Thursday, January 26, 2012

Re-working the CPU Arm system

Back in March of 2010, I began the process of installing the CPU Arm into R2-D2.  Over the next few months, I got the power antenna to work at making the probe extend and retract.  However, the trick in doing so wasn't reliable.  

That system had a problem with the plastic hose which caused some kinking and made it very difficult for the servo to move the arm up and down.  As a result, sometimes when the arm was retracted into the body, the servo was fighting the tension of the plastic tubing to stay upright.  This would cause tapping from inside R2...a pretty unique problem to solve!

Over the months, I found the Firgelli L16 100mm stroke actuator.  It only has about 5 pounds of force it can handle but for pushing a resin piece that weighs a few ounces, it should work!

I hollowed out the resin cpu arm to 1 inch diameter, which is enough for the actuator to fit inside with a bit of extra space.  I had two 1 inch diameter pieces cut and enough of the center removed for the actuator to not quite fit into.  To assure a snug fit, I used a file to remove a bit of material and now the actuator fits inside and stays centered.

Surrounding the shims with electrical tape keeps them properly aligned 
Then it was time to work on the tip of the probe.  I trimmed the end a bit since it was rounded.  I found a 10-24 thread female piece and bored out the holes to accommodate 4-40 size screws.  I drilled and tapped into the resin and now have it so that the adaptor simply bolts into position.

And here is what it looks like all put together...

The next challenge is to make a a way for that assembly to connect to the high power servo.  After a little trial and error...and a lot of thoughtful staring with a fresh pot of coffee, I came up with this...

At first glace, it looks like this entire assembly is a bit too tall...but we'll see!  More in a day or two!