From: =?iso-8859-1?Q?Mathieu_Ren=E9?= <creaturiste-AT-primus.ca>
To: <puptcrit-AT-puptcrit.org>
Date: Sat, 20 Sep 2008 14:21:55 -0400
Subject: Re: [Puptcrit] Mini animatronic hands help?


Thanks Joe.
Your input is very clear, and will be useful when we move on to another 
method.
Friction is something we neglected to consider within the finger tubes, 
although we tought about it for the cables once past them.

Just now, we were following the instructable, meaning we were relying on the 
"memory" of the tubing to act as the spring back, so a softer tube would not 
work, therefore the tension to pull it closed is a lot.

I think we'll have to make very loose joints, and add a second set of 
strings to the back of the fingers, to keep tension and open the hand again.

I've seen this done, but the model is much larger than what we need.
It makes a whole lot more sense, and I think there is no tension problem 
with it.
Doing this on the size of fingers we use seems rather insane, not to mention 
unsightly, with all the strings.
The weakness of such a small wooden dowel is a big problem.
I wish we were equipped and skilled to make the whole thing in plastic or 
metal.
http://www.instructables.com/id/Science-Fair---Articulated-Hand--20#allstepslogin





----- Original Message ----- 
From: "Joe Dunfee" <joe-AT-dunfee.com>
To: <puptcrit-AT-puptcrit.org>
Sent: Saturday, September 20, 2008 8:00 AM
Subject: Re: [Puptcrit] Mini animatronic hands help?


> There are a few issues to address. The first being the lever
> arm.  This is how far away from the center of the joint is the from
> the place the monofilament pulls. The next is the resistance to
> bending that the fingers have.  Then, finally the amount of friction
> being caused by the pulling the monofilament through what ever tube
> you are using to guide it (though I see to recall that it is just a
> straight pull from the hand to the elbow)
>
> You can increase the lever arm by moving the monofilament attachment
> point further inward.  Or, perhaps more easily by attaching a bump or
> bead underneath the monofilament right where it attaches. If the palm
> must be visible and the mechanism not show, then you might disguise
> it by thickening the palm.  As an alternative, If the back of the
> hand is hidden , then perhaps modify it by cutting into into the back
> of the hand and severing the existing connection. Then create a new
> pivot point by gluing a strip of cloth over the back of the hand
> while the hand is held in its most closed position.  This may also
> provide a softer joint that is easier to bend.
>
> Of course, you can make two sets of hands, and only use the one
> necessary for the particular footage being shot.
>
> The Thunderbirds (the British science fiction show) had their own
> solution... actual human hands being used for close ups.  Perhaps a
> composite image made possible by modern imaging techniques could be
> another alternative along the same lines.
>
> Joe Dunfee  joe-AT-dunfee.com
> Gordonville, Pennsylvania, U.S.A.
>
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