Inner and Outer Domes

Lots of work this week. I had been struggling with the fit on my R and J dome for a while. The odd thing was that the inner dome was too small. This made it fit with a gap when you slid it into the outer dome. So there were gaps in all the panel cutouts, and it made it impossible to get the inner dome to slide onto the ring that they sit on. I finally resolved to fix it by cutting the inner dome into two pieces. I took a deep breath, double checked my measurements and went at it with the dremel tool and a cutting wheel (I managed to burn the dremel tool up with this project). Here's the result:



You can get away with these cuts because the horizontal cut here is hidden on the solid middle section on the outer dome, and the vertical cut will line up with a wide section on the back of the outer dome that runs between the panels. These cuts solved the fit problem I was having entirely.

I have also been thinking about the best way to attach these domes together. I know the standard method is to glue them together. I have read that a lot of guys used silicone. I ran some tests and that stuff had almost no sticking power here. Again the gel type super glue was by far the best stuff to attach aluminum to aluminum (or anything else, for that matter.) But the glue attachment method is messy, risky, and inelegant. I tried a few other things and came up with this first:


That's a piece of 1/8" by 1.25" aluminum stock that I had bought for the foot strips (it worked great for those.) I cut it to length and then put a bend in it so it would match the curve of the inside of the dome. Then I drilled holes and screwed it to one side of the vertical cut in the inner dome. Remember that the the goal was to get the too small inner dome to fit snugly up into the outer. So I used this piece to add a little more than 1/8" in circumference to it and the fit was perfect. I was proud of that trickery.

Then after thinking about the glue problem, I realized that with the radar eye there was already some substantial mechanical fasteners attaching the inner dome to the outer. So I put them together and then drilled out counter sunk holes for more machine screws around the perimeter to attach the inner dome to the mounting ring.



I put 8 of these around the bottom edge--high enough to be hidden by the blue dome panels when I put them it, and low enough to go into the inner lip on the mounting ring. The result was really secure and I was able to avoid glue. After I got all of these in and once I was sure that I had all the holes in the domes I needed, I went through and made sure all the counter sinks were deep enough to recess the screw head entirely (I don't want them pushing the outer dome up), and I ground down the slag that was sticking up inside and out from making the holes.

A few more points about cutting holes in the inner dome. I tried several methods including the ones that some club members like Chris Lee has on his blog. In the end, the hole for the holoprojectors was pretty easy. I had a 2.5" hole saw bit in my box:


And that worked just fine. The diameter of the holoprojectors I got from Frank Fesquet was about 2.6 inches. So once I used the hole saw, I finished up the edges and increased the diameter with a rounded edge file. I was surprised at how workable the aluminum was. I was able to get some clean, round holes with files and eyeballing it. Same procedure for the dome bump holes.






And here you can see the first results of taking the hole saw to the dome. The thing slops around a bit and makes a horrendous noise and the hole it leaves is rough. But readily cleaned up.

It's not necessary, especially with an opaque radar eye lens like I have, to cut a hole under the radar eye. But I've got it in the back of my mind that much later when I have all the basics done, I'm going to mount a wireless surveilance video camera inside the radar eye and have it feed to a monitor. Then you'll be able to look at the "R2 Cam" and see what he's seeing--mostly screaming kids intent on destroying him, I imagine. And if I'm clever I might even be able to get a servo mounted on the camera so it will pan up and down. That would be very cool, I think.