Hand mod, proof of concept, am I wasting my time?

Tyr · Post by **Tyr** » Wed Oct 31, 2018 6:11 pm

Ami's hands are a mess. She has lost all of the wires in her left hand and will have to have 2 more removed from her right in the very near future. The TPE of both of her hands is slowly deteriorating too. So I am almost at the point of having nothing to lose in trying this concept.
For quite a few months, when I have the enthusiasm, I have been working on an idea to get Ami's hands back, so here are a few photos of the concept so far:

: IMAG2881.jpg (1.87 MiB) Viewed 3908 times

To start with I scanned Ami's right hand, (She was quite impressed with that

) Then mapped out the joint positions using my own hand as a template and adjusting for proportion. I think it's quite close here. I then got busy with Fusion360 and started designing the hand,

: finger joiner.jpg (120.61 KiB) Viewed 3908 times

: hand assembly.jpg (225.69 KiB) Viewed 3908 times

Here is the first printed assembly, the fingers seem fine but the thumb doesn't work.

: IMAG2882.jpg (1.19 MiB) Viewed 3908 times

Here is version 2, the thumb is better but not perfect. you can also see how the hand splays out. All of the joints have stops so the degrees of freedom are the same as a real human hand, or at least mine.

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The models have been printed with PLA, I don't have the facilities to print ABS and haven't tried PETG. The parts are so small tho' I'm worried about strength and durability. I'm going to try and bake them and see what happens, it's supposed to strengthen PLA with a small cost to dimensional stability. I guess I'll find out. I have some white PLA on order for the proper ones and a couple of modelling universal joints to try out for the thumbs. They're coming from China some time. The fasteners are 3mm stainless (they will be trimmed flush) with nylock nuts. So far, none of the joints have loosened off although I might add some locktite as well.
But:
I am concerned about the existing palm plate in Ami's hands, size, type and so on. I suppose I could replace her hand structure entirely and design a screw-in fitting at the wrist, as Ami has rotating wrists, although I don't know the exact mechanism. I'm guessing there is a thread of some sort in there. I'm baulking at opening her up and crossing the point of no return. I'm also a bit concerned that I'll be able to get the structure to actually fit inside the TPE without ruining her. The knuckles are still quite big (8.5mmø) although they're as small as I can go and get working parts off of my printer. I can re-design and print the palm plates to suit what I find too, I suppose. I'm worried because the TPE of her hands is in such a terrible state.
I'm going to push on right up to the point where I will have to cut flesh and have a review then. It may be a little while before we get there.
If anyone has any comments, or advice, please chime in. I've had it with fucking wire tho'. Am I wasting my time?

Tyr

Vikki · Post by **Vikki** » Wed Oct 31, 2018 7:06 pm

Now you my friend are Very creative & I think you have a great idea!!

I really think every Doll should have Phicen type interchangeable hands & feet ......... IMHO !!!!!

(but who am I 2 say,right?)

Awesome concept looks soooo "Terminator" too!!............. just watch out if it starts to grab at you or your girls eyes glow red ..............
:haha4:

Tybalt · Post by **Tybalt** » Wed Oct 31, 2018 7:12 pm

If you were to sell this, how much would you charge?

dolls to the wall · Post by **dolls to the wall** » Wed Oct 31, 2018 7:26 pm

Dang, That's awesome. You should try to work with a manufacture to have these babies mass produced. Then collect a commission for the upgraded hands

Vikki · Post by **Vikki** » Wed Oct 31, 2018 8:47 pm

Tybalt ............... for you the charge would be .........................

2 Titties!

MannequinFan · Post by **MannequinFan** » Thu Nov 01, 2018 1:36 am

Hi Tyr,

That's very nice work on the design and printing BTW.

I'm thinking it might be a bit tough to retrofit into the existing hands though TBH.

