Normally the fingers on an e-NABLE device all work together from the tensioner system. That is if one of the fingers grips an object, the tension created in the tendons prevents the other fingers from gripping any further; often resulting in a weak grip (one of the biggest issues with current devices)
For some time several e-NABLER’s have been experimenting with a way of achieving adaptive grip on devices. Adaptive grip allows a degree of independence in the individual finger actions, thus if one finger starts to grip the other fingers can still continue to move to help improve that grip. To date these excellent developments have been based on the use of a whipple tree design.
Myself and Stephen had built these devices but for reason unknown neither of us had managed to get the same level of adaptive grip as other people were able to re-produce.
Fellow e-NABLER from France Theirry Oquidam posted a picture of a rapor hand which he had wired the fingers 1&2 and 3&4 by lopping them through the tensioner pin and back to the other digit, creating a simple adaptive grip.
This idea sounded almost to simple to work, but Stephen and myself though its worth trying out. Stephen quickly created a 3 pin tension block to use on our Reverse Dovetail Gauntlet to test, at the same time we both created tension pins with a rounded internal surface to help the tendons move freely through them.
A quick print later and we gave this idea a test; and it worked really well. I'm sure a more complex Whipple tree gives a better adaptive grip, but given the simplicity with this Stephen and myself have decided to stick with this design for the moment.
To date both Mollie and Abbi have received devices with this modification for them to evaluate.
We look forward to their feedback and also releasing this back to the e-NABLE community for all to re-use / progress. For anyone who wants to test this out, the files are HERE.