Video of my Final Motor

Here is a video on how my final motor ran. Enjoy!

Problems with My Motor

Problems with my Motor

As you must know, Mr. Bostian, I had some issues with my motor working, so I will have no problem filling this post up!

Problem #1: The Armature

 The entire concept of the motor deals with electromagnets and electricity. My main problem with my motor was that, for a strange reason, my armature was not acting as an electromagnet even though I wrapped it in parallel lines, sanded the ends of the enamel off, and had a firm contact point with the copper. It turns out that since I had used aluminum as my metal for the center of the armature, it wasn't magnetic enough. It took quite a lot to realize that that was the issue, including multiple trips to your classroom and a lot of confused phone calls. I ended up rewrapping the armature twice before I knew that it was not my wrapping skills which were the problem, but the very core of the armature. After I replaced the aluminum rod with 4 inch penny nails, it was easier to make the motor move (as it was actually physically possible now).

Problem #2: The Brushes

The brushes play a key role in the motion of the motor. They switch the poles and conduct the electricity from the magnet to the commutator to the armature and back. The brushes, since they are flared out like paintbrushes (hence the name), also have a tendency to get caught in the copper and stop the entire motion of the motor. This took issue took a lot of playing around to deal with it. I first made my brushes vertically hanging down instead of rising up so they would get caught less. It then took a lot of playing around to get my brushes in the perfect position so that they wouldn't get caught on anything or touch the tape on the ends of my commutator. Once that was figured out, electricity could travel through the brushes without getting caught on the copper.

Problem #3: Excess Friction on the Axle

The holes that were pre-drilled in my metal strips were actually too large for the axle (the metal rod) that held my commutator, loom, and armature. It was banging around when it spun and creating excess friction that slowed down the motion. I solved this problem by putting a washer and two bolts on each side to lock it down. 

Conclusion

There were many more smaller issues when building the motor, such as buying the wrong wire (multi strand 14 gauge wire instead of single strand), the copper always falling off the cork (solved it by taping it down on the ends instead of underneath), and general crossing over of wires (when you rewrap each thing three or four times, you tend to be a bit lazy), but all of those were solved by the end of the building process. Problems with the motor were annoying, but it also was a learning experience on being more careful and learning how to problem solve efficiently to complete the task at hand.

My Motor

My Motor

My motor basically consists of the main five parts listed in the previous post, a.k.a:

• Field Magnet
• Armature
• Commutator/Brushes
• Shaft (Axle)
• DC Battery

And an extra piece, the loom, to pull the car. With all of these parts working together, it can pull a car four meters. As I explained how each piece works in the previous post, here I will explain how I built each piece and how they flow so that it can spin.

Field Magnet

My field magnet consists of a steel strap bent into a "U" shape that is around 5 inches wide. I then wrapped 14 gauge single strand (must be single strand) wire around it to form and electromagnet. The wrapping must be parallel to the strands next to it and underneath it. Any crossovers in the wrapping, it could cancel out the entire magnetic field. The wire must be single strand as the multiple strands could get crossed over and also cancel out the entire field. The single strand makes it a lot more difficult to wrap, but it will also actually work, so that's good. Using a strong vice like I did will make this job a hell of a lot easier (excuse my unscientific language there). Mine turned out like this:

Armature

The armature is another electromagnet that spins above the field magnet. It is made up of two penny nails wrapped in 24 gauge magnet wire, and then is attached to the commutator. I made it by taping the two nails together with electrical tape, and then wrapping it with the magnet wire. The same wrapping rules apply as with the field magnet: no crossing over. Also, I sanded off the enamel at the ends so that the electricity could flow through the copper on the commutator. Here's mine:

Commutator/Brushes

The commutator consists of something round to go around the shaft (mine is a cork), and two pieces of copper. I made mine by drilling a hole in the cork in order to get it on the rod, and then when it was on, i taped two pieces of copper around it. The two pieces of copper should have spaces in between them, but not have them too large because the brushes should be able to touch the metal at all times. The commutator is attached to the armature by the wires from the armature. These wires must be soldered on, and have had the enamel scraped off. The brushes consist of two pieces of multi strand lamp wire, flaring out to look like paintbrushes. These must touch the copper at all times, to allow electricity to flow into the copper and then into the armature. 

