A simple inline mechanism that will offer adaptive grip for robotic and prosthetic hands.
With a single tendon pull, you can close all the fingers together, if resistance is met by any of the fingers then the balancing mechanism will react by "seesaw" to stop that finger and carry the travel to the other finger tendons.Once all fingers are gripped around the irregular object then the loads equal and further pulling will tighten the grip across all fingers.
If you offset the the linkage towards the little finger, then this will close the index finger first, then the middle finger etc, for a progressive and adaptive grip.
See this video, to visualise the mechanism working : http://youtu.be/ch6IuaLgQxo
Print two of the small balance links and one of the larger ones.
Assemble according to picture.
For Standard Adaptive Grip
Try to tie off the tendons so the balancing mechanism is roughly central and balanced, i.e. there isn't a particular tendon pulling noticeable more than another, otherwise adaptive grip travel is a little compromised. However, it is a little forgiving on this requirement.
For Progressive Adaptive Grip
If you want to have a progressive grip where you want the index finger closing first (example), followed by all of the others in turn , then make these finger's tendon shorter and offset the balancing mechanism away from the fingers you want closing first. If you have a standard Flexy-Hand 2 gauntlet (or others), you now have 3 empty tensioner slots to move the balancing mechanism sideways to.