A rigid body (one that does not crumple) transfers energy (into, say, a
passenger compartment). A non rigid body (one that crumples)
absorbs/dissipates energy as it crumples. Hint: Go back to basics.
Force with zero motion is zero energy; motion without force is zero
energy. Energy = force applied over a distance. Crumpling (motion with
force applied) reperesents extraction of energy from the body creating
the crumpling. It's all about controlled energy dissipation so that the
energy does not get transferred in full into the passenger compartment
(by a rigid body).
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')
If she was buckled in properly, maybe. But I would NOT bet on it.
Don't recall the episode, but if it was a Big Ol' 50's Chrysler Boat
Vs. an Inner-city Bus, the Chrysler could soak up enough of the hit to
Just look what happens with a car Vs a Light Rail trolley car - the
car looks like bug-splat on the windshield, and the train gets off
with minor damage. Full freight locomotives sometimes come out of the
wreck without hardly a scratch - it bends the front coupler...
Buses and Semis are only one notch down on the Vehicular Mass scale,
a small car is either bouncing off or going under.
--<< Bruce >>--
Exactly, but more importantly so that the energy is absorbed to below a
speed at which the seat/shoulder belt and the SRS can absorb enough of the
remaining energy, to a point the terminal speed is well below what the
properly belted passenger body can withstand, when one organs strikes their
skeleton. That is why larger vehicles are safer, since there is more room
into which we can design those energy absorbing zones to reach the minimum
terminal speed goal.
The short answer is that they're DESIGNED to crumple in order to
dissipate energy in crashes, which is why cars are safer today (much
more of a real impact on saftey than airbags, IMO. I think they've gone
way too far, though, when a 5 mph "oops" with a pole can tear up an
entire bumper cover. But that's not really a problem with the energy
absorption philosophy as much as it is with the implemenation. By the
way, "crush zone" design really started way back in the 50s. Steering
wheels were changed so that the center shaft wouldn't spear you in the
chest, then steering columns were made collapsible (68 model year),
drivetrains were made so that the engine/transmission would slide down
under the passenger compartment rather than punch into it, door beams
for side impact protection were mandated (circa 1973) etc. etc. etc. To
read some commentary, you'd think that collision safety applied to
chassis design appeared out of whole cloth in the 90s, but that's not
true at all. Truth be told, a 1973 autmobile has all of the *most
effective* features that a current car has. IMO its sort of an 80/20
rule- 80% of the survivability improvements came with the first 20% of
design effort. All the complex stuff- self-retracting belts, air bombs,
side-curtain air bombs, etc. really don't add much on top of that EXCEPT
for the persistent idiots who won't wear their shoulder belts.
I worked on designing some of the safety equipment for Ford in the early
fifties. The "safety package" was offered on the newly designed '55 models
for $150. Virtually nobody chose the option. We made it standard on the
It didn't in the early 80s implementation.
The early Chrysler Horizons had shocks supporting the bumper bar.
I was rear ended hard twice ('81 Horizon) with no more damage than a
scuff on the plastic bumper cover.
The easing of regulations resulted in more fragile bumpers that are
trashed in slight bumps.
Based on the small amount that I've looked into that, it seems to me
that a lot of people zeroed in on the fuel tank installation simply
because "its different." The fatal crashes have tended to be such
violent high-speed things that my initial reaction is that *ANY* car
would probably have suffered a ruptured fuel tank and fire, but scrutiny
descended on the Crown Vic because its the only car on the road that has
a fuel tank situated just that way (although, for example, my wife's
Chrysler LH car is not terribly different in general principle, but
rather different in implementation being a front-drive).
But that doesn't mean a lot. The fuel tank placement in the Ford Panther
platform (Crown Vic, Police Interceptor, and Town Car) should,
theoretically, in many ways be much safer than other cars and SUVs- its
buried deep in the chassis, away from the rear and sides of the car, and
is rather hard to actually crush the thing because its so far forward in
the chassis (its AHEAD of the trunk well, behind the rear passenger's
seat and above/behind the axle, and pretty well inboard of the
structure). Its got a lot of "crush zone" around it, certainly more than
your average vehicle with the tank slung under the trunk well and only
8-10 inches forward of the rear bumper. It was also used on a whole,
long line of Ford cars that predated the Panther (yes, there *were*
Fords older than the Panther platform yet younger than the Model T, hard
as it is to believe!) such as my high-school friend's 1971 LTD. Having
spent a lot of time under *that* car only bolsters my contention that
the location of the fuel tank is fine, but it was physically larger than
the current Panther and had more room around the tank.
Now what may be more of a problem with the Panther than the older
designs is the possiblity that once the fuel tank is breached, fuel and
vapors intrude into the passenger comparment. Ford *did* build a lot of
cars where the wall of the fuel tank was actually the floor or wall of
the trunk itself (the "drop-in" Mustang tank, for example) and that was
pretty much a bad idea in most people's view. But the Panther is NOT
built that way- the tank is outside the passenger area and doesn't share
a common wall with it.
Bottom line- its all a moot point because the Charger police-package car
is going to kick the Ford Interceptor right out of the market segment
anyway ;-) Heck, the 3.5L HO v6 Charger is faster than the 4.6L v8 Ford
Police Interceptor, and the 5.7L Hemi is back in late-60s CopCar
performance territory, though not quite as fast as the legendary '69
Polara Pursuit package but it does corner better ;-)
And yet, there is no history of that particualr design being more fire prone
than other cars of the era. Take a look at many cars of the era that had the
fuel filler behind the licence plate - in some cases the filler tube ran
naked trhough the trunk. Or for that matter look at station wagons from the
50's, 60's, 70's, and 80's. The fuel tanks were usually in the passenger
side rear fender with no inner liner. Or how about pickup trucks before the
70's - the gas tank were usually in the cab with a flexible hose connecting
the tank to the external filler neck.
That's true, but its still questionable engineering.
Nothing wrong with that at all- its still outside the passenger
compartment. And those tubes were designed to simply slide further into
the gas tank through the rubber grommet around them in the event of an
impact- without leaking. I've seen examples of them doing exactly that-
they work very well.
Yeah, even my beloved Mopars. When they started cutting corners on the
A-bodies (Valiant/Dart) in the early 70s, they shifted from a reasonable
filler tube to one that passed *diagonally* through the trunk, eating
into usable space. I always hated that one....
Well, tank-in-cab pickups *DO* have a higher conflagration history than
contemporary vehicles. And while drop-in tanks might not be
statistically worse, it still doesn't sound like a good idea to only
have 1 layer of sheet metal between the passenger compartment and fuel.
- The crash energy levels associated with post rear impact fuel tank
failures in the CVPI vehicles are significantly greater than the levels in
FMVSS 301 tests.
- Fuel tank failures during high-speed rear impacts can result from numerous
causes in addition to the hex-headed bolt and U-brackets identified in the
Ford TSB. Crash reports identify many causes for loss of fuel system
integrity during a high-energy rear crash, such as puncture from a deformed
frame rail, lower shock absorber supports, or stowed items in the trunk,
hydrostatic rupture, and other causes.
- Based on analysis of FARS data, the risk of fire per fatal rear crash in
the subject vehicles is comparable to that of the GM B-body vehicle
- The vast majority of reported post rear crash fires in the subject
vehicles (over 80%) occurred in CVPI vehicles, even though they constitute
less than 15% of the total Panther vehicle production.
- The Florida Highway Patrol Study did not identify a difference between the
post rear impact fire risk in CVPI vehicles and that of the Caprice police
- Ford-sponsored testing indicates that the subject vehicles are not unique
in their inability to maintain fuel tank integrity in at least one example
of a severe rear impact crash.
- There have been numerous high-energy rear crashes involving CVPI vehicles
within the scope of Ford's TSB that exhibited little or no fuel loss and no
The available information regarding fuel tank failure mode, the risk of fire
per fatal crash, field performance, and crash testing indicate that the
performance of the subject vehicle in high-energy rear crashes is not unlike
that of the most comparable peer vehicle, the GM B-body.
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