PushBot - Construction: In this case, I started the design by fiddling with the medium motor and a cage assembly, using the rounded gears at a 90-degree angle. I based it on an earlier design that used a large motor. But since I am using the retail EV3 kit, I have two large motors and one medium motor. So I started working on that problem first. I knew that designing a driving base would be fairly easy, but I had never designed a jaw assembly like this one.