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[wobblyas]

Electric miniature race bike
Help needed to scope out some ball park specs for a race bike project.

I am a complete novice on electric vehicles but have a basic understanding of electrical stuff. So please be tolerant and excuse me in advance if I say dumb things or ask silly questions.

I want to scope out some ball park specifications for a mini race bike. I have quite specific performance goals for this bike.

I have done a bit of race bike fabrication before and modifying my steel donor frame and motor and engine mounting is something I feel I can manage.

The first step is to scope out what it would take to create an electric bike with competitive performance to a 20 hp miniature motor bike with 11 ft/lbs of torque that weighs 85 kgs. The bike needs to be able to complete 16 x 35 second laps around a 500 metre long kart track. The bike will not need an onboard charger as it can be charged in pits from a 230V power supply and external charger.

I guess I need to know as a starting point to see if the project is feasible is the following?

1. A rough estimate of how many hp and ft/lbs of torque I might need given that I will be trading off hp in favour of ft/lbs with and electric engine.

2. How much battery capacity I will need to complete 16 laps of above track (16 laps includes warm up and return to pits laps). I have two options to consider here for doing multiple sessions in one day....having extra battery capacity and topping up between sessions or using hot swap batteries). Bike will need to be capable of doing about 4-5 sessions in one day with about 1 hour between sessions.

Once I have scoped out the basics I can think about what motor to use, what controller to use, and what battery pack to use or assemble.

[willbrunner]

You might have more luck on the endless-sphere forums for this kind of question.  There are a lot more home-builts over there.  Torque vs power is just a matter of gearing, so for your example, 20 hp and 11 ft-lbs gives about 10500 RPM at the motor.   Power is often limited by the battery size, so that will drive your battery selection more than range in this kind of race.  Have a look at some of the production bike specs for an idea of how battery size affects power, and the size of motor you will need.

[Robinev]

If I may suggest using lithium polymer pouch type cells. 80ah cells the problem you’ll be faced to accept is cramping ev parts in a mini motorcycle frame   You’ll be over weight with motor and controller size you choose. I bet you’ll consider a swing arm motor mount to allow batteries to be fit comfortably. It will change ride characteristics for sure not having motor in central position. I built a similar dream 1988 Yamaha ysr50 ev one off bike.