ElectricMotorcycleForum.com

Hello guys,

I am working on some maths to build an Electric motorcycle but i am bit confused with all the maths.

The main problem of the many problems is:

1. Motor Selection - How to know what motor( power, torque, rpm, etc.) i'll need?
2. Battery Selection - How to calculate power required from batteries to motor.

My requirements are:

1. Top Speed = 100 km/hr
2. Cruise Speed = 60km/hr
3. Acceleration = 0 to 60km/hr or 0 to 100km/hr in 3 seconds
4. Range = 20kms

My constraints are:

1. Motorcycle Weight (without batteries) = 100 kg
2. Rider Weight (My Weight) = 68 kg
3. Motor Weight = ??
4. Battery Weight = ??
5. Overall Motorcycle Weight (with rider) = 302.5kg

I am planning to use the following tire as rear:

90/90 X 17, which is = 593.8mm in diameter,
The circumference for the same is = 1865.5mm, which is = 536 rev./km
so for

60km/hr this tire will need 536 RPM and,

for 100km/hr it will need 894 RPM

Now based on the calculation on above parameters i get the following results:

for 60km/hr on flat track,

Total force required to move the vehicle from stand-still to 60km/hr = 53.79 N
Gear Ratio = 3:1
Torque at Wheel (wheel dia = 593.8mm) = 15.98 N-m
Torque Required at motor = 5.33 N-m
Power Required to cruise at 60km/hr = 1.2Hp
Power required to accelerate from 0 to 60km/hr = 19.91Hp

and for 100km/hr on flat track,

Total force required to move the vehicle from stand-still to 100km/hr = 142.83 N
Gear Ratio = 3:1
Torque at Wheel (wheel dia = 593.8mm) = 42.45 N-m
Torque Required at motor = 14.15 N-m
Power Required to cruise at 60km/hr = 5.32Hp
Power required to accelerate from 0 to 100km/hr = 57.49Hp

Can some one explain the process for selecting the motor and battery based on the above calculations.

Also i'll be thankful if anyone can verfy the above maths.

Thanks

WSR