PTO speeds

[rambler]

To answer the 'big tractor' questions: It becomes physiclly difficult to transmit more than 75-125 hp through an 1 3/8" shaft spinning at 540rpm. The iron wants to snap off (Case got up to the higher hp by using some very expensive rare-earth metals in their 540 shafts). So the 1000rpm pto with 21 splines became the standard for higher hp requirements.

On a lower hp tractor, if you've never had 1000 rpm, you won't miss it & I wouldn't let it stop me from buying a machine I liked.

As mentioned, some brand-specific implements are designed to use the special pto speeds available on those brands; and it can be useful or dangerous to use a 540 rpm machine on an idled back 1000rpm tractor. But if your implement is sized to your tractor, it will need most of the hp anyhow, so you'll need about full power in the first place.

--->Paul

 

[ZJ_HR]

Paul,
Sorry for misunderstanding. I was talking about tractors up to 50-80 HP. You're right, when power requirement is high, then is no question which speed range you need.
BTW, 21-splines PTO shaft I didn't ever see on tractor here, even on big (120-150HP engine) tractors.

I just want to say that 540E(750) is excellent choice for many uses, where 10% less power output is not a big loss.
MF 35, for example, has only 720 rpm speed, I mean no real 540, because it runs 540 at about 1700 rpm engine.

ZJ

 

[keeney]

Turns out that the Mid/Front PTO on my 4100 is 2100 RPM's. Since the tractor is only 18 Hp or something, I am pretty sure the higher RPM speed is not for high power output.

It must be because its easier and/or cheaper either in building the Mid PTO, or it makes the mower deck and/or front snow blower cheaper or easier to build somehow with less gearing-up or something.

Maybe its to be compatible with the 400 series garden tractors that share the same mid and front attachments?

- Rick

 

[rambler]

A faster spinning shaft can be smaller/ lighter, and use smaller gears to drive it to transmit the same hp. Most mid pto's run faster, your 2100rpm problably is _very_ close to the engine rpm..... Should be cheaper to make.

540 became an industry standard for rear pto under 65hp, & 1000rpm for over 100hp. Any other rotating shafts are up to the manufaturer. /forums/images/graemlins/wink.gif

--->Paul