Simple electric motor demonstration kit by JustReadTheInstructions

Last crawled date: 3 years ago

Years ago my son brought home a very simple electric motor made of a coil of wire supported on brass contacts above a D cell battery holder. I thought it was quite an elegant little demonstration. I was recently asked if my company could support a STEM night an an elementary school. Since we build a lot of products with electric motors, I said I'd provide an activity where the students could build and take home their own electric motor. They also said to plan for 150 kids. Those D cell batteries were going to be very expensive in that quantity. This is a variation of a C cell design I found on line using safety pins to support the coil and a rubber band to hold it together. It had no base and just rolled around on a table. I thought the project would be improved by a base, and C cells were still too expensive. An AA battery fit my budget but it is too small for the rubber band to stay on. I designed the two plastic ends to provide a base, to steady the pins, and to grip the rubber bands. The cost of the kit was about $1.10 each, including a color printed instruction sheet and a baggie to take it all home.
The STEM activity was a complete success. We saw over 160 kids in an hour an a half and ran out of some parts in the last five minutes.
On my Flashforge Creator, a set of the two parts takes about 21 minutes. I used the Lulzbot Taz 5 at work as well, which can print more but was a little bit slower, perhaps because of different settings. The parts were printed in several colors of ABS. All the parts were purchased from Amazon except for the plastic, the batteries (Costco), and the sandpaper (Home Depot). You could get the cost down another few cents per kit by just using one magnet. I used two so they stood up closer to the coil, which made the coil itself less critical.
Assembling the base is easy and nobody had trouble with it. There are two keys to success in making the coil:
1) Get the coil as evenly balanced as possible. It spins on the axis formed by the extended wires. if it is out of balance, gravity will be fighting with the magnetic forces and may win.
2) The enamel on the wire is sanded completely off on one end and just on one side on the other end. The side to sand is what I call the "top". Hold the coil vertical (so that it would be flat if you pressed it against a wall) and just sand the top side of one wire. The coil will work equally well if you sand only the top side of both wire ends, but that means you have to be careful on both ends and I was trying to make sure a first grader could make this work.
If the motor doesn't work, it's usually the coil sanding or the balance. Some motor builders needed a little help getting the wires sanded and the coils balanced, but in the end everyone went home with a smile and a working motor.