Calculating Horsepower & Torque: A Small Dynamometer Guide

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To calculate horsepower and torque, one can use the formula T = WK² * ΔN / 308 * t, where T is acceleration torque in ft-lbs, WK² represents total system inertia, ΔN is the change in speed in rpm, and t is the time in seconds for acceleration. The discussion emphasizes that torque is measured in foot-pounds, not foot/pounds, and power is defined as work over time. For those unfamiliar with physics, additional resources, such as articles on torque, can provide foundational knowledge. The user seeks clarification on whether their approach to using constant load as moment of inertia is correct and how to derive horsepower from the calculations. Overall, the thread highlights the need for clear understanding and guidance in calculating engine performance metrics.
linguist
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Hi everybody, just wondering if you could help me with calculating horsepower & Torque.

If I have a known "constant load" in ft/lbs & the engine accelerates it from a starting rpm to a peak rpm figure in X time, how can I calculate the Horsepower & Torque.

Not really sure where to start?

Can I assume that my "Constant Load" is the same as the moment of inertia of a flywheel & use the appropriate calculations for mine?

Thanks
 
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linguist said:
Hi everybody, just wondering if you could help me with calculating horsepower & Torque.

If I have a known "constant load" in ft/lbs & the engine accelerates it from a starting rpm to a peak rpm figure in X time, how can I calculate the Horsepower & Torque.

Not really sure where to start?

Can I assume that my "Constant Load" is the same as the moment of inertia of a flywheel & use the appropriate calculations for mine?

Thanks

Torque is measured in foot * pounds, not foot/pounds. Power is work/time, which is force*distance/time.

This article may be helpful (the equations are part-way down the article), but if you don't have much background in physics, please ask more questions here so we can help.

http://en.wikipedia.org/wiki/Torque

.
 
berkeman,
Thanks very much for the reply, your correct I am not experienced in physics but I will see how I go with the link you have provided as I need to learn more about this for my small dyno.

Thanks again
 
Not sure if I have this correct.

Ok, I have a "constant load" of say 5 ft-lb & want to acellerate this from a starting rpm to the final rpm figure, find the Torque of the driving engine.

T = WK^2 * ΔN / 308 * t

T= Acelleration torque ft-lb

WK^2 = Total system inertia includes my (constant load value + the moment of Inertia of the Load Cell shaft, Couplings etc.

ΔN = The change in speed (rpm)

t = Time to acellerate total system load (sec)

As mentioned I'm not sure if this is the correct method & I am not sure yet how to get the Hp figure from this?

Any help would be greatly appreciated.

Cheers
 
Anyone?
 
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