Speedy DC Motor: My Design

Building my motor was a pain (I cannot tell a lie). I had lots of trouble figuring out how to modify the dimensions of my motor to fit my armature, and even more trouble trying to get it to work. In the end, I made two different armatures on my motor.

The Parts of a Motor:

Armature and Shaft:

This is the part of the motor which turns. In my design, it's an electromagnet. On many other motors that I have seen, it is usually the ONLY electromagnet. Instead of doing what the instructions said by using two 2 1/2 inch nails, I ended up using four 5 inch nails (Link). 

First, I put two nails together, the tip of one meeting the head of the other, and wrapped it up with tape. I did the same with the second pair of nails. Then, I taped the two pairs together, and wrapped some 20 gauge magnet wire around it (That was the highest AWG wire Marvac Electronics supplied).

I found that this worked out better than the design on the original instructions because the two nail heads prevented the magnet wire from slipping off of the ends. 

For the shaft of my first armature, I used a wooden dowel, and that worked really well. However, for my second one, I used a threaded metal rod which wasn't as easy to work with. Since my armature was already attached to the shaft I was forced to stick with the metal rod.

Commutator:

At first, the commutators were quite tricky to figure out. I was planning on using the copper pieces Mr. Bostian gave to me in class, but my soldering iron didn't work very well and messed up the connection between the wire and copper plate. 

I looked at the instructions I found on the above link again, and found a way to make a different set of commutators. I took the two ends of the magnet wire that hung out from my armature to create an alternative for the terminals. I folded the wire into a zig zag pattern and taped it down onto the base of my commutator. I repeated these steps on the other side, and sanded the enamel off of both terminals. This worked much better than soldering as the wire's electric current didn't have to be reconnected to anything.

I was quite pleased with how well it ended up working too.

Brushes:

The brushes were the trickiest part of the motor. They had to be close to the commutator to keep the current going, but also far away from each other so as not to hinder the shaft's movement. Instead of using copper stranded wire because it was way too delicate, I just sanded the ends of two wires.

I had a bit of trouble getting it to touch the commutator. I adjusted it a lot, and ended up nailing a piece of tape-wrapped metal over the end of the wire where it connected to the board. I wound the wire around a nail to secure it.

Field Magnet:

Finally came the field magnet. I would just like to say, 12 gauge stranded and insulated wire is EXTREMELY difficult to wind. I ended up using 16 gauge magnet wire (also courtesy of Marvac Electronics). I wrapped it about 400 times around two L brackets that I had taped together. To secure the field magnet to the board, I glued a piece of wood to the side and screwed it in (much easier than using metal strips).

Testing 

This part was both fun and frustrating. I took a couple of aligator clips to create a circuit on various places on my motor. I was trying to test how everything worked on its own to make sure my motor was functioning perfectly. First, I isolated the armature from the rest of the contraption. I put a nail to the coil and found that the magnetism was very strong. Next, I checked the field magnet and got a similar result. My brushes ended up being the biggest problem. The current wasn't going through due to bad connection. 

I sanded the brushes and commutator, which ended up being the only thing I needed to make my motor spin like crazy.

Finally I attached the spool to the shaft. Since it was a strong motor, I used something pretty large. I found some cardboard in the shape of a ring and cut circles from the back of a notebook to attach to the ends. I screwed a picture frame hanger into the side to act as a fish eye hook, and tied a toy jeep to the end of the spool.

And Voila! I finished my motor!

Speedy DC Motor: History

The original ideas and concepts of electromagnetism were discovered by Oersted, Gauss, and Faraday. over time, their principals were built upon to create the successful motor that we use it many appliances today.

Alessandro Volta:

Though the ideas of electromagnetism were not originally his, Volta is credited for beginning the revolution in electric current. In 1800, he created the world's very first battery. By stacking together plates made of copper and zinc with brine-soaked cardboard in between each plate, Volta was able to create what is known as "The Voltaic Pile."

