximum engine power is also generated at this approximate engine RPM for applications where that might be needed.

 

[Andrew]

All the mowers we’ve ever had have a 90 degree gearbox on the linkage. Switching this round converts it from 540 to 1000rpm. Then if you change your mind it’s a simple swap.

 

[Farmer_Joe]

I would get 1000 don’t worry about shaft I’ve not seen a 21 spline for years and we used to run some right old crap

Better on torque loading as said

 

[essexpete]

Obviously if 1000 PTO rpm is at 2000 engine revs then 540 using the same gearing will require the engine to be de-revved to 1080 rpm, which is usually too slow and lacking in power for many jobs. Specifically it will be below the speed at which the engine produces peak torque and in the rapidly declining part of the torque curve, leaving no reserve whatsoever for any overload situation.
This is the reason many tractors have 540 ECO setting as an option to use. This is actually a 750 PTO rpm gearing but provides 540 at around 1500 rpm, which ideally gives a bit of torque rise as overload causes revs to drop slightly further. A reserve against sudden stalling in other words.

If using a front rear combination of PTO driven implements, obviously their speeds need to be matched and there is unlikely to be scope to reduce engine revs below where either conventional 540 or 1000 shaft speeds are rated.

One issue regarding the use of a topper or mower rated to work at 540 but using the 1000 rpm gearing on the tractor at reduced engine revs, typically at around 1100 at the engine, is that the implement will accelerate from a stop much faster than it is designed to. This may or may not be a problem, depending on the inertia of the implement, how sharp the PTO clutch engages, and the strength of the implement driveline. Believe me it can twist topper shafts and gearbox splines etc.

I use a small disc mower on my 8340 in the 1000 setting. I start in 540 and rev up a bit drop the revs suddenly and flick over to 1000. As you point out if more power was required either due to implement size, ground conditions or crop it would not work well with little torque in hand. I run a small fert spinner the same way on an IH 895 but have to be vigilant with rpm.

 

[bobk]

Saves absolutely zero diesel. What is your attempt at a logic to explain your fantastic hypothesis?

You rev the tractor enough so that it cuts the grass off , unless you wish to sit there all day revving the nuts off it cos that's how you've always done it

If you buy a pack of bacon rashers you're not obliged to eat them all .

 

[Dman2]

I would get 1000 don’t worry about shaft I’ve not seen a 21 spline for years and we used to run some right old crap

Better on torque loading as said

trouble is some tractors you have to turn the shaft around to get 1000 rpm
our Mf 5465 was like that