The Traffic Accident Reconstruction Origin -ARnews-
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Re: Speedometer Locked in Position Following a Collision
Dave Lohf (dlohf@ibm.net)
Sat, 7 Feb 1998 21:01:49 -0500 (EST)
My hat is off to the creation of this thread....the poem is priceless (but, he DOES need to get out more often). I built a box that would allow only ultra-violet light inside and mounted a camera on top of the box. I used the camera to take photos using various exposure times of speedometers which were bathed in the ultra-violet light. Once in a great while (emphasis on great while), it was possible to see evidence of the needle "slap". I noted that several things had to have occurred. First, the impact had to be almost fully head-on; second, there could be no pre-impact skidding because if the wheels are locked up, there is no indicated speed; and third, the needle had to be coated with fluorescent paint.
I gave up on the idea after the manufacturers quit cooperating and began using plastic needles. It appears that, if one uses a verrrrry sophisticated box, we can still find evidence of needle contact with the speedometer face. The problem of unreliability remains very much in the forefront. No doubt, we all have encountered speedometer needles stuck in various attitudes and cannot provide adequate explanation as to how the needle got there. Impact speed may be one way, but, there are several other explanations available.
It's all too much trouble for too little result. I gave up on the idea long ago.
Dave Lohf
dlohf@ibm.net
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