Prony brake calculation help (for determining engine horsepower)

In summary, the person is seeking help in determining the horsepower at the axle of their engine using the numbers they have obtained from their Prony brake. They mention getting a reading of six pounds of torque, 4 inches off the center line of the axle, and at a rate of 30 rpm. They are also considering using a calculator to help with the calculations. The conversation also includes a discussion about the correct spelling of "Prony brake" and the potential use of a pony to calibrate it. The expert then provides a summary of the calculations used to determine the horsepower, including conversions from pounds to newtons and inches to meters.
  • #1
Pinon1977
126
4
TL;DR Summary
I need some help here. I'm trying to determine how to use the numbers I'm getting for my pony break to determine horsepower at the axle of my engine. Right now I'm getting a reading of six pounds of torque, 4 in off of the center line of the axle at a rate of 30 rpms. Can someone help me determine what the horsepower is here?
I need some help here. I'm trying to determine how to use the numbers I'm getting for my pony break to determine horsepower at the axle of my engine. Right now I'm getting a reading of six pounds of torque, 4 in off of the center line of the axle at a rate of 30 rpms. Can someone help me determine what the horsepower is here?
 
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  • #4
HP = Torque x RPM / 5,252

Torque is in foot pounds.
 
  • #5
6 pounds of torque, 4 in from the center line of the axle, at 30 rpm.
Let us know your setup and how you measure 6 pounds.

6 pounds = 2.721 kg. If pounds are a weight, then
convert to force 2.721 * 9.8 = 26.7 newton.
4 inch = 0.102 metre. Torque = 26.7 * 0.102 = 2.723 Nm.
30 RPM = 0.5 rev/sec. Angular velocity = 3.1416 rad/sec.
Power = 2.723 * 3.1416 = 8.555 W.
HP = 8.555 / 745.7 = 0.0115 HP.
 
  • #6
Baluncore said:
I assume by "pony break" you mean "Prony brake".
https://en.wikipedia.org/wiki/Prony_brake

I used to think it was a pony brake. I mean, it does make sense that you would measure horsepower on a pony brake.

Edit: Maybe use a pony to calibrate it?
 
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  • #7
Yes you would assume correctly. Proney. Stupid voice to text misspelled it for me. That's what I get for not proofreading. Haha. Anyhow thanks for the feedback. Much appreciate itQUOTE="Baluncore, post: 6893999, member: 447632"]
I assume by "pony break" you mean "Prony brake".
https://en.wikipedia.org/wiki/Prony_brake
[/QUOTE]
 
  • #8
Baluncore said:
6 pounds of torque, 4 in from the center line of the axle, at 30 rpm.
Let us know your setup and how you measure 6 pounds.

6 pounds = 2.721 kg. If pounds are a weight, then
convert to force 2.721 * 9.8 = 26.7 newton.
4 inch = 0.102 metre. Torque = 26.7 * 0.102 = 2.723 Nm.
30 RPM = 0.5 rev/sec. Angular velocity = 3.1416 rad/sec.
Power = 2.723 * 3.1416 = 8.555 W.
HP = 8.555 / 745.7 = 0.0115 HP.
Hello there. This is the feedback I was looking for. Thank you!
 
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