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Use one of the longest wires to connect the two motors together

If you put gears on the crank, make sure you build it very strong (brace the gears on both sides), otherwise the gears will slip and grind, or you may break a peg or bend an axle.No matter what, crank smoothly and be gentle with your crank motor, you don't want to damage it!

Hold the crank motor firmly in one hand and crank smoothly with the other hand.  Important: Be smooth and gentle so that you don't stress the motor parts.  Notice that if you crank the other direction, the car will change direction too.  If you are left-handed, or if you want your car to go the other direction, you can switch the hand crank to the other side of the motor.   

Try using gears on the car (or possibly on the hand crank) to change the rotation speeds and see how this affects the speed of the car.  Here is an example of using gears to speed up the car, if you can figure out how to build it or make something similar.  

Using the Generator Car

Try some other designs for the car.  There are lots of possibilities. Does this generator trick give you any other ideas that you could use it for?  For example, if you had an NXT robot that used one motor powered by the NXT for something, you could power and control the speed and direction of something else by using a second motor powered by a generator from the third motor.

If you carefully note now much the car wheels turn for each rotation of the crank, you will notice that one full turn of the crank results in somewhat less than one full turn of wheel rotation.  This is because the electric generator is not 100% efficient.  There are some losses due to friction and other things.  For example, if the car wheels turned 270 degrees for each 360 degrees of rotation of the hand crank, then the generator would be 270/360 = 0.75 = 75% efficient.  Can you estimate the efficiency of your generator?