PTO Speed

[8ntruck 7,256]

My mind wanders on the daily walk with the dog.  Today, I got to wondering about how 540 rpm got picked as an industry standard?

 

Anybody out there know that story?

[WHX?? 49,941]

Limited to power output of equipment at the time???

[c-series don 9,266]

I do not know the answer to this and never really gave it much thought, but now I too want to know!! 

[wh500special 2,247]

My assumption is that the speed just  followed IH’s defacto standard of their equipment.   They were first to market a rear PTO shaft and were the biggest tractor manufacturer that offered shafts in the 20’s and 30’s so I assume the market just followed them with their matched equipment.  
 

I’m not patient enough to go model by model to verify, but I suspect if i

looked up the specs for their early tractors (8-16, 10-20, 22-36, Regular, etc) that we’d see them all hovering in the same 540 neighborhood.  The only outlier I can think of is the Cub which ran faster and backwards compared to the standard…of course it came around much later though. 
 

Definitely an odd speed. 
 

Steve

Edited November 12, 2024 by wh500special

[ri702bill 8,761]

The 540 RPM speed is rather slow - 9 revolutions per second. Probably kept on the low side to keep vibration issues to a minimum.... 

[peter lena 8,976]

@8ntruck  from what I regularly see / hear ,due to COMBINED ROTATIONAL DRAG , just amazing to me to wonder why nobody sees the relation  to deck speed . first  problem track , how about rusty / binding  PTO LEVER ENGAGEMENT , SQUEALING CLUTCH ??????, attempting to move lubrication failed pulleys ?? , BTW , my outer pully cone , does not have the brake pad / bracket on it , spins easily in total silence .not had a bearing fail or related noise , since RE GREASING  all my rotational movement points . make a change , pete 

[WHX?? 49,941]

I had guessed we are primarily talking about rear PTOs on bigger tractors? 

Then another guess Steve mentioned. An OEM came out with a PTO (IH)? that was matched to what they offered at the time. Brush hog or stalk chopper cones to mind. Other OEMs designed  speeds & implements to suit. Again this is all blind outhouse guessing on my part but 702 Bill might be on to something??

 

You keep walking the dog Truck we might come up with answers to the origins of the universe ... 

[WHX?? 49,941]

2 hours ago, wh500special said:

only outlier I can think of is the Cub which ran faster and backwards compared to the standard…of cou

So one would have to buy their implements? 

[8ntruck 7,256]

@WHX?? - we already know the answer to life, the universe, and everything - it is 42.

 

And, yes, I am talking about full size reactor PTO speed.

Edited November 12, 2024 by 8ntruck

[wh500special 2,247]

5 hours ago, WHX?? said:

So one would have to buy their implements? 

Possibly.  

Might have also been to prevent hooking cub implements to bigger tractors which might destroy them or to deal with some kind of space constraint in the little transmission.  

[wh500special 2,247]

4 hours ago, 8ntruck said:

@WHX?? - we already know the answer to life, the universe, and everything - it is 42.

 

Sounds like you must have some kind of guide book…

 

Steve

Edited November 12, 2024 by wh500special

[8ntruck 7,256]

4 hours ago, wh500special said:

Sounds like you must have some kind of guide book…

 

Steve

Yes, I do.

[wh500special 2,247]

On 11/12/2024 at 6:41 AM, ri702bill said:

The 540 RPM speed is rather slow - 9 revolutions per second. Probably kept on the low side to keep vibration issues to a minimum.... 

 

Everything on those old tractors was slow and steady.  I would guess it was the practical limitations and precision of the time, marginal lubricants, etc.  And the power transmitted was pretty low too so the torque was manageable so there was little need to go faster.  Most likely, the 540 rpm was approximately some

convenient gear ratio off of rated engine speed that just happened to work out. 
 

As tractors got more powerful (in the 1960s especially) the PTO speeds increased to 1000 rpm on larger tractors in what I suspect was an effort to keep the PTO shaft size reasonable.  Doubling the speed for a given power cuts the torque by  half.  
 

I think the big innovation came with the live PTO shaft which premiered on the 🇨🇦 Cockshutt 30.  That must have been a game changer. 
 

Steve

[Lee1977 6,923]

It was for speed reduction most PTO equipment runs a lot slower. Even a 5' bush hog proable needs more gear reduction to keep the blade tip down to the right tip speed. 

thoes old wood finish mowers ran the PTO back to a 16" or so belt pulley to speed up the short blades.