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I What is the name of this Heat Engine?

  1. Dec 5, 2018 #1
    We all know how a thermostat works 2 different type of metal are attach together, when temperature changes 1 metal strap expands more than the other strap causing the straight metal strap to bend.

    45 years ago when I was in college the professor brought a desk top heat engine to class. He told us the name of this heat engine and I wrote it down. In the past 45 years I have lost that information. It was not called a sterling engine but it might be a type of sterling engine.

    Here is how the engine is build and how it works.

    2 different types of thin flat metal straps are made into a donut round circle shape about 3" diameter and connected together. The 3" round double strap is on rollers so it is free to rotate on rollers. I don't remember the details of the rollers, I think there were 3 rollers on the inside and 2 on the outside near the top. The 3" metal ring sets in a cup of cold or hot water when you give the ring a spin it keeps on rotating around the rollers as long as it continues to stay in the water. 1 roller is near the water surface left side of the cup while part of the 3" round ring is in the water. Water temperature makes the strap bend so the metal ring continuously pushes away from the roller and keeps rotating as long as the metal strap stays in the water. As the strap rotates near the top its temperature returns room air temperature the strap returns to its original shape near the top. If water is made colder the strap spins faster. I don't remember if it will rotate the other direction if put in hot water, teacher did not bring hot water, I don't recall he mentioned if the ring rotates the other direction in hot water.

    If I knew the name of this device I could do Google search and read about it. I might even be able to find a desk top model for sale.

    Does anyone know that this engine is called?

    I might be able to draw a picture with paint brush and post if here if anyone would like to see a picture. Is it possible to upload photos here or do they have to be posted some place different then linked here?
  2. jcsd
  3. Dec 5, 2018 #2


    Staff: Mentor

    I think a picture would be very helpful. Use the UPLOAD button, then after the upload click on full image.
  4. Dec 5, 2018 #3


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    Staff: Mentor

    I don't know a specific name, but googling "thermodynamic engine bimetallic" brings up some interesting hits, although nothing that appears to be what you are describing.
  5. Dec 5, 2018 #4

    Water level has to be almost to roller 1. The whole assembly might need to be rotated counter clock wise a little bit. Once you get it adjusted correctly in water the bi metal rings spins at a fairly fast speed. It appeared to me like the ring was spinning about 3 turns per second.

    Give the bi metal ring a spin the red color ring has to contract more then the green color ring so the bi metal ring develops an inward bow towards the roller this puts pressure on roller 1 forcing the bi metal ring to rotate. Like all sterling engines you need to give the bi metal ring a spin to get it started. Colder the water is the faster the ring spins.
    Last edited: Dec 5, 2018
  6. Dec 11, 2018 #5


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    Gold Member

    Another place to search is the U. S. Patent office, I think it is classified as a bimetal heat engine...
  7. Dec 11, 2018 #6
    I think it is named after the inventor.
  8. Dec 11, 2018 #7


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    Staff: Mentor

    And his name is...?
  9. Dec 12, 2018 #8


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    Gold Member

    This isn't it, but does work on a temperature differential for the metal loop.
    It uses Nitinol, memory shape wire, and one end has to be heated.
    the bi-metal engine should work under a similar fashion.
  10. Dec 12, 2018 #9


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