My son gave the idea for the model. The model was supposed to be remotely controlled, playable and it was supposed to be a motorbike. So the choice fell on LEGO® Technic. At the beginning, I thought that the Power Functions elements should be placed on a trailer that would be pulled by a motorcycle. At the same time, the trailer would ensure that the motor will not tip over and it will be possible to steer it. Unfortunately, subsequent attempts and failures with such a solution meant that the idea had to be different. I gave up the trailer. I built a motorcycle passenger from Power Functions elements. They turned into a pretty cool robot. By the way, the center of gravity of the model shifted to the center, between the wheels of the motorbike. To make the model stable and not tip over while driving and turning, I added two small wheels to the sides. The robot is both a passenger and a vehicle drive, and the location of the drive axle itself prompted me to define such a solution as PDS. Phallic Drive System ;)