[AT] Horsepower Question

[Will Powell]

Ben, 

You said: 

"So in reality, horsepower is not really the important number; torque and 
RPM is what matters?" 

The Torque and the RPM are variables in the HP calculation... Tourque and RPM matter based on their application. 

High HP low torque = Light engine, good for lawn mowers, automobiles, race cars, airplanes, usually high ware, shorter service life. Cheaper to build? 

High Tourqe, Low RPM = Heavy engine, good for Trains, Tractors, Trucks, excavating equipment. Applications that welcome weight for pulling or pushing. Low wear, long service life. More expensive to build. (more metal) 


The other factor that makes things different between a lawn tractor and a farm tractor is weight... 
The main measure of a tractors pulling strength is related to its weight... Try pulling a 1 row plow with your 20hp lawn tractor...... 

Regards, 

Will 


----- Original Message ----- 
From: "Ben Wagner" <supera1948 at gmail.com> 
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com> 
Sent: Wednesday, October 6, 2010 10:17:32 AM 
Subject: Re: [AT] Horsepower Question 

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 
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