The Big Think

July 9, 2016

The R2 Project: My Feet Are Killing Me

Filed under: The R2 Project — jasony @ 9:57 pm

Not my feet, actually. R2’s feet. When I look back on the 5ish years that I’ll spend doing this crazy project I believe that “Tig Welding the Feet” will probably be one of the hardest parts. I have spent 77 hours practicing TIG and used almost 500 feet of welding rod. Not sure what that translates to in actual weld length since there’s not a 1:1 relationship between rods and weld beads laid down, but it has got to be close to 1000 feet. In the last week I’ve spent nearly 15 hours under the hood welding parts. And, oh, what parts.

I’m currently working on the foot shell assemblies. These:

R2d2 feet

R2d2 third foot

There are two outer feet (the top picture) and one center foot (bottom pic). All aluminum. The side details are applied later, as are the vertical strips on the ends, but the rows of rectangles around the bottom skirt are part of the assembly.

So far it has taken 13 hours to weld up the center foot and it looks great. I ground it down (2 hours) and noticed that some of my welds hadn’t penetrated enough, so I had to go back and re-weld everything. I really hope that I did it right. Grinding isn’t fun.

The side feet (the top pic above) has been a real bear. Everything wants to warp and crack and the shape is just a crazy one to start with with a 3″ diameter curve and a delicate little edge on the backside (of this pic). Several times I found myself wanting to slap whoever designed this part. The curved edge in particular has been it’s own special joy. I tried to bend the part using a hydraulic press but just couldn’t get it to fit correctly, which meant that I had to toss the part and start over. This time I spent 13 hours milling the curve on the manual mill, as well as the bottom corner piece. Then when I welded it all up the pieces warped so badly that I had an air gap, so I had to grind most of the corner bit (which I had gotten accurate to .004″) so that I could weld in a patch.

This frustrating part has been bedeviling me for several weeks now, but I think I see a light at the end of the tunnel. I spent 11 hours at TechShop today (I had a 4 hour water jet class in the middle) doing nothing but welding. I still have to grind, but here’s what I did:

IMG 2340

It’s upside-down in this picture since I weld better right-to-left and that top weld was the last one I did. There was a point tonight around hour 5 where I felt like I clicked up to the next level. My coordination with the pedal, rod, and torch was much better, I was able to direct heat into tiny little areas without melting nearby edges or corners, and, most importantly, I even bridged a 1/4″ gap and created new metal to do it. That’s pretty advanced. Basically, even with my patch I still had a couple of spots that gapped. I had resigned myself to using lab metal to fill them in. However, I was welding so well that when I got to that spot I just said screw it and dove right in. In hindsight I could have really messed things up but I guess I was feeling confident. Well, I absolutely nailed it, adding in several cubic centimeters of new metal by pushing the rod into the puddle before it had a chance to drip or ooze away. I nearly whooped for joy! You can see the spot where I did that in the above pic. It’s the upside down corner nearest the camera where the curve meets the edge. I did a similar spot on the back side and got that as well. BOOM!

Once this piece is ground down (a long and messy job) I’m sure there will be a few spots that I’ll have to go back and patch up. Then I’ll have to grind it down again to finish the part. These feet have been a struggle at every point and I consider it one of the hardest and most satisfying things I’ve ever done from a maker/builder standpoint. I still have one more foot to go (ugh!) and it’ll be a month or two before they’re all ground down, rewelded, and reground. I’ll post pics then.

In the meantime, here’s a picture of the whole leg stack coming together. I ground the welds on the main leg box and it looks like one solid piece! That’s what the rest of them will look like once I’m done. This pic has the leg assembly, horseshoe, ankle, battery box, and foot shell. I stacked this together tonight and nearly cried. 🙂

TIG welding aluminum! Can’t believe it.

IMG 2341

IMG 2345

IMG 2343

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