Track Tac

Horsepower, what is it?

alvin l nunley

alvin l nunley

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The word work is defined as; force times distance.
Horsepower could be described as; how fast you're working. The "rate" of work.
If I raise 550 lbs., 60 feet in 60 seconds, I would be described as working at the "rate" of one horsepower.
60 feet x 60 seconds = 33,000 lbs. ft of work.
There are 2 x pi radians in a circle.
33,000 / 6.283 = 5252.1
the formula for calculating horsepower:
RPM X torque / 5252.1 = Horsepower
On a horse power chart, the torque curve and the horse power curve always cross at 5252.1 RPM. If they don't, the chart you're looking at is worthless.
Torque x 5252.1 / 5252.1 = HP. So, 5252.1 / 5252.1 = 1. Torque x one = HP
The story of James Watt, and how, and why, he came up with this formula, can be found on Wikipedia.


In
 
So, how much "work" does my engine do at high idle (governed speed), with no external load.

Only torque consumed is that which is needed to maintain governed speed.

Where does the rest go?
 
So, how much "work" does my engine do at high idle (governed speed), with no external load.

Just enough to keep the motor running. Enough to keep the piston going up and down, enough to keep the crankshaft turning, enough to keep the valves opening and closing. Etc. etc.


Only torque consumed is that which is needed to maintain governed speed.

Torque is not consumed, it's produced. Governed speed is a result of limiting the torque that can/is be[ng produced.



Where does the rest go?

There is no "the rest" to go anywhere, the governor, whatever that is, is limiting the amount of torque the engine can produce.
 
If torque is produced, it must be consumed somewhere.

Now, think about gearbound.

The engine is capable of producing more torque, but the is no demand for more.
Therefore, the engine governs itself.

(Of course, within reason ).
Reasons engine will govern itself.
Beyond airflow capabilities of intake, or exhaust.
Beyond mechanical ability of the system (ie, valve springs, or cam profile, spark timing, etc.

Or, simply not putting enough demand for torque on the engine.
 
95 shaw said:
If torque is produced, it must be consumed somewhere.
Click to expand...
Torque is a force, sometimes there is not enough of it, but it's not consumed.
Maybe I can come up with an analogy.
Think about throwing a baseball, you know you can throw it 200 feet, but you only throw it 100 feet. Throwing the ball consumed calories, but it did not consume force, you expended force, you expended half the force you could have. Nothing left over. I don't know if that works, but I tried.
 
alvin l nunley said:
Torque is a force, sometimes there is not enough of it, but it's not consumed.
Maybe I can come up with an analogy.
Think about throwing a baseball, you know you can throw it 200 feet, but you only throw it 100 feet. Throwing the ball consumed calories, but it did not consume force, you expended force, you expended half the force you could have. Nothing left over. I don't know if that works, but I tried.
Click to expand...
How can force be expended, that is not consumed.
Either it did work, or it did not exist

See your formula for "work".

Perhaps better, the definition of torque.
Without resistance, there is no torque.
 
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My understanding, I expend the energy to perform a task, the task is consuming that energy, if the task consumes more energy than I am expending, the task doesn't get done. Maybe not scientific.
 
Now, if you expend more energy than the task requires, where does that energy go?


All that, to get to this.

Gear bound is simply engine producing more torque than is consumed.
Since torque is not consumed, it does not exist.

Same thing happens when we reach target rpm, and torque demand is less than available, but necessary, to increase overall speed.
If resistance is reduced, horsepower is also reduced.
Some will see the correlation.
 
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Bottom line, in order to benefit from maximum horsepower, you must demand maximum torque available.
Simply obtaining the rpm is not enough.
 
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95 shaw said:
Bottom line, in order to benefit from maximum horsepower, you must demand maximum torque available.
Simply obtaining the rpm is not enough.
Click to expand...
You and I seem to see things from a totally different perspective. I'm working from the perspective that Engines don't produce horsepower!!
Engines produced torque. The word that is used to describe how fast they produce torque is "Horsepower".
 
The point is that it is just potential until there is resistance.

Change the resistance, change the actual work being done.
 
The resistance (in a kart) is going to be:

- accelerating the mass of the kart/driver
- aerodynamic drag
- rolling drag (tires, chain, bearings, etc.)
- increased drag in a corner due to tire scrub, etc.

If the weight of the kart were increased.... say 50 pounds, the "resistance" (to acceleration) increases. The engine is already producing all the power it can produce, so the rate of acceleration decreases.

PM
 
My thoughts were heading more toward the gear bound aspect.

Did we become "driver bound" if we can change the driver size larger, maintaining same speed ratio, and the kart responds with better lap times?

Food for thought.
 
95 shaw said:
My thoughts were heading more toward the gear bound aspect.

Did we become "driver bound" if we can change the driver size larger, maintaining same speed ratio, and the kart responds with better lap times?

Food for thought.
Click to expand...
You said "same speed ratio", did you mean same gear ratio?
Going with the latter, I'd say go for it. But I'm wondering, why wouldn't you start off with that gear ratio, the one that goes faster? Almost like they have some "innate" ability to recognize the changing conditions that call for a change in gear sets.
I've had people say that they can tell when to change gear sets. Almost intuitively! I find that so hard to believe!
 
simple example, you are going down straight and you have reached the limit of gaining acceleration because the engine is past it operating range and you need more speed. But engine just won't develop more at that rpm. Need larger driver or smaller axle gear.
Or you are geared so high that when you come out of the turn and start down the chute, you are below max torque and lose a lot of forward exceleration. Need smaller driver or larger axle gear.
Remember that is simple answer. not technical one.
 
One Fast Kat said:
simple example, you are going down straight and you have reached the limit of gaining acceleration because the engine is past it operating range and you need more speed. But engine just won't develop more at that rpm. Need larger driver or smaller axle gear.
Or you are geared so high that when you come out of the turn and start down the chute, you are below max torque and lose a lot of forward exceleration. Need smaller driver or larger axle gear.
Remember that is simple answer. not technical one.
Click to expand...
I don't understand the request for a simple answer.
 
Thanks SMC -- you're absolutely correct. I probably should have said: "acceleration decreases", NOT the "-rate- of acceleration decreases"

PM
 
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