Friday, April 12, 2013

08 Joint Design Nº 156

These diagrams are one way that I try to understand what I am trying to do with the knee joints. Click on any image to enlarge it.

1. This is the upper leg and lower leg, with the ball attached to the lower leg and a solid socket in the upper leg.
2. The knee joint needs to be able to bend at least 90 degrees, but this is not possible unless the backs of the legs are each trimmed at a 45 degree angle.
3. When trimmed at a 45 degree angle, the leg can be bent 90 degrees. The bend goes around the center of the ball.

This diagram tries to show what happens with elastic tensioning.

4. The ball is attached to the lower leg and the upper leg has a full socket with a hole drilled in the top of it. Tha backs of the leg parts have been trimmed 45 degrees.
5. With the leg in a standing position, the elastic goes straight through the middle of the leg. The dark blue line in the ball indicates the slot in the ball.
6. When the leg is bent, the elastic follows the slot down the ball joint.

I labeled the upper legs Front and Left/Right with some masking tape.

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