Gearing down a PTO shaft

[gdh]

A bit of background first. We've got a new firewood processor that requires 40hp and we run it off our old Massey 35x. That tractor is 40hp on the PTO shaft but as they say on top gear 'I think a couple of horses have escaped over the years'. It runs it fine but you can hear it struggling when you split a big log 12 ways and use the chainsaw simultaneously.

 

The tractor only runs the machine at 420-430rpm so I wondered if I put a cog on the tractor PTO and an 80% smaller (ish) cog on the processor and ran a chain round them then ran the tractor at 540 (ish) would that give me more power? Or am I missing something really stupid?

 

To be honest I don't need to do this now I'm used to the machine but I'm curious if it would work.

[Tom D]

Its possible but you still only have 40 horses, the machine will run slower and you will be screaming the tractor.

 

Get a bigger tractor.

[cornish wood burner]

A bit of background first. We've got a new firewood processor that requires 40hp and we run it off our old Massey 35x. That tractor is 40hp on the PTO shaft but as they say on top gear 'I think a couple of horses have escaped over the years'. It runs it fine but you can hear it struggling when you split a big log 12 ways and use the chainsaw simultaneously.

 

The tractor only runs the machine at 420-430rpm so I wondered if I put a cog on the tractor PTO and an 80% smaller (ish) cog on the processor and ran a chain round them then ran the tractor at 540 (ish) would that give me more power? Or am I missing something really stupid?

 

To be honest I don't need to do this now I'm used to the machine but I'm curious if it would work.

That would make things worse. Other way around to increase torque. Still only same power and only Shetlands in the 35 anyway.

[IVECOKID]

Low speed high torque

 

High speed low torque

 

Better Tractor working under load than ticking over without load , glazed bores are prone .

 

Ste

[gdh]

Oops I put the cogs the wrong way around in my original post, I should have said small to big so I run the tractor at higher revs and the machine at the same speed as now.

[Logged On]

I'd leave it as is.

 

Our processor is hooked onto a 210hp Case tractor.

 

It's only ran at 420rpm, (through the 1000 pto gearbox so the tractor's just above tickover), so you hear the pump and tractor tone change when it's under load.

 

I'd rather have that, than it going at the full 540, so when it gets loaded the tractor doesn't 'give in' and keep banging out full power at 540rpm and damaging / wearing out something early...

[gdh]

I'd leave it as is.

 

Our processor is hooked onto a 210hp Case tractor.

 

It's only ran at 420rpm, (through the 1000 pto gearbox so the tractor's just above tickover), so you hear the pump and tractor tone change when it's under load.

 

I'd rather have that, than it going at the full 540, so when it gets loaded the tractor doesn't 'give in' and keep banging out full power at 540rpm and damaging / wearing out something early...

I know what you mean, it's nice to hear the revs drop to tell the strain on the machine. I'm not planning to do anything, the 35 has done 50 years here so it deserves to take it easy. I was just wondering if my theory was right.

 

Interesting that you say about your tractor, I've been meaning to run our deutz 180 on 1000 economy and see how much fuel it uses compared to the massey.

[cornish wood burner]

To answer your question your theory was right assuming you gear down your processor. If max engine power is achieved at or near 540 pto speed running closer to that you should see an advantage.

From memory isn't max power of the 35x just above 540 pto speed, if it is you should squeeze a bit more from the old girl.

Edited February 29, 2016 by cornish wood burner

[Ilnumero]

You say the tractor runs the machine at 420rpm, is that whilst at rest or under full load?

 

Is the tractor capable of higher revs, or is that all it will manage?

 

You should run it at 540 obviously, as all implements are designed to run at this speed, and it's a lot healthier for the tractor to run with a good load on it.

 

I have several vintage tractors and they always feel more responsive and start better after a good day's hard work. It's not good to have them ticking over all day. They like a good workout.

[gdh]

It runs the machine at 420-30 at rest, that's about 2 thirds revs on the tractor. The machine is rated to be used between 400 and 430rpm, any more could overheat the hydraulic motors (and presumably run the chainsaw much too fast).

 

I'm wondering if gearing it down 80% so I can run the tractor on higher revs would increase the power going through the pto from 40 to 48hp or if it would make no difference between the torque would be the same.