I designed a gearbox for a radio control tank hull. The gearbox has three gear speeds forward and reverse. In the video below you can see bench test of these mechanics. The switching is done by servo motors which are controlled by an Arduino unit. The Arduino is connected to the radio receiver. Although it runs quite nice on the bench the model isn’t fully problem free at the moment. The reverse gear has to much tension, so that has to be resolved. But for a self designed and self built design it does work pretty good.