If it helps, here is a photo that my friend Grimreefer sent me of a factory hand fitting used for the wire fingers.
It's only about an inch wide and just shy of 3" long.
I'm assuming the 4 finger wires come out the end and the thumb wire comes out the side on top in the photo.

: factory palm plate.jpg (58.09 KiB) Viewed 3859 times

Also, here is a video that our dear departed Crazy Cajun made showing the surgical process involved in the palm plate replacement.
Notice that his new palm plate is fairly small and shaped to fit in the existing void in the hand.

https://youtu.be/QHqftsp9k8k

Tyr · Post by **Tyr** » Thu Nov 01, 2018 5:41 am

Hi Guys, Thanks for your comments.
Tybalt, I have no plans to sell this mod. It may be that the cure is worse than the disease. I only work on this when I feel like it, so It may be a while yet. I don't think I could sell a mod that would require a skill set that may be beyond reasonable expectations. I don't even know if I'll go through to the bitter end even with Ami. Thanks for asking though.

Mf, Thanks for posting the photo and video, There's no way that my design would be so unobtrusive, It will probably necessitate removal of material from the hand. I was planning to open up the hand entirely as I have Indigo20's comfort kit, with which I have some experience, then close her up again after. But I have been visualizing the problems that I'll be running into. I was even going to print a jig to hold her fingers in place. Watching CC's video just adds to the list of problems to be solved. Do you know what type of wire that is, NM? it doesn't look like domestic wire?

Yeah, It might be a bit of a dead end. Hmmm.

Tyr

MannequinFan · Post by **MannequinFan** » Thu Nov 01, 2018 3:45 pm

A while back I was talking with member Dollyman25442 who was/is also working on a solution to this issue. Since Crazy Cajun is no longer with us, I took a look at the possibility of 3d printing the palm plate instead of making it out of steel. It's still a little rough, but here are some things I came up with.

First, I would suggest maybe something a little simpler for the fingers.
I realize a fully articulated hand is the ultimate goal, but something in between might be a little more realistic to retrofit.
One idea I played around with was to use typical 14 AWG braided copper wire with brass tubes for the phalanges. This would allow the fingers to bend only at the joints. The braided wire should be more resistant to breaking than solid wire. Yes, you'll be able to bend the fingers the wrong way, but at least they will look natural when bent the proper way.

The 14 AWG wire with insulation fits perfectly inside the 5/32" brass tubing (I.D. about 1/8"), so the tubes could be easily epoxied to the wires.
Leaving about 1/4" to 5/16" gap between the tubes gives a nice natural bend.
I got the tubing at Hobby Lobby and wire at Home Depot.

: IMG_4610.JPG (597.68 KiB) Viewed 3813 times

In order to facilitate the retrofit, I think the palm plate needs to be kept as small as possible.
This one is about the same size as the one CC did. I'm not showing all the finger tubes here, just the ones that would be epoxied into the palm plate.

: Hand photo from Dollyman25442; palm plate-tubing.jpg (445.85 KiB) Viewed 3813 times

I think the easiest way to assemble this in place would be to have a two piece palm plate.
The finished finger wires with tubes would be fitted into the fingers then bent as required to fit into the palm plate. The the second half of the palm plate would then be screwed on with epoxy to cement it all together.
The thumb tube was moved so this is a little rough, but you should get the idea.
If you want the design file I'd be happy to share it.

: palm plate-tubing2.jpg (325.11 KiB) Viewed 3813 times

da_putzler · Post by **da_putzler** » Thu Nov 01, 2018 3:50 pm

This is such a great idea, if only this were an option when buying dolls.

