During my appreticeship, and final years of high school physics I studied a little about power, acceleration, work etc... Since then, I've lost all of my old text books and am trying to relearn and further my knowledge on this subject. Where I work we build electric scooters for mobility impaired people. When I asked the boss, how he worked out the size of the motors that we use, he said he looked at what was in other scooters on the market, added an oohaah factor and came up with the final choice. (.250kW @ 1800rpm
12V)The problem seems to have a number of steps.
-Inertia (I remember this well from high school, Mass is 170kg)
-Wind resistance
-Rolling Resistance in the bearings and wheels
-Torque (the wheels are 15" in diameter)
-Friction losses within the gearbox. (Standard NMRV50 from Motavario)
-Motor Efficiency
-Battery Life and Power Consumption (Batteries are 12V 44Amp/Hour with
56Amp peak.)The drive train consists of two motors driving a wheel each. They are wired in parralell to the controller providing an electric limited slip differential. The system is 24Volts, and runs of a standard forklift controller manufactured by Curtis.
The maximum speed by law for these type of vehicles is 10km/hr, however we have made some for "private use" rated to 15km/hr by using different reduction gearboxs. I'm assuming an acceleration to topspeed in 0.5 sec.
I thought this might be an interesting head scratcher.
View some photos here:
Regards Dominic.