You will remember this missing gear from yesterday's post. Who knows where it went, perhaps it was never there (I remember that we got these robots cheap as part of a "damaged stock" sale along with a bunch of other toys, maybe this one never worked).
Since I want to separate the leg movement from the torso rotation, I need to make some changes to the current drive mechanism. I have been staring at it for a while now and I think the best way will be to find a small, low rpm, gearmotor and drive the vertical groin shaft (ahem) directly. This solves the missing gear problem and also allows the torso to be mounted via servo on top of that motor assembly, so that it can rotate relative to the legs.
Here are two short videos of the legs moving. In the first one you can sort of see how the ratcheting wheels (which can only rotate in one direction) allow the robot to shuffle forwards.
So now I just need to source a small cheap gearmotor in no time at all... Dealextreme would have been the answer (isn't it always?) if shipping time wasn't an issue.