WATER WHEEL

You Will Need:

• 2 Styrofoam plates

• 10 Small plastic or styfofoam cups - disposable type

• Scizzors,or X-Acto knife

• Hot melt glue gun

• Ruler

• Dowell rod (1/2" - 1" diameter works good)

• Small nail

• String

• Hammer

• 2 Chairs

• Small weight (you can use a toy, or small rock)

• Pitcher of water

• Squirt gun

• Garden hose

MAKING YOUR WATER WHEEL

Using the hot melt glue gun, glue the 2 plate bottoms to each other so that the tops of the plates are facing out, making a wheel (see drawing).  

Cut off all the cups to about 1-1/2 inches high.  Make sure you cut them straight, and that they are all the same size when you are finished.  Discard the top part of the cup, and save the bottom.

Using the hot melt glue gun, glue the cups around the edges of the plates, evenly spaced, so that the openings are all facing the same way (see drawing).

Find the center of the plates, using the ruler, and mark it.  Using the hot melt glue gun, glue the dowell rod firmly to the center of the wheel.  It might help to cut a hole in the center of the plates, exactly the same size as the dowell rod, and glue it from both sides.

Put a small nail into the dowell rod, about halfway down it's length.  Attach a piece of string, about three feet long to the nail.  This will be how your water wheel uses its power to pick up the weight.

USING THE WATER WHEEL

Set two straight back kitchen chairs, back to back, about two feet apart.  Make sure you use chairs that will not become damaged when they get wet.  You might want to do this outside, so that you don't get the floor wet.

Place your water wheel so that the dowell rod straddles the chair backs, with the string hanging down between them.  Attach your small weight to the end of the string.

Pour water into the cup that's almost at the top of the wheel, like in the picture.  As the cup fills, the wheel will turn, don't move the pitcher, just continue to pour, you will now be filling another cup. Continue to fill cups, as the wheel turns. There should always be another cup needing filling.

Now, try using the squirt gun, and the garden hose to supply water to your water wheel.  Is there any difference in the weight it can pick up?  Is there any difference in the speed that the wheel picks up the weight?  If you make the water go into the wheel with more force (from the squirt gun, or hose) does it affect how much weight the wheel can pick up?

EXPLAINING HOW IT WORKS

You should have found that the force of the water going in doesn't affect the amount of weight the wheel can pick up.  Water wheels work on the principle of the lever.  So, the force doesn't come from how fast the water is moving, it comes from the size of the wheel.  In the picture above, the buckets painted blue are the only ones that have water in them.  So, they are the only ones actually providing any force to turn the wheel.  The red buckets are simply along for the ride, waiting their turn to be filled.

There are two ways of increasing the amount of force that a water wheel can produce.  The first one is to use a larger wheel.  The second one is to use larger buckets.

With a larger wheel, the weight of the water in the buckets is multiplied over a greater distance.  This produces a greater force for the same amount of water.  You can try this by making another water wheel, using large cardboards disks, instead of plates.

With larger buckets, there is more water, therefore more weight.  The wheel doesn't need to be as large, because the balance of weight is closer to being the same.  You can try this by making two water wheels, and attaching them together, side by side.  The two cups next to each other will act like one larger one.

The speed that the water wheel turns is dependent upon the speed that the water is flowing into the buckets.  So, although the water wheel can't pick up any more weight when you are filling it with the garden hose, than it can with the pitcher, it will pick the weight up faster.  When water wheels were used for a source of power in mills, they would prefer a site where the water was moving fast.  Otherwise, they could adjust the speed that the mill turned by putting large wooden gears between the water wheel, and the mill.