This is a contribution to the eNABLE community of open-source prosthetic hands.

The Falcon V2 is a new hand design for test of a number of new concepts. The key features we focused on for the falcon were:

1. High degree of field maintainability: If a finger breaks, it is easily snapped off and a replacement is snapped on. Control cables are fished through one channel and crimped in place, requiring no tools and no knot tying. It is suggested that users are provided with 3-4 extra fingers with control cables run for easy repairs.
2. Reduced (removed?) knot tying – ideally no knots are required for assembling a falcon hand (and by extension no knots to fail).
3. Two position thumb: Allows for both key grip and cylindrical grip
4. Modular Palm: The hand has a structural frame with a mostly cosmetic palm cover. If someone wishes to design a modified palm cover they simply need to match the hole pattern used for securing the palm cover to the palm frame. In doing so they can create artistic covers in any modeling software without having to deal with the structure or function of the hand itself. A sample palm cover is provided but improved ones are very much desired
5. Rubber band return springs: To reduce build / assembly problems, dental rubber bands are used instead of elastic line for the return springs. These are easily available, cheap, and easily replaced should they fail. It removes the need for threading and knot tying of the elastic lines.
6. Increased adjustability in proximal attachment: Since no knot is tied in the cable crimps they can be tweaked in and out and crimped and un-crimped until the right position is set. This is also key to item 1 (field maintainability) in that the user does not need to untie and retie with precision.
7. Modular bracer (forearm part): A modular mount is provided on the bracer to allow for custom covering of the cable crimps. Preliminary designs have been proposed for picture frames, “ben ten” wrist communicators, watches, smart wearables, etc.
   Coming soon to a Falcon V2 near you (work still in progress)
8. Locking system
9. Modular palm designs
10. Modular bracer covers
11. Improved bearing surfaces on knuckle joints pins (covering the pins with cut-off bic pen barrels)
12. Improved cosmetic appearance of fingers (cosmetic covers)
13. Improved mounting scheme for palm cover
14. Better scalability
15. Improved printability (bridges)
16. Your ideas here…

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SPU Design Team:
Dr. Adam Arabian
Barrett Estep
Sean Russell
Nicholas Rogers
Parris Anawati

This design is a product of the engineering department at Seattle Pacific University.

Falcon V2.0 preliminary assembly guidance
SPU Design Team:
Dr. Adam Arabian
Barrett Estep
Sean Russell
Nicholas Rogers
Parris Anawati

This design is a product of the engineering department at Seattle Pacific University.
Introduction:
The Falcon V2 is a new hand design for test of a number of new concepts. The key features we focused on for the falcon were:

1. High degree of field maintainability: If a finger breaks, it is easily snapped off and a replacement is snapped on. Control cables are fished through one channel and crimped in place, requiring no tools and no knot tying. It is suggested that users are provided with 3-4 extra fingers with control cables run for easy repairs.
2. Reduced (removed?) knot tying – ideally no knots are required for assembling a falcon hand (and by extension no knots to fail).
3. Two position thumb: Allows for both key grip and cylindrical grip
4. Modular Palm: The hand has a structural frame with a mostly cosmetic palm cover. If someone wishes to design a modified palm cover they simply need to match the hole pattern used for securing the palm cover to the palm frame. In doing so they can create artistic covers in any modeling software without having to deal with the structure or function of the hand itself. A sample palm cover is provided but improved ones are very much desired
5. Rubber band return springs: To reduce build / assembly problems, dental rubber bands are used instead of elastic line for the return springs. These are easily available, cheap, and easily replaced should they fail. It removes the need for threading and knot tying of the elastic lines.
6. Increased adjustability in proximal attachment: Since no knot is tied in the cable crimps they can be tweaked in and out and crimped and un-crimped until the right position is set. This is also key to item 1 (field maintainability) in that the user does not need to untie and retie with precision.
7. Modular bracer (forearm part): A modular mount is provided on the bracer to allow for custom covering of the cable crimps. Preliminary designs have been proposed for picture frames, “ben ten” wrist communicators, watches, smart wearables, etc.
   Coming soon to a Falcon V2 near you (work still in progress)
8. Locking system
9. Modular palm designs
10. Modular bracer covers
11. Improved bearing surfaces on knuckle joints pins (covering the pins with cut-off bic pen barrels)
12. Improved cosmetic appearance of fingers (cosmetic covers)
13. Improved mounting scheme for palm cover
14. Better scalability
15. Improved printability (bridges)
16. Your ideas here…

