Re: Re: Re: What kind of horses are tractor horsepower measured in?
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Posted by Woody on June 16, 1998 at 13:52:16:
In Reply to: Re: Re: What kind of horses are tractor horsepower measured in? posted by Paul Fox on June 16, 1998 at 13:39:06:
: : : Maybe someone with a mechanical engineering bent could explain to me (in simple language) how a tractor horsepower would relate to an automobile horsepower? : : : Cars have these really big HP numbers, but tractors have plenty of displacement, and not real high HP numbers. I know the score on torque and RPM, but remember back about 1970 (or so) when the horsepower ratings of all the cars went way down suddenly and everybody thought it was the #$% smog equipment? They just changed the test the stated numbers were based on. The old test was an engine on a test stand with no belt-driven accessories, tailpipe or muffler feeding it's exhaust into a collector maintained at a slight vacumn! : : : Now I have a feeling that tractor horses and car horses might not be the same thing at all. Anybody know? : : Doug: : : The same kind that are used to pull tractors out of creeks! (Percherons) But seriously, folks, a HP is a HP is a HP...a measure of work done over time. You are on the right track with your comments about how the test is done. Car ratings went down drasstically when they started measuring at the rear wheels and accounting for all the losses in the drive train. Not sure how the Nebraska Test numbers were determined, and I'd sure be interested in finding out. I've done an incredible amount of work with a tractor rated at 18 drawbar horsepower! : Meant to say "drastically"...I can spell, really I can...just can't type!
You will need to do a little research to get the full story, but in a nut shell, the original horse power ratings were based upon actual horse. The tests and the standard were set up somewhere in Michigan (forgive me, I cannot recall all the details) and were based upon the load a single horse could pull from the bottom of a shaft...I'm not kidding! The actual apparatus and correlation methods? I don't recall, its been too long since school! Keep digging! Woody
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