[AT] Horsepower Question

[Ben Wagner]

  On 10/6/2010 10:00 AM, charlie hill wrote:
> Ben,  the lawn mower engine is rated in gross hp with no drive train load.
> The tractor engine is rated at net hp, either at the wheels or the PTO.
> There may well be some fudging on the lawn mower engine as well.  Also, HP
> is torque in ft/lbs.  times RPM.  You can make hp with high rpms and low
> torque or high torque and low rpm.   Your tractor is high torque and low
> rpm.  that is what allows it to move a load easily.
>
> Charlie
>
> --------------------------------------------------
> From: "Ben Wagner"<supera1948 at gmail.com>
> Sent: Wednesday, October 06, 2010 9:00 AM
> To: "At"<at at lists.antique-tractor.com>
> Subject: [AT] Horsepower Question
>
>>   Here is a puzzler that maybe someone with a better knowledge of
>> engines can answer.   I was asked this question, and had to announce
>> that I needed to look it up.  What better place than the AT Mailing?
>>
>> I have a Super A with four cylinders, producing c. 20 HP.
>>
>> I have a lawnmower, with an engine that says it is also 20 HP, with only
>> two cylinders.
>>
>> What is going on?  Is this two different measures of HP?  Or has
>> technology improved that much?   What makes a little two cylinder "small
>> engine" have the same HP as four cylinder "tractor" engine.
>>
>> Thanks,
>> Ben Wagner
>>
>>
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So in reality, horsepower is not really the important number; torque and 
RPM is what matters?

Ben Wagner