Peak Horsepower

Tal said:

Torque is how many wet towels you can hang on your old fella first thing in the morning!

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The old fella aint very big but it gets so hard a cat couldn’t scratch it. So that is torque not hp?

Azisbest said:

The old fella aint very big but it gets so hard a cat couldn’t scratch it. So that is torque not hp?

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hmmm...not sure...but i do know as im getting older im getting stronger cos i couldnt push my old fella down with two hands when i was a boy...now i can bend it with one hand!!

Horsepower is torque over time. Think of horsepower showing how much work the torque is getting done. Torque is just a force, there is no RPM or speed to the number. I can say I make 150ft lbs of torque at 4000 rpm but that is when that force is happening and has no bearing on the 150ft lbs calculation. If you want to imagine it, when you say you are making 150ft lbs of torque, if you had a 1 foot bar connected to your crank shaft and the other end of the bar was sitting on a scale, it would push down with a force of 150 lbs. Another way to think of it is when you torque a bolt down, you are putting a set amount of force, it doesn't matter how fast you turn the bolt, you are just turning it until you hear the click or you see the needle point to the proper amount.

Horsepower is work that is getting done. Pretend I am going to power a generator and I have my Rocket 3 and I have a steam engine. I am making 150 horsepower with both. They both are going to do the same amount of work. The difference is the Rocket 3 is making that 150hp at 6500 RPM, while that steam engine is (from a real world example but lots of rounding and fuzzy memory) making that 150hp at around 180rpm. For the steam engine to make that much horsepower at that low rpm it was running something like 3000ft lbs of torque. They both are going to make the same amount of electricity but they are doing it differently, we need to gear the bike down to slow it down to spin the generator at the correct RPM and we are going to have to gear up the steam engine to make it spin the generator fast enough. Same amount of work is being done.

You could even think of it like a moving water with a bucket. Torque is how big is your bucket and horsepower is how much water you move. You could have a big bucket but you are slow moving, or you could have a small bucket and move it really fast. While you move the same amount of water, you are not using the same size bucket and the speed you move the bucket is important.

In drag racing to get the best times you want to shift 10% past the horsepower peak. (has to do with maximum area under the curve and we start down the calculus path if we want to explain deeper)

Tal said:

Torque is how many wet towels you can hang on your old fella first thing in the morning!

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For me, 1k rpms.

Horsepower = (Torque x RPMs) / 5252

and best explication of the consequences of gears here :

Jerry C said:

Hi all,

From a high school physics book: Torque is a twisting force. Torque can be produced when no motion is present. A good example is pulling on a wrench when the nut doesn't turn. In the USA torque is measured in the units of ft-lb (foot pounds), some people say lb-ft (pound feet) but order doesn't matter.

Power is the rate at which work is done. Horsepower is one of several units power can be measured in. In the USA we typically use horsepower. 1 horsepower is 550 ft-lb of work done in one second. Please note the ft-lb in the power unit are NOT the same as the ft-lb in the torque unit. In order to do work, a force must move and object.

For a rotating shaft Power is Torque X rpm divided by 5252 provided that torque is measured in ft-lb.

I asked a fellow that used to build dragster engines at what rpm should a person should shift and to what rpm should the engine drop to in the next gear to get maximum acceleration. He replied, "Shift when you hit maximum horsepower and the transmission should be geared so you will drop to maximum torque in the next gear. All you are doing if you rev beyond maximum horsepower is burning more fuel than you need to and making noise."

Later,
Jerry C

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Like I said, about 6k rpms.
Don't get the peak torque at 4k rpms.

Jerry C said:

Hi all,

From a high school physics book: Torque is a twisting force. Torque can be produced when no motion is present. A good example is pulling on a wrench when the nut doesn't turn. In the USA torque is measured in the units of ft-lb (foot pounds), some people say lb-ft (pound feet) but order doesn't matter.

Power is the rate at which work is done. Horsepower is one of several units power can be measured in. In the USA we typically use horsepower. 1 horsepower is 550 ft-lb of work done in one second. Please note the ft-lb in the power unit are NOT the same as the ft-lb in the torque unit. In order to do work, a force must move and object.

For a rotating shaft Power is Torque X rpm divided by 5252 provided that torque is measured in ft-lb.

I asked a fellow that used to build dragster engines at what rpm should a person should shift and to what rpm should the engine drop to in the next gear to get maximum acceleration. He replied, "Shift when you hit maximum horsepower and the transmission should be geared so you will drop to maximum torque in the next gear. All you are doing if you rev beyond maximum horsepower is burning more fuel than you need to and making noise."

Later,
Jerry C

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maurice said:

Not getting to 60 in 2.7 sec. Changing gears at " peak torque 4k rpm".

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A professional racer got the 2.7. If you want instant acceleration, as in passing, gunning it at peak torque is the way to go.

This is a pretty cogent explanation of how the units of horsepower.

Tal said:

Torque is how many wet towels you can hang on your old fella first thing in the morning!

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You can hold up wet towels? When I get up in the morning I have to be careful not to step on my balls. I hate you.

dougl said:

A professional racer got the 2.7. If you want instant acceleration, as in passing, gunning it at peak torque is the way to go.

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As someone mentioned, to 60 probably did not change gears. So you are saying racer changed gears at 4k rpms to quarter mile time? I say it defies common sense.