-- MattSpenko? - 19 Dec 2005

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To make the extension simpler, I will tap some holes that already exist on the leg modules. This will allow me to bypass the current plates that are holding the modules together, which in turn allows me to manufacture a spacer that is rectangular instead of hexagonal. This should make manufacturing simpler and faster. I need to get the exact specs for the modules from BDI so I can get the correct hole spacing. After looking through the Mcmaster catalog to find plastics with the suitable dimensions, the possibilities are:
Nylon
Acetal
PVC
Polypropylene
Fluoropolymers
Polyethylene

I remember working with polypropelene and I don't think it is suitable. I'm leaning towards the acetal or maybe nylon. I don't have a good feel for acetal, but it appears to be easily machined, relatively hard, with good impact and tensile strength. Any suggestions???

Acetal is Delrin, if I remember rightly. Super machinable. Strong. Stiffer than Nylon I think. -mrc

• Ensinger_Delrin.pdf %ENDCOMMENT%

The more I thought about it, I figured it would be easier if I just sent this thing out to be manufactured instead of making it myself. Thus, I might as well make it using the holes already in place. I received the measurements of the module, and came up with the following two designs. We were thinking of making the design with a small amount of yaw compliance in it. That is why the design narrows in the middle. The main difference between the two designs is that one is lighter than the other (~270g to ~100g). The lighter one may be more expensive to manufacture. The extensions will give us 50mm of clearance between two of the body segments.

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• extension_v3a.jpg:
  

CMU wants a rigid design. This is what I'm going to send out to be made. I'm sending it to mfquote.com for a quote.

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