Michael Faraday:

This British scientist set out to prove whether or not a current could produce a magnetic field. On October 1821, Faraday used the following experiment to prove this:

He placed a permanent magnet in the middle of a bowl of mercury. A free hanging wire hung from above, long enough to pass the surface of the mercury. When he connected the wire to a battery, it moved in a circle around the magnet. Faraday then reversed this by making the wire secured and hanging a magnet from a wire, and the same phenomenon occurred. By doing this, Faraday demonstrated the basic concepts behind electromagnetism.

Joseph Henry

Henry improved Faraday's motor in the year 1831. His electromagnet was held on a horizontal axis. As it spinned, the polarity reversed as the two permanent magnets attracted and repelled the electromagnet. In was able to spin at 75 cycles per minute. He believed his experiments to be nothing more than "Philosophical Toys"

William Sturgeon

In the year 1833, this British scientist's motor included the very first commutator. It continuously rotated and became a simpler yet less stable version of the modern motor. The most important detail about Sturgeon's motor is its ability to carry more than its own weight. This became a phenomenon that sparked the creation of many modern day machines.

http://www.solarbotics.net/starting/200111_dcmotor/200111_dcmotor.html
http://www.aip.org/history/gap/Henry/Henry.html
http://www.eti.kit.edu/english/1376.php
http://inventors.about.com/od/utstartinventors/a/Alessandro_Volta.htm
http://www.britannica.com/EBchecked/topic/570124/William-Sturgeon

Speedy DC Motor: How it works

In order to create an efficient DC motor one must first understand how it works. Below is an image of said motor, and though the design is not entirely the same as the one I built, it works in the same fashion.

DC Motor

This motor runs by using two electromagnets (In the diagram above there is only one, as the second magnet is a permanent one). An electromagnet is a metal object that becomes a magnet when a current is sent through a wire wrapped around it. As soon as the current is removed, the metal object returns to being nonmagnetic. Why does this happen? 

Before a current is run through it, the metal object's domains are randomly aligned. Each electron that runs through the wire has its own small magnetic field which is increased each time the coil is wrapped around the rod. This magnetic force straightens out the mismatched domains of the metal object, and gives it a north and south pole.

Electromagnet Diagram

The motor spins as the similar poles of the two magnets repel. The commutator holds two copper pieces that aren't touching, and that is what allows the motor to keep spinning. The brushes temporarily lose contact with the copper, breaking the circuit. When the they touch the copper pieces again, the poles of the electromagnet are reversed. Thus, as the magnet turns, the like poles repel, and the cycle continues.

Design of my DC motor

http://www.evilmadscientist.com/2006/building-an-electric-motor/

http://science.howstuffworks.com/electromagnet2.htm

Mousetrap Catapult

Building the mousetrap catapult required me to do some thinking structure wise. To make the catapult work, I first had to figure out how to even launch a projectile with it. 

I decided that I would use a spoon to launch a test wad of duct tape:

Catapult version 1

The wad flew relatively far, but I noticed it skidded on the ground a lot before reaching its furthest point. I thought up of a new design to improve my old one and came up with this:

Catapult version 2

I stuck two eraser on top of one another to stop the hammer from snapping the spoon all the way to the other side. This gave the wad more time to travel through the air before it hit the ground. It landed much further than my first model, much to my relief.

Stacked Erasers

I thought over my catapult a little and then decided to add a metal spoon. However, the spoon was too heavy and slowed down the initial velocity at which the wad left the catapult. Disassembling the contraption was a nuisance.

Catapult version 3

In the end, I added a stool under my project by 1 foot to give it a height boost. The duct tape wad went further than when it was on the ground. I also put my plastic spoon back on, after the metal one proved to be useless.

Final Catapult version 4

Of course, like any project involving things that snap, I had my share of technical problems such as injuring my finger, breaking the mousetrap, trying to find mousetraps in the store, and getting duct tape stuck in my hair. One of my biggest problems I faced was the fact that when the hammer snapped, the back side of the mouse trap came up and the projectile went off course. I solved this problem by taping the mouse trap down to the top of my stool.

Overall it was a fun experience and much better than doing my other homework. Hopefully I don't fail when we launch ping pong balls next Monday