The Big Think

June 1, 2016

Outer Ankle Solo Welding

Filed under: The R2 Project — jasony @ 7:37 pm

I spent another 4 hours at the TIG welder today (for a total of 34 hours) and did my first solo TIG part! I did one of the outer ankles and it took me the whole time.

Once I got all set up and ready I took the ankle layers into the machine shop and used the 90 degree jig and a flat plate to stack the parts so that they lined up exactly. One of the issues I discovered on the center ankle that I did with Keith last week was that I rushed the setup and the ankle is now just barely skewed. It’ll still fit its mounting bracket but I have to persuade it slightly. No big deal since the part that’s off is up inside next to the frame where you can’t see it. The outer ankles are much more visible so it was more important that I get those just right.

Once the layers were aligned and clamped tightly I brushed them with the stainless wire brush and then some acetone to get them perfectly clean, then I hit them with 150 amps of TIG POWER! Since the parts were room temperature, and since aluminum is such an incredible heat sink (ever wonder why your pans are aluminum?), I had to concentrate all of that power into a few spots for almost four minutes before the part heated up enough to start puddling. That part got hot. Unfortunately, the Lincoln 225 TIG machine I’m using is rated at a 40% duty cycle, and after about six minutes it went into overheat shutdown mode.

Whoops.

So I had to wait almost 10 minutes for the machine to cool down before I could continue welding. Fortunately, the ankle part is so dense that it lost heat slower than the welder cooled down. Otherwise it would have been a losing race. Still, I managed to overheat the machine two more times before I finally got into the groove. I’d weld a few lines (about 3″ per line), then put the torch down to let it cool a bit and inspect my work. Eventually I got the timing right and didn’t have any problems after that.

The end result is that I welded up the ankle to a good degree. There are still some holes but instead of torturing the part with super high heat for another hour or two (which can weaken aluminum), I’ll eventually fill the remaining v-grooves with Lab Metal and then Rage Pro body filler (high end Bondo).

I’m going to grind down the welds and inspect them to make sure that I got good penetration into the v-grooves. I was using 3/32″ 4043 filler rod but suspect that many of my welds are just on the surface. If, after welding, this turns out to be the case then I’ll have to go back in and re-weld so that the part is strong enough and I don’t get stress cracks once it’s painted.

For the other ankle I’m going to preheat the part in the powder coating oven until it hits a 200 degree surface temp, then move it to the welding bay and start TIGging it immediately. Hopefully then the welder won’t shut down and I can get the welds done sooner and not torture the poor part.

I won’t grind the welds down until I get my super breathing mask in from Amazon. I figured $24 was a small price to pay for not inhaling aluminum dust.

After the ankles are done I’ll move on to the leg boxes, which look to be slightly easier (less heat-sink-ey since there’s less metal) as well as more harrowing since I haven’t been walked through the part by Keith. But I’m slowly gaining confidence and know what to look for. I might practice on some 1/4″ first, though, to see how it behaves. I’ll be right next to the edge the whole time and don’t want to blow an edge out. Oy.

I can say that the last 30+ hours has been tremendously educational, and Keith’s help was very, very appreciated. He wouldn’t take any money for helping me after I told him that I’d like to take R2 to a Children’s hospital. He just flat refused (he’s a softy). So I’m donating $50 in his name to the St. Jude’s Cancer Center via Baylor Tri Delta (that’s their sorority charity). I’m sure Keith will cry when I give him the card. 🙂

In the meantime, here are some pics from my work today. Pretty happy with progress, though it remains to be seen if those welds are deep enough.

IMG 2226

IMG 2227

Ankle attached to leg box! Box still has to be welded up.
IMG 2228

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