Torque = Hp x 5252 / Rpm (5252 is a constant) - still a valid formula ?

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Originally Posted by 67-LS1

OK! Figured out how to attach the curve!

I clearly don’t understand this, hence my OP and I do appreciate you guys trying to explain it. I know this formula is tried and true and has been since the invention of the horse.

But then I see a curve like the attached and hopefully you can see why I ask the question. The HP curve rises as the torque curve remains flat.

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Thanks for posting the chart. The 5252.113 unit conversion is specific to ft-lbf and horsepower.

For Newton-meters and kilowatts, the formula would be as follows:

KW = Tq (Nm) * RPM / 9549.3

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Originally Posted by 67-LS1

OK! Figured out how to attach the curve!

I clearly don’t understand this, hence my OP and I do appreciate you guys trying to explain it. I know this formula is tried and true and has been since the invention of the horse.

But then I see a curve like the attached and hopefully you can see why I ask the question. The HP curve rises as the torque curve remains flat.

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Lets just pick an RPM from the graph, say 1800 RPM. It's making roughly 350 Nm of torque, convert that to Lb. ft. and you get roughly 258 Lb. Ft.

258 x 1800/5252 = 88 hp. At the same 1800 RPM on the graph, it shows 65 KW's of power, convert that to HP and guess what, 88 HP.

Try it at any RPM point on the graph and you will get the same results. The formula with always be correct!!

Right -- just piling on here, but the relationship between HP, torque, and RPM isn't "tried and true". It's true by definition:

1 horsepower is a unit of power equal to 550 foot-pounds per second (745.7 watts).

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Originally Posted by parsonsj

Right -- just piling on here, but the relationship between HP, torque, and RPM isn't "tried and true". It's true by definition:

1 horsepower is a unit of power equal to 550 foot-pounds per second (745.7 watts).

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What he said! :twothumbs

Getting the units right in any engineering exercise may just save a life.

Just sayin....

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Originally Posted by CarlC

Getting the units right in any engineering exercise may just save a life.

Just sayin....

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I always wonder why by doctor and lawyer friends just "practice", when as an engineer I have to get it right every time.

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Originally Posted by cornfedbill

I always wonder why by doctor and lawyer friends just "practice", when as an engineer I have to get it right every time.

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Right every time... that's what the safety multiplier is for!

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Originally Posted by CSG

Right every time... that's what the safety multiplier is for!

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Yup!

All engines power is measured by torque, we get HP by an equation. Physics isn't hard if you understand what hat there are some constants in the world.