Shaft (Axle)

The shaft is the metal rod that holds the commutator, armature, and in my case, the loom. This is the rod as seen from above: 

DC Battery

The DC battery I used is 6V (fun fact: 6V is half a car battery!) and powers the motor. 

(Double fun fact: in much older cars, they did use 6V batteries. So I surely hope mine can simply pull a toy car!)

Overall Motor and Final Connections

In the end, one brush connects to the battery, one connects to one end of the field magnet, and the other end of the field magnet connects to the other end of the battery. This completes the circuit, sends the electricity through the field magnet, into one brush, into the copper, down through the armature and back, then to the other brush and back to the battery, making the motor spin!

 My final motor. 

How A Motor Works

How a Motor Works

Parts of a Motor

Building a simple motor, while seemingly daunting, is actually a simple task to do. A simple motor requires five main components: 

• Field Magnet
• Armature
• Commutator/Brushes
• Shaft (or Axle)
• A DC Battery

With all of these pieces working together, the field magnet will make the armature spin, allowing for motion and uses such as pulling a toy car on a loom. Here, I will explain a bit about magnets and how each piece works and connects so that the motor can work.

Magnets/Field Magnet

A motor uses magnetism to create motion. A magnet has two poles, a northern one and a southern one. If you have ever played with simple magnets, you know that like poles repel and unlike poles attract. This is the basis for the electric motor. Furthermore, an electric motor uses something called an electromagnet to create motion. An electromagnet is a device that creates a magnetic field through electricity. It simply requires some single strand copper wire and a piece of metal. By wrapping the wire around the metal, and attatching each end to a battery, the current flows through the wire and creates a magnetic field around the electromagnet. This is the basis of building a simple motor. The field magnet is an electromagnet that has a strong magnetic field so that the armature can spin rapidly. More on how the armature reacts with the magnetic poles in the next section. 

                         An Electromagnet                                                                         Field Magnet Diagram

Armature

The armature is made up of two pieces of metal with lower gauge magnet wire wrapped around them. They go through the shaft, or an axle, which is basically a metal rod in which the armature and commutator goes through. The armature is what causes motion when it reacts to the magnetic field caused by the electromagnet. When the wire is wrapped around the two pieces of metal, it basically becomes a magnet as well, with two poles at the north and south ends. When the electromagnet is activated, it has two poles as well. Naturally, the two like poles are repelled from one another, so the armature spins so that the unlike poles are near one another. This motion is what makes the motor spin.

Commutator/Brushes

The "flipping of the magnetic field is accomplished by the brushes and the commutator. The brushes are what send the electricity into the commutator. It allows the electricity to flow into the armature and is what flips the direction of the poles. By reversing the current each half turn, it keeps the armature spinning in the same direction. The brushes are made wider than the insulated gap, to make sure that the brushes are always touching a bit of copper. It is connected to the armature from the magnetic wire wrapped around the armature.

  Shaft/Axle

The shaft is a metal rod that contains the commutator and armature. 

DC Battery 

A DC Battery is necessary to provide electricity and complete the circuit. 

Connections

With all of these pieces connected, electricity can flow through a complete circuit and the armature spins rapidly over the electromagnet. Then it can pull a toy car (hopefully!). A gif of how the motor is supposed to work.

Sources for this post:

http://electronics.howstuffworks.com/motor6.htm

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motdc.html#c2

My Bridge

My Bridge

In order to construct a bridge that will be able to support a mass well over fifty times its own, a balsa wood bridge must be carefully crafted with supports in order to dissipate force throughout the bridge, not just in the middle sector where the two-by-four will rest. In order to do that, the bridge that I am building will have trusses, or framework that supports a bridge or other structure, that will equalize the tension created by the weights. The trusses dissipate the force so that the bridge shares the force equally, so it does not bend and break such as under this beam bridge.

