Trailer motor mover

[Saltfever]

Your hitch-ball-standpipe is a simple lever (or moment arm). Its pivot point is where it is attached. The trailer weight (load, brakes, incline, etc.) is a force. When the ball moves, the trailer force reacts against it and wants to rotate it around its attach point. The wheels on the ground resist this movement until the force is great enough to start lifting the other end. The ball is not located in the center of the chassis so the tipping force will vary depending on the direction. I believe your "lock" restricts rotation of the ball, greatly minimizing the tipping effect. This is why I am interested in your locking mechanism.