The fun
We converted back one of the RobonAUT cars to a regular RC car. It had a decent speed by default but we managed to make things more interesting by replacing the motor and the motor controller. We chose a brushless motor and a suitable controller. We configured the controller with it’s programmer module to have the vehicle controllable acceleration/brakint/etc. parameters. It would be interesting to see the protocol used by the programming card.
After these modifications the became able to achieve brutal speeds. By using a not so precise measurement method (counting video frames between to points) we are estimating the speed about 80-90km/h. We created a video of this whole fun.
The accident
We already had problems before the set, like when one of the arms of the suspension broke but fortunately we had replacement parts in the other cars. Once after we put a larger amount of load on the car it didn’t want start anymore. The motor twiched a bit and the current was so huge that made a cables twich too. We quickly disconnted the battery. A motor was very hot.
The fix
We took apart both of the parts that my cause the problem. We found surprising things in the motor. The coils unsoldered themselves from the contacts. The coils otherwise looked good according to their resistance. We soldered back them but the rotor didn’t look promising because one of it’s side was worn out.
The motor controller looked bad too, on half of the six pairs for FETs I measured short circuit between the drain and the gate. I managed to get replacements FETs but it was not easy to replace them. One of them was literally welded to the PCB and I only could remove it by grinding it off with my Dremel. After replacing the FETs it still not worked possible because of the failure of the FET drivers and maybe other parts.
We decided to buy a new set of motor and controller with a larger performance.