Sunday, March 11, 2012

Hinging the top dome panels

As many R2 builders can attest to, there are parts of the build you dread or just opt to put off to another time.  For me, this was a little bit of both.

Hinging the top dome pie panels is tricky.  You have a curved surface (the dome) and are trying to make a curved piece (the panel) line up.  You need to remember all that geometry you learned in high school plus use some clever methods to test things.  

When I first put R2-D2 together, I was racing to meet a Halloween deadline in 2009.  I did make the cut outs to the inner dome and used silicone adhesive to attach the top panels to the dome.  I did not keep the cut outs as I was under the impression they were not needed.  Oh how wrong I was!

That said, I needed to remove the silicone adhesive from the inside of the dome in order to free up the panels.  I found some spray on stuff at Lowe's that removes silicone adhesive and spray foam.  

Before we start spraying, we want to protect the dome panels on the outside.  We don't know if this spray will eat paint or damage it.  

One pie panel is already hinged so we tape the top so it can not pop open.

Here's how everything looks before we begin...

To be safe, I am also going to cover up the hole at the top with painters tape too.

The tools needed with me a plastic and metal scraper and plenty of paper towels

The spray states that it reduces the molecular bond of the silicone adhesive.  Its more or less a spray on gel, so be sure to wear protective gloves so you don't get this stuff on your hands.  After letting it set for 30 minutes, I used the plastic scraper to gently pry the silicone off.  Some pieces came off to large clumps, others took a bit more work to pry off.

I had one panel that had a really thick layer of silicone that required a lot more force than I was comfortable using.  I decided to spray a heavy layer of the remover and let it set overnight.  The next morning it was significantly easier to pry away.

Here's how it looks after scrapping and then using a spray bottle with water in it to clean the affected areas (note the panel labeled One is staying attached for now)...

I flipped the dome over and began to slowly remove the panels and tape.  I removed the tape from the panels so any residue could be cleaned off and then put new tape back on.  We'll want to protect that paint for the clean up on the other side.

Next up, we want to sand away any left over residue using the dremel sanding head.  Once cleaned, we can use some scrap aluminum (from the body skin cut outs) to add some material for the hinge point.  This will help make sure the panel sits flush with the outer dome.  I'm using Loctite Super Glue which is a gel solution...and it is also a more vibration resistant formula, which should help!

 The nice thing with superglue is the fast drying time.  Just to be sure, I let it stay clamped for 30 minutes since the basement is only around 50 degrees or so.

Now it is time to match each panel to its respective opening (you DID label them, right?).  On most of them, I cut out a bit too much material from the inner dome, so lining up the panels is extremely intricate work!  Once in position, tape securely and move on to the next.

I know from experience with the hinges that I generally want the hinge to attach to the lowest point on the pie panel.  Just to err on the side of caution, I am going to use the high strength (10 pound) double sided foam tape from 3M.  I am going to adhere it to the lower portion of each pie panel piece (well, the piece I glued to each).  Then, I'll place the tape on the bottom of each hinge.  What I will do is start at the pie panel attachment, then gently attach the other portion of the hinge to the inner dome.

The red is the plastic material on the tape.  It is removed before adhering the hinge

 After each hinge has been placed into position, I gently turned the dome over and very slowly , removed the tape to see if the hinge opens smoothly...

Success!  So we know the hinge placement will work.

However we need to check how the panels line up and I know right off I need to add another layer of material where the hinge attaches to the panels.  Easy to do, superglue another layer of aluminum scrap to it.

Then its time to permanently attach the hinge to the panel.  What to use?

I opted for JB Weld.  Why?  The hinge will be visible when the panel opens.  I can sand JB Weld and clean up the panel later.

After taping all the panels down again and flipping the dome over, its just a matter of gently removing the adhesive from the pie panel hinge, dabbing some JB Weld in its place and slowly pressing the hinge into it.  Be careful for don't want it drying and jamming up where the panel opens.

 For the hinge-to-inner dome portion, I decided to try something odd...I left the double sided adhesive on and place JB Weld on top of it.  Why?  I do not want to remove material from under the hinge since everything lines up well.  Will it work?  We'll see!

24 hours later...

Next time, we'll work on getting micro servos and a decent linkage assembly together!