PTO HP

[MHarryE]

Hydraulic power P=gpm x psi / 1714 at 100% efficiency

First assume 85% efficiency

Try 2,000 psi for an example. At 85% efficiency, it’s 27 HP.

If you search the Internet enough you often can find the power curves for the engine in your tractor. I have found the curves for Kubota and John Deere engines as they are also sold commercially and the engineers need that information for their design work. All the CUT engines I have found start to drop power right from max speed. Large ag tractors are different. I randomly selected a JD 8235. In its Nebraska test it put out 206 HP at rated 2100 rpm and 235 HP when pulled down to 1751, the tests maximum observed power. JD CUT 4320 measured 42 HP at rated engine speed and dropped to 37 HP at peak torque 1600 rpm.

So it’s wrong to say that tractors have higher power at lower engine speeds. Large tractors do, small tractors don’t. That’s kind of a general statement - there may be some outliers.

540 became a standard in the early 1900s because of some common implement working best at that input speed - I can’t remember the specifics. But once it became standard that was it. Trying to change would cost interchangeability. But drive lines became too costly as power went up so the 1000 rpm standard came into being. Most larger ag implements use 1,000 rpm. They use a different spline to prevent mixing things up. The PTO driveline on the chopper I run for my nephew has a decal stating max power 90 when used on 540 PTO, 120 when used on 1,000 PTO.

 

[Kingston61]

Hey everyone - rather than reply to each I'll blanket with a huge thanks for the input. It all makes good sense. So 540 is the optimum and there is a mark on my tach for that and historically I adhere to it. It sounds from you all that I may get better performance/power from some implements if needed by going over but there could be risk. I understand the 1000RPM standard now as well adnd do not think I'll be using any of those implements in my near future so won't worry about that.

So in my own scenario I think -
Brush Cutter 540 seems to be optimum
Wood Chipper, might experiment with a little more power to see if helps if/as needed
New PTO hydraulic pump for the front rotary cutter says do not go over 540RPM and guessing that is to keep the hydraulic flow and pressure at the optimum range to prevent overheating the pump or having excess pressure

There were not any comments about running to many RPMs for the tractor motor itself but I kinda figured for driving on a smooth surface trying to maximize the speed it is okay to open the throttle as far as it will go.

Again, thanks for the great insight!!!

Steve from Kingston61