Doll hand that grips
Doll hand that grips
The basic premise is a hand that is naturally closed but can be opened with fingers splayed out. When the hand is let go the fingers gradually curl back into a closed position but on a gentle scale instead of a death grip.
Just imagine a doll that gently holds your hand as you hold hers, or spreads her fingers against a wall as you caress her from behind.
The only problem is I have no idea how this would be feasible but I've seen robotic prosthetic hands and a hand that either opens or closes has to be less complex than that.
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Re: Doll hand that grips
Small cables pulled by coil springs. Each finger joint end slightly beveled so the hands curl.dtm1234 wrote:I've been reading Panther's ongoing open hand surgery and it's given me an idea.
The basic premise is a hand that is naturally closed but can be opened with fingers splayed out. When the hand is let go the fingers gradually curl back into a closed position but on a gentle scale instead of a death grip.
Just imagine a doll that gently holds your hand as you hold hers, or spreads her fingers against a wall as you caress her from behind.
The only problem is I have no idea how this would be feasible but I've seen robotic prosthetic hands and a hand that either opens or closes has to be less complex than that.
Would not be pose-able.
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Re: Doll hand that grips
Have faith, a solution shall cometh!
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Re: Doll hand that grips
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Re: Doll hand that grips
Substitute the bendable finger wire with thin spring steel wire that's already curled.
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Re: Doll hand that grips
I wonder if this would work...Technician wrote:The simplicity of this idea from dtm1234 has a lot of merit, and if we're not re-inventing the wheel it's stupid easy to accomplish.
Substitute the bendable finger wire with thin spring steel wire that's already curled.
https://www.mcmaster.com/spring-temper-wire
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Re: Doll hand that grips
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Re: Doll hand that grips
Annealed wire is too soft. Generally formed into shape then tempered to spring steel.
Some spring steel is tempered so hard it will snap if you try to bend it to some set shape.
I've made springs before by annealing the wire, forming then heat treating.
Heat treating makes it super hard then you have to draw out the temper so it won't be brittle. I dropped a fully tempered .190 wire spring on the concrete floor and it shattered like glass.
Maybe a leaf rake that uses the flat steel tines?
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Re: Doll hand that grips
Re: Doll hand that grips
The universal joint above has two pivot points allowing for rotation on 2 axis however removing one of the pivot points will restrict movement to a single axis like a finger.
You could mill out a small slot in the center to insert the torsion spring and that would give the joint resistance. Just use one or two turns on the spring to keep it thin and also a small gauge to keep the force required to move the joint low. The arms on the spring could be set to the appropriate angles to make the fingers have a default resting position of a closed fist.
I might have over-engineered this though, the proposed flat spring steel wire idea might be the way to go I just feel like it's going to give you curved fingers.
**Now we just gotta cram a motor in there and we can move the fingers with our smartphone**
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Re: Doll hand that grips
Dtm, The 14 GA wires that were are doing are actually pretty stiff and will hold a "grip" to a certain extent.dtm1234 wrote:I've been reading Panther's ongoing open hand surgery and it's given me an idea.
The basic premise is a hand that is naturally closed but can be opened with fingers splayed out. When the hand is let go the fingers gradually curl back into a closed position but on a gentle scale instead of a death grip.
Just imagine a doll that gently holds your hand as you hold hers, or spreads her fingers against a wall as you caress her from behind.
The only problem is I have no idea how this would be feasible but I've seen robotic prosthetic hands and a hand that either opens or closes has to be less complex than that.
Exhibit A...
If you folded the fingers into a loose fist, you could open them around your member and they should exert a slight grip. Not a lot, but enough to perhaps feel some pressure.
I think Panther did a little "bedroom test" for this function. He didn't go into details but from what he said I think it must have worked...
viewtopic.php?p=1464642#p1464642
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Re: Doll hand that grips
All of my better ideas require casting a new hand, because the finger bones would be much larger than the wire.
(unless one of you out there has figured out how to hollow out TPE hands easily.)
14 gauge spring steel wire is not bendable.
The stuff can put a dent in your vice.
Yes, it is flexible over the length of the finger, but you will never bend its joints.
You will probably need to use a thinner wire. And wrap it out to original size (like using brass tubing K&S)
The guys doing the stranded wire with the brass tubing have many good things going for them.
It can be retrofitted on most dolls easily. (just like replacing wires)
However, the end result will be broken fingers and future replacement.
Its what happens when you bend copper; it gets work hardened, and then it snaps.
I wish i had my tools, then i would machine you all a wrist, instead of trying to 3D print a part that needs to be steel.
My thoughts on doll hands... human hands are cast in a half curled form. Doll hands are cast flat as a pancake because making those molds are EASIER.
Now, would closed hands or open hands be better? Well, for pictures, one or the other is always what you need.
For expression or touching, and open hand.
For holding an object closed.
My feelings are to make a half closed hand with friction joint finger bones. Because the TPE / silicone will try to push the bones back to its cast shape.
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Re: Doll hand that grips
BOC, the hand plate part does not need to be steel, just the wrist connection. It just needed an eye bolt.BuilderOfCastles wrote:The guys doing the stranded wire with the brass tubing have many good things going for them.
It can be retrofitted on most dolls easily. (just like replacing wires)
However, the end result will be broken fingers and future replacement.
Its what happens when you bend copper; it gets work hardened, and then it snaps.
I wish i had my tools, then i would machine you all a wrist, instead of trying to 3D print a part that needs to be steel.
Panther has been testing these for a while now and so far they are holding up just fine... The problem with friction type joints is that with wear, they will eventually lose their friction.
We see this happening all the time with other hinge type joints in dolls. Eventually they will get loose.
Then you will be looking at replacing, or at a minimum, needing to remove and make adjustments to a much more expensive item.
Not sure what your costs would be, but the two printed palm plates cost less than a dollar for material and the only labor is pressing print and removing some support material when they are done. The eye bolts are a little over a buck for two at Home Depot. Wire is dirt cheap.
The question we have to ask ourselves is how far and to what expense and complexity we want to go for dolls that are only designed to last a few years anyway. It's kind of like putting a Rolls Royce engine in a Ford Pinto and then welding the hood shut. It just doesn't make a lot of sense unless that expensive engine remains serviceable. For more advanced skeletons to be realistic what we need are dolls that are designed to be serviced and maintained just like your car.
Unfortunately we're not there yet - at least not for cheap.
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Re: Doll hand that grips
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Re: Doll hand that grips
At that size of part, it is all machine time, and no material cost.
If i had my CNC mill, it would be less than a dollar of steel, and press the button and come back later.
The thing i really do not like about the eyebolt is the wearing surfaces not being ground flat. So, the pressure from tightening is only on the most raised edge, which is easily worn down.
But, i am glad to hear that it is holding up.
Things involving springs and machined wearing surfaces.
But, that will require a lot of experimentation.
Such as cap head screws.
Then, when you need to tighten, you stick a hex wrench through a tiny hole, and tighten.
You may even be able to get away with the hole just squishing itself closed.