Horsepower question

Folks I have a 1964 Ford 2000 tractor. It has a 4 cylinder gas engine w/4 speed transmission. I keep reading how certain implements such as mowers are directly related to the horsepower of the tractor. My question is the horsepower based on the PTO, the claimed drawbar, or actual engine horsepower?
 
Well that's just it. When looking at Tractor Supply or Agri Supply at their rotary mowers the list a HP range (ex 25-45 HP at 540 RPM)? Is that PTO HP or the actual engine HP rating?
 
I'm seeing more engine h.p. ratings lately, but for
many years pto h.p. was th ge most commonly used
figure. I think a pto rating makes more sense, as it's
more easily measured (many dealers have a pto
dyno), and it's a rating of useable power... only a
percentage of engine h.p. is actually available for
use.
If a pto driven implement requires xx h.p., you can
safely go by your tractor's pto rating.
 
I would consider that PTO HP, it seems PTO runs just a little below engine HP, wth drawbar HP bringing up the rear.

It is all about losses and traction.
 
(quoted from post at 17:56:35 06/13/17) Well that's just it. When looking at Tractor Supply or Agri Supply at their rotary mowers the list a HP range (ex 25-45 HP at 540 RPM)? Is that PTO HP or the actual engine HP rating?

I believe they intend to say the mower requires 25 - 45 HP available at the PTO, at an RPM of 540.

My 8N engine needs to run at 1500 RPM for a PTO speed of 540. So, I look in the operators manual to find a HP rating at an engine speed of 1500 RPM. It lists a rated belt HP of 23.22 however, that is at 1700 RPM. Belt HP is pretty much PTO HP for an 8N however, slowing the engine to 1500 RPM means it will fall far short of the 25 HP minimum.

Typically PTO HP ratings are given. If you only have engine HP as measured at the engine crankshaft - then subtract 10% from the rating to account for gear train loss. Regardless the HP has to at an engine RPM corresponding to a PTO RPM of 540.
 
I would agree, PTO HP difference is basically frictional loss on the gears from the engine, so 10% is probably good estimate of the loss.
 
Manufacturers of PTO powered implements generally list their hp requirements as PTO hp. Wouldn't make much sense to do otherwise. Even though most tractors in any given hp range are close in the amount of hp drop from engine to PTO, they all vary slightly. It would be foolish for an implement manufacturer to spec engine hp as there may be some off brand of tractor that has a very large drop from engine to PTO, and then the implement manufacturer would be stuck trying to support their implement on an under powered PTO.
 
Engine HP ratings in ads sells product. Driving HP does the work be it ground power or PTO. Implements are rated in driving hp
requirements. I'll 2nd or 3rd the 10% off engine HP for a SWAG on implement drive capability. I have a 4 cyl 2000 4 sp, tranny PTO. I don't
expect much out of it. My 3000 with 10 more hp, Live PTO and 8 speed is 2x the tractor and 10x the usability.
 

engine hp has NO water pump, NO power steering pump, NO generator or alternator, No transmission input shaft, No hydraulic pump on it.. So yes, its a lot higher, but pretty much useless for seeing what the tractor will really do.And yes, new tractors are sold by engine hp.


PTO hp is actually measured and REAL!!!!!

Drawbar hp is actually measured and REAL!!!!!
 
I don't know for sure, but why would the mower manufacturer
list the HP @ RPM if they didn't mean PTO HP?
 
"engine hp has NO water pump, NO power steering pump, NO generator or alternator, No transmission input shaft, No hydraulic pump on
it..".............old Motors Auto Repair Manual referred to that as "Brake" hp; nothing but what it takes to roll the crankshaft. BS small engines
are rated that way too and tell you so.
 
Move that to 15% and you are closer to the PTO HP that the 10% is and that 15% might still be low. Some sales lit will give both the bare engine HP and the PTO HP
 
I have a few pieces of literature that list both engine and pto h.p., so I figured I'd see what the % drop is from bare engine to pto ratings. My 1968 catalog lists bare engine, net flywheel, pto, and drawbar h.p.
The percent drop varies between models, but averages 18%. This was for the 2000 through 5000, with 8-speeds (except the 2000, which is listed as 4-speed only). Losses on the Select-O-Speed models are greater.
I guess this might partly explain a couple of ads I've seen lately - one for a 3000 diesel, the other for a 861. Someone asked the h.p. of the 3000. Someone replied 47 h.p. (bare engine is listed as 46 for the diesel) The seller replied that is was 60 h.p. I didn't see any comments about the h.p. of the 861, but the seller had it listed as 62.5. That would be almost 24% higher than the Nebraska Test pto rating.
 
One has to assume that is the referral as the mower mfgr. is only interested in what is applied to the input shaft; he knows not as to what it took to get that what/which is used to
turn the input shaft to turn the load.
 
I agree. I also assume that is the way they rate the gear box max HP.
Then again, I am assuming. I have no documentation to prove it.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top