Tyr · Post by **Tyr** » Fri Nov 02, 2018 4:36 am

I also started to think about printing a palm plate similar to CC's one and getting some Hex electrical standoffs and modifying them to fit, so the grub screw method of attaching the fingers would still work. I have a small bunch of 3mm ones on order so I will be able to make an assessment when they get here. I may have some small diameter aluminium tube in my shed too. I may make a trip into town and see what wire is available locally, so far I haven't seen anything that I would deem suitable. CC's wire looks like the stuff we used in the aircraft game, Not the kind of thing you can buy a few feet of over the counter,

well not here anyway.
Mf, if you would share your design I would appreciate it, I could get the basic sizes and develop my thoughts from there. It would save me from opening Ami up prematurely. It also occurred to me that allowing the joints to bend both ways isn't such a bad thing as it allows for small mishaps, I sleep with my doll and I was worrying about snapping a finger with my design, although the test prints do seem to be pretty strong. Fit and forget is what I'm looking for now.

Cheers,

Tyr

djcdoll · Post by **djcdoll** » Fri Nov 02, 2018 7:38 am

I really like the ideas here.

The 3D printed palm plate looks a good idea too.
It would be great if somebody could use the 3D print files that MannequinFan has kindly created to manufacture some of them for use by TDF members.
I'm sure that members would be interested in buying them.
I think MannequinFan is already snowed under creating his other 3D printed parts like the fabulous eyes!

MannequinFan · Post by **MannequinFan** » Fri Nov 02, 2018 3:09 pm

Looks like Fuson 360 can import a Rhino file so I can post in that format, or I can also export to IGES or STEP. I'm using Rhino 4.0 so that would be the easiest.
I'll need to clean it up a bit before I post.
I can post a basic solid one that you can modify for a different finger attachment and the 2 piece one set up for the 5/32" tubing.

The wire I used in the test is this stuff (14 gauge copper stranded)...
https://www.cerrowire.com/product/circu ... hn-thwn-2/
They sell it by the foot at Home Depot.

The 5/32" brass tubing is made by K&S Engineering. I got them at my local Hobby Lobby but I'm sure you could find them elsewhere online.
https://www.hobbylobby.com/Crafts-Hobbi ... 32/p/24131

Tyr · Post by **Tyr** » Fri Nov 02, 2018 4:39 pm

Whatever file format is best for you, .3dm, iges, step I don't mind. Don't worry too much about the model quality, I will only take o/a dimensions to rough out sizes. There's no rush either, I'll be waiting a couple of weeks for the samples anyway.
Thanks for the links to the hardware. The tubing won't be a problem, as for the wire, I've downloaded the specs. I'll see what I can find here.
Appreciate your help.
Cheers.

MIGuy1740 · Post by **MIGuy1740** » Fri Nov 02, 2018 6:27 pm

I love the idea and love that you took it to prototype and if I can add to this, your knuckle issue can be resolved by making them different and "pinning" them instead of using nuts and bolts.

I have worked on a similar idea and will have to post screen captures of my Solidworks models, which I can also share with you in various formats.

I made mine so that one connection of the knuckle goes in between the next knuckle. I have 120 degrees of rotation on each knuckle.

The biggest part, for me at least, will be making a "cast" of the hand, putting the skeleton in the hand cast, and then pouring TPE or Silicone in the cast. Then you have to replace the entire hands. I am sure it will be noticeable at first, but maybe with enough bracelets or a watch, it won't be as noticeable.

By the way, the printer I have available is a Markforged and it prints with Onyx carbon fiber which is really strong and durable.

MannequinFan · Post by **MannequinFan** » Mon Nov 05, 2018 3:06 am

Alright, here's my finished palm plate prototype for the 14 GA wire with tube phalanges.
I thought I may as well finish this idea while I was thinking about it.
It actually worked a little better than I thought it would. At first I thought the wire would be too stiff, but with the tubes added the fingers bend quite nice.

During the installation process, each finished finger bone can be super glued to the plate after they are inserted in the fingers and the thumb tube can be snapped in place.

The attachment IMG_4611.JPG is no longer available

The cover is screwed on with a generous amount of epoxy to make it all solid.
For the fingertip I might want to strip the insulation so it bends a little easier and glue on a printed tip with a rounded end instead of a brass tube.

The attachment IMG_4613.JPG is no longer available