Introduction: Simple Animatronic (robotic Hand) Made of Chain
This is very similar to:
I was originally going to build this as the link recommended - but I hate glue, tape and plastic. I want it welded/brazed/bolted together so I opted for what you see in the picture.
Took quite a few tips from the Mythbuster’s episode – (in hindsight not enough as it turns out)
I had the materials laying around the garage so I decided to see what I could come up with. I spent a couple of hours after work in the garage over a few nights & put it together. Originally I was planning on making this a proof of concept and doing a cleaner version with more detailed instructions but too many things going on so this is the best it’s going to get.
Sheet steel for the hand
# 50 chain for the fingers
Copper tubing for the cable guides
Steel cable for the ‘tendons’
½ square steel for the back frame
1” tubing for the grip & finger pulling rings.
3/16 bungee cord for more 'tendons'
3/16 collars to retain the cable (from any decent hobby store for RC planes)
1/8 steel rod for the knuckle stops
Small washers & bailing wire
Weld pack 100 mig welder
Gas torch for soldering the copper guides to the steel
Some tools to cut & grind the steel – (band saw, sheet metal sheers, angle grinder, belt sander, etc)
If you notice in the Mythbuster video & on my hand I use the 1/8 steel rod on top of the fingers as ‘stops’ to keep the fingers from flexing backwards. You have to watch the Mythbuster video quite a few times to catch this. Also the mythbusters video used a ‘C’ shaped piece of material for this. I didn’t’ and this caused me some grief because I wasn’t able to thread the bungee cord under the guides witihout binding. Something that they did in the video and I didn't catch the first time around.
With this configuration you cannot have more than two joints move. That’s just how it works. On the longer fingers I originally tried this but had to not use one of the bends/indexes in the fingers. Again in the video you will notice just two joints move on any finger. The thumb & small finger actually work the best. If I were to make another one all of the fingers would have two joints.
Friction is your enemy. Even with a short a pull as this is, minimize any binding and try to make the smoothest straightest guide for the cables as you can.
The rings for the fingers were cut from some steel tubing. They are VERY uncomfortable on the fingers. I would suggest buying some steel rings to do the job instead.
I retained the bungee in the tip of the fingers by threading it through a washer and used a bailing wire to retain it. Using the 3/16 collars is a cleaner idea. Also, dip/coat the bungee ends/tips in super glue to harden them. Works better for the collars to bite on for retention.
I actually soldiered the copper tube to the steel. I could of silver solder it but soldering it worked fine.
Welding the 1/8 inch rod to #50 chain with a MIG welder is kind of messy.
Also there are only 4 rings. I tied the thumb & forefinger together. I couldn't make 5 cable guides fit.