I have a bunch of large geared motors and have directly connected them to my wheels. However, the wheels keep falling off. It seems like wheel hubs are ALWAYS problematic because those little hex screw things are not enough to hold them in. Is there a reason why people don't just drill a hole through the shaft and hub and put a screw through the center of the motor shaft? Seems like it would hold a lot better but I wouldn't want my shaft to break or something. The shafts I have are pretty big and the wheel hubs have a long end. Is there a better solution than those hex screws for the wheel hubs?