OPEN HOLE DOUBLE BALL JOINT
These photos were posted here
quickly and I did not have time yet, to include the specific measurements for
this ball joint example.
The particular demo joint that was shown above, is called a Double Ball Joint .... two balls on either side of tension screw. If you have Brazing skills, you can do a poor man's conversion to a Single Ball Joint which can give you more options in armature designs. On the right here, look at this quick side view sketch and study it. You are actually Freezing "one" of the balls in place to the bottom plate. If you want to do it more quick & dirty, try freezing the ball with high strength overnight cure epoxy such as J-B Weld. Roughen up the bottom of ball with dremel burr or coarse emery cloth to help the epoxy bond. Apply the epoxy thoroughly to bottom of ball & to the lower plate (plate A) and make sure it sets overnight or one can accelerate in very low temp, in oven or place close to mild heat of a light bulb. This Single Ball joint conversion may not look pretty, but it works similar to the Single Ball Joints which are fancy slicked machined.
The pictorial demonstration of the basic steps in making "open hole"- type joints can be quite versatile and applicable to many puppet designs; one just has to be creative & use their imagination. The double ball joint size shown above was 1/4 inch diameter and the plates were .125" thick x .250" wide x .650" length. The length of the plates can be changed to any size. As an example, the photo on the right was one of my very early & numerous secretive experiments (years ago); testing armature designs and joints....they were never used for actual puppets. This one used all "open hole' socketing method.
An animation puppet will often use different ball joint sizes. The torso or hips for example, where there might be more foam rubber mass; you would want to use larger ball joints because you need to push & pull more foam rubber (in those areas) while animating, and the bigger ball joints provides more strength & joint tension.
I only demonstrated 1/4 inch "open hole" ball joint, but the same fabrication steps can be applied to larger ball joints. Of course, for larger ball joints one would have to use larger steel plates. Ball joints can be any sizes and these are only general sizes to meet general armature needs (ball diameters):
The type 302 Stainless Steel Balls can be obtained from Small Parts Inc and I think, from Enco also. They have an online catalog and also a printed catalog that they will mail to those who request it. Small Parts carry some Cold Roll Steel Flats (rectangular) but somewhat limited sizes. Also Online Metals. The 1/8" thick x 1/4" wide steel flats is about perfect for 1/4" ball joints and does not require much machining, filing, etc., to get to the final joint size. Other size joints, you need to cut down & manipulate the metal more .... and just use more "elbow grease". This is where machining skills & equipment is most needed to sculpt down the metal with accuracy. But as I have said before, basic simple ball joint armatures can be fabricated without machining equipment. For one size smaller ball joint, the 3/16" balls, "Steel Keystock" can be used, which is also cold roll metal. Keystock comes in 1/8" thick x 3/16" wide .... that is the size you want to get for the smaller ball joints. Some keystock are plain finish and others are zinc-plated, which, if you braze without ventilation, the oxidized burning of the zinc plating can be harmful. Here is a manufacturer of keystock but you can only get it through a distributor. Enco Manufacturing Co and J&L Industrial both in USA, if I remember, might carry keystock ....or enter rectangular keystock in Google search to find suppliers that will sell retail. 302 Stainless Balls are slightly tough material and it can be drilled with standard "high speed steel" drill bits, but I like to use the longer lasting "M42 Cobalt Steel" drill bits. I drill at lowest speeds and use plenty of cutting lubricant. See drilling metal balls.