Measuring power output by modified prony brake

In summary, the speaker is trying to measure the power output of a water wheel by connecting it to a DC motor via a pulley system. They are using a potentiometer as a brake and have calculated the power output using a specific method, but the results are smaller compared to another method. They are seeking suggestions on potential errors in their calculations.
  • #1
Helmizar
1
0
Hi guys

I have problem, basically I want to measure the power output from a water wheel.
so basically I measured the power output by connecting the pulley that attach on the shaft of the water wheel. then this pulley is connected to other pulley which sit on the shaft of the DC motor.
this DC motor is braking by using potentiometer as controller (which act as brake to the wheel). may be much more easy to see the drawing http://www.thescienceforum.com/images/smilies/smile.png
currently I calculate the power output by using method as shown in the attachment. but when I compared it with prony brake method, the power output is smaller than prony brake method. I get confuse now, is there any suggestion regarding my equation, probably something wrong with my calculation method
Helmizar
 

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  • #2
Could it just be due to mechanical losses in the pulley system?
 

Related to Measuring power output by modified prony brake

1. What is a modified prony brake?

A modified prony brake is a device used to measure the power output of an engine or motor. It consists of a wooden block that is attached to the engine's output shaft, with a small lever arm resting on top of the block. As the engine turns, the lever arm applies pressure to the block, creating friction and allowing the power output to be measured.

2. How is power output measured using a modified prony brake?

The power output is determined by measuring the force and rotational speed of the engine. The force is measured by the weight applied to the lever arm, and the rotational speed is measured by the tachometer attached to the engine. The power output is then calculated using the formula P = 2πNT, where P is power, N is the rotational speed, and T is the torque or force applied.

3. What are the advantages of using a modified prony brake to measure power output?

One advantage is that it is a relatively simple and inexpensive method compared to other techniques. It also provides real-time data, allowing for immediate adjustments to be made. Additionally, it can be used for a wide range of engine sizes and types, making it a versatile tool for power measurement.

4. Are there any limitations to using a modified prony brake?

One limitation is that the accuracy of the measurements can be affected by external factors such as temperature and humidity. Another limitation is that the device may not be suitable for high-powered engines, as the friction generated may be too great for accurate measurements.

5. How can the accuracy of power output measurements using a modified prony brake be improved?

To improve accuracy, it is important to ensure that the device is properly calibrated and maintained. This includes regularly checking and adjusting the weight applied to the lever arm, as well as keeping the device clean and free of any debris. It is also helpful to perform multiple measurements and take the average to reduce any potential errors.

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