PTO h.p. vs. DRAWBAR h.p.?

It is kind of a "personal" thing as to what you are going to use the machine for and where.

My plowing wouldn't be the same as Hugh's nor would my discing be the same as the other Paul's requirements. Further, a tractor pulling a tub grinding grass hay will see a difference grinding alfalfa hay.

So at the end of the sales pitch, if a guy looks at the weight of the animal to determine how "beefy" it is overall, then go for the drawbar horsepower for one's own needs.

Since PTO horsepower is almost always higher, heck, why even worry about it? It is either there or it isn't. A feller about has to hook up to his own equipment to determine if any given "horsepower" is gonna work for him.

Just the way I see it,

Allan

Two tractors that stand out on my farm were Farmalls 560 diesel and 656 diesel Both with the 282 diesel, truly the most efficient HP I ever owned. You probably already know I also farmed with a 300 and a 1066, but neither measure up to the old 282's when it comes to efficiency and longeviety. I think Nebraska told us that in advance.

Also, with PTO's you don't have to factor in tire slippage on how much useful work you are getting for your buck.

Mark

That would be 11 horsepower. Naw, just kiddin'. :>)

It is just how tractors are rated for size and power.

I always ignore the PTO rating 'cause it is kind of a pig in a poke. I like to look at the tractor's weight and it's actual drawbar horsepower.

Allan

Afterall it was guys on your home turf that brought about official compareable testing.

The tranny has more gears, bearings, etc. which cause loss of efficiency, so the tractor delivers 50 hp to the rubber.

Many times the pto rating is the 'universal' number that is used, because that one is easier to measure.

Your engine will probably be rated around 70 hp??? Again, that would be at the shaft sitcking out of the engine, no losses through the pto gearing....

--->Paul

A dyno, I believe, measures maximum torque at various RPM. RPM gives you time so HP is caclulated from the torque curve.

Remember HP is WORK, move something over a distance in a certain amount of time. Double the horsepower and you cut the time in half.

One horsepower is 33,000 lb-ft per minute, for those who are interested. So lifting a 33,000 lb weight two feet in one minute would develop two horsepower or lifting it one foot in half a minute would also be two horsepower.

That's not exactly right, but maybe gives you a visual idea.

Hp is the work done (water applied), while torque is a rating of how much potential work might be there (pressure) but doesn't really mean anything was accomplished yet.

--->Paul

Torque is then easily calculated: Torque = the force measured by the scales (in lb) x the length of the lever arm (in feet).

Now to determine horsepower you must know the torque and ALSO engine speed. Horsepower is then calculated by the equation HP = Torque x RPM / 5,250.

Modern dyno's will take the above measurements, do the calculations and display HP directly.

That's my point. I've got a little lawn tractor that is rated at 22 horsepower. I know darned well, if I hooked it to the H, it would not tow that old beast 2 inches.

End game is that it is all a bunch of smoke and mirrors and a feller has to use his gut instict more than the given "horsepower ratings" to determine his needs.

I'm ready to come after that tractor of yours, by the way. :>)

Allan

--->Paul

H.P. is mathmetically determined once the torque/rpm has been determined.

Joe

Joe

It has to do with figuring the exact moment the engine stalls & fries, and figuring that as the max hp from the motor.....

--->Paul

That one irritates me just a little.

Anyone who has ever seen a 5hp electric motor knows that there is some serious fabrication going on in those ads. :>)

Allan

• Cat vs Mustang

Testing your memory but a long time ago tractors were rated by the number of plows they could pull. If you had a 2-3 plow tractor you best go with the 2bottom plow.

Would your H pull 3-14,s at 3.5mph. Now your 966 should pull 5-16"s on the fast hitch, right?

My 706 ger.would pull 4-16"s at 4.5mph. and a 14" swather in heavy alfalfa at 5mph.

steveormary

Dad would pull 3-16 with an Ollie 88, but for alfalfa would have to chain & tire the H on in front as well. The 300 would pull the 2-16. Could not pull a 3 bottom of any size with an H. I know the experts _say_ a 3-14 pulls easier than a 2-16, but theory & heavy clay reality were at odds on that. :)

I remember growing up, always puzzled at those plow ratings, as they never made a darn lick of sense. Seemed as foolish as the '5 hp air compressor motor' I mentioned elsewhere - nothing close to reality. :)

--->Paul

PTO Hp - power delivered out the PTO simple huh?

Drawbar HP - Power delivered out the drawbar, simple too eh?

Drawbar hp is all about drawbar pull, how many pounds you can move and how fast it goes. The shuttle transporter would have huge drawbar pull but it doesn't move fast so the drawbar power is low.

A lawnmower doesn't have enough weight to get any drawbar pull so it can't make much drawbar power.

A high PTO hp/ Low drawbar hp tractor can be ballasted up to increase the drawbar hp.

Re the comments on new cars with high hp numbers and such, if you drive an auto with 4 or 5 speeds, it doesn't matter what the torque is, you're driving the engines hp peak.

If you have a manual or a 3 spd auto, you can feel the flat torque curve of an older engine.