Theory

This is a single-acting steam engine. That means that the steam only pushes the piston one way. The flywheel pushes it back again.

1. The valve lets steam into the cylinder. 
2. The piston moves in the cylinder and makes the flywheel spin.
3. When the piston gets to the end the valve opens.
4. The piston pushes the steam out through the open valve.
5. When the piston gets to the other end the valve closes and the cycle starts all over again.

Video:

Click here to see it on YouTube

Valve

The first step is to make the valve because that is the hardest part.

1. Cut a hole in the side of a straw but not too big.


2. Put some hot glue around the hole but not in it!


3.Stick a short piece of bendy straw over the hole. Put some glue
around the hole to seal it because the engine will not work if air
leaks!


4. Straighten a paper clip to make the valve stem.


5. Cut a small circle out of a small piece of plastic for the valve plug. It should just fit in the straw. Make a hole in the middle for the stem.


6. Glue the circle to the end of the stem.


7. Cut a circle of soft material that is a little bigger than the plastic circle. The woven side of a face cleaning pad works well.


8. Glue this to the plastic circle.


9. Glue the paper clip in the end of a straw.


10. Make a hole in the other end of the straw. This will go on the crankshaft.



11. Now the valve is done! Try it by blowing in the end and sliding the plug up and down. It should not leak much when it is closed. If it leaks try step 7 again with a bigger circle of material.

Piston!

1. Put a balloon over the mouth of a small plastic bottle. The bottle is the cylinder and the balloon is the piston! Make hole in side of the bottle that is the size of a straw.

2. Glue the bottle to a piece of wood with the hole facing to the side.


3. Make a frame of sticks to hold the crankshaft.


4.Cut out a circle of plastic about as big as the top of the bottle and glue it  to a craft stick.


5. Now you glue the other side of the circle to the balloon which is the piston.

The awesome crankshaft and flywheel!!!

1. Bend some coathanger wire to make the crankshaft. The part for the piston has to stick out more than the part for the valve, and the part for the valve has to stick straight up when the part for the piston is lying flat. The flywheel goes on one end and the valve goes on the other end, with the part for the piston between the sticks on the frame. A grownup can help make the right angles.

2. Cut out a big circle of cardboard about the size of a dinner plate for the flywheel and make a hole in the middle to fit the crankshaft.


3. Now it's time to glue the crankshaft on the flywheel. The crankshaft has to stick straight up when the flywheel is lying flat.


4. Cut three short pieces of medium-size straw and poke a hole through for the crankshaft.


5. Two of these straws will go on the wood frame for bearings. If you get the right size straws they will just fit over the craft sticks.


6. The other one is for the piston. Put the straws on the crankshaft like this.


7. Then put the two bearings on the wood frame like this.


8. Now connect the piston. Make the straw for the piston longer or shorter to fit so the shaft turns easily without pulling on the balloon at the top or hitting the bottle at the bottom.

Steam line and boiler

1. Glue a little piece of bendy straw to the bottom of the valve. Glue a long straw to this for the steam line.

2.Glue the valve to the hole in the side of the cylinder.


3. Put the valve plug in the valve and slide the straw on the valve stem onto the crankshaft.


5. Make the straw for the valve stem longer or shorter so that the plug is just next to the straw on the side of the valve when the crank for the valve is halfway up or down (like it is in step 3).


6.You are the boiler! ! ! ! ! ! ! Just blow! ! ! ! ! ! ! Or you can make something like this to hold a balloon. Then the balloon is the boiler.