Looking for How to scratchbuild Moveable Joints

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Rafael
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Looking for How to scratchbuild Moveable Joints

Post by Rafael » Sun May 15, 2011 10:07 am

The title says it. I'm bitten by the mech bug and I want to scratchbuild robots and legged vehicles with poseability included. I saw polycaps and the likes at the store but for the moment I am unable to buy via Internet, so the only way out is scratchbuilding. Can anyone point me to good tuts or examples, please?

Rafa

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AbsoluteSciFi
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Post by AbsoluteSciFi » Sun May 15, 2011 6:08 pm

Unfortunately the only thing I can recommend is to take up metal working, of a limited sort, tooling aluminum in order to tool your own armatures. Easiest way I can think of is to drill an aluminum block so that you can work a hinge and screw, giving you versatile and pose-able joints.

I would start with a search for "stop-motion armatures" and work out from there.
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G-man
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Post by G-man » Mon May 16, 2011 1:13 am

do it how they did in the old days of Stop motion
Take two round smooth balls ( 8mm hollow brass jewelery works well)...some brass tubing, and some solder.. , drill hole in the brass ball larger if necessary, drop a few small pieces of solder in it, drop in the rod, heat with torch, and voila you have a ball joint on the end of a rod, or bone, similar to a hip or shoulder. Next sandwich the joint between two metal plates with holes at either end, so that it works like a retainer for the balls, and drill and tap another hole in the center of the two balls, put a bold and nut/wing nut on the end of it, tighten until the rods will hold some weight on either end, but can still be easily moveable, and you have armature joints, each joint will cost you about 3 bucks, less depending on how long the "Bone" needs to be coming off the ball.

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modelnutz
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Post by modelnutz » Mon May 16, 2011 1:17 am

You might try using short lengths of silicone tubing ( available at RC plane stores ) in place of the polycaps.

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naoto
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Post by naoto » Mon May 16, 2011 12:15 pm

Naoto Kimura
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Tankmodeler
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Post by Tankmodeler » Mon May 16, 2011 4:14 pm

Rafael,

I think the basic point here is that if you can't buy what you want, scratchbuilding such a ball-type joint is not for the faint of heart.

On the other hand, if you can wait a bit & buy or if you can get a friend to buy stuff for you, then there are several options that are significantly less work than making a ball joint on your own.

Hobby Link Japan sells a line if Mecha parts from Kotobukiya, all kinds of useful bits & pieces, whether you're scratchbuilding mechs or not. They have two ball joint sets and the individual small packets are quite cheap. Take a look:

http://www.hlj.com/product/KBYP-142
http://www.hlj.com/product/KBYD-116B

If you look on this page:

http://www.hlj.com/scripts/hljlist?Dis= ... Maker1=KBY

you can find all the Kotobukiya parts HLJ has in stock.

HTH

Paul
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TazMan2000
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Post by TazMan2000 » Mon May 16, 2011 8:53 pm

Here's a picture of a movable joint. :lol:

http://www.flickr.com/photos/sonomapicman/3052624453/

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srspicer
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Post by srspicer » Tue May 17, 2011 7:54 pm

I will ditto everything posted so far accept for using a hollow ball in the joint, you will crush it.

You can also use BIONICAL parts. I used them to breadboard a concept of a robot for a client, worked great. All of the products suggested will work fine. Good luck.

Scott

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Post by Valdore » Wed May 18, 2011 6:30 am

Not sure if this is appropriate. But what about plastic pearl beads like these?

http://www.beadandcrystalheaven.com.au/ ... /pID/4608/

With the a length of Evergreen, or aluminum tube glued in the center, you should then be able to get the ball joint you need. I can pick these type of beads up from a dollar store here in OZ. You should hopefully be able to find them where you are as well.

Reason I know about these? My Mother does bead work. And I've looted beads from here before :D

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Post by ajmadison » Wed May 18, 2011 2:26 pm

For scratchbuilders, some of you need a bit more imagination.

I've created all kinds of moveable joints. Mostly hinges, but some are no wider than a section of tube. Making hinges isn't a lot different from standard scratchbuilding, with one caveat. Smear the smallest drop of superglue in the wrong spot, and the joint quickly changes from moveable to fixed.

If more description is needed, I can describe various hinges I've made. But the short version is, you need an interior section that rotates on a pin, which is held in place by fixed parts. For a door or hatch hinge, I take two pieces of telescoping tubing that start out at the same length. The interior tube is the pin. The exterior part is cut into 3 (or 5 or 7...) parts and at precise right angles to the long axis. The outside two exterior pieces of tube are glued to the pin, trapping the interior part/s on the pin. Glue half of the exterior tube sections to the 'base.' The other half are glued to the moving part, e.g. the hatch. One trick to keeping superglue where its not wanted, is after each application of glue, move the hinge around. Sometimes you really luck out, and just enough glue slops into the hinge to make it tighter. So I'll glue the hinge to the base, and wiggle the moveable parts. Then glue the hatch to the hinge, and swing the hatch open and closed a few times.

Once you have master the technique, you can make the exterior tubing parts arbitrarily short. If you're really game, take some 20 to 40 thou sheet, and use those as separate leaves of the hinge, albeit, you'll need to drill holes that matches the pin perfectly.

As for the shoulder joint, a combination of a hinge for up & down side motion, and an axle, for rotation of the arm forwards and back, should suffice. It gets a little tight, sticking a 3mm hinge on a axel part, but it can be done. Elbow and knees are just hinges. The neck can be an axel on the chest, with a hinge at the base of the head to allow it to tilt up and down.

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tetsujin
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Post by tetsujin » Wed May 18, 2011 4:28 pm

It's kind of a broad question, like asking "how do you scratchbuild a thing?" It really depends on what kind of thing.

For instance, if you were building ankle joints for an AT-ST (small joints that are really part of the design of the leg) that's a lot different from building a Zaku's shoulder (essentially a great big box with a couple axes of rotation on it)

One trick I came up with that I'm kind of proud of: years back I was working on making movable fingers for a 1:60 scale Zaku, so I needed a hinge joint in the shape of a 3mm sphere. I built a hinge out of three pieces of wire (the center axis was a piece of soft floral wire, the eyelets that formed the hinge were bent pieces of steel sewing pins) - then to get the look of the hinge I cast the half-spheres around the hinge pins.

It's pretty easy to make moving parts with polycaps - the bigger problem usually is getting the look you want, hiding or disguising those polycaps so they don't look silly.
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eeun
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Post by eeun » Thu May 19, 2011 3:31 pm

Some of the newer Gundam kits use ABS in place of polycaps. It offers a bit more gripping power than styrene, and unlike polycaps, holds paint well.
I haven't tried it, but I see no reason why you couldn't use ABS plumbing materials to create elbow/knee type joints.
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CB2001
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Post by CB2001 » Sat Jun 04, 2011 4:06 pm

There's two joints that I can think of. The first one is the Minimates-type of joint, like what you see on the arms in this photo. (it's also discussed in a link above as well)

http://www.hobbygen.com/images/STREET%2 ... 202-PK.jpg

The other one is the what is typically what I refer to as the "action figure" joint, where one piece over laps another and a piece goes through it to hold the joint together, like seen here with the 1996 Peter Parker action figure.

http://www.figurerealm.com/Galleries/sp ... er2-S2.jpg

I'm sure there are others, but those are the two that come to my mind.




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CB2001
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Post by CB2001 » Thu Jun 16, 2011 4:21 pm

I was informed of this particular type of joint which may be useful. The revoltech joints. I've got to admit, it looks impressive. Below is a diagram covering one of the types they have.

http://fanmode.net/graphics/2008/photos ... rjoint.jpg

Here's another picture with a lot more. Dude.. Impressive.

http://images.wikia.com/revoltech/image ... _Chart.jpg

Mad-Modeler
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Post by Mad-Modeler » Thu Jun 16, 2011 5:10 pm

While on the HLJ site also look at the Wave Option System.

Similar to Kotobukiya but offers slightly different stuff.

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Bar
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Post by Bar » Fri Jul 08, 2011 4:01 pm

Buy a pack of Bionicle parts. They have very tight ball joints for figures. I have a bucket full of them.
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srspicer
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Post by srspicer » Fri Jul 08, 2011 5:06 pm

Great minds.............^^^^

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Bar
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Post by Bar » Sat Jul 09, 2011 6:24 am

srspicer wrote:Great minds.............^^^^
Lol. Then i find myself in great company.
:D
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