Hey folks,

I finished up another set of functional prototypes. This time for the selection knob, scroll wheel and select button. These worked perfectly as designed, and very little will need to be adjusted. The detents in the scroll wheel and selection knob feel great. The huge throw on the switch is also satisfying. I didn't think that the little details required to hold the potentiometers in place would even be possible on a FDM printer, but the part came out surprisingly good. I only had to ream out the various holes, and file away a few stray bits of plastic. The only change I want to make is to try and beef up the macro knob shaft. Currently it wobbles too much for my taste. As much as I like the 360 turn pots, I may switch the knob back to a normal panel mount type pot; if only so that there is a metal shaft instead of plastic.

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I also printed up the internal arm band, if only to ensure that the Pip-Boy will actually fit onto my arm. It does fit, but will be tight near my forearm, and require padding near my wrist. This tightness is actually required if I locate the heart-rate monitor on the inside of the Pip-Boy.

I am still very much lost on the best way to secure the Pip-Boy to my arm. I don't want the Pip-Boy to be able to rotate out of position like a heavy watch, and this will be a VERY heavy smartwatch.

Here are my ideas so far:
1) Design a form fitting 3D printed structure. I may even go as far as mold my arm and then 3D scan it to get a perfect fit. A velcro strap would be used as backup to the latch.
2) Just try to add padding as in the game model. The padding would have to have variable thickness. I worry however that even with a loose knit thread, that any padding will make it very hot under the Pip-Boy.
3) Design a magnetic gauntlet. Strong magnets in the gauntlet would mate with magnets in the arm band. I like this idea as the gauntlet could be made to look like the in-game leather armor. The magnet would hold the Pip-Boy steady, and if strong enough replace a velcro backup. I could even put the heart-rate monitor and other bio-feedback sensors into the gauntlet. However this idea still has the problem of not breathing, however sweating is apparently step one in any cosplay costume.

Note, I will NOT be adjusting the design to make it one size fits all. It isn't as simple as scaling up the 3D model, as all the electronics are effectively fixed in place. If I go with idea #1, I will release 3D files that allow you to design your own Pip-Boy to Arm interface.

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I redesigned the cable reel for the third time. This time I changed to a double sided reel, which prevents the cable from touching the non-moving side of the case.
I changed the pawl such that it has lower friction moving in the retraction direction. I reduced the number of catches to just three, however I may change this one last time as landing on a catch point right now is a bit difficult.

Without the slip ring in place a single spring can handle the load, and the cable return works perfectly. With the slip ring attached I have to double the spring. With the spring doubled, the whole thing works great. Thanks to @loonitick for the double-spring idea. I still am going to try to find a thicker spring as loading two springs into that tiny spool is dangerous and nerve racking. If you let go for just a second the springs explode out and you could easily get cut or loose an eye if you're not wearing protection. I already have a permanent scar on my hand from flying metal, I don't want more.

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