Tools and Materials Needed:
1/16” drill bit
5/64” drill bit (optional)
Channelock type pliers
Needlenose Pliers
Wire nips
Metal file (sometimes)
Lighter
Scissors
Dyneema (preferred) or curtain cord
Needle or other small pointy thing
Soldering iron or nail for fusing joints (see step 1d)
“Extra Heavy” (6-6.5 oz) dental rubber bands
Broad head screwdriver (or a quarter should work too)
Parts to Print:
1x Gauntlet
5x Control Cable Crimper
2x wrist pin
2x Wrist Pin Retainer
1x Palm v2_2 OR Palm v2_3
1x Palm Cover OR Palm Cover v2_3
1x thumb rotation module
1x thumb rotation retainer
5x Falcon Prox Finger
5x Falcon Mid Dist Finger OR 5x Falcon MidPhil and 5x Falcon DistPhil
5x Finger Cover

Printing guidance:
If possible fingers should be printed on their sides, NOT top to bottom. This is particularly important for the proximal section. This is tough since they have some overhangs so you may need to add a support.
The palm cover and gauntlet will need supports in the palm area if you normally use them in printing.

Step 1: Build 5 Fingers:
a) Ream out the transverse holes on both the proximal and distal parts using the 1/16” drill bit. You can do this by hand or with a drill but be careful with the drill – it melts the plastic and it tends to fuse your bit in place – I usually do this by hand. You may find that in order to have minimum friction you need to ream out the proximal component (the inside one of the two) with a slightly larger bit; alternatively you could just work the 1/16” a bit longer and clean it out to a slightly larger diameter.
a1) If you are doing the three phalange build then repeat the above for the Falcon MidPhil and Falcon DistPhil joint as well then proceed as below, repeating as appropriate for those parts.
b) Ream out the control cable paths with the 5/64” drill bit if available; if not just work the 1/16” in and out to clear out the rough edges.
c) Cut a 1.5” length of scrap filament and drive it through the joint. You can use shorter but you want enough left on the outside that if it doesn’t seem to bend well you can re-ream it again. What often happens is if you cut the hinge pin filament too short it gets stuck in there and you can’t get it out. If this happens, just pull the joint really hard and it should (may) come loose.
d) Once you like how the joint is moving, get a soldering iron set to about 650 degrees (don’t use your good tips for this) or a nail heated on the stove (or an awl since they have wood handles) and fuse the filament to the outside of the finger.
e) Check that each of the five fingers moves freely.
f) Do F, G, and H five times, once for each finger: Take a piece of Dyneema (recommended – if you use curtan cord you will have to do lots more drilling of the paths but it should work since they are sized for dyneema) about 18” long. Use a lighter and just barely pass the dyneema end through the flame – this will melt away the little whispies of loose fiber around the core.
g) Thread the dyneema in from the proximal (knuckle) end to distal. It takes a bit of art but it feeds well since you already reamed it out. If you ever have problems threading the dyneema I find that running it once very lightly over a light wax (I use chapstick) gives it just a bit of stiffness that makes it much more "pushable" and removes any fraying tendancy. You will see it poking out near the tie off bar. Fish the loose end out of the outer slot past the end of the tie off bar.
h) You can either
a. tie off the dyneema on the tie bar (recommended for now- I'm finding b and c below don't work well but I'm going to keep trying with more or different knot types because I hate tying to tie off bars) OR
b. tie 2-3 square knots on top of each other (untested but we believe this will hold in the hole), OR
c. take the end of it and, using the lighter, set it on fire. You want it to actually flame, not just melt. Once its on fire, let it burn for about half a second then gently blow it out. This will melt the nylon outer layer into a big ball of plastic. Let it cool for a few minutes then tug on the loose end. This will pull the knot into the hole where it will stick tight. We THINK this works as a permenant securing scheme but we haven’t had a patient on which to field test so please give feedback here.
i) You now have five floppy fingers… time to move on to the thumb assembly…
2. Thumb Assembly
a) The thumb itself is one of the five fingers you attached above, but the pivoting thumb assembly has a few extra parts; namely the thumb pivot and c-clip.
b) Take one of the fingers and thread the control line UNDER the bar, up through the slot, and through the little window on the thumb pivot.
c) Snap the thumb over the crossbar on the pivot
d) Loop a rubber band around the mount on the pivot and then over the mount on the proximal end of the thumb. Its kind of a pain to get it onto the mount on the pivot.
e) Put an elastic between the mounts in the proximal and distal segments
f) Thread the control line out through the hole on the palm frame
g) Insert the thumb pivot post through the hole on the palm frame
h) Using the channel lock pliers, snap the C-ring into place around the post
i) Test the thumb pivot – it should move and engage in position with some resistance but the thumb cable assembly should flex the thumb with little noticeable resistance.
j) You now have a thumb attached – time to move on to the…
2. Palm
a) We don’t currently have supports on the palm since our printer doesn’t require them and we are still waiting for our ultimaker to try them out. They may be required for the main palm frame and will almost certainly be required for the palm cover.
b) Test the three palm cover attachment holes for fit for a 1.75mm filament section – it should be quite snug but pass through. If it does not ream it with the 1/16” bit but do NOT over-ream it. You want it to be a tight fit. See below if its too loose.
c) Similarly ream out the holes on the palm cover. This has a bit more freedom since you will be melting the filament pins in here but still keep as tight a fit as possible.
d) Cut three 1.5” lengths of filament and drive them into the palm frame holes until they bottom out. Then carefully set the palm cover on top for a fit test. If it fits, cheer, then remove.