The weight of the elephant causes tension on the bottom of the bridge, with the bridge trying to support the weight. But without trusses, the part of the bridge where the elephant is would not be able to support that weight and it would eventually break. 

This is a picture of the way forces dissipate in a truss bridge, such as the one I am constructing. The forces now can be shared throughout the entire bridge.

This is a basic design of the bridge that I am constructing. The tresses and abutments on the ends help equalize the forces so that the bridge does not bend and break as easily under high amounts of pressure.

Static Equilibrium

Static Equilibrium

When all forces on an object are balanced, then an object is said to be in a state of equilibrium. Objects that are in a state of equilibrium must have an acceleration of 0 M/S/S. This does not necessarily mean that the object is at rest, though. An object could be moving at a constant 75 MPH but still be in a state of equilibrium as it is not accelerating. This derives from Newton's first law, or: 

•  An object is in rest and stays at rest, or
• An object is in motion and stays in motion with constant speed and direction

If an object is at rest and in a state of equilibrium, then the object would be in a state of "static equilibrium" with static meaning stationary or at rest. Bridges use static equilibrium to balance their forces. Structures on the ends of bridges, or abutments, help equalize the forces on the bridge so that the bridge does not collapse. In an arched bridge, the abutments at the end of the arch take the brute of the force and help dissipate it throughout the bridge. Some bridges such as suspension bridges try to dissipate it through the ground with the help of anchorages, towers, and cables.  

Forces at work in an arched bridge.

Another example of static equilibrium are balancing toy birds. The birds have weights in their wings and beaks that help the forces spread out and balance. This helps them reach static equilibrium and helps them balance on almost all surfaces.

 

Bridges

Bridges

Bridges are structures that span over some sort of obstacle such as a body of water, a trench, or a valley in order to provide transportation over said obstacle. Certain bridges must be able to withstand certain conditions such as the terrain or weather in which the bridge is anchored. For instance, in San Francisco, bridges must be able to withstand the frequent earthquakes that occur as the city is placed on a major fault line.

The Golden Gate Bridge in San Francisco

There are many different types of bridges that have spanned throughout history such as the beam, truss, arch, suspension, and many others.

Beam Bridge

The beam bridge is constructed of horizontal beams which are supported by structures at each end. These components support the downward weight of the bridge and any traffic traveling upon it. In supporting weight though, the bridge endures compressional and tensional stress. To try and spread out the forces, sometimes a longer beam is used. Sometimes the pressure is too much though and a truss may need to be used.

These are both examples of beam bridges.

Truss Bridges

A truss bridge is a bridge whos lattice-like superstructure that bears the load of the force. The support truss adds rigidity to the structure, greatly increasing its ability to dissipate the compression and tension caused by weight on the bridge. Once the beam begins to compress, the force is spread through the truss. 

Arch Bridge

The arch bridge has been used for over 2,000 years. Its elegant structure is composed mainly of two abutments, or structures at the end of the bridge where the superstructure mainly rests, at the end of each side of the arch that take the main amount of force. The curve of the arch and abutments greatly dissipates the amount of tension on the underside of the bridge. 

The second picture shows how the tension dissipates throughout the bridge.

Suspension Bridge

Suspension bridges suspend the roadway in between two towers held by cables. The towers support much of the weight as weight pushes down on the roadway, is transferred to the cables and then to the towers. The towers then dissipate the force directly into the earth. The cables however, receive most of the bridges' tensional force. The cables are attatched to anchorages, or large slabs of rock or concrete in which the bridge is anchored to, and the tensional force travels through the cables, to the anchorages, and then is dissipated into the ground.

Bridges come in all shapes and sizes, but they all basically do the same job: support weight over a certain obstacle. In order to do that job, they must find a way to dissipate the forces so that they do not buckle and break.