Requirements
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Weighs less than 6 pounds.
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Does not cost more than $100.00.
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Comply with all rules outlined by ASME (link above).
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Travel 20 MPH.
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Accelerate to top speed in under 7 seconds.
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Able to drive upside down with 1.5’’ of clearance upright and upside down.
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Differentials 15 inches apart.
The first analysis determined how large the body of the car could be; given our clearance and wheel size requirements. After the width of the body was determined, I was able to select the maximum size of the gears in the drive-train/differential.
The second analysis was determining the output rpm of the motor. This was determined using the voltage of our selected battery and the specifications of the motor.
The third analysis was determining the rpm value of needed at the wheels for the car to travel 20 mph. This was done converting linear velocity into rotational speed.
The fourth analysis was determining the gear ratio necessary for the gear-train. This gear ratio reduces the rotational velocity from the motor to a desired rotational velocity at the wheels.
The fifth analysis was determining the diameter of the belt given gear and the amount of teeth that gear would contain. The size of this gear was limited by the body specifications. The amount of teeth on the gear was determined by the pitch of the timing belt.
The sixth analysis involved using the torque value from the motor specification sheet, to determine the car's acceleration. This resultant value would help determine if the car would reach the acceleration requirement.
The seventh analysis was figuring out the exact size of the gears and how many were needed for the gear train. This was limited by the gears available on the market and the body size restrictions.
The eighth analysis was determining the actual linear velocity of the vehicle based on the gears that were available on the market (and used in this project).