Hello. Welcome to our mini project where we made a mini, perhaps not so mini motor car.
Step 1: Overview
This post includes how to build a mini motor car as well as the results of testing it and a physics explanation. We had fun creating this car in our high school Physics class within the realm of a few weeks as well as designing and trying out numerous designs to make it work better.
Step 2: Materials
The materials you will need are:
-2 small motors
-2 wire connectors (you can have more)
-Duct tape (it is important that it is non-conductive or at least mostly non-conductive)
-2 plastic cups
-6 wheels (you can use 4 instead however it may affect how well the car drives)
-A battery holder (not necessary but is very helpful)
-Hot Glue gun
-Materials to build a frame out of this could include Knex, tinker toys, etc
Step 3: Fastening the Motor
You will need a way to connect the motor to the wheels. After trying many methods we determined this way to work the best. For this step, you must connect the motor's axle to the plastic cup (make sure it is connected straight) with hot glue. The real point of this however was just to serve as a connection to the motor, if you have a different way of connecting the two then all the better. We tried using a rubber band belt shaft earlier however we faced connection issues.
Step 4: Creating and Attaching Wheels to the Motor
Next take your plastic wheels and attach them to the open end of the cups with tape on the inside of the cup as well as the outside. Also take rubber bands and put them around the wheels for added traction. Caution: If your wheels aren't perfectly straight attached to your axle then they may hit the side of the car and too much traction will cause them to be stuck and not move. So you can adjust the traction by adding or removing bands. In the end we decided not to use the rubber bands due to not needing the extra traction.
Step 5: Creating the Chassis of the Car
Our group used tinker toys to create a chassis for our car. Nearly any other material can work for this step (such as Knex) as long as the chassis is sturdy and has a section in the middle for 2 motors to attach to. Keep in mind that depending on what material you use the way you connect everything will be different, we recommend using a material most compatible to your motor.
Step 6: The Finished Car + Battery Connnection
Attach your motors and their wheels to the middle of the chassis to complete your car. You must have wires go from the two motors to the battery pack. In our car the battery pack was too heavy so we held it while our car ran, however, if the motor car is built a bit differently then it can hold the weight. A drawback of our design is that it did not move very fast and was unable to support the weight of the batteries. this issue was due to the method of how we connected the motors to the wheels. the better the connection the better the mobility of the vehicle.
Step 7: Test Results
Our vehicle worked but was not very effective.The drawbacks of our design is that it did not move very fast and was unable to support the weight of the batteries. This issue was due in part to the method of how we connected the motors to the wheels, and by the materials used. The better the connection the better the mobility of the vehicle, if the motor is more directly connected or even just simply attached directly with out any parts in between, there would be no issue with the wheels moving straight forward. So as a result, our motor connection was the primary issue however, we made the car move just not as straight nor as fast as we had wanted.
Step 8: Physics Explanation
The physics behind this comes from circuits and kinematics, in particular angular kinematics. The circuit is fairly simple, consists of batteries that supply voltage to the system, a motor that serves as a resistor and wires. The voltage provided current which then spun the axle on the motor making the wheels turn. Torque is the rotational force. The more torque the easier the wheels move. Having larger axles provides more torque. However given that, it is also important to consider speed, the more torque the slower it goes. Another thing to consider is traction. Different materials interact differently, that is to say some materials will have greater traction. This too helps move the vehicle. with out it the car wouldn't move. Weight also adds to traction so keep that in mind as well. We hope you enjoyed reading about our physics project and how we dealt with problems by modifying our vehicle design!