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
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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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FAQ: Prony brake calculation help (for determining engine horsepower)

What is a Prony brake and how does it work?

A Prony brake is a device used to measure the torque produced by an engine. It works by applying a braking force to a rotating shaft and measuring the resistance. The brake typically consists of a lever arm and a friction surface that presses against the rotating shaft. By measuring the force applied to the lever arm and the rotational speed of the shaft, the torque and subsequently the horsepower of the engine can be calculated.

How do you calculate engine horsepower using a Prony brake?

To calculate engine horsepower using a Prony brake, you need to measure the torque and the rotational speed (RPM) of the engine. The formula to calculate horsepower (HP) is:

HP = (Torque x RPM) / 5252

Where torque is measured in pound-feet (lb-ft) and RPM is the rotational speed of the engine.

What units are used in Prony brake calculations?

In Prony brake calculations, torque is typically measured in pound-feet (lb-ft) or Newton-meters (Nm), and rotational speed is measured in revolutions per minute (RPM). Horsepower is the resulting unit of power, which can be converted to other units such as kilowatts (kW) if needed.

What are the common sources of error in Prony brake measurements?

Common sources of error in Prony brake measurements include inaccurate force measurements, frictional losses, heat buildup, and incorrect RPM readings. Ensuring precise calibration of measurement instruments and accounting for frictional losses are essential to minimize errors.

How do you ensure accurate measurements with a Prony brake?

To ensure accurate measurements with a Prony brake, it is important to calibrate the force measurement device accurately, maintain consistent friction surfaces, and regularly check the RPM measurement device. Additionally, conducting multiple tests and averaging the results can help improve accuracy. Proper maintenance of the Prony brake setup is also crucial to ensure reliable performance.

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