The upper arms are the same gearing and partial assembly as the shoulder front/back axis. This is so they can both run together at the same speed:
I’ve designed a gearbox assembly for the forearm which allows one motor to switch between several outputs:
The worm gears are printed in Taulman Alloy 910 and the rest of the gears are ABS. The motor will be driven back and forth with a servo so that it can engage with any of the three worm gears – these will drive the hand, elbow, and wrist rotation:
I designed the elbow mounting to be as compact as possible, this leaves the arms just the right proportion for the rest of the robot:
The elbow hinge works pretty well keeping the pulley and string central. The arm rotates on its own track also, the front pulley is spare to operate the hand:
Some pictures of it all in one piece. There are plenty more cosmetics parts to go however…
My name is James Bruton, I live in Southampton, UK.
Please note that this is my personal project website, I have no products for sale, most of the information is provided so that you can have a go yourself... Read More