TJ snow angels and pulley kebab
April 22, 2009
Today I decided on the arrangement of my Theo Jansen legs on the side of my future robot. I place one prototype on a piece of cardboard and traced the outlines with the legs in all possible positions. Like a robotic snow angel. This way I know what the "footprint" of the entire mechanism against the side of my robot will look like. And if one leg will hit a neighbour when flailing about.
Turns out that the belts I bought are just a little longer than the shortest possible distance. Center to center they will be spaced 28 cm apart. The board you see will be the flank of my creature and measures 80 cm. The rear and front legs will overshoot this board by just a tiny few cm.
Because I do not wish to run six shafts all the way starboard to port side, I came up with a "double hull" idea. Each flank will consist of two sheets of plywood, seperated by a piece of pine of the exact size required to house two pulleys. Here is a prototype of my pulley kebab.
From left to right you see: a bearing (buried in the plywood), brass washer, two aluminium timing pulleys, a brass washer, a bearing and a collet.
The legs will sit left in the picture, hugging the outer hull. In between the sheets of ply sit the pulleys and belts. Protruding on the inside is just short stub of the shaft. I think. Not decided yet.
Still to figure out: a way to make a crank that will sit firmly on a 4 mm steel shaft. And I have no idea how much torque it will endure. Somehow plywood feels inadequate.
[edit 24 april: trying out my new Theo Jansen banner]