Thursday, September 10, 2009

Started Working on Utility Arms

Time to fill some more holes in the body. This time, the utility arms.

I had strongly considered building a sturdy harness for the arms on droid #2, but in the end, I decided to build a heartier version of what I have for droid #1. It turns out I didn't copy Mike Senna exactly with droid #1. I used a lot of 1/8" material, this time things will be beefier.

The first example is the rod I'm using as the pivots for the arms. On droid #1 this is 1/8" brass stock, for droid #2 it is 3/16" steel. I cut a segment that should be provide enough length for both arms.

I took the segment, and marked the length required for the bottom arm.

I went a tiny bit long on the cut, and filed it to size.

Time to drill the 3/16" hole in the resin arms.

Using just friction for the time being, the fit is very snug, but that's what I want at this point. I may sand or file the segment of rod just a little more, later.

Next, I needed to address the geometrical problem of having the arms swing open without having them hit the skins. This is not a blueprint error or manufacturing error with the arms, it's just the way three-dimensional objects interact.

My solution is to file some material from the sides and back of the resin arm, leaving the front face fully intact. Here I've almost finished one half of one arm. I'll try to get better before/after pictures later.

If the bottom arm is placed perfectly (which is a challenge at the moment), then I can get it to swing open without hitting the skins. I may have to file off a little more material to provide a wider tolerance for arm placement (we're talking probably +/1 a millimeter or less).

At this point, I should attach the portion of the outer skin that goes around the arms before going much further, so I can make sure the arms don't catch on the outer skins as well. I plan to use my friend/enemy silicone for that. I also plan to reinforce the MDF above the top utility arm with plywood, as the arms need something beefier to mount to.

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