The Fixed 3-Leg Shoulders

My Fixed 3-Leg Shoulders (formerly called Shoulder Hubs) are a tab and slot conversion of Dave Everett's plans. The Shoulders have been re-designed to incorporate countersunk bolt holes. For reference, the original design can be found here. This means that there's a set of parts for the left side Shoulder and a set of parts for the right side Shoulder. Each set has been marked so you can tell them apart. Since the bolt holes are countersunk it's easy to tell the outsides from the insides. As with Dave's design, make sure you put locktite on the bolts before the final 1mm styrene wrap goes on.


This is the shoulder hub before the outer skin is applied

The image links to a 3d pdf file, click on it if you want to be able to rotate the image around and examine it from other angles. (Note, the 3d.pdf file opens in a new window. If you have problems with the 3d feature you may have to upgrade to the latest version of Adobe Reader).

The shoulder hubs are meant to be cut out of .25 styrene but can also be cut from two sheets of .125 which are then glued together. If you do that you'll have to cut the countersink holes after the parts are glued.

Shoulder Hub Hardware: Just a short note. Not shown above are the 1/4-20 flat head machine screws and mating nuts/bolts. You'll see those in the assembly instructions. The machine screws should be 2 1/4 in. long. That's long enough to go thru the hub assembly and stick out far enough to bolt onto a 1/4 in. plate (either in the frame or the leg). The problem is that most local suppliers (Lowe's or Home Depot) only carry 2 1/2 in. and then only in the 2-3/package plastic bags. You'll need 16 of them and it is a lot of work to cut them down to size. 
[Observation: buy your washers & nuts by the box from a local supplier. It's handy to have extras so you don't have to look like a Jawa turning your droid upside down and shaking him to retrieve the nut you dropped into the leg! ] I found one Internet supplier who stocks the 2 1/4 in. length and doesn't require you to buy a box of 100. So, if you are ordering other hardware you can spread the shipping costs over other projects. Bolt Depot might be cheaper even with the shipping cost. The bolt heads that stick out into the leg will need to be ground down so that they are flush with the bolts. See the notes in the assembly instructions (below).

The design drawings are available as both Autocad .dwg files and Adobe .pdf files download drawing files with the understanding that the drawings are copyright to Media-Conversions and are not to be used commercially. (That note also appears on each of the drawings). I've also put together a set of assembly instructions to help you put the shoulder hubs together. Don't want to cut your own? You can try this parts source.



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