Sunday, June 3, 2012

Some downtime for an overhaul

As you have noticed from following my blog, R2-D2 and I have been on the go for several months straight!  During that time, we've ironed out a few kinks here and managed to make many modifications to R2 as the ideas kept coming to mind.

While transporting R2-D2 to my last two events, I kept hearing a squeaking.  The high pitched type, like an old mattress box spring.  R2 is strapped down using three tie down straps, the same I used to use to tie down my motorcycles when I had to transport them in my truck.  I also heard a machine screw rolling around in the center ankle.  I also noted R2 was swaying a bit more than usual when moving around.  All of these things went into my "To Do" list of things to check when it was tear down time.

As it turns out, the squeaking has been caused by some play in the ankle.  The bolt that secures it to the center foot has worked itself out.  It was still held firmly in place with the plastic ankle lock holding the position firmly.  But, every bump in the road gave just enough jiggle to make the noise and get that loose washer ratting around.

The male and female halves of the ankle bolt have worked themselves apart.
 Another area of concern I have had is the frame.  I had a replacement frame but had an opportunity to sell it to another builder who was eager to get a fast build rolling.  Back in April of 2010, I made several modifications to the frame, removing two vertical rod pieces that were blocking access for several of the doors and panels.  The early frame design hadn't taken any of the door, panels and other clearances into as much consideration as later designs did.  However, being our clubs first aluminum frame, it gave many of us builders the foundation we needed.  

To add vertical support to the frame, I used thick aluminum rods under each shoulder.  This allowed for R2 to have doors and panels that opened, plus ample room to accommodate the CPU Arm and Gripper Arm assemblies.

Frame as seen with skins removed

Frame with top ring , shoulders, utility arm carrier and center vent rails removed.

Over the months, the support under the shoulders has developed some slack.  The machine screw and lock washer loosened up from the twisting loads.  As those did that, the bottom of the shoulder structure did the same.  That said, as I was dismantling R2, one side had 2 of 3 screws about ready to fall out while the other was a bit better.  That's the cause of our swaying!

Now none of this is the fault of the frame's design.  The modifications I had are.  Thankfully there is no damage or failures to report.  Actually, I could just insert some thread-lock such as LocTite and put everything back together.  However in light of the advances and mods made to the newer frame, I am currently planning to replace this frame.  I have some quotes out on having the materials fabricated, so we'll see how competitive those are...and how they work with my limited budget of ...well...what's a robot budget?  (*chuckle*)

This R2-D2 has a lot of miles logged on it, a testament to the many little systems inside that have worked so well.  With this downtime, I plan to keep tweaking a few things!

More soon!