Horsepower, torque, rpm's and pulling

Pulling is limited to 4 mph by most clubs, at least in the antique and classic divisions--so speed comes into play only to maintain movement. Torque, which translates into power at the rear wheels, would then determine how long you keep the wheels spinning.

Tractors seldom power out, but normally stop by a loss of traction. So, at 1,200 rpm's would I get just as far as I would at 1,740 rpm's?

Thanks to all for the posts. This has been a topic of discussion with my friends for some time; and all the input that I can find is helping me to understand the dynamics of tractor pulling. Dynamic loading of tractors has some interesting points; which may border on more art than science. Thanks again.

The reason why a tractor might pull a plow or weight at a slower speed than a faster one is that the power required is less....not that somehow "torque" does the work at low speeds and horsepower does it at high speeds. For example, say it takes 20 hp to pull a plow at 8 mph. Then it will take only 10 hp to pull it at 4 mph.

So the advice to run the engine at an engine speed which gives maximum horsepower and select the gear which gives the right speed is exactly correct.

As you know, you want max torque & HP, which boils down to the lowest gear, and highest RPM possible and still stay below 4 MPH. I negelected to do my homework on this last night, and don't have the necessary info here now. I believe the owners manual has the gear ratios in there, and maybe even the max. ground speed per gear. With a little number crunching, you can calculate the best gear to stay below 4 MPH and nearly full RPMS. From reading a few posts in the archives, I have concluded that the best gearing for pulling is achieved by using a Sherman or Hupp aux. tranny, but that is not essential, as it appears that most tractors in the lighter classes lose traction before the engine gives out.

I noticed right away that my local club has NO Fords or Fergys that pull... ever, which is disappointing. Upon investigating the rules, I think I know why. My local club classes tractors by weight, the lightest class is <4000#. SO a Fergy would be pulling against Farmall M's, JD's, MMs, and several other tractors that weigh A LOT more, with bigger tires. The Fergy was made light intentionally, and was built to rely on downpressure from the draft of a plow to provide extra traction... don't have that downpressure when pulling. The heavier tractors will out-traction a Fergy every time. I can't imagine adding 1500#'s of weight to my Fergy to get it up to the weight of those Super M's. I wish the local club had a N/Fergy class... if they did, I would have been pulling by now!

Don't know if that helps or not...
George