The hardest thing about bug impact testing is dealing with the crickets. It was not too difficult modifying an air gun with top useful speed of three hundred miles per hour to operate at five to six hundred miles per hour. All it took was replacing the old solenoid valve with a larger one, upping the operating pressure from twenty or thirty psi. to one hundred and fifty psi., making Styrofoam sabots, developing a compressed Styrofoam wad for stopping up the chamber, and making custom tools for packing the chamber. All pretty standard stuff. And it is not as if the crickets are physically difficult to work with. They fit in the 1/4² barrel nicely. Their weight is not such that the gun has a hard time pushing them. They take special care to use, being delicate and all, but that is no big deal. No, the part I did not like was killing them. Even though they are just bugs and I put them out painlessly with cold before they knew what they were in for, I just did not like it. So I was not disappointed when it turned out that even at speeds in excess of five hundred and fifty miles per hour they do not damage an F-18 windshield. For that, I had to call in a stunt double.Disclaimer:
The following contains scenes of violence against dried fruit which some readers may find disturbing, or at least convince them the author is disturbed.
To bring you up to speed, as it were, my company's F-18 windshield has run into a little problem in flight testing. A lot of little insect-shaped problems. Little insect-shaped problems from the everglades that do not wash off our prototype windshield. My job for the past few weeks has been to find out what bugs are damaging our windshield, obtain samples, and set up a lab test to simulate the effect. In Chapter 1 I described my quest to find out what insect might be the problem, and why I could not 0btain any specimens. What follows tells what I use instead.
Everyone has been under a lot of pressure over this bug thing. It is this month¹s big emergency. Even the head salesman for the F-18, Chuck Seagle, has come into to town to add his personal touch. Chuck is a Texan, and loud of it. The chemists have been getting a little tense lately. Fortunately for me, I just have a hard time taking bug impact testing seriously.
With crickets out of the running for bug damage simulation I had to cast about for a replacement. Obviously, the impact part of the bug damage (if any) is caused by hard bodied insects like flying beetles instead of soft bodied insects like crickets. I decided to try one of my very first ideas which I had discarded in favor of crickets. So on Monday morning on my way to work I opened up the Kellogg¹s Raisin Bran and sifted out five raisins. The way I figure it, raisins are squishy like a bug, but not bouncy like rubber or silly putty. They are not hard on the outside, but I did not have any Raisin-Nut-Flakes, so there you go. (Raisin-Nut-Flakes have raisins which are coated with chopped up nuts.) However, they do hold together a lot better than soft bodied insects.
I went to work with my raisins early in the day. My air gun is loaded at the breach end through a hole in the side of the barrel. To get fast shots I shove the projectile down into the barrel from the chamber, and then pack in compressed Styrofoam behind it. The Styrofoam holds back the in-rushing air just long enough to get really high pressure, then disintegrates and flows easily down the barrel. (Now don¹t go stealing my techniques. As someone pointed out, I am probably the only person in the world working on this problem right now, and I don¹t want to be scooped.)
Unfortunately, I had not counted on “plump, juicy raisins.” My first fruity victim would not quite fit. So I shot it anyway, without bothering with the Styrofoam. By luck, I got over 500 mph anyway. It made a nice mark on the windshield, except for some scratches caused by the sugar crystals. Incidentally, it also went right through my cardboard backstop, bounced off the back of a tensile testing machine, and disappeared into that strange limbo world that raisins disappear into when they have lived a life of evil.
Having proved the concept, I then tried to refine the process. For the next three shots I cleaned the sugar off with water, but could not get the speed I needed. Sure, even a measly 350 mph is enough to imbed a raisin in the lab ceiling on ricochet, but it does not hurt the window. (Clean through the cardboard backstop again. I switched to something more substantial.) For my fifth and final raisin of the day I put it in unwashed, sugar and all, to see if that first shot was a fluke. Washing with water also removes a raisins natural stickiness, which may help give that all important delay. I try it, and it is a perfect shot. Not washing the raisin is key.
Having used all five raisins I wandered off to do the rest of my work-- you know, the stuff besides emergency bug impact testing. Towards the afternoon, along come the chemists. (They often travel in pairs. I don¹t know why.) They want to know if I have made any progress today. From experience, I have learned not to supply partial results if I can at all help it. So of course I told them that I had two good hits and would do more tomorrow. (Hey, wait a minute...) They want to know why I do not do more right now. I used all my raisins, I say.
Here it comes. I know what they are going to say. And yet, they say it anyway.
“Why didn¹t you bring more raisins?”
Two years at this company as an engineer. Four years at Caltech. I can do calculus in my head, I can machine precision devices out of brass and aluminum, I can write a test report that is clear and concise (the hardest of the three), and what now? I get flak because I did not pull enough raisins out of my Raisin Bran. These guys are actually annoyed that I did not sift more raisins out of my Raisin Bran that morning. What can you do?
I pointed out how silly they were being, and eventually they acknowledged I was right. I pointed out that it was just enough to test the idea, and since the results were encouraging I would bring in lots of raisins tomorrow. So the next morning I came in ready. There was a whole box of raisins in the fridge at home that I had not known about, and I had some of them-- nice sticky raisins that do not need the sugar washed off. Unfortunately, they would not work. First off, they just would not go fast enough. Still in the measly 350 mph range, wadding or no wadding. Second, disintegrated Styrofoam and raisin residue play cute little games with my speed trap's sensors, sticking in the wrong places and all. Third, when I do get them going fast enough, they bounce harmlessly off the window. I even got some dry trial mix raisins from the cafeteria, and they did the same. It turns out that the raisins only work if they are sugar coated after all.
The next day I come in with a nice fresh box of Kellogg¹s Raisin Bran. It has been working wonders. Since they do not need wadding I can do one shot after another in rapid succession. No little Styrofoam bits to confuse the sensors (though they do need to be cleared every dozen or so shots). And best of all, the chemists (still going around two by two) really like the scratches left by the sugar. So I start telling people, “The sugar is useful because it provides the cutting action we expect from the hard edges of insect shells.” I have learned to say this with a perfectly straight face, and, this is the stickler, no one even bats an eye. Unbelievable.
To sum up, the chemists are happy with the test. Chuck is happy with the test. My bosses can¹t help but smile when they see me working away with my safety glasses, ear protection, and box of Raisin Bran. (Look for the upcoming add campaign: Raisin Bran; Not Just For Breakfast Anymore.) The only complaints are from other people working in the lab. From one end of the room I get “My notebook pages are sticking together because of little raisin bits!” From the other end of the room comes, “There are little pieces of raisins all over my computer!” But this does not discourage me. For science, sometimes you have to make sacrifices.