In a previous post I discussed a problem with the differential bar mechanism. Here I present two possible solutions.
The first uses two linear bearings with a swivel joint between them:
The second uses an armature with a ball-joint at each end:
The advantages of the linear bearing mechanism are that the differential bar can be close to the rocker mechanism, whereas in the ball-joint method there needs to be enough space between the differential bar and the rocker for the ball-joint armature to have enough room to swing. However, if using the linear bearing mechanism then the bearings will need constant maintenance, the rods would need greasing, and at the moment, I haven’t thought of a way to effectively enclose the mechanism to stop dirt getting into the grease. The linear bearing method also looks like it could create a lot of friction whereas the ball-joint method appears to move more freely.
I have some 8mm diameter steel rods and 8mm linear bearings lying around that I can make use of to see if this solution works.