Re: Demystifying (for me) torque and horesepower

Posted by flyingace on March 02, 2012 at 07:47:01 from (64.77.223.91):

In Reply to: Demystifying (for me) torque and horesepower posted by VADAVE on March 01, 2012 at 12:02:07:

buickanddeere said: (quoted from post at 08:28:56 03/02/12) JMOR said: (quoted from post at 21:45:45 03/01/12) flyingace said: (quoted from post at 20:23:19 03/01/12) Thanks for the replies. At issue for me is torque. To say a motorcycle engine could pull as much as a JD 'R' just seems ludicrous, even if you could negate the gearing loss. The JD has much more twisting power than the MC engine no matter what RPM the MC engine turns. HP is a measure of work, not force. I found this quote on another forum and it makes the most sense to me: Torque is how much work CAN be done. HP is how fast it can get said work done. Now this makes sense. The motorcycle in no way can pull what a 120 HP tractor can pull, but it it can get the same amount of 'work' done as the tractor if you reduce the torque requirement so it can spin fast. I think a good analogy is if you hook up both to water wheels. The tractor could lift out massive buckets of water but not at a very fast rate. The MC could lift only small buckets, but at a much faster rate. In the end they would generate the same amount of water. One horsepower will lift 550 pounds, one foot, in one second. Doesn't matter if done by a horse, a 12,000 rpm engine, a 400 rpm engine, or a piston receiving a pressurized column of water from up the mountain. HP = HP and HP = torque X rpm/5252. Simple physics coupled with James Watt's (1736-1819) definition (measured with actual horses) of HP. . Torque is not work. Work is force over a distance during a known length of time . Power is force over distance.A beam in your barn is holding up tons but it is doing no work because there is no movement. You can hang on the end of a torque wrench pulling 100lbs force for 8 hours but if the wrench hasn't moved, you have done no work.

I think the word 'work' for the first phrase was misapplied. I think a better phrase would have been 'how much force can be applied' then maybe

'how fast that force can be delivered' or something like that.

Now, another question. Torque is a measure of twisting force. What is the

equivalent measure for straight line force? For instance, what unit of measure would you use for describing the force required to pull a plow in

a straight line?

This post was edited by flyingace at 07:57:10 03/02/12.

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