It will be a few more weeks before we receive the motor and controller, so to be able to design and test motor brackets we are now building a mock-up motor. We are almost done with our investigation of battery technologies and will take a decision within a few days.
A lot of energy has been and will be spent on calculations and simulations for power consumption, battery charging and optimizing the drive train. We will have a lot of power, but still need to find the gear ratio, battery capacity and so on that gives the best lap time.
We have also ordered a new suspension system to prepare the bike for the extreme Isle of Man track. The surface quality is far away from normal race tracks, and it also includes some "airtime" that is highly appreciated by the audience.
We have received many questions of how the bike will run compared to normal combustion engine bikes. One thing that differs is of course that the torque will be almost the same from start to top speed. On electric bikes that don't have regenerative breaking the experience when releasing the throttle is a big difference. A combustion engine has a lot of moving parts that have a "rotating resistance". Many drivers use this behavior as a controlled breaking function, normally between the start of a curve and apex. The rotating resistance is very low in a brushless AC motor and compared to a normal bike it will feel like the motor is still "on" after the throttle has been released. After some training this behavior can be compensated by using the brakes.
Our controller has the option to enable regenerative breaking, which use the motor as an generator to charge the batteries when the throttle is released. It also has an option to enable an electromagnetic break function depending on the throttle position. This means that we can set up the bike to act as a normal bike if we want to.
When the bike is up and running we will spend a lot of time at the test track to optimize the settings of the controller.
Another common question is how to compare the power between a combustion engine and a electric motor. There are three major differences:
Efficiency
On a normal modern combustion engine between 25-30% of the energy added will be transformed to power on the drive axle. Almost all of the remaining energy will be heat. On a modern AC electric motor 95-98% of the energy will be transformed to power. Note that the most of the bikes that ran the Isle of Man 2009 had a battery of 5-15kWh. One liter of gasoline has about 9kWh energy.
Power/rpm distribution
A combustion engine normally has it peak power almost at the highest rpm. The difference between the power on low and high rpm can differ a lot, and a gearbox has to be used. On a electric AC motor the power is much more even from zero to highest rpm.
Overload
Normally, when referring to an 100kW combustion engine it is the peak power that is meant. It is weaker than 100kW on lower rpm and only has the output of 100kW in a limited rpm range.
Normally, when referring to an 100kW electric AC motor, it is the continuous power that is meant. The power the motor can deliver without being overheated. In a normal design, the controller will not exceed this power. It is however possible to apply approx 2,7 times more power in short time periods without damaging the motor. It is very important that the temperature is kept within the motors limits; if the magnets gets too warm they will permanently be damaged.
The electric motor is a cool thing! Also keep in mind that it is quiet and a modern AC motor will run many many many years without any maintenance.
