Monday, December 03, 2007


So one of the strain gauges on a test grader needed to be replaced today. There was a "pick a number" contest to see who got stuck with it, however I volunteered to do it anyhow because really, having something to do beats having nothing to do.

This job was more ummm... "interesting" than originally putting the strain gauges was because the grader has been reassembled. So instead of standing on the floor (well I'm short, so a box) and reaching inside the frame I was climbing up onto the tandem case and squishing in between the frame and the wheel. Squishing is really the right word, too. As in it's what butyl rubber (which cover all the strain gauges after they've been put on) does to jeans. More accurately, it's what butyl rubber does into jeans.

When I started to move and realised I was stuck I called for the engineer who was right there and explained what had happened. After wincing he told me to just pull myself off the side of the grader. And let me tell you, I have aim (I believe of the kind that one would call bad). In pulling the cover away from the strain gauge I took two wires with me. Not so bad, except that the wires decided to bring the solder pads from the strain gauge. The engineer was very nice about the fact that I had just ruined some expensive test equipment (to wit, the strain gauge), although he did seem to enjoy explaining that that stuff doesn't come out. (He was wrong. My jeans are in the dryer with no black patch now).

Actually it's not killing that strain gauge that bugs me. It's that when I went to glue the strain gauge to the inside of the frame (I had to try twice) I managed to kill it - popped a pad off. At that point I declared that I wasn't gluing any more strain gauges. I had already soldered two (one at least was done well, it was posited that I may have not had a good enough connection to the sink and the heat warped the pad). And I prepped the surface (sanded it with acid until it was smooth) twice on one side (once for the replacement and once after the strain gauge that I killed) and once on the other (for the first strain gauge I killed).

Given that it's probably close to half an hour to prep the bonding surface normally, plus soldering the leads to the strain gauge, gluing it to the grader, testing everything, etc., and that I had to squirm around behind the wheel, it's rather understandable that it took most of my day. What took the largest part of the rest was scrubbing my hands. And my face. And my wrists. See, not only was this grader (still) covered in coal dust, but a) my hair falls out of its braid all the time, so I constantly have to wipe it away from my face, to the point where only the part under my safety glasses wasn't grey, and b) my shop coat is too large, so I have to push it up quite a ways to keep it out of my way.

Oh, well. At least I've stopped rubbing black on other things.

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