Robo Hips                                                                                                                                                                         

Well, before I build legs, I needed something to attach them to... hips if you will.

Snippet of Erin Mckeown's song – My Hips

Download complete Erin Mckeown songs at Amazon,com.

Temporary leg stand.

I built a three foot high temporary leg stand that holds the plank to which the legs will eventually be attached. Nine-inch diameter lazy-Susan swivels are mounted on each side of the plank and they turn in unison because they are firmly connected through a 4.5” diameter hole in the center of the plank. This swivel has a ratcheting/locking mechanism mounted on the top side and has hangers for the legs mounted on the bottom side.

Ratchet mechanism and drag adjustment.

I must admit, the ratcheting/locking mechanism is a bit odd. I needed a mechanism where the ratcheting direction on the right side was in the opposite direction of that used on the left side. What I did was to cut an unused 7¼” fine toothed circular saw blade in half, flip one half up-side-down and then weld the halves back together. Now half the saw teeth point one way and half the teeth point the other way. Steel ratchets are located on lateral aluminum “U” channel arms that can rotate in 30º bites around a central metal shaft made of 1” black pipe (shaft welded to the center of the saw blade). 

Ratchet arms.

A 1/8” nylon line threads through the end of each lateral arm and is attached to the ratchet release of the opposite arm. So when the right line is pulled, two things happen. First, the left ratchet is released allowing the hips to rotate to the right if so inclined. Second, the line tugging at the end of the right arm supplies the force to rotate the hips to the right with the help of  the right ratchet. When the right line is released, the right arm ratchets back to it’s lateral position with the help of a return spring. Now with both opposing ratchets engaged, the hips should be locked into its current position. The line though the end of the left arm works in the same way; ratcheting the hips to the left and when released, locking the hips in place. Pulling on both lines at the same time would release both ratchets allowing the hips to move in any way they wanted and that is probably not a good idea. I had to add an adjustable drag  mechanism  to the lazy Susan swivel to allow the swivel movements to be less erratic and more deliberate. 

Leg hangers.

A 5/16” all-thread axle runs though each vertical segment of two hefty “┌─┐” shaped steel bar hangers. Those bars are bolted to a thick plywood base and the bolts run through both lazy-Susans to the ratcheting saw blade above. The leg hangers and ratcheting mechanism move in unison with a range of + 90º from the central forward facing position.

So now I have hips and a place to hang the legs.