NOTE - this isn't the best solution for the palm cover - if anyone has ideas please let me know. I want a modular cover but I've tried a few options and nothing has panned out.

e) Loop the control cables for each finger UNDER their crossbar and up through the slot, then snap the finger over the crossbar.
f) Loop elastics around the mounts on the palm to proximal segment, and a second from the proximal to distal segment.
g) You should now have a palm frame with three filament pegs sticking up and five fingers attached. When you bundle those cables together and pull the fingers should flex reasonably smoothly. You may need to do some filing on the proximal segment near the mounts to make them truly smooth. Tolerances are a bit tight on this model to keep it from being sloppy but it requires some occasional filing to make sure it all fits.
3. Palm Cover
a) For the four fingers (not palm) do a quick pass with the lighter over the dyneema ends and fish them through the channels. Should go pretty easily.
b) For the thumb, do the same, but the path is a bit oblique since its coming from the side of the hands.
c) Pull those tight and seat the palm cover onto the pins
d) Using your soldering iron or hot nail, melt the pegs into the palm cover. The palm cover is now held in position by the three pegs, and held down by friction into the palm frame. This is assisted by the fact that the cables, when tensioned, are also pulling the palm cover down into the frame. That’s the theory at least… we may need to revise this attachment scheme.
e) You now have five cables hanging out the back of the palm cover, so move on to the…
4. Bracer/Gauntlet (not sure what everyone else calls this but a bracer is the forearm cover in armor so I figured what the heck)
a) Align the bracer holes with the holes in the palm frame. Insert a printed pin into each side from the INSIDE (so the nice round head is on the arm side of the wearer). Use a C-clip to secure it in place. IF the pin breaks when inserting the C clip (happened only once but it can happen) just use your nail/soldering iron to melt the hinge pin in place.
b) Thread the leftmost control line from the palm cover through the leftmost bracer hole. It will poke out and you will need to fish it out with your needle (maybe). Thread THIS through the hole on a cable crimp and snap the cable crimp into place with the control cable aligned so it feeds straight in. DO NOT TWIST IT YET!
c) Repeat for the remaining four fingers.
d) Position the bracer in the “neutral” (hand open) position desired by the user with the fingers flat on the table. Put the thumb in the KEY GRIP (out to the side) position. Pull the control cables taught so there is no play in the fingers
e) Tricky bit here – if the cable comes in from the LEFT SIDE of the crimp, you want to turn it CLOCKWISE. If it comes from the RIGHT you want to turn the crimp COUNTER CLOCKWISE. This means the two on the left go CW and the middle and two on the right go CCW.
f) Using your broad headed screwdriver (or a coin should work as well) twist the crimp about 180 degrees in the direction indicated above. The control cable should be well secured in position.
g) Clip the excess control cable and you’re done except for:
5. Velcro
a) The velcro on the palm frame screw into the four mounting holes. These will need to be drilled out to the right size for your screws (this may need some work)
b) The bracer Velcro wraps through the loops
c) It is suggested that we investigate lycra or canvas embedded with oogoo and make the palm area more of a “sleeve” than a Velcro fit but this is an area for investigation.