The Big Think

June 10, 2016

Leg Welding, Burned Boots, and R2 Takes His Pound of Flesh

Filed under: The R2 Project — jasony @ 10:40 pm

Major progress the last few days and I even got a decent little injury to show for it (more on that later).

I’ve been practicing my TIG welding for around 40 hours and decided to just go ahead and give the leg welding a try. Before I did that, though, I had to strip the old anodizing from the parts. I’d gotten the 1/4″ metal for free when I had the frame anodized black. The only downside was that the two sheets of free metal were clear anodized, and since you can’t weld anodized metal I had to strip the parts in a concentrated lye bath.

First a 10 minute dip in the hot lye solution, constantly agitating each part while the anodizing was dissolved (but not too long or the aluminum will be eaten away!), followed by a neutralizing bath in vinegar, then a water rinse/soak, then pressure washing each part to remove residue. At the end of this 4 hour process all the clear anodizing was gone.

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I doubled up on protective gear. Lye is nasty stuff.

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Then into the welding bay! It took me 5 hours to set up and tack all of the parts in the first leg just on one side of the leg. A tack weld is when you just do a quick spot weld in a few places to hold the parts together firmly– once they’re tacked you then go back over and run beads that hold everything together. Tack welds are a pain because everything wants to shift and slide around and it’s hard getting all of the loose parts to behave until they’re secured. And at the tolerances I’m dealing with I have to get them all positioned as close to perfect as I can.

This took me five hours to tack weld just one side. I was holding the torch sideways (a hard angle), I kept dipping my tungsten rod in the molten aluminum (necessitating regrinding of the tungsten), and just generally going glacially slow. It sucked. It was very frustrating. I felt like I’d forgotten everything I’ve learned about welding. It was a frustrating session.

But then yesterday I went back in and tacked the other side of the leg on and then ran beads. They weren’t the prettiest welds I’ve ever done, but once I got the aluminum hot it welded pretty well. Success! Felt great. No, it felt fantastic. Erin brought home some ice cream in celebration. Yum.

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Seven and a half hours…. for one leg!

Tonight I went back in to Techshop and set everything back up again. It generally takes me an hour to get the TIG bay ready to rock. I had to grind the edges of the 2nd leg parts, clean them with Alumiprep 33, rinse with water, scrub with a stainless brush to remove the remaining oxides, and then clean with acetone a final time.

Grinding:

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You have to have aluminum as surgically clean as possible, with zero oxidation, before it’ll weld correctly. Any contamination and things go south very fast. I decided to clamp everything together tonight before I tack welded and it went much faster. I was able to tack weld around the perimeter of the whole piece in about an hour and a half, then remove the clamps and run beads in a couple of hours. All told, I finished the second leg in just about 5 hours. Much faster

And something funny happened a few hours into welding. Suddenly all of this practice I’ve been doing the last few weeks just…. clicked. When TIG welding, you have to control the torch angle and speed with your right hand, the distance of the tungsten rod to the surface (around 1/16th inch separation is really hard to hold), the angle and speed of the aluminum rod you’re dipping into the molten pool with your left hand, and the torch power with your foot. It’s a lot to keep track of and if you change one of the factors then the equation alters and the weld pool does weird things. Tonight I was like Daniel-san after waxing on/off Mr. Miagi’s car for hours. Suddenly it just got a lot easier and I was like Neo in the Matrix watching the bullets come down the hallway. It was weird and fun and exciting. As a result I put down some of my best weld beads I’ve ever done. I could watch the puddle form and actually control where it was going. Things were predictable and I had a more subconscious sense of what to do when things went a little wrong. It was like that feeling when, after months on training wheels, you take them off and your body just “knows” how to balance on a bike. I’m sure I got great weld penetration down into the metal and everything cooperated. I got it, and it was a blast.

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One funny thing happened, though, when a glob of molten aluminum dropped free from the leg and disappeared between the slats of the table down toward the floor. Hmm… hope that doesn’t hit anything important. I then smelled burning fabric for a few seconds, then nothing. So I kept on welding. Later I noticed a 3/4″ long scar right in the top of my new Zamberlain leather hiking boot! So my right boot toe has a brand from R2. It’s not very noticeable and didn’t do any structural damage and kinda makes me smile when I look at it. That mark has a story. Kind of like the scars you get on an adventure: some you love for the stories they tell. No biggie.

The worse one today was when I was finishing up a weld and used my left hand (the one holding the super hot aluminum dipping rod) to raise my welding hood. Unfortunately, the rod got caught on the mask, popped up under my hood, and smacked me right in the upper lip.

While semi-molten.

So now my upper lip has a nice little burn mark and blister right smack dab in the middle at the very top. The lower lip got hit as well but didn’t get burned as badly. I hollered and hopped around for a minute, ran some cold water on it, and then hit it with some burn cream with 2% lidocaine. It’s numb right now and will take several days to heal and probably won’t scar. The joke around the R2 builder’s board online is that R2 requires a blood sacrifice every so often. Guess it was time. Working with 160 amps and 12,000 degree plasma, though…. it could have been much worse.

So anyway, the leg welds are done! I’ll need to spend a day or two grinding them down, but this is a huge step that I’ve been stressing about for over a year. I never thought I’d be able to learn TIG welding and seriously considered jobbing it out. I’m really glad I stuck it out and did it myself. So satisfying.

Next step is the foot assemblies and then the battery boxes. There’s still a lot of welding in my future. Once all that is done I’ll grind everything down (I am not looking forward to that day…those days) and then back fill any minor holes with Lab Metal, then sand it to a decent finish. I’ll still be throwing the legs on the mill for various operations (tapping, some more drilling, etc), so I won’t go crazy on the finish work until they’re all done.

Still, a really good week, in spite of the sartorial and facial scars. I’m really proud of what I’ve done.

Onward.

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