PTO horsepower

[VroomVroom]

You will never increase your HP through gearing. The engine, combusting a specific fuel will provide "X" amount of Horsepower. How that horsepower is used or geared will change the torque values for you. The lower HP rating at the PTO is through efficiency loss. The only thing you can multiply in this case would be the torque. 540 is a lot slower in revolutions then say 2400 engine RPM. So comparing the torque at the crank and at the PTO shaft you will see the difference.

Basically, you got what the engine is going to give you and that's it. From there, its up to how its transmitted to the PTO how much you may have left after parasitic losses. How its geared along the way will dictate how much torque you have back there.

 

[ruffdog]

Torque is the twisting force. HP is a measure of the work that can be done. You can have all the torque in the world but if it is only turning 1 rpm, not much "work" is getting done. If you had the same amount of torque but at 5000 rpm, now you can get much more work done. That means more HP.

 

[Texasmark]

".......Any other system of gears or pulleys that goes thru an approximate 4 to 1 reduction will increase useable power by a factor of 4." Say what?


Power is the consumption of energy, referred to as "work". HP is [torque (in ft-lbs) x RPMS]/5252 for a simplistic equation usually relating to engines and gear trains.

What happens in a tractor is the engine HP "being applied" is transmitted to the drive train via a geared system of shafts. The ratio of the gears between the source and load determines the speed and torque of the final drive, not necessarily 4 and at the same HP less losses in the system.

The gears change the RPMS of the applied HP and in doing so change the torque; usually at a higher ratio which reduces the RPMS of the power while multiplying the torque which is necessary for moving heavy loads. The losses are in the transfer mechanisms due to friction.

The transferred HP is still what it was, it just went different places and changed characteristics!

 

[Opti-Mist]

You will never increase your HP through gearing. The engine, combusting a specific fuel will provide "X" amount of Horsepower. How that horsepower is used or geared will change the torque values for you. The lower HP rating at the PTO is through efficiency loss. The only thing you can multiply in this case would be the torque. 540 is a lot slower in revolutions then say 2400 engine RPM. So comparing the torque at the crank and at the PTO shaft you will see the difference.

Basically, you got what the engine is going to give you and that's it. From there, its up to how its transmitted to the PTO how much you may have left after parasitic losses. How its geared along the way will dictate how much torque you have back there.

Parasitic losses, mostly due to friction associated with the numerous mating surfaces involved in the transfer of power. A 12% loss between engine and PTO is about what one can expect.

 

[CincyFlyer]

A question. Why is PTO horsepower alway rated less than engine horsepower? Any other system of gears or pulleys that goes thru an approximate 4 to 1 reduction will increase useable power by a factor of 4.

Example: My Kubota M6040 is rated at 62 engine HP and 55 pto HP. My engine turns approximately 2000 rpm when the pto is turning roughly 540 rpm. Almost a 4 to 1 reduction - yet, rather than the pto being rated at around 240 hp - its rated at 55 hp.

Why?

Power is force times speed. If you get 1/4 the speed, you get 4 times the force (usually in the form of twisting motion, torque), so the math always comes out to be the same horsepower.
Or else we'd all have tiny little electric motors in our cars, geared up to make a thousand horsepower.

 

[oosik]

Sincerely - thanks to all who posted so far. I think I have a better idea of the answer to my question. I've wondered about that situation for a long time.