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Re: impact results and homebrew projects
Although it has been a while since I have taken classes covering these
issues (I have).
First the assumptions, same weight vehicles and like you stated removing
small factors like wind and rolling resistance.
What you end up with is that the ONLY major factors in the impact is the
speed of the vehicles realitive to each other, so (60,0) and (30, -30) would
be the same.
keeping in mind (as you also mention energy squares with speed) the result
of a 60,0 immediatly after impact would be both cars traveling at 30.
I will also chime in at this point my opinions about IC's and other
projects, I have tried many similiar projects with varieing success. This
includes my Ram-Air which I believe the only downside is an air filter that
gets dirtier quicker, and a Throttlebody enlargement that even though
completed was never driven due to vacume pulling it open and it would not
come down to an idle. There is a LOT to be learned by trying things (even
with design flaws) and I complement the copper IC attempt even though I
doubt success (real or imagined). If everybody only tried things that
everybody else agreed with there would be no progress and less learning.
Once my MC is running in my 84 4kq I will be homebrewing IC's mysel
although I my current plan is to build new tanks and/or downsize IC cores
that I have or will be getting (I got one of Neil Swanson's) I have
homebrewed an air filter box for my conversion out of AL and it can be seen
at my site.
> > ... Be aware that two cars travelling towards each other,
> >each at 30 MPH is an extremely severe collision, visually, it would LOOK
> >like driving into a parked car while you were doing 60 MPH, brakes OFF.
> >I believe physics shows us that 2 cars head-on each going 30mph is not
> >same as 1 car going 60 into a parked car. Each car absorbs 30mph, not 1
> >absorbing none (unless it is a semi-truck) and the other car absorbing
> >Small point, but a common misconception.
> Hey Guys,
> Believe it or not, it gets even a little more complicated than this. With
> the risk of this starting to sound like the T*rsen list...
> Yes, there is more energy stored in the one car going 60, than in two cars
> going 30.... that's because the energy stored in a moving mass increases
> the square of the speed, (but mass only to the first power). So, in
> actuality, the single car going 60 has twice as much energy stored up as
> the pair of cars going 30...
> And, both cars absorb the same amount, no matter how fast either one is
> BUT, it's not just the amount of stored energy which is dissipated which
> determines the results of a crash-- it's also the amount of time in which
> this energy is dissipated (dissipated power). For example, if you are
> going 60 mph and you put the car in neutral, you are hitting the wind, and
> letting the impact with the wind *slowly* decelerate you to (almost) zero.
> You would experience all of that energy being dissipated, but over a
> time, so there would be no impact on your health...
> So, the point is, that if you send two 30 mph cars into eachother head on,
> the two cars will stop in a VERY short period of time (ie high dissipated
> power). This is because the two cars will end up stopping right about
> where they hit-- they won't go sliding together in either direction, since
> they are the same mass.
> However, in the case of the car travelling at 60 into a stopped car (twice
> the energy of the two cars travelling at 30 needing to be dissipated), the
> collision will start to accelerate the stopped car, and the car travelling
> at 60 will end up coming to rest somewhere far down the street from the
> initial point of impact...
> But, it's the initial impact that counts, and computing it requires
> specific knowledge of the structure, materials etc., so I don't have the
> means or reason to try and compute it right now.
> The point is that the two scenarios aren't the same (two cars at 30, one
> car at 60). But to determine which one is worse is not that simple (but
> it's probably the single car going 60).
> In any event, if you are inside any of these cars, brake and steer, and
> won't have to find out.