Rotary Cutter 540 -vs- 1000 pto & rotary cutter

[N80]

Don't have much to add except that my B-I-L rebuilt the gearbox of an old JD, 7', heavy duty, pull-type mower. He said the gear box was made for a 1000 rpm pto and we switched it to gearing for a 540 rpm pto. I aksed him why it was geared that way and he didn't know. And that's all I know about the whole deal as most of my time was spent over at the parts washer.

It will now work on my 540 rpm pto (and his).....but the gearbox leaks so I don't use it anymore.

 

[Tom_Veatch]

There could be some confusion here between "power" and "torque".

Power (Foot-Pounds/Second) is the product of torque (i.e. Foot-Pounds) and rotary speed (i.e., RPM or Radians per Second). With the engine developing any particular power, the power input to the PTO transmission will be the same for either 540 or 1000 RPM. Assuming ideal conditions (100% mechanical efficiency in the PTO gearbox), the power available at the PTO output shaft will also be the same for either 540 or 1000 RPM.

The difference between the two speeds is the amount of torque avaliable. With 540 RPM, the torque available at the PTO output shaft will be approximately double the torque available at 1000 RPM.

Power available to the implement will be the same in either case except for whatever differences there may be in mechanical losses in the PTO transmission between the two speeds. Torque applied to the implement input at 540 RPM will be approximately double the torque at 1000 RPM.

 

[Fredex]

Here's what I think, and have been told, about 540 vs. 1000 rpm pto. Came about as pto hp hit 100 or thereabout. Users were snapping pto shafts (540's). Now the torque to transmit 100 hp at 540 rpm is 185% of the torque required to transmit 100 hp at 1000 rpm. Ergo change to 1000 rpm and twist off fewer pto shafts. Some tractors have both shafts (or reversable shafts). Many of these have lower pto hp load limits at 540 than at 1000 even though the tractor might be capable of delivering the same hp to both. Be aware that I haven't seen this in writing from mfgr's, just word of mouth.

 

[Soundguy]

I'm not so sure that the 1000rpm pto speed cutter rotates twice as fast as the 540? I think it may refer to the cutter being used on a 1000rpm pto rather than one used on a 540rpm pto? Maybe I'm wrong on this???
In other words, the gear box is different in the cutters, for they (the cutters) may spin at the same speed. One just takes more pto rpm to get it to that speed. Now, if that were the case, then the 1000 pto cutter would have more power because it's geared lower than the 540. What do you think?

I agree.. I believe the input side of the gearbox is what is different on the 1000rpm pto .. that is.. they both probably have similar output shaft speeds.. etc.

Soundguy

 

[3RRL]

I agree.. I believe the input side of the gearbox is what is different on the 1000rpm pto .. that is.. they both probably have similar output shaft speeds.. etc.

Soundguy

Right, thank you...that is what I was trying to get at. However, I still really don't know because my first post was just guessing that may be the case.

 

[Soundguy]

I have a JD 1517 batwing, however the manual from JD covers the 1517, 1518, and 2018.. Mine is a 540 input, but the manual covers the 1000 input version as well. Blade tip speeds on the output are listed as the same for all 3 models regardless of input shaft speed... so that leads me to believe, that it is input gearing only that is changed. I guess of course that each manufacturer could be different.. etc.

Soundguy