Got Physics?

MY ELECTRIC MOTOR

To make a homemade electromagnetic motor, you will need magnet wire, coated stranded 14 gage cooper wire, electrical tape, 2 L shaped brackets (or 4 if you choose not to use the wood), a threaded metal rod, 2 cooper pipe coverings, 2 wooden scraps for supports, a wooden base board, 2 pieces of malleable strips of metal, 2 alligator clips, a 6 volt battery, and screws, washers, and nuts. FOR class assignment: a toy car, thread, and a spool.

The commutator and armature are all placed, or “skewered” on to a threaded rod. This rod is then drilled through two wooden supports. The wooden supports are made from a 7x2.5x.75 pieces of scrap wood, and are screwed onto a base that is 12x7x.75. An alternative for the wooden supports would be 2 L-shaped brackets, or any type of scrap metal that you can drill hole through. If using the wooden supports, it helps to insert a small metal pipe to coat the wood. This reduces the friction between the threaded rod and wood, so when it rotates it’s rubbing up against metal. Screw the ends on with washers and nuts.

Motion from the motor I built comes from the basic principle of a magnetic force. In a magnetic field, opposites attracts and likes repel. In an electric motor, these forces are used to create rotational motion. Two magnets are created in this motor, the armature, and field magnet. The armature is also called an electromagnet. In building my simple motor this was made by simply wrapping magnetic wire around 2 nails. Tape the two nails together and then pirce a hole through he middel of the tape and put the threaded rod, the axel, through it. Next begin wrapping the nails with the 24 gauge magnet wire, the wrapping is a key part of this motor. Make sure you leave a few inches of wire out to connect to the commutator later, and then tightly wrap the wire from one side to the end and back down in the same direction so you create 4 layers. Then cross underneath the axel and wrap the other side in the same fashion, then leaving extra wire out to connect to the commutator. Once connecting everything to the battery, the nail eventually becomes a magnet once with a north and south pole. After creating this electromagnet, this is attached and suspended in between the middle of a field magnet. The field magnet is also created by wrapping wire around a metal bracket. Now you have the main part of a basic simple motor. If you connect the armature to the commutator and then the battery to the brushes that touch the commutator when it rotates it creates a series circuit. The motor (hopefully) then will spin because the north end of the field magnet will reply the north end of the electromagnet, and the same with the south end, in turn creating the thing to spin 1/2 way around. Then, the field of the electromagnet flips, causing the thing to rotate fully around. This flip is caused by the direction change of electrons flowing from the commutator and brushes. (diagram below)

The commutator was made simply by cutting two cooper pipe holders and fitting them onto the shaft that is wrapped with electrical tape to the desired width. The purpose of this split ring commutator is to keep the torque of the motor from reversing overtime it rotates around the magnetic field. The commutator reverse the electrical current direction when the brushes make contact. It is important to make sure the two cooper pipe holders fit around the shaft so they are close together, but not touching; otherwise the circuit will short out. 

The 2 brushes are made from a flexible stranded copper wire, that is connected from the battery on one side, and to the electromagnet (the coiled wire on the bottom) on the other. The brushes “brush” up against the commutator and transfer the electricity. The placement of the brushes and the commutator are critical for your motor to work properly. To make sure the brushes make good contact with the commutator fan out the threads of thin cooper wire strands. The brushes are supported up by pieces of scrap metal, and bent at an angel that reaches the commutator and so the brushes touches it smoothly.

This project takes a lot of patients, trial and error, and some tools that may not be readily available to you. However there are ways to make this motor without some of the tools. For instance, a solder is helpful to stick the two cooper commutator plates to each wire from the armature. However you can simply twist the wire around the cooper plates, but, the connection may not be as strong. A drill will be required to make holes to screw various brackets into the base. The different angels the brushes are at, also takes a lot of time to adjust so that its not hitting both ends of the commutator. Its also key that you strip the clear coating off the magnet wire otherwise the electricity won’t flow through. I made that mistake the first trial of my original motor.

One of my original models of the motor (above) worked, however there were some technicalities that made its operation irregular and not that great. First, the wire I originally used was just cooper lamp wire. This wire isn't insulated (like the red magnetic wire in the photo). Therefore when connected would spark, and generate to much heat which made it dangerous. Second, the model i made was made out of PCVP pipes which were really heavy and created a lot of friction and drag when rotating.   After adjusting these details the motor ended up working very well and efficiently. Below is a photo and short video of the final motor I made.

In class our assignment was to pull a toy car 4 meters, in the shortest amount of time using the motor. To make this happen, I put a spool onto the threaded axel shaft, and secured it with washers and nuts. I put 2 different sized spools to see witch works better when winding the thread up. Initially, I thought the larger circumference the spool, the faster the car will travel because the motor will pull more string in in one rotation. Although, the smaller spool makes the winding more accurate and tighter. In the end both will work.