Puppet armature (skeleton)

[MarcusMM]

Yes, you can solder steel, but then it is just soldered. I have to admit that I have no idea of the durability for soldered steel. All I know is that copper pipes are soldered, using a big surface and there's typically no mechanical stress except for the water flowing through the pipes.

I would buy cheaper joints, or let them 3D print in Nylon or Carbon (USD 60 is really too much). Same type with teeth. E.g. that one is EUR 3 and 20 cents:

tmp.jpg (13.56 KiB) Viewed 295 times

That's not round, obviously, but it shows that things don't have to be that expensive. But since it's a hobby, cost doesn't matter

[Brunch]

On topic, also check this link:
https://www.rkdanmark.dk/en/news/new-pr ... all-joint/

I've had my mind on those "KG MM – Sleeve clamp with double ball joint" 4th down on the page. For building a skeleton they would give more opportunities for the longer parts (bones) - steel, pvc, wood etc.

KGMM30.jpg (170.88 KiB) Viewed 291 times

Robust Clamps made from stainless steel for heavy loads and shock-proof applications are engineered to be highly resistant to temperature and corrosion. They feature a particularly high flexural strength, and retain their excellent stability even when exposed to dynamic loads.

[RevJack]

On topic, also check this link:
https://www.rkdanmark.dk/en/news/new-pr ... all-joint/

I've had my mind on those "KG MM – Sleeve clamp with double ball joint" 4th down on the page. For building a skeleton they would give more opportunities for the longer parts (bones) - steel, pvc, wood etc.

KGMM30.jpg

Robust Clamps made from stainless steel for heavy loads and shock-proof applications are engineered to be highly resistant to temperature and corrosion. They feature a particularly high flexural strength, and retain their excellent stability even when exposed to dynamic loads.

Brunch,
GREAT FIND!!
Can you contact them? From the USA I was not able to see their catalog or prices. All I want is a catalog with prices to see if they are realistic.

Thanks
Reverend Jack

[MarcusMM]

https://www.rk-rose-krieger.com/english/contact/

And check these, too:
https://www.kippusa.com/us/en/Products/ ... astic.html
https://www.kippusa.com/us/en/Products/ ... astic.html

https://www.kippusa.com/us/en/Products/ ... ctors.html
https://www.kippwerk.de/de/de/Produkte/ ... inder.html

Anyway, I'd say ball joints will get loose really quick: The contact area is much smaller, and after adjusting it a few times they will be loose. And "... and retain their excellent stability even when exposed to dynamic loads." says you can't adjust them. The standard method of screwing the metal plates together is most likely the one that will last the longest, the bigger the contact area the longer they will remain reasonably stiff.

[RevJack]

On topic, also check this link:
https://www.rkdanmark.dk/en/news/new-pr ... all-joint/

I've had my mind on those "KG MM – Sleeve clamp with double ball joint" 4th down on the page. For building a skeleton they would give more opportunities for the longer parts (bones) - steel, pvc, wood etc.

KGMM30.jpg

Robust Clamps made from stainless steel for heavy loads and shock-proof applications are engineered to be highly resistant to temperature and corrosion. They feature a particularly high flexural strength, and retain their excellent stability even when exposed to dynamic loads.

At $68 per joint for the plastic version that's a little pricey. OK A lot of pricey.
Plus shipping and handling of course.

[Technician]

Actually I still don't think stainless is the best choice. It's the industry standard but we have to remember this industry is 20 years old now so this is really dated thinking.
Looking at the 2 main problems with doll skeletons, Breakage and Loose joints, neither are escapable with a metal skeleton. In the world of metals stainless is actually brittle, it's used for doll skeletons because it doesn't oxidize like other metals. But when it comes down to it our skeletons break, and break at a weld because stainless steel starts out brittle and then we compound that weakness by welding and in turn tempering the connections of pieces making it even more brittle.
I've soldered A BUNCH, like thousands and thousands of solder joints, many have been flame soldering, I also MIG and stick weld, and braze.
Solder AND good engineering could certainly make for good connections but there's parts where there's no really good option like the bottom of the spine to the hip hoop thing. That needs to be butted, though one could fold some more metal around it and make a scab on both sides so it would be more along the lines of a soldered copper pipe connection to maximise the footprint of the solder joint.
Realistically, solder, while easy to work with compared to TIG welding which is how stainless is welded (TIG welding is a bitch to do), isn't a great option because it's a 60/40 tin & lead composition and will oxidize. Since avoiding oxidization is the reason for stainless in the first place, soldering is a step backwards and one might consider using cheaper and tougher mild steel, welding it, and powder coating or plating it to avoid oxidization. Of course there's other brazing materials and silver solder that would be somewhat less prone to oxidization but now we're coming full circle back to high heat and tempering (and weakening) the metal unless the temp is closely monitored and cooled slowly so it anneals.
Then there's another thing to consider, since stainless skeleton technology is 20 years old maybe it's time to reevaluate?
The goal was never to make a stainless steel skeleton, it was the solution to the real goal of mimicking a human skeleton. So if we go back to the beginning and look at the goal from a 2022 perspective instead of a 1998 perspective plastic really is a more viable option for a hobbyist.
A 3D printer and a bunch of material is far more cost effective than an oxy-acetylene torch, cutting tools (stainless is a bitch to cut and drill), and the stainless material when the numbers get crunched. Creality CR-10 and Artillery Sidewinder are both very large machines in the $300.USD range.
So again, nylon can be printed, and it's very strong - much stronger than a human bone which is the real comparison. Also there's PET (PET is the plastic our Pepsi bottles and such are made from). PET offers some unique advantages over nylon because it's easy to grind and extrude into filament in a hobby environment. Lots of people recycle PET at home with a hacked paper shredder and a DIY $200.USD extruder which makes it environmentallly conscious as well as strong.
PET would be a poor choice for a TPE doll skeleton because the temperature it melts at is too low for the molten TPE skinning, but Nylon should have a high enough melting point. Either would work for a silicone doll.
But regardless of what plastic is printed, plastic has many more advantages like a hobbyist can make an entire part without seams, so no seams to crack. Good engineering, making wall thicknesses of say 2mm, with a nice prismatic lattice inside can yield a part that rivals stainless steel for strength, and is ready to assemble without any fabrication.
Not to mention weight, plastic parts could be printed thin and a little larger so they occupy more space inside of the doll and are just as strong. So a part that's lightweight, displacing heavy silicone or TPE for a significantly lighter doll.
Then there's joints, using metal most certainly means using hardware for joints which will loosen. But, printed parts can be any shape we dream of so eventually some clever fella would engineer a joint that can be tightened (or loosened) by squeezing or pushing on it, eliminating the current necessity for a surgical solution. There's currently no joint (that I've found) that lends itself to adjustment without cutting the doll open.
Sorry my post turned into a thesis, there was a lot to convey.

[MarcusMM]

Sorry my post turned into a thesis, there was a lot to convey.

Almost A+, but you missed carbon pipes. Airplanes have been build using steel and aluminum many years ago, nowadays it's all (composite) plastic glued together. 3D printing at home isn't easy, except for PLA. ABS is already more complicated, and Nylon is even worse (warping, especially if you really want to print large parts). There are also 3D printing services, but they are expensive. If I wanted 3D printed joints, I'd interconnect them with carbon pipes.

The skeletons made of stainless steel are well known, including all typical defects. Building these skeletons in a different method (soldering or using different joints) must be considered an experiment (that I wouldn't do for a doll to last 15 years). And let's face it: There are many different variants of stainless steel, and the cheapest variant is used to build the skeleton, and screws are attached with simple electrode welding using standard electrodes, I've never read of TIG/MIG on any doll manufacturer - or I am wrong?
It's not wrong to try something new, but it's risky.

Someone knowledgeable on which steel to use and how to process it can produce much better results than a company using the cheapest material it can find on the market. If you ever tried stainless steel screws from a standard supply shop vs. some from Spax you know what I mean(The no-name stuff will work, too - if you first drill a thin hole, add extra lube and use a powerful electric screwdriver. The Spax will just work, no extra work and you can drive in twice as many screws with the same battery).

[Tailor]

Such discussions are interesting
Yes, it could be possible to invent some new idea with new materials and you had some interesting suggestions. I have thought about vacuuminjection molding with carbon fiber, it would be possible to make more organic shapes and reduce the weight at the same time. I intend to spend some time studying human autonomy a little more deeply in the future. If you understand how the human skeleton, joints and muscles work together, you might be able to come up with some revolutionary concepts with new materials, who knows

The reason I intend to use stainless steel is because the doll will accompany me outdoors in freezing temperatures on hot tent trips in the woods, among other things. This doll will be exposed to extreme temperature fluctuations and condensation can form inside the skeleton.
Also grinding endurance/resistance I suspect is very good on stainless steel. This is wanted because the joints won't wear down as quickly and become loose, I hope. I actually have no idea how nylon compares on that front.

I have bought silver solder and flux specifically for stainless steel so that it does not oxidize and become poorly attached, this shit was surprisingly much more expensive than regular solder, but with a 55% silver content, it's not so strange.
I know you have to be very careful with heat and that's where most of the problems lie with our dolls' skeletons breaking, I guessing wildly .
Does anyone know the difference between cold hardening and hot hardening? I ordered stainless steel 4301 and 4403 and believe it was cold hardened.
But I will have to learn Mig/Mag welding and have found a collective that has a lot of machines and equipment for metal work, they even have a vacuum pump and a vacuum chamber for silicone degassing . They also have 3D printers and much much more and the whole park costs 30 dollars a month to use freely

I have been working on a sketch and started making a blue print of a skeleton based on the dimensions of the doll model I made and the dimensions of the metal I ordered. I'm not an engineer just creative and a bit autistically obsessed with the subject now.
It's just a first sketch and I will definitely change the design after I try to make some joints, and it should definitively be double joints in the knees, took forever to draw this, so not worth spending more time correcting it.

It will be 87.5 cm, exactly half scale of a fasion model, it will not be sexually capable, the posing possibilities and mobility are the important things.
Maybe I should create a new thread, this isn't a puppet skeleton anymore

Skeleton Blue print 2.jpg (6.43 MiB) Viewed 237 times

Skeleton Blue print 1.jpg (7.02 MiB) Viewed 237 times

[MarcusMM]

From my point of view: Maybe too many joints, posing will be more difficult the more joints you have. However, it's not clear from the picture what is a joint and what is just a screw.

> Does anyone know the difference between cold hardening and hot hardening?
Different methods, same result. Cold=by pressing, hot=but heating then cooling. 4301 is 'the standard' steel, most commonly used (cheap). I would bet most doll manufacturers use exactly this, too. It can be welded with electrode (cheap), MIG and other methods, and there's no extra treatment/heating required after welding (cheap). 4003 (not 4301) might be better suited for joints, as it has a higher abrasion resistance - but I don't think that any doll manufacturer is using it for joints.

One problem you might have with the skeleton: With solid pipes you will get more weight compared to pipes/tubes, which requires tighter joints everywhere (legs, hips, arms). And tighter joints means more and faster abrasion, resulting in loose joints. I'd build a first prototype with the solid pipes you have, but for the doll skeleton I'd use a square tube profile (or 'insanely expensive' pipes), 4301.

[Tailor]

Ok thanks for reply, so it doesn't matter much how it is hardened when welding the steel if I understood correctly? Almost thought I might have to harden the steel myself in an oil bath or water bath after welding to strengthen it.

I can hardly understand that drawing myself
But yeah since it's half scale it looks like too many joints and will probably have to remove some on the prototype. Also don't know how small I can make the joints.
The solid tube is only 0.8mm wide so wonder if it weighs too much, but yes hollow would be better but a price increase of 550% is almost 100 dollars in extra cost.
Unfortunately, the range for private individuals is very limited when it comes to material and steel choices in my country. 4301 and 4404 are what I have to choose from.