A rotary steam engine

We can use the same steam engine that pushes the boat in a different way. We can arrange that the engine causes something to turn.

We start with an aluminum soft drink can, which we cut about a third of the way up from the bottom to form a small cup.

Side view

We then carefully (so as not to cut our fingers) bend over the sharp edge, and crimp it with a pair of pliers to form a neat edge. Don't worry too much about neatness, since it will not affect the operation of the engine, only the looks.

We also put a large dent in the bottom of the can, which is normally bowed up in a dome, which is inconvenient, since we want to put a candle there later. We punch two neat holes in the side of the can, opposite one another, with a paper punch. These holes will hold our copper tubing.


Next we put in the candle, using the same kind of candle (with its convenient little cup to hold the melted wax) as we used for the boat. Around the candle, we put a rope of crumpled aluminum foil, to keep the candle centered in the can.

With candle

Now we make the tubing coil in the same way as we did for the boat. This time, however, we bend the ends out to fit through the punched holes. This is a little tricky to do at first, but you soon get good at it. In the version shown, I have added an extra coil to the engine, but this is not necessary, and does not improve the engine.


Next we bend the ends of the tubing gently so they curve into a right angle. Each end is bent opposite the other, so the can will spin when it is placed in the water and the engine started.


The final photograph shows the engine in operation. With a candle, it spins at about one rotation per second.

In motion