I don't think this is inconsequential.
The Raptor hands have all the fingers mounted at the same place, which is quite different from our natural hands.
- finger knuckle comparrison.jpg (57.99 KiB) Viewed 1635 times
I believe this affects grip. I have a series of pictures to illustrate this point.
- finger offsets.jpg (37.62 KiB) Viewed 1635 times
In picture one, I'm trying to hold the cup in a very unnatural way. Picture two shows why this is unnatural. It requires keeping the fingers straight up and down, perpendicular to the hand. The thumb is not moving directly against the fingers.
In picture three I'm holding the cup much more naturally. Picture four shows why this works. The fingers actually form a diagonal line against the rest of the hand. This makes the thumb and the fingers move directly against each other. When we discus an opposable grasp, we tend to focus on the thumb placement, but the finger placement can be improved also.
Just try picking up a cup and drinking from it in the position from picture number one. That's what we're asking our hand recipients to do.
In fact, one thing I often notice when I grab things with my test hand is that the ring and pinky fingers don't contribute much to the grasp. The object won't stay in the position of the cup in picture one, it twists away from the ring and pinky finger. I think this is part of the reason why.
The Raptor Hands put the fingers in a straight line. However, the Flexy Hand puts them at an angle. I've mocked up something to show what a Raptor style hand would look like with finger placement that is more similar to the Flexy hand.
- hand shapes.jpg (59.28 KiB) Viewed 1635 times
I'm pretty sure I can fit the knuckle pins in, it would just take 3 instead of 2. I am working on a new hand design, and I'd really like to arrange the fingers in this way.
My concern is leaving enough space inside of the palm for the recipients. That's where I need some advice from people with more experience with recipients. I see three ways of changing the shape of the hand.
- hand options.jpg (75.17 KiB) Viewed 1635 times
Option one would cut off a lot of space from the current design. Is that okay? Is that empty space for most recipients?
Option three just adds more space. Everyone who can use a Raptor now will be able to fit into this. However, this will leave empty space and elongate the hand, possibly enough to make it unwieldy.
Option two is in the middle. It cuts a little corner off the side of the hand on the pinky side and raises the index side a bit. This seems like my best bet.
By the way, I'll obviously need to make the inner cavity a straight angle in the finished hand, not a stairstep like in the pictures.
So, any opinions? People who have worked with the Flexy Hand, do you like this palm cavity shape better than the Raptor's? Does option two still cut off too much space?