Is PTO HP dependent on tractor ground speed?

   / Is PTO HP dependent on tractor ground speed? #1  

MARKMILES77

Member
Joined
Oct 29, 2010
Messages
39
Location
Australia
Tractor
Yanmar EA 2400
Quick question for the wise.
When a manufacturer lists PTO HP is that with the tractor stationary?
Presumably the faster you drive a tractor or if you drive it up hill, more HP will be used to move the tractor and less will be available at the PTO? Is that correct thinking?

Thanks

Mark
 
   / Is PTO HP dependent on tractor ground speed? #2  
PTO HP is based on engine rpm. I would assume the HP rating is taken at whatever engine rpm is needed to achieve 540 PTO rpm. Basically, it doesn't matter how fast you are going, at a certain rpm you have a certain amount of horsepower.

I hope that makes some sense. Somebody will explain better than I can.
 
   / Is PTO HP dependent on tractor ground speed? #3  
Quick question for the wise.
When a manufacturer lists PTO HP is that with the tractor stationary?
Presumably the faster you drive a tractor or if you drive it up hill, more HP will be used to move the tractor and less will be available at the PTO? Is that correct thinking?

Thanks

Mark

That is correct.
 
   / Is PTO HP dependent on tractor ground speed? #4  
I would think ground speed would make a difference. The engine has a given HP and some is used to propel the tractor, the rest is available for the PTO. Think of it this way: If the tractor were straining to go up a hill at high speed and needed a lot more HP to do it, that would reduce the hp available for the PTO.

The sum of the PTO load and tractor load can't exceed the HP of the engine.
 
   / Is PTO HP dependent on tractor ground speed? #5  
All of the above are very correct answers. What size of HP vs tractor are we pondering the issue on. Masseys had a rpm vs gear range engine tachometer. The smaller tractors only have a engine tachometer.
Craig Clayton
 
   / Is PTO HP dependent on tractor ground speed? #6  
The sum of the PTO load and tractor load can't exceed the HP of the engine.

What if you are going DOWN that steep hill:D
 
   / Is PTO HP dependent on tractor ground speed? #7  
Depending on how the tractor is designed you may achieve PTO speed at less than full engine RPM.

Example: 1966 Ford 5000 and 1978 Ford 5600 both had a PTO speed of 1900 RPM and rated around 58 - 60 HP if I remember correctly. Full throttle was 2600 RPM.

Put the 5000 on the dyno once and it was turning around 700 RPM PTO speed and developed 86 HP at full throttle. This was with an aftermarket turbo installed. I do not remember what the HP was at rated PTO speed.

Roy
 
   / Is PTO HP dependent on tractor ground speed? #8  
However, many newer ag tractors will give a boost to engine hp when the pto is engaged. Most will give about a 10% boost. If the engine rpm begins to fall while the pto is engaged, the boost will get the tractor up the hill, though the tough spot ect. It also works with the tractor in the higher road gears. Go up a hill pulling and implement and get up to a 10% boost. This is becoming very common on tractors with over 100 hp. All done by the ECM.
 
   / Is PTO HP dependent on tractor ground speed? #9  
I would think ground speed would make a difference. The engine has a given HP and some is used to propel the tractor, the rest is available for the PTO. Think of it this way: If the tractor were straining to go up a hill at high speed and needed a lot more HP to do it, that would reduce the hp available for the PTO.

The sum of the PTO load and tractor load can't exceed the HP of the engine.

X2. If I'm using 20 HP to climb a hill on my 42HP tractor, I don't magically have another 42HP for the PTO, regardless of engine speed. anybody who's bush-hoggged thick grass up a hill is familiar with this.
 
   / Is PTO HP dependent on tractor ground speed? #10  
Reading the responses I would have to agree. The HP is at 540RPM while stationary for most tractors. The bushhogging thick grass made me grin. Good point!
 
 
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