Katey's Motor Project

Science Project - Building an Electric Motor

Well, Katey and I decided to dive into her 5th grade science project by building an electric motor. The actual evaluation will take place after we build the motor. You may notice in the above photo that this motor has three separate electromagnets. These electromagnets all have the same number of wire wraps, but are constructed of different sized wire. We are going to measure whether the wire size affects the speed of the motor in any way.

As you can see in the photo, the electro-magnets are placed in a wooden dowel that is designed to spin, depending on what one you are needing. Now that we have this built, I realize that there is a simpler way to achieve this (see below). The above design would require an more elaborate method of getting juice to the electromagnet, otherwise we will end up with a tangle of wires.


Installing an electro-magnet

Since the experiment calls for evaluating the speed of the motor with different sized electro-magnet coils, we needed an easier way to switch them out. I scrounged around and came up with a part of a bolt latch and two plastic barrels that are used for peg board holders. I had to cut the barrels lengthwise (imagine taking a bite out of one side of a doughnut) to make it compress enough to have a decent hold on the 16d nail used for the electro-magnets. It is still loose enough for Katey to switch out the different electro-magnets.


Two other electo-magnets for experimentation purposes

The two electro-magnets in this photo are the smallest wire and the medium wire. All electro-magnets were wrapped with 145 wraps of the wire. The wire used is called magnet wire and can be purchased at Radio Shack in a package with all three sizes of wire together. The black part is electrical tape wrapped around the nail.

Below is a close up of the rotor. It is constructed of a 1" wooden dowel with two 1/2" round ceramic magnets taped on each side. We were going to glue them on, but why mess with glue when you have electrical tape? The beads on the nails are to reduce the friction when the rotor is rotating. The trick on the rotor is that the magnets must be facing in such a direction that they repel each other. In other words, the south poles or the north poles must face each other in order for the electromagnet to properly repel the magnet on the rotor.





Here is a picture of the entire motor without an electro-magnet installed. Note the metal contraption on the left side of the motor. This is the magnetic switch, an important part of what makes this motor run.


Close up of magnetic switch contact

The plans that I designed this motor around used a magnetic switch that can be purchased from RadioShack. I figured it would be easy to construct one from a piece of flashing. The screw at the end serves for both a contact point and also allows you to adjust the gap. When the magnet on the rotor is not attracting the piece of flashing, there should be a very small gap. The larger the gap, the slower the motor runs. With flashing, you can bend it very easily, which allows you to adjust so that the gap is close. You can see in some of the photos that the part of the flashing is bent toward the magnet so as to maximize the pull of the magnet. You can fine tune with the screw adjustment.


Ready to run!

Here you can see the electro-magnet installed. Note the proximity to the magnets on the rotor. The shaft of the rotor sits in two washers that were JB welded in place. I drilled out enough space inside so I can easily remove the rotor when changing out the electro-magnets.

You can get an understanding of how this motor works by this photo. The magnet closest to the switch is attracting the metal flashing, which in turn closes the contact points. This causes power to flow through the coils of the electro-magnet, creating a magnetic force that pushes the opposite magnet away. (TIP: If you reverse the wires that come out of the electro-magnet, you reverse the poles. This means that if the electro-magnet is attracting the rotor magnets, you have the wires backwards.) As soon as the rotor turns enough, the switch opens back up and doesn't re-energize the electro-magnet until it is closed by the other magnet. It continues to operate in this type of 'pulse' fashion, spinning the rotor.