Foot Surgery (A happy accident):

I had just returned my 1:100 Altron to its shelf above my wife’s dresser. It was still in an action pose (essentially same as the photo to the right), which meant it was a bit off balance. I thought I had it tilted so if disturbed, it would fall back against the wall instead of taking a header off the shelf. I was wrong. When I came back later that day, Altron was in several pieces on the dresser. I immediately rushed it to my “emergency” room, and began to clean up the (thankfully) minor paint damage. While it was apart, I decided to make a mod I had been planning on for some time, and one I had picked up from a B-Club conversion—double ball ankle joints. The cause of the fall was due in part to the floppy knee joints Altron suffers from and also to the lack of good foot balance. As can be seen, the left foot is barely in contact with the ground—only the inside edge of the foot is keeping this guy up. Even with the offset ball joint on the foot, ankle mobility is not good. The kit is indeed leaning backwards in this photo, just to keep from pitching over into a face plant. I had ordered some Kotobukiya #111B double ball joints from HLJ a month ago, and figured now was a good time to use them.

The mod plan was simple—cut off the ball joint on the foot, add a ball socket, then reattach the foot to the kit with a double ball joint (left), using the existing ball socket in Altron’s lower leg. I started by clipping off the foot ball, and then drilling it out with progressively larger drill bits. I wanted the hole to be large enough to slightly countersink the socket. If you want to bury the cup even deeper into the foot to keep the same height, it wouldn’t be a problem. But since this kit was already painted and finished, I didn’t want to take too many chances with the paint on the foot sides.

The next step was to attach the cup portion of the ball joint to the foot. The Kotobukiya joints are made of ABS plastic, which like the Bandai PV caps, can’t be glued well to styrene. To fix the cup, I needed an anchor to mechanically hold it in place whether the glue worked or not. Using my trusty lighter, I slightly singed the end peg and smooshed it into a shape that would give me the anchor needed. I then completely filled the interior of the heel section with superglue/talcum powder (SGT). After putting the cup in anchor down, the SGT will completely fill in around the anchor, totally locking the joint in place.

There were two major problems remaining: The Kotobukiya double ball joint is too loose in the Bandai ankle socket, and the double ball joint is too tall, which would give Altron a very exposed, odd looking ankle. To get around that, I scratchbuilt my own double ball joints. The first step was to completely fill the kit ankle joint cup with SGT. Since the kit cup is PV, it acts as a mold for the SGT, which I took out 10 minutes later. One trick here for strength and ease debonding: put a wooden toothpick into the SGT as it is setting up. This gives you something to grab to help pull it out, but also gives the SGT a bit of strength. The toothpick was trimmed down to as long as I wanted the foot side ball to be and then stuck into the111B joint cup filled with liquid SGT. When the SGT is dried, you have a complete, well bonded, and tough double ball joint. The homemade double ball joint was carved and sanded into a figure 8 so it could give better flexing. The finished homemade joint and the original joint are shown side by side for comparison. You may find that using the joint cup for a ball joint master mold gives you a slightly loose joint—the ball should actually be a little bigger than the size of the cup. A quick fix is to apply clear nail polish to the ball until it is sufficiently tight. A longer term fix is to take the ball and spray a ton of paint (in multiple coats!) on it, building up the size of the ball. You can then make RTV molds and resin copies of the joint. Either way works. The finished foot is shown to the right (make sure to put the slightly smaller ball into the foot side cup—test fit on the leg side first). There was minimal visible damage to the foot from the drilling, which is easy to touch up, but also covered by the lower leg. Now the whole unit can be plugged back into the lower leg.

Results!

Comparing the original to modified foot in a normal pose. Modified ankle on right; the new ball joint adds about 1-2 mm of height to the leg, depending on how it is posed.

This photo shows the original and modified leg at maximum side deflection. In both cases, the feet are flat on the ground, and the heels are aligned. The toothpicks were required to keep the new foot/leg from toppling over.

Original to new ankle posing (similar poses); note how much better the modified feet plant.

Modified Altron Gallery (a selection of poses. > 100 kb):

Pose 1 Pose 2 Pose 3 Pose 4 Pose 5