I bought two of these for a robotics class I'm teaching. While the students had a good time assembling them, the instructions for attaching the wires (make a loop and attach it to the spring) results in a very loose connection. In fact, the robot did not start to move at all with this connection. I straightened the wires, and put the wire in between the coils of the springs, and one of the robots worked that way. However, the robot moved very slowly, and the students were disappointed (this might be because the wire from the battery to the motor still isn't connected well). I'm going to use a multimeter to verify the other one doesn't have issues with the motor before I try soldering the connections. The datasheet is particularly unhelpful (the pdf link above). It states that the robot comes with a 1.2 volt battery, but ours did not come with a battery, and needed a AA battery to run (which is fine if you're using it at home and have a drawer of batteries, but not so helpful if you're away from home). Also, when the kids were trying to adjust their models from a short stride to a longer stride, they had trouble getting the joints apart (not wanting to break them). It would be great if there were instructions for upgrading the robots, too, but for the price, it's still a fun project for the kids to work on.
