Saturday, January 25, 2014

prosthetic hand: milwaukee prt.11 (talon hand drilling and threading)

I've been looking at the Talon Hand created by Peter Binkley and then some of the pics that Ivan has posted of building this particular hand. They are using leather for the gauntlet and palm cap. Peregrine Hawthorn had posted comments on e-NABLE about how nice the leather was in contrast to the thermoplastic so I thought Shea should take one of these Talon hands to test as well. I decided to throw the model into Rhino and see if I could size it to the model of her hand. I made some adjustments to the scale and then printed it out. I'm not quite certain if this will be the best hand for Shea as it seems like her thumb may require more space in this design and therefore, she may not fit into it in it's current scale. When I made the palm section larger to accommodate her thumb it was simply too large. Regardless, I printed the smaller version and I hope that Shea will be be able to use it. If not, I will adjust things and we'll get one that works for her. 

Yesterday I went to my studio and in between grad student meetings I was able to drill holes for hardware. I drilled the cable guide so I could countersink some cap head bolts and attach it. I also drilled and threaded all of the holes on the underneath side of the palm where the leather attaches. I used a 6-32 tap and plan on using countersunk head bolts for this. The tap actually cuts decent threads and I think these will hold well if I put some thread locker or finger nail polish on them when I assemble for the last time. 

I designed a "washer" surround plate that has the countersink designed into it, that will keep the fastener heads from pulling through the leather. I believe Peter and Ivan just used washers under their hardware which works perfectly fine. I just happened to have 6-32 countersunk hardware and thought this would look really clean and be flush with the face of the palm. I need to thicken the plates so I can drop the bolts down in a bit further so they become flush. 

I absolutely love the fit of the pivot pins that Peter designed. They allow for easy assembly of the fingers without the need for additional metal hardware. The fingers came together flawlessly  I had purchased some beading cord off of Amazon, but when it arrived it was too large. Jill ran out to Michaels for me yesterday and she picked up some stretch magic beading cord. She purchased two sizes and I went ahead and ran the smaller diameter cord through Shea's Talon hand fingers. They spring back really nicely, so I just need to do a little file work to the palm knuckle joint and make sure all of the cord holes are free of debris and I can run the shade cord. I made a cardboard template for the gauntlet and I'll look for some leather tomorrow. When I get the leather, we'll laser cut a pattern into it so we can fancy it up a bit for Shea. I've had a lot of fun putting this together.

1 comment:

Unknown said...

Brilliant work Frankie! I like the leather mounting plate you printed. Thanks for all you are doing for open-source prosthetics.