Rolling Chassis

Been working the last few weeks on figuring out the center casters. None of the previous 2.5 - 3 inch casters seemed to be working for me. A couple builders, mainly the R2.0 guys, had mentioned trying a beefy 3.25 inch Gladiator Caster from McMaster. After a lot of staring at the issues with every two wheel combo I could find, I finally decided to go ahead and get the Gladiator. 

I'd hoped that the holes in the Gladiator Caster would line up with the JAG mounting plate, it was a little hard to tell based off the CAD drawing alone. Once I got it in hand, it was obvious it would be way off the mark. So the next phase of deciding how to mount the thing began. I didn't really want to modify the bottom flat JAG plate, which I would have to since the taller caster would need to sit higher up in the foot that the standard plate allowed. So I went looking at Lowe's and found a 4x12 inch piece of 1/4 inch steel. It was a little thicker than the JAG plate, but I figured its better to try cutting an off the shelf $10 piece than a hard to replace custom part.

I tried a couple methods to cutting this thing, but once I got a hard metal Jigsaw blade, it went pretty smooth, and cutting it exactly in half would be just the right size. I laid the JAG plate over the now 4x6 inch piece, centered it and marked hole locations. Then used a drill press to both drill and counter sink the holes where the plate would attach to the angled half of the JAG mounting system. I had figured out earlier that mounting the Gladiator Caster flush with one side of the new plate would put it almost exactly centered in the foot when moving forward, perhaps just dumb luck. So I marked the holes of the Caster and drilled those out next.

The biggest problem was that the caster would sit on top of the screws that mounted the plate to the angled piece via standoff couplers. I'd originally thought I'd just lock the caster screws in with nuts on the bottom side, screw in the plate, then place the caster over the caster screw nuts and get them to fit inside the rather large mounting holes of the caster itself. But, my Dad has a neighbor that can do Tig welding, so we gave him the plate to weld nuts onto the top side of the plate, thereby allowing a rather easy install of the caster itself.

Once I got the piece back, it was time to see if this plan was going to work out. I found some 7/8th inch standoffs at Lowe's, thinking that I'd try it with those first and then order whatever length I'd really need later. They ended up being the exact length I needed, another stroke of dumb luck. I also found a handy right angle ratchet driver set for $20 bucks that worked perfectly for attaching the JAG angled piece to the Center Foot.

The new custom plate went on with ease, and then the Gladiator Caster screwed in tight with some washers helping to span the rather wide holes it has. The great thing about this caster, other than being nice and heavy duty, is that it perfectly swivels 360º without hitting the side of the Foot. Its like it was made for this exact use.

So once I got the Center Foot all together, it was time to get R2 somewhat back together again. I put the Outer Feet complete with JAG Drive System installed back onto the legs. The now quite heavy legs went back on the frame, and the pretty hefty Center Foot went on as well. I immediately realized I'll have to lock the Center Ankle before I'll be able to see the whole thing in action, but holding the Center Foot down I moved R2 around with relative ease.

The other thing that became apparent was that I will have to cut a hole in the bottom of the frame and use the COM-8B adapter plate for the center leg. The Center Foot is still not sitting level, just like before I had the wheels installed. But all-in-all, I think the Gladiator Caster will work out well. It really makes me want to get the motors, batteries and RC elements in ASAP and get R2 rolling around on his own power.

Chrome Dome

Well, the long, long effort to shine the dome is complete. I've been working on and off at sanding the outer dome over the last year. With so much elbow grease involved, it's not something I cared to do all in one shot, but rather whenever I got an itch to. My goal was to get out the spin lines and have a nice dull shine, similar to the medal ceremony scene at the end of Episode 4.

I initially attempted to get the spin lines out by hand, but soon realized that it was probably too big an undertaking without getting carpal tunnel. So I broke down and bought a Black & Decker Mouse Sander at Lowe's. The reviews were mediocre, and had many reports of breaking rather fast. I can vouch that within a few minutes, my first one broke while using the attachment piece. Luckily Lowe's took it back no questions asked and I got a second. I didn't bother with the attachments and it ended up doing a great job. Over the period of a few weeks I used the 80 grit to get out all the spin lines in both the Inner and Outer Dome. Then I used 120 & 220 grits to get the dome to the point you see here:

From that point I resorted to hand sanding using two 3M sponge sanding blocks at 100 and 180 grit. These can be found in the painting department at any Lowe's Walmart, etc. I really liked these since they were able to bend to the shape of the dome and made it a little easier on the hands. I went over the whole dome using vertical motions from top to bottom several times with the 100 grit until I was satisfied that most of the pitting from the mouse sander was gone. Then I used the 180 grit sponge several times as well.

From there I used 400 grit paper dry, and then started a round with it wet. Being single has its advantages in that I just sat the dome hanging over the kitchen sink without anyone complaining. Plus, I was able to watch the living room TV during this phase. I spent an evening each on a grit of paper, wet sanding with 600, 800, 1000 and finally 2000, always using the same vertical motion. At this point the dome felt silky smooth but still had visible sanding lines.

That's where a little tip I picked up watching the webcast of last year's DroidCon came into play. I bought some Bombs Away Metal Polish last year after hearing about it during the Dome presentation. I'd used it a few times on some of the other parts, including the Center Vents. It seemed to do a pretty good job so I decided to go ahead and use it on the Dome as well. After seeing Lasse's results with a drill polishing attachment, I'd had my eye on one from the auto department at Walmart. I finally broke down and got it once I'd finished all the sanding on the dome. You can see the results of using the Bombs Away and polishing ball together.

One pass of the polish still left some unevenness so I worked my way around the dome with two applications to each area. I was very careful on the lower portions where the aluminum is quite thin. I kept the drill as slow as possible in those areas so I wouldn't accidentally break anything if the polishing ball caught the metal. Then I made one final application to the middle, wide section of the dome in order to get out as much of the splotchiness as I could. All-in-all I'm fairly happy with the results. It has a nice shine to it, there's no spin lines at all, and its not quite a mirror finish while still having a few very small imperfections when you look close. Its a good start before I eventually weather it down the road.