Thomas Arnold has been competing in motocross and Enduro races in his spare time for many years. The great thing is that the IAV Team Leader Engine Concepts & Mechanics has recently been on the podium much more often than before. Besides his riding skills, it is his bike that makes the difference: Arnold has been racing for around two years on an e-bike that regularly makes his rivals look old.

The electric motorcycle is based on a Honda chassis for which Arnold has developed a customized drive system. The high-voltage battery made from cylindrical lithium-ion cells supplies 370 volts and has a capacity of five kilowatt hours. It provides sufficient energy for short races of 30 minutes. For longer distances, the battery can be replaced with another in just a few simple steps.

The electric motor, which was also developed in-house, delivers 54 hp and a maximum torque of 55 Newton meters from 0 to 7,500 revolutions per minute. "The e-bike also has no gearbox, so there are no shifting times," explains Arnold. "Hence, there is constant tension on the chain." This is how the system engineer manages to leave even better riders behind in races time and time again.

The technical highlight of the e-bike is the innovative phase-change cooling of the electric motor, power electronics and battery. The cooling medium extracts heat from the hot components through evaporation, which is then released into the environment via condensation. Due to the large temperature difference to the ambient air, the radiator could be designed smaller.

Above all, however, Arnold can operate the electric motor continuously at full load thanks to good cooling – instead of only at around half its maximum power, as is usually the case. The concise formula for this is "peak power = continuous power". "With conventional cooling, I would have needed a 100 hp motor for the same performance," reports Arnold. "This would have significantly increased the weight and the required installation space." 

The innovative e-bike is already proving itself in its second season and has around 300 hours of racing behind it. "The technology has delivered a convincing performance in real life – in other words, off-road and not just on the test bench", says Matthias Krause, Department Manager Future ICE at IAV. For him, the electric motorcycle is also a good opportunity to present innovative technologies that IAV otherwise focuses less on. 

"This applies in particular to the possibilities of phase-change cooling, which we have been working on intensively over the last few years," says Krause. Thanks to Thomas Arnold's racing successes and the numerous trade fair appearances of his e-bike, their level of awareness should soon increase significantly.