There are lots of different kids of heat engines, from stirling engines to big jet turbines to the engine in your car. They all use clever ways to convert a temperature difference into motion.


Remember that the molecules in steam move around a lot faster than in an ice cube. So when we stick hot steam in a container, we can blow off the lid (used with pistons in a steam engine). or we can put a fan blade in hot steam, and since the molecules move around a lot, they start bouncing off the blade and cause it to rotate (as in a turbine). Or we can seal up hot steam in a container and punch a tiny hole out one end (to get a rocket).


One of the first heat engines was dreamed up by Hero of Alexandria called the aeolipile. The steam is enclosed in a vessel and allowed to jet out two (or more) pipes. Although we’re not sure if his invention ever made it off the drawing board, we do know how to make one for pure educational (and entertainment) purposes.  Are you ready to have fun?


THIS EXPERIMENT USES FIRE AND STEAM…GET ADULT HELP BEFORE YOU OPERATE THE ENGINE.

Here’s what you do:


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Materials:


  • soda can
  • fishing line
  • razor
  • stand
  • drill or large nail and hammer
  • adult help
  • candle


IMPORTANT NOTE: As the water boils, your can will spin. The hot steam shoots out the sides, so take care not to get burned. As the can spins, it may wobble and shake, especially if it’s off-center.  Be careful not to get shot with boiling water!!


What’s going on? When the water boils, the molecules inside are turning into hot steam and moving very quickly, bouncing off the can and out the pipes. Rockets and balloons use this same principle – the pressurized air shoots out the open end and the balloon (or rocket)  moves in the opposite direct.  Newton’s third law in motion! The two jets at an angle work together to spin the can.


  1. Do you think the size of the hole matters?
  2. Does it matter how many candles you use?
  3. What if you used four holes instead of two? Six? Twenty?
  4. Are beer cans better?

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Comments

9 Responses to “Hero Engine”

  1. emilyannejon says:

    The Dollar Tree

  2. The grocery store… any can should work for this experiment.

  3. Eunice LaCoy says:

    Where do you buy your soda from??

  4. Try it – see what happens! (That’s what science is all about!) 🙂 Remember, it’s the steam you want, and it doesn’t take much water to fill the can with steam.

  5. Rachel Moser says:

    Wouldn’t it be better to put the holes closer to the top so you can fill it with more fuel (water)? 😀

  6. You need a container that doesn’t melt (no plastic) and you can empty completely by piercing with two small holes (so tuna cans are out). Does that help?

  7. Elaine Deppe says:

    We don’t have any kind of soda can. Is there any other kind of can we can use?

  9. Debra Thomson says:

    Could you add three holes to the can to make it go faster?
    Holly Thomson