HST/ PTO SPEED

[First one]

If your tractor is rated at 32hp (HST) and 25 hp at the pto is that all the time, even if the tractor is sitting still using ,like a winch? or is it diff. like running a mower with the tractor moving? By moving in the tractor does that change the pto hp or by keeping it at 540 gives you the 25hp?:confused2:
thanks Scott

 

[johnrex62]

Someone on here will be able to give a more precise and technical answer, but my understanding is that HP is a function of RPM. When you operate your engine at a reduced RPM level you will see a corresponding reduction of available HP. As long as the engine is running at the required RPM, it does not matter if it is stationary or in motion.

I do not know if the rated HP of the tractor is at 100% RPM or at the PTO 540 level. I do believe it should be very close at that point if not fully at the rated HP. I do think that the rated PTO HP is when the engine is operating at the PTO 540 RPM.

 

[JDGreenGrass]

I think with a hydro transmission the pto is independent.??

So, I think your pto will always be rated 25pto hp, though don't take my word for it.

Man, I wish I had 25ptohp. I got 20ptohp.

 

[TripleR]

Any maximum HP is given at a set engine RPM, this should be in your specs. No engine has a flat power curve or none that I know of.

HP/PTOHP does not change between stationary and underway, but "available" HP will as some is being used by your transmission.

 

[J_J]

Any maximum HP is given at a set engine RPM, this should be in your specs. No engine has a flat power curve or none that I know of.

HP/PTOHP does not change between stationary and underway, but "available" HP will as some is being used by your transmission.

Just to be a little more clear, the PTO HP will vary from 1 HP to the rated PTO HP, based on engine rpm. I have seen people run their bush hog at half throttle, and they can cut some things well, but when things get rough and tough, they have to use full engine rpm, and therefore max available engine HP. Some PTO's also run at different rpm's for certain attachments.

 

[rjkobbeman]

I think the OP was wanting to know if the PTO HP would change base on the engine running multiple things. For example, if the tractor is not moving ALL of the engine HP is being fed to the PTO... whereas if the tractor is moving, the engine HP is being fed to both the PTO and the tractor's drivetrain.

My GUESS would be that the PTO HP would vary based on what I said above. RPM obviously varies the HP output... but I would think the multi-tasking of the engine would also affect how much power is routed to the PTO.

 

[dfkrug]

RPM obviously varies the HP output... but I would think the multi-tasking of the engine would also affect how much power is routed to the PTO.

That is correct.

Your engine can only put out a certain amount of power, and do only
a certain amount of work.

If an engine can put out 32hp at the crank, it has to work to turn all those
mechanical and hydraulic bits before it can turn the PTO. If you are
asking the engine to turn the wheels, too, that takes more power. And,
an HST tractor is always pumping oil thru the charge pump whether the
tranny is turning or not.

Bottom line is if you are driving along at full RPM and driving up a hill
that takes 15hp, your PTO will have only something like 10hp available to
mow that grassy slope.

 

[beppington]

Only a guess:

The stated PTO HP figure must be a max figure, otherwise, taken to an extreme, owners could damage their implement(s) not rated for an occassionally higher HP figure, possibly hurting themselves, & opening the tractor manufacturer up to potential lawsuits.

I suspect OP's 25 PTO HP is a best-case scenario, i.e. true only when nothing else is drawing power from the engine (& of course when the engine is running at its highest output RPM). :2cents:

 

[J_J]

Here is a 2003 PDF, listing of PTO HP ratings.

http://docs.google.com/viewer?a=v&q...kOSp-9&sig=AHIEtbR84HulWyq9etgIkwzHl2xZsX1ugQ

The standard tractor will have more PTO HP than a hydrostatic tractor.

I don't believe the drive train is figured in the ratings.

Reg this:

http://www.ext.colostate.edu/pubs/farmmgt/05007.html

 

[Redgoatea]

The standard tractor will have more PTO HP than a hydrostatic tractor.

I don't believe the drive train is figured in the ratings.

Reg this:

]

I was wondering where all his HP was going 32 - 25 seems like a big loss to me. I go from 28 - 25. But I have gears. 7