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[RE: OT but interesting story]
I should know better than to jump into a thread like this after several
glasses of wine...
You can calculate the speed the car was travelling from the skid marks
based on things like coefficient of friction, weather, etc. You can't get more
than a very wide range from the distance the engine travels after it seperates.
You have to allow for the shear strength of whatever mounts and other hardware
directly attached the engine to the frame (which are generally within a range
of values) plus the forces required to get the engine out of the compartment.
Then you have to allow for tumbling and rolling, which is not deterministic,
especially not related to coefficient of friction for the engine itself.
AFAIK, accident evaluations are done by specialists working on contract to
the police, not the cops specifically. I know of several companies that
specialize in accident reconstruction. From the engine's final resting place,
you can determine direction of travel and the lower limit of velocity at the
time of collision, but not much more.
I have to admit, I'm much more interested in the level of forces relieved
by the seperation of the various major components. I understand better than
60% of the forces involved in a Grand Prix major accident are absorbed and
carried away when the engine seperates, as designed. I guess that's why these
guys can hit a wall over 200 Kph and walk away (well, their feet and legs could
present a problem).
Cheers,
Colin
On 15-May-2002 Justin Pennington wrote:
> Actually it can be done. Police do it all the time... Thats how thy can
> prove
> how fast a car was going... However very precise measurments must be taken.
> Ie Road conditions, type of tires, tempature, etc.
> Cuase they must figure out what the coefficent of friction is (you physics
> people out there will understand that) between the tires and the road. And
> now that you are talking about a motor going down the road... well you would
> have to know the motors Coef. of Fr. Which I have a feeling is going to be
> more trouble than it is worth. (after all the motor would prob tumble.
> So yes it could be done. But I doubt anyone has the time among us. :)
> And we would have to get the exact measurements and stuff, which I doubt was
> taken.
> Justin
>
>
>
> "Wes Brockway" <kywes@bellsouth.net> wrote:
> Well all of this has become very interesting to me. I had heard about
> the crumple zone but didn't realize how much more the manufacturers do
> to help in case of an accident. Any physicists out there who could
> calculate from the distance the motor traveled and the weight of the
> motor how fast they were going? I'm not that smart if it can be done.
>
> -----Original Message-----
> From: scirocco-l-admin@scirocco.org
> [mailto:scirocco-l-admin@scirocco.org] On Behalf Of Justin Pennington
> Sent: Tuesday, May 14, 2002 7:58 PM
> To: scirocco-l@scirocco.org
> Subject: Re: OT but interesting story
>
>
> Eric is right... I'm a Medic and have been so for a few years. And when
> it comes to accidents some of the oddest things can happen. Mainly due
> to car designers making the cars to basically fall apart in the event of
> a collision. After all the Energy has to go somewhere in an accident.
> Hence the crumple zone idea. Sure it totals a car, but if the car can
> absorb more of the energy then less gets transfered into the person.
> Ive seen several accidents where Engines have come apart from the
> vehicle. And even some where Hoods and Hatches/Trunks have come apart.
> After all the more energy that gets diverted the better off the patient
> usually is. Just my input. Justin
>
> Ps. Anyone in the MD/PA/DE/NJ area that is looking for some scirocco
> project contact me. I am considering selling both of mine (one needs
> work to run, one is parts car)
>
>
> Message: 77
> Date: Mon, 13 May 2002 19:49:05 -0600 (MDT)
> From: Night Shadow <soltwede@privateI.com>
> To: Wes Brockway <KYWes@bellsouth.net>
> cc: Larry <rocco16v@netzero.com>, Michael Abatzis
> <abatzis2@hotmail.com>, scirocco-l@scirocco.org
> Subject: Re: OT but interesting story
>
>> Interesting thread responses here but I had listed the stoy because of
>
>> the info that the engine had pulled loose from the car and traveled 65
>
>> ft. Is this not a surprise to anyone? Not what I would expect to
>> happen.
>
> Actually, yes, this is normal. Volvo has done this for years. In the
> case of a head on crash, the motor is supposed to drop out the bottom of
> the car instead of getting pushed into the passenger compartment. What
> happened hear is the forces just pulled the motor out...I imagine not a
> head on crash but more that the GTI slid sideways into a pole or
> something...
>
> Eric
>
>
> --
> Eric
> Northglenn, CO
>
>
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--
Cheers,
Colin
If you can read this line, you're probably not illiterate.