Motors

     An electrical motor converts electrical energy into mechanical energy. It uses a magnetic field to generate force.

     A motor has three main parts. The first is the rotor. This is the part of a motor that spins. It is usually wrapped with many coils so that when electricity passes through it, it makes a magnet. The rotor spins in the magnetic field created by the stator.

The stator is the part of the motor which creates a magnetic field that spins the rotor. It usually surrounds the rotor entirely, creating a strong field. It too is usually wrapped with coils of wire to make a magnet when electricity passes through it.

The final part which makes a motor work is the commutator. This is the piece which makes sure the rotor spins. When the brushes of electricity touch the conducting sides, the magnet turns on, and the rotor spins. However when it spins, the brushes move to where there is no conductor, and the rotor keeps freely spinning. This cycle happens over and over again very quickly, making the motor turn full revolutions.

My Motor

     For my motor, the construction is very simple:

First, I constructed my stator.

My stator consisted of five layers of single strand 14 gauge copper wire wrapped around two L-brackets made of galvanized steel. I also put a layer of duct tape in between each layer so that the layers wouldn't mix and mess up the field. Next, I made my rotor.

The rotor is made around a thin iron rod which spins. The rotor is wrapped with two layers of 24 gauge magnet wire, and secured in place above the stator. The magnets will power on, and the rotor will spin.

Finally, I built the commutator. The commutator is quite simple. The ends of the magnet wire from the rotor come to the commutator, and each end touches a different piece of copper taped over a cork. Both pieces of copper have a space between them on either side, allowing the electricity to easily turn on and off. This constant turning on and off causes the motor to spin 360 degrees.

This is the finished product:

Also, I attached a spool of thread near the back of the commutator to pull a toy car. I found a large space and tested how powerfully the motor can pull the car:

 

Problems with my Motor

     Most of the building process was quick, and easily done. However there are a few problems I encounter even now:

1) Inconsistency

     My biggest problem is inconsistency. Due to the way that the brushes are done, the speed of the motor is very inconsistent. Often the commutator pushes and bends the brushes out of the way, blocking the contact between the two. This can severely change the power of the motor and how fast it spins, making the difference between a C- and an A+.

                 

2) Winding the spool

     Often when the toy car is being wound, the thread will wind itself off the spool and into the way of the brushes. This could be a serious problem if it tangles with anything important.

My Balsa Wood Bridge

     For my Balsa Wood Bridge, I am going to attempt to create two different types of bridges, then work further on whichever proves stronger.

For my first prototype, I will be using a simple design of the truss bridge:

     I personally like the truss design the best because it is the strongest in architecture. The triangles formed in the center will relieve stress from the bottom of the bridge. It also uses the smallest amount of wood most efficiently. With the wood and mass that is saved by using less for a better design, I will have room to make adjustments and improvements.

For my other prototype, a very simple arch bridge will be made:

The arch bridge is stronger than most others, due to the curvature of the bridge. It will ease the tension from the center of the bridge, and distribute it to the sides.

As for my adhesive, I am going to test both wood glue and various epoxies, because these have different properties and bond differently than normal glue.

Because these are very early prototypes, I do not yet have exact measurements. As I progress through the stages of planning and building, the measurements will become clear,  also keeping in mind the rules and regulations provided by the B-Meister. 

Static Equilibrium

     Static Equilibrium is when an object has many different size forces acting upon it, but the sum of forces equals zero.

For example, have you ever tried balancing a pen on your finger? It won't balance in the middle because the forces are unequal. You have to find the balance point, or the fulcrum (which in this case is toward the cap of the pen). At this very point there is static equilibrium- the forces acting on the pen are unequal but are zero at this very point.

Here is another example:

These birds balance on your fingertip. Normally, they would fall off because the forces are not balanced. The birds are weighted just right, however, that the fulcrum is on the beak. Here there is static equilibrium.

Bridges also use the concept of static equilibrium. Bridges need to be durable and be able to withstand lots of weight. Different bridge types use different methods to ease the force on the horizontal bridge itself. This is an example of how suspension bridges work.

Bridges

     Bridges are structures that are built to get from one place to another without having to go around obstacles. Usually they span over water, cliffs, or even other roads. Different obstacles call for different types of bridges, which can vary in length, width, height, and structure. There are four main types of bridges:

Beam Bridges

 Beam bridges are simply a straight beam, usually made from wood or metal. Forces are distributed to the ends of the beam, which is distributed into the ground. Because of their ability to bend easily, they cannot span far distances.

Suspension Bridges

  Suspension Bridges are beam bridges with tall towers connected by a cable. The cable significantly takes force off the horizontal part of the bridge. This allows much longer bridges to be built.

Truss Bridges




 A truss is a structure, usually made of metal, which forms small triangles. Truss bridges are extremely useful in relieving compression and tension from heavy loads. They is also very economical because of the small amount of materials needed for a strong design.

Arch Bridges
  Arch Bridges have abutments on both sides. The force from the weight is pushed into the bridge, into the abutments, and into the ground. Arch bridges have a history of being built from stone, especially by the Greeks. Like the suspension bridge, they too can stretch long distances because of the even distribution of force.

Robotics

Robots are used for all sorts of things. They can be built and programmed different ways to accomplish different tasks. Not all robots are built out of metal and gears. Legos can be used to create robots too.

 There are two main components to a robot. The first is the actual structure. The structure of a robot has to be built specific to the task of the robot. If you want a robot to walk upright, then the balance must be equal so it doesn’t fall over.

 The second component is the program. A robot needs to be told what to do. A program can be made specific to the structure and task. For example, you could write a program that tells the robot to wait until it sees a certain color to move a certain way. There are many possibilities for a program.