The UnLimbited arm has arrived

Stephen's 1st build was for Isabella; it was also one of Team UnLimited's most complex builds to date as it was our first venture into building an arm. 

Isabella received a RIT arm; the RIT Arm is an adaptive device for people with an elbow but no wrist. It can be actuated by bending the residual elbow or via a bowden cable connected to a shoulder harness.

The RIT arm was originally developed by e-NABLE members at Rochester Institute of Technology in America; it is a "1st generation" open source assistive device and provides functional usage to the recipient.

e-NABLE's combined arm team are currently working on a new arm; however Team UnLimbited thought we would have a go at creating our own arm !

Following the build and delivery of the RIT arm to Isabella myself and Stephen discussed what we would like to improve :-

  • Total print time of the RIT arm came in at 44 hours; we wanted to reduce this.
  • The cuff for the upper arm is very bulky and while still relatively light it could be improved.
  • The forearm socket is also very bulky and also introduces the complexity of cup fitting for the residual forearm.
  • Potential problems of heat / sweat in the forearm socket, complexity of padding etc.
  • The front forearm requires a tube to interface the socket and the hand; we used a carbon fibre tube from a RC helicopter, but in many parts of the world where these devices could have the biggest impact this might be hard to source.
  • The RIT arm requires various screws and fasteners (if used with the original RIT hand) to be completed, again proving a challenge for people to source components.
  • We wanted to make building an arm easier. To help reduce the list of arm recipient who are waiting.

Stephen took inspiration from a post he saw on instagram of a picture of a girl using an arm adaptation made to fit Gyrobot's world famous Flexyhand.

The adaptation was developed by fellow e-NABLER Christian Silva and he has been having great success with it to date.

So with the development goals set, some inspiration from fellow e-NABLER's and our existing love of thermoforming (as seen in our reverse dovetail gauntlet design) we set out on designing the Unlimited arm.

As the design developed we kept re-printing parts, testing them, evolving the design, re-printing. Working as a team firing ideas and changes between us.

Given that neither of us had developed an arm there was a large amount of thinking, trial and error and more thinking involved ! Stephen had a unique insight into designing what was needed as a recipient himself, and spent many long evening and nights modelling, and remodelling the designs to achieve the best possible outcome.

We decided to cover all eventualities and build 2 devices, Stephen would build one at 100% and Drew at 110% that way we were sure that at least one would fit and let Isabella experiment with one and provide valuable feedback.

  • Colour scheme was to be same as before, pink, purple and green.
  • Phoenix hand to be used as this is what she had adapted to on her custom RIT we built her.

Drew asked Isabella's father Matt if they were any shapes / theme Isabella would like including; apparently starts and hearts would both be good.

Drew's arm was to be customised with colour inlays; this was done by modelling the inlay shapes in Fusion 360, printing them separately and then forming and super glueing them into position. By using inlays we wanted to see what was possible for people who have a printer with a single extruder; often people think this limits them to one colour, but that does not have to be the case with a little cleaver thinking.

Some pictures of Drew's design and build below.

And after final construction, the end result :-

Some picture of Stephen's design build below.

And after final construction, the end result :-

So with the arm's all built and ready for our first alpha test Stephen set off and delivered them both; the results can be seen below, it's fair to say we are over the moon with the results so far !