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Homemade Dynomometer for 1HP Engine

  1. Nov 14, 2011 #1
    Hi guys.

    I'm building a dynomometer for a 1hp engine. I plan to use something like an alternator or a dc generator to do the braking. I will mount the alternator or generator so it is free to rotate around the shaft and measure the force at a distance to get the torque.

    The idea is to vary the load on the alternator or generator to increase the amount of torque needed to turn it (therefore RPM will decrease), then use a data logger to plot torque vs RPM and thus calculate power.

    My electrical knowledge is limited. Is it possible to configure an alternator or generator (capable of the same/more power of the tested engine) to work in this way? i.e. increasing the load on the alternator/generator to increase the torque required to turn it? If so, how exactly would it be wired?
  2. jcsd
  3. Nov 14, 2011 #2


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    Sure. Get 100 ten watt light bulbs. Wire these in parallel to your supply. Switch them on individually. Then, you can apply whatever load you wish! It's a simplistic view but you get the idea, hopefully.

    You can actually calculate your power by measuring the current going through this circuit, and the voltage at your supply. If you can estimate (or calculate) your alternator efficiency, you know the power your engine is providing.
  4. Nov 14, 2011 #3
    Cheers for the reply, brewnog.

    That's good to know it's possible. So the load is wired in parallel to the supply and cranking up the load makes it harder to turn... What would I wire to the armature? (if anything)

    What sort of generator would be best to use for this? I have at the moment an alternator off a ford sierra but may think about buying a DC generator if its better as I can get a through shaft one and measure the torque like I was saying. (or maybe measure current and work out power this way like you mentioned)
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