The Big Think

June 11, 2015

Anodized

Filed under: The R2 Project — jasony @ 3:19 pm

I visited a local anodizer today and took R2’s frame in for a quote. It was much less than I thought to have the entire frame anodized. The only issue was that I really had my heart set on a vibrant blue color (think R2’s external blue but on the frame). The very helpful Bob at the anodizing place said I could have any color as long as it was black (or clear/natural). There’s one more place in town that I’m going to check on Monday to see if they can do a blue economically. My suspicion is that it would be around quadruple the price for them to do blue. At that point I have to ask myself if it’s worth it since the frame will be covered anyway.

One of the benefits of a black frame is that the laser etching will stand out much nicer against a black background than on blue. Black will also blend into the shadows much better if any part of the frame is exposed, though I think I would like to see the blue frame anyway (kind of like seeing contrasting brake calipers on a hot hatchback at the stop light). The place that does blue may not have a big enough tank to to R2’s 18″ rings, though, so it might be a moot point.

Black is nice, though. It’s just different from what I’ve been clearly pictured in my mind for a long time so I’m trying to decide if I can make the mental switch or not. Hmmm… maybe if I went to Dallas or Houston I could get blue done. How much do I want blue vs black? Gotta think a bit.

In other news, the skirt has been giving me fits. What I thought was going to be a two or three day job has turned into a month-long hassle. I designed, water jetted, and prepped the skirt pieces over a two week period. Then I carefully slip rolled the curved end pieces, sneaking up on the proper diameter until I got the pieces just right. They’re still just slightly off but they’re close enough that they will “spring” together under slight pressure to form the skirt. Here are the parts precut in wood and cardboard to check fit:

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And here are the parts cut in aluminum after I slip rolled them:

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Realizing that my TIG welding skills are nonexistent, I talked to a pro aluminum welder at TechShop and he agreed to try and tack a few parts together (welding aluminum is a pain and I didn’t want to burn through the thin metal) in exchange for a few bucks. I’m going to try and do just as much of this project myself as I can but my goal is verisimilitude over self-reliance, so a (very) occasional professional is okay with me if it means the difference between perfection and something that looks like a 3 year-olds’ crayon drawing on the fridge. Aluminum welding is a skill that takes years of practice and I don’t want to go down that particular rabbit hole right now. Unfortunately, the guy who did the welding kind of blew it:

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Ouch.

He did his best but we determined that it wasn’t his fault but rather the result of very thin material (.063″) and a mating surface that wasn’t a true butt joint (look closely and you’ll see that only the corners of the edge really ever touch). It’s SUPER easy to blow through that kind of weldment, and that’s what he did. We only did this one joint and I called it off. So much for welding the thin skirt material. So what to do? After a few hours of research I found a product called Alumaloy. It’s a low temp (“low” meaning 728 degree) brazing rod for mating aluminum and filling aluminum gaps. It doesn’t get stellar reviews (2.5/5 stars) online but I think/hope that’s because people are trying to heat up giant heat sinks-worth of aluminum. Since I have thin material I hope to be able to get it hot enough with a propane/MAPP gas torch. Right now it looks like the only solution to my problem. The Alumaloy is on its’ way via Amazon Prime so I’ll tackle it next week.

Once it’s here I’ll need some way of bracketing the thin pieces together, so I did a quick test with some broken coffee stirrers:

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Aha. now we’re talking. I found some scrap thin material in my TechShop locker and cut it out on the hydraulic shear/beverly shear:

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And, after much trial and error, bent the small brackets to the correct angle with the bending brake:

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Voila! I now have some small custom aluminum brackets at the proper angle that I can clamp onto the parts to make a lap joint. Hopefully this will be enough to form a decent base for the Alumaloy.

One more part I milled up last week was the main mounting bracket for R2’s center foot. I opted to go all manual mill on this piece instead of water jetting. It ended up taking me 10 hours since I had to thin the aluminum hunk from 1.125″ down to .75″ with a monster facing bit I borrowed from the TechShop machining instructor (who, in a very cool bit of trivia, worked on the Saturn V rocket booster 2nd stage!):

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After milling, facing, tapping 8 holes, and creating an incredible mound of aluminum shavings I got this

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Yeah, I’m really proud of that sucker. Most of the other parts on R2’s frame have leaned heavily on CNC techniques, and, while I can take credit for the design and pathing of the files, having a machine do most of the cutting work and just cleaning things up and tapping doesn’t feel as complete as taking a raw hunk of aluminum and shaping it like this. That part feels beautiful in my hand.

So that’s the state of things. My goal is to have the frame anodized and laser etched and the skirt assembled and powder coated by the end of August. Sept 1st is the “official” beginning of my 2nd year. It’s not a brick-wall deadline but I’d like to stay on track. I don’t think it’ll be a problem.

I’m also researching LabVIEW and my new myRIO that I was given (!) by National Instruments. They got wind of the project and wanted to be involved. They also want me to come update their engineers periodically once I enter the electronics/programming phase. Man, I’m excited about this, but a little nervous about the physical wiring and virtual programming/logic. With plans to pack R2 with sensors and make him a semi-autonomous robot I just hope my reach isn’t going to outstrip my grasp. I’m realizing that I’ve set myself kind of a ridiculous bar here. Can I meet it?

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