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.
How deep are each of the angles?
ReplyDeleteHow deep are the angles on the crankshaft? Like the space between the base and the bottom.
ReplyDeleteThe valve leads the piston by 90 degrees. You can advance this by up to 10 degrees or so to get the best performance, but we did not bother with fine tuning. The piston crank length should be no more than half the full stretch of the balloon, and the valve crank length should be at least half the diameter of a straw, but we just guessed and our first crank shaft worked fine (about 3/4" for the piston and 1/4" for the valve).
ReplyDelete