Recently, I passed one of my Kyosho Mini-Z RC Monster Trucks (AM 27 MHz version) on to my son, who recently turned 7. He enjoys playing with it, but like most young kids, he does not really know the proper care of the truck. As he was keeping the antenna, he pushed it in with his palm instead of pulling the segments in from the base (my fault for not teaching him that). The result was a broken antenna, near the base of the second top-most segment.
To remove the two top-most segments, I simply took a screwdriver to the third-segment, and pried it open a bit. This allowed me to retrieve the broken part as well as the copper plates that was inside. As described in the caption below, the copper plates limit the movement of the antenna segments, and are critical to proper function.
After drilling new holes in the remaining part of the second segment (a little too far from the edge, but as I was freehanding the Dremel, I didn’t want to risk tearing the bottom of the segment) and putting all the segments back together, the challenge was to somehow roll the top of the third segment inwards, to prevent the newly-fixed second segment from being over-extended.
While I had some success bending it back inwards with a sprue cutter, the tolerance for this part is actually very small, especially when one considers the force an excited child might exert on the segment when extending it. So, I had to go much further than this, and really bend the tip in (a bit too much) and get it back to round-ish by forcing the segment out.
After finally completing the fix, the antenna is almost good as new, much to the relief of the culprit, who can be seen in the last photo. 🙂