ROBOT SCOOTER
Before I could begin laying out the parts, I needed to do calculations to make sure the design is feasible. Once I was sure about that, I needed to calculate the required gear ratio to push a person around while being as fast as possible.
This was the first spreadsheet I used to determine whether this ideas is even feasible. My initial calculations showed that it would be feasible to move a 150 lbs person 6 feet in 1.5 seconds. Only looking at the required power, ignoring any losses due to friction, and assuming the motors are running at max power, it would take about 3 CIMs, the maximum that could realistically fit in the desired dimensions.
This spreadsheet is the newest edition of the gearing calculator created by the one and only John Vielkind-Neun, one of the foremost robotics experts for competitive high-school robotics. The purpose of this spreadsheet is to calculate the required motors and gear ratio in order to move a certain weight at a certain speed. It uses complicated physics and motor theory to adjust for motor load, rolling friction, and intrinsic gearbox losses. By changing the constants to reflet my scooter, I used this spreadsheet to find the gear ratio best-suited for a fast scooter that can also safely accelerate to top speed without catching fire. In the end, I found that the best way to get my desired gear ratio is to have idler gears linking the three CIMs, the output of which is then run through an 11:84 spur gear reduction, and then a 15:36 #35 chain reduction. This will get me a top free speed of 7.61 ft/s (5.2 mph) and an average loaded speed of 6.17 ft/s (4.2 mph). Using a standard 17 Ah marine deep cycle lead-acid battery, the scooter should be able to run for approximately half an hour on a single charge.