Prony brake calculation help (for determining engine horsepower)

Click For Summary

Discussion Overview

The discussion revolves around calculating horsepower using a Prony brake, based on torque measurements taken from an engine setup. Participants are seeking assistance with the conversion of torque readings to horsepower, including the specifics of their measurements and calculations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant seeks help to determine horsepower from a reading of six pounds of torque at 30 RPM, positioned 4 inches from the axle's center line.
  • Another participant suggests using an online calculator for torque to horsepower conversion.
  • Several participants clarify that "pony break" is likely a misspelling of "Prony brake" and provide a link to a Wikipedia article for reference.
  • A formula is presented: HP = Torque x RPM / 5,252, with a note that torque should be in foot-pounds.
  • One participant performs a detailed calculation converting pounds to kilograms and then to newtons, ultimately calculating the power in watts and converting it to horsepower, arriving at approximately 0.0115 HP.
  • Another participant humorously suggests calibrating the brake with a pony, reflecting on the initial confusion over terminology.

Areas of Agreement / Disagreement

Participants generally agree on the terminology correction from "pony break" to "Prony brake." However, there is no consensus on the final horsepower calculation, as different methods and interpretations of the measurements are presented.

Contextual Notes

The discussion includes various assumptions regarding unit conversions and the setup for measuring torque, which may affect the accuracy of the calculations. The exact method of measuring the torque is not detailed, leaving some uncertainty in the results.

Pinon1977
Messages
126
Reaction score
4
TL;DR
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?
 
Physics news on Phys.org
HP = Torque x RPM / 5,252

Torque is in foot pounds.
 
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.
 
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?
 
  • Like
Likes   Reactions: weirdoguy and SammyS
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]
 
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!
 
  • Like
Likes   Reactions: Baluncore

Similar threads

  • · Replies 31 ·
2
Replies
31
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 7 ·
Replies
7
Views
7K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 2 ·
Replies
2
Views
4K
Replies
26
Views
6K
  • · Replies 10 ·
Replies
10
Views
7K
  • · Replies 7 ·
Replies
7
Views
4K