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How do you test the efficiency of a wobbler steam engine

  1. Feb 10, 2009 #1
    I have a project for my sophomore design class to test the efficiency of a wobbler steam engine. I have heard people talk of using a dc motor and connecting it with a belt to the flywheel to see what voltage it produces but I don't know how to do that. In addtion, some have suggested to just hang a rope with a known mass off the flywheel. If anyone could help me think of a simple way to test the efficiency of my wobbler that would be great.
  2. jcsd
  3. Feb 10, 2009 #2


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    You need to have it do a measured amount of work.
    The suggestion of making it pull a string and lift a weight seems easiest.
    The energy to lift a weight = mass * g *height
  4. Feb 10, 2009 #3
    okay. I think that a lot of people are going to do it that way so i looked into doing it with a DC motor. So far i figured out that i have to make the motor turn with my flywheel and then multiply (current*voltge) produced which equals work. Do you have any advice on if that sounds acceptable and how would I test the efficiency of the DC motor I have included in the project?
  5. Feb 11, 2009 #4

    That's a great idea in theory. That isn't how it's done in the real world though. You (ME-student) want to construct what is called a prony brake. This is what you described. I'm currently making one. They are very easy to make. If you want to be crude, a Fish scale and RPM gun will suffice. If you want real measurements, you need strain gauges and hall effect sensors.

    Prony brake: Google it.
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