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 | Nellie
Join Date: Posts: 1 
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2002-05-04 38147
Someone responded to another post and indicated the B-2910 HST is only 22 HP. This raises the question as to how to rate a tractor. I know that the PTO HP is 22, but does this mean the wheel HP is also 22?
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2002-05-05 38156
Wheel, or drawbar HP which is another term used, differs from PTO HP. Drawbar HP depends in part on traction, which in turn depends in tire type, weight, ballast etc. that can differ a lot on particular tractor configurations. There undoubtedly is a standard definition for drawbar HP, but most people don't find it too useful for comparing tractors because most tractors probably don't conform to the standard definition very well. ....
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| Nellie
Join Date: Posts: 1
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2002-05-05 38169
Just to clarify, I want to know what HP I should rate my tractor at when considering implements. I know the PTO HP is 22, but what about towable implements that don't use the PTO? ....
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2002-05-05 38179
Terms can be pretty confusing. Deere rates compact tractors by gross horsepower and PTO hp. Gross is what a free standing engine will produce before it loses anything through the turning of gears or the pumping of hydraulic fluid. PTO hp is what the net is after such losses; in other words, it is what is left over to do the actual work. One must assume that drawbar hp means what the machine would produce if attached to a dynometer or the horsepower produced at the wheels. It would certainly be closer to the PTO hp than the gross hp rating. HST models generally lose one or two horsepower more at the PTO than the same model with a gear tranny. My JD 4100 Gear has 20 gross hp, and 17 at the PTO. The 4100 HST is rated at 20/16. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-05-06 38186
I interpret all recommended HP specs from implement manufacturers as PTO HP, even for implements such as blades and plows. I think drawbar HP is an older rating definition that hasn't been used much since the mid-80's. However, when rated DB HP is less than PTO HP, which makes sense. I can lug my engine with a posthole auger, but the tires spin before the engine quits with a box scraper. My mid-80's Ford 1710 is rated 24 PTO HP and 20 DB HP. I assume that the DB HP ratinf is in 4wd, with ag tires and without ballast.
I think that manufacturers of blades plows etc. define their specs from typical differences between PTO and DB HP. Given recommended HP's, owners of relatively light but powerful tractors who have turf tires may have some traction problems, but should be able to manage by going slower, taking smaller bites, adding ballast etc.
The Nebraska Farm Tests (available on-line) provide very detailed test information on power pulling etc., but only for farm tractors. The tests have been conducted for decades and were designed to allow farmers to actually compare various tractors and configurations. The problem then and now is that comparisons are virtually impossible using only manufacturer specs.
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