[LAST] Re: Kyoto, Driving our car

Brian D Williams (talon57@well.com)
Thu, 11 Dec 1997 08:04:44 -0800 (PST)

From: Michael Lorrey <retroman@together.net>

>No I just get knida tired of hearing people making preposterous

>> The composite body of a Hypercar is not paper-mache thin, and in
>> fact its monocoque construction makes it much stronger than a
>> conventional car and probably your 1/2 ton pickup.

>Not bloody likely. Ever wonder why more vehicle occupants that are
>hit by trucks are killed than occupants of the trucks??? Law of
>inertia. A smaller vehicle is a)not going to have the same
>structural strength as a much larger utility vehicle and b) will
>be stopped faster than a larger vehicle, causing much more
>traumatic injury.

>>It will not crumple like tissue paper.If I could not stop short
>>ofthe Moose, I would accelerate. (law of inertia you know.)
>>letting Mr Moose with his now broken legs land behind me.

>Considering that ALL cars are now required to be designed with
>what are known as "crumple zones", I highly doubt that this would
>be the case.

Hypercars: Safety, Performance, and Aesthetics

A common generic objection to fuel-efficient cars is their alleged
crash risk. But this confuses fuel economy, mass, size, and design.

Fuel economy and light weight need not compromise safety. There is
no correlation, far less a causal relationship, between present
cars' crash-test performance and their mass, nor between their fuel
economy and their on-the-road death rate(67a,67b). That is chiefly
because occupant protection systems are lightweight, and because
vehicles' design and materials are vastly more important than their
mass. It may also be partly because light cars can avoid more
accidents by stopping sooner and handling more nimbly(68a,68b).

Existence proofs suggest that the general lessons invited from
gross correlations between light cars and higher death rates are
misleading. Americans can now buy a 4,2 l/100 km (56 mi/gal) car
with a lower death rate than a 10,2 l/100 km (23 mi/gal) car; cars
with identical efficiencies but over tenfold-different death rates;
and cars at any mass that differ in crashworthiness by more than
tenfold. Such comparisons reveal some unusually dangerous cars now
on the road at various levels of mass and fuel economy, but they
make no case that fuel economy does or must conflict with superior
safety(69a,69b) Rather, their high scatter emphasizes the
importance of design differences.

Theoretically, collisions between two cars identical except in mass
tend to damage the lighter car more. (Practically, this is often
incorrect because other, unequal factors such as design dominate.
The National Highway Traffic Safety Administration sought to show
the danger of light cars in recent light/heavy crash tests; the
light cars reportedly came off better until stronger heavy cars and
flimsier light cars were substituted.) This idealized theory leads
some to propose that you should drive a heavier car--thus reducing
such collisions' risk to yourself while raising others' risk
correspondingly(70a,70b) But the right answer is to make all cars
(71a,71b)s afe whatever their weight, without putting all the
adjustment burden on light cars. Heavier vehicles should be made
less aggressive (Kdser 1992)--softer, less angular, more
absorptive, with bigger ridedown distances--and the road fleet's
mass distribution should be further narrowed, e.g. by incentives
for replacing inefficient with efficient cars (section 11). Heavy
lorries with slightly relaxed length limits could even be equipped
with a highly energy-absorbing structure on the front to help
protect any car they might hit (M. Seal, personal communication, 24
March 1993).

Better control of destructive driver behaviour such as drunkenness
is often crucial: behaviour may be up to a thousandfold more
risk-determining than the car itself (L. Evans, personal
communication, 1992), and only about a twentieth of crashes do not
involve driver factors (Evans 1991). But as to the car, modern
designs and materials can do far better than Henry Ford had in mind
when, in 1926, he said that " A heavy man cannot run as well as a
trim man. You do not need weight for strength"; (S. Abouzar,
personal communication, 3 July 1991).

GM's Ultralite confirms that mass per