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chaotically-deformed metal
Sunday, September 8 2013
Late this morning I put on some podcasts and went out to do whatever I could to fix the Honda Civic Hybrid, the hood of which had been dented by an impact with a deer while we were off in the Adirondacks. That deer, by the way, hadn't died immediately. While Onesha (our housesitter, who had been driving the car) waited for the State Police to show up, some local gentleman showed up and offered to shoot the poor thing and then butcher its remains so they wouldn't be wasted. But Onesha hadn't been sure at that point whether the deer might be saved. The State Police (or whomever the State Police send) decided the deer was a lost cause and gave it a lethal dose of tranquilizers, thereby rendering the meat unfit for human consumption. Compounding the tragedy, the corpse probably ended up in a landfill.
The hood was attached to its hinges with four 10 mm bolts. I removed it, ripped off some sort of sound dampening material from underneath it, and decided how to proceed. The problem with a modern car's hood is that it is not a simple piece of pressed sheet metal. It is comprised of two pieces of pressed sheet metal that have been bonded together into a sandwich whose "meat" is a pocket of air. If a dent is placed in one side, there is no easy way to knock it flat again because the approach from the other side is blocked by the other piece of pressed sheet metal. In the case of Honda Civic's hood, though, the second piece didn't completely cover the bottom of the top sheet. There were voids cut into it in various places, though only a few of these were beneath places where there was a dent in need of flattening. But I realized that it was possible to force a thin board into the gap where the two pieces of sheet metal hand been bonded. Those bonds consisted mostly of pads of adhesive rubber and quickly gave way as I pounded the board into the gap and beyond. Using this method, I was able to get most of the dents out. The hood still looked like shit; its surface retained distortions and waves. But it was an improvement that will probably help to restore the car's ærodynamics. All my hammering also forced the hood back somewhat into its original geometry, which had been skewed towards the the rear wheel on the driver's side. I was beginning to wonder if my tinkering was causing more problems than it was solving.
The problem with getting the hood back into its original shape was that, once I place it back on its hinges, it no longer lined up with the engine compartment and it couldn't be closed. Obviously, that was never going to work. The problem was that the driver's side hood hinge had been compressed backwards. In order to get the geometrically-restored hood to fit, I was going to have to geometrically-restore that hinge. By comparing it with the other hinge, I could see precisely what was wrong with it. But there was no easy way to remove it so that I could throw it in a vise and work it over with my various high-leverage tools. I had to try to restore it in place. To do this, I used various heavy metal tools to limit its range of motion while I yanked it in various directions either with pliers or my bare hands. The steel the hinge had been made from was not all that robust and it wasn't too hard to deform and twist it. For every little fix of one geometric problem it was easy to unfix another. At a certain point I realized that to get it into a better state I had to first pass through a number of worse states. This is, it seems, how one must deal with chaotically-deformed metal.
Even with the hood lined up better with the engine compartment, the damn thing refused to latch. Part of the problem was that I had to precisely bend the steel latching loop (that rounded-cornered rectangular loop of heavy wire that slams down into the latch mechanism) into the correct near-vertical plane so that it slammed down into a very narrow target in the latching mechanism. But even with it hitting the ideal spot, the hood would not latch until I removed a number of the rubber bumpers protruding up from the center-front of the engine compartment. They were keeping the hood (which was still somewhat deformed downward) from falling low enough for the latching mechanism to grab the latching loop. Once I fixed that problem, the hood not only sat better on the car than it had before I started tinkering, but it both opened and closed with greater reliability. And, of course, it also looked better.
The one other thing I needed to fix was the plastic reflective diffuser on the back of the driver's side rearview mirror. Evidently the deer had also hit that part of the car, shattering the diffuser but not affecting the underlying electronics (which consisted of some sort of semiconductor and a white LED). All I needed to do to fix this problem was provide some sort of weather seal. So I applied a bit of clear greenhouse tape, a material that has demonstrated its ability to survive years of exposure to ultraviolet light.
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http://asecular.com/blog.php?130908 feedback
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