Horsepower: What is it?

Just the other day a customer was asking about the horsepower rating of a particular shaft. I answered, "About 100 at 540 RPM."

He said, "But we're using a 1000 PTO with a 350HP tractor."

Unfortunately, this is becoming more and more the case. Infinite horsepower on the supply side, a demanding implement, and not enough PTO driveline.

The fact is, we are fast approaching the mechanical limit of power transmission via a universal joint driveline. And no one wants to pay thousands of dollars for a super sized, custom made PTO shaft. Believe me, we can build it.

Today, however, all too many implements require over 100 horsepower at 540 RPM or 200HP @ 1000 RPM. And there are very few, very expensive shafts that can do the job and last any length of time. So manufacturers are using the biggest shaft they can get for the most reasonable price they can pay and most of the time, undersizing the actual requirement.

It's been going on for years, but today it is far more prevalent in a far higher torque range. The result is a PTO shaft that needs replaced much sooner than anticipated.

The fact that power sources are increasing with every model makes torque protection devices more and more necessary. More expensive also, so we recommend servicing all of the PTO components according to the manufacturers' instructions.

Remember, a 100HP driveline will transmit 180HP. It just won't last. All torque ratings are based on life, not where they will actually break. Remember too, the higher the RPM, the more horsepower that can be transmitted.

Horsepower is not torque. It is a function of torque!

We use the following formula: Horsepower = foot pounds of torque / 5252 x RPM.

We are not engineers. As any engineer will tell you, torque is a complex function beginning with "What is the source of the torque?" Is it a gas powered engine? Is it diesel? Wind power? What is the angle? The driveline length? What is the resistance? Continuous or intermittent? On and on we could go which is why engineers go to school. All I am sure of is that no two engineers ever gave me the same answer for the same question. We are just practical people who work hard selling the best products we can find to sell.

"CAT" or "Catagory" is suppose to represent a standard torque requirement. But our research indicates this measurement to be misused and misapplied by many manufacturers.

As near as we can tell, at 540 RPM:

THE MOST IMPORTANT FACT IS "HOW MUCH TORQUE DOES YOUR IMPLEMENT NEED TO RUN EFFICIENTLY ?"

Other things will come into play. Do you require a clutch or other type of device? Do you need a constant velocity joint on either the tractor or implement side ? Do you use a three point, or hitch? And finally, what is the purpose of the implement?

With the correct information, we have fit thousands of applications correctly. In many cases, we have improved upon the original equipment's design in order to increase life expectancy or improve performance.