Although I’ve been doing lots of research this week, it felt like not much tangible progress had been made. Frustrated, I quickly mocked up and printed a working differential bar which uses ball joints.

As you can see in this video, it works, sort of:

Movement is restricted by the dimensions of the system, so I’d need to work out how far the rockers need to move and calculate the required size of the ball joints accordingly. Also, this prototype is unusable because the ball joints pop out far too easily, although this is mostly because they are a very rough, plastic print. As discussed previously, the full size version could use Land Rover ball joints.

For the current prototype I’ve ordered these ball joints which are used in Radio Controlled Cars and some M3 threaded bar.

M3 Threaded Bar

RC Ball Joints

These ball joints will help, but I can still foresee problems. Of the three solutions I’ve found though I do think using ball joints is the best because it provides the most freedom to change the position of different elements, can be easily embedded within the frame, and can be built using off-the-shelf parts.