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Horsepower

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Donald Holden

07-11-2001 06:36:37




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What is the differences between drawbar and belt/pwr takeoff horsepower and how is it determined? I have noticed that the powertake off horsepower is typically higher. I am just curious at how this is arrived at.

Thanks!

Don




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Butch (OH)

07-11-2001 10:16:20




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 Re: Horsepower in reply to Donald Holden, 07-11-2001 06:36:37  
PTO or belt horsepower is determined by loading the engine with a dynometer attached to them. A dyno loads the engine through a brake devise.The horsepower is calculated by a forula that takes into consideration the shaft speed and torque delivered. Modern dynos do the calulations and give readings in horsepower delivered, older ones require the use of a slide rule type calculater. Drawbar horsepower is determined by a dyno too, but it is a much different machine. A draw bar dyno is a heavy, trailer type affair that is hitched to the tractor. Sensors determine the amount of pull on the hitch while others determine the speed it is being pulled. The combination of speed and pull is again what determine drawbar horsepower. There are two reasons that drawbar and pto HP differ. 1 To deliver power to the rear wheels requires that it be transmitted through more gears than the PTO. Each extra gear takes power. 2. Tire slippage affects drawbar HP. It is important to remember that horsepower is a measure of the amount of work being done by the tractor, not a measure of speed or torque individualy. A tractor that is hitched to a drawbar dyno and is weighted to X pounds will be loaded until it spins to a stop or lugs the engine down. Readings are then calculated to determine what the maximum effort was. If the tractor spins out, the drawbar HP could be increased by adding weight to it, or by pulling the dyno in a higher gear that will load the engine more effectivly. Look at the Nebraska test sheets sometime. The maximum drawbar horsepowers are either at high(for field work) speeds or with a bunch of weights hung on the tractor.

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Brian Ahart

07-13-2001 06:26:33




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 Re: Re: Horsepower in reply to Butch (OH), 07-11-2001 10:16:20  
Excellent explanation Butch.



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Donald Holden

07-12-2001 13:59:26




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 Re: Re: Horsepower in reply to Butch (OH), 07-11-2001 10:16:20  
Butch, I thank you for your response. It was very interesting to read.

Don



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Donald Holden

07-12-2001 13:58:30




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 Re: Re: Horsepower in reply to Butch (OH), 07-11-2001 10:16:20  
Butch, I thank you for your response. It was very interesting to read.

Don



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Donald Holden

07-12-2001 13:57:39




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 Re: Re: Horsepower in reply to Butch (OH), 07-11-2001 10:16:20  
Butch, I thank you for your response. It was very interesting to read.

Don



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