A more powerful motor

We made another motor from four 3/4" x 1/4" NdFeB magnets taped to a used water bottle. Between the magnets are strips of aluminum foil to make contact between the brushes.  The brushes are held onto the cardboard box frame by clothes pins.  Also, an axle running through holes in the bottle was made from a coat hanger wire.  At the base is an angled electromagnet (enamel coated 32 AWG wire wound onto a glued together paper spool and mounted onto a cut plastic cup).  The setup is timed so that as a magnet just passes the coil the circuit is connected and the magnets push apart, then the circuit is broken as the bottle rotates and the next magnet comes into place. 

 

It can run on only six volts but it is more fun to hook up twelve volts in series to run it faster (top picture).  After running for a while the aluminum foil was almost completely worn through so we replaced them with stripped wires, which worked a lot better.  

And we needed one further modification.  Only using the magnet to push the bottle around means it is turned off most of the time.  I added a second set of brushes to make contact at a different point and hooked it up to reverse the flow of electricity through the coil.  The results in a pull of the next magnet toward the coil, then it switches off briefly as the magnet swings by, then kicks back on with a push of the magnet away. 

The pull-push configuration spins the bottle much much faster than before.  It will run on a minimum of 3 volts.  With 9 volts it will self start (not requiring a push to start spinning).  We hooked up all the batteries we could find in series and got it up to 33 volts, at which point it seemed like the motor was about to fly apart.  It was getting dark at this point and with the lights off we could see lots of little sparks flashing between the brushes and contacts as it spun.  

The wiring was trickier for a pull-push setup.  At least two batteries are needed because the current is set up to flow in both directions, so if one battery were used for everything it would short circuit.