Sunday, June 12, 2011

CPU Interface Arm complete re-do ( Part 1 )

Last September I spent several days working on my first attempt on a functional CPU Interface Arm for R2 (Link).  While that did work well for a while, a few consistent kinks kept making the device unreliable.  

The automotive power antenna motor was bulky and awkward to install inside the body.  The "plumbing" that attached the CPU arm to the power antenna had some serious drawbacks.  The problem was that thick plastic tubing going from vertical to horizontal made for some real challenges.  It eventually became too much for the large scale servo that would pivot it in and out of the body.  The poor servo would jitter and rattle as it struggled to hold the arm inside the body.

Tonight I started on my new plan to hollow out the resin cpu arm with a one inch diameter drill bore.  As luck would have it, my drill press isn't tall enough for the drill bit and the resin arm to fit, so I will have to use my vice and power drill.

The nice thing about drilling in resin is you can use wood or masonry bits.  Have the shop vac handy, it gets messy quick!
As you can see, I didn't do a great job being right in the center as I had hoped to be.  The pre-existing holes from my previous version made that a real hassle.  With this bored out to 1 inch diameter, the Firgelli actuator will not fit without some additional work.  This is a good thing since we have a square peg in a round hole.  The idea i went with was an double-cut metal file, which removes more material than a single-cut one.  Essentially, I am creating four flat sides, checking often to see how the actuator fits inside.

After cleaning up all the resin debris with the shop vac, I sized up how the actuator fits...

 Since its getting late, I decided to stop there.  The next step is going to be cutting some Lexan circles and cutting out some material in the middle.  This will create a mount for the thin part of the actuator so that it lines up straight.  Eventually the CPU arm probe will attach to the tip and needs to retract and fit flush.

There is a little more work to be done to determine how far into the CPU arm the actuator needs to go.  As you can see in the picture below, the actuator is a really good fit for arm.

Next time we'll work on those mounts and see how this idea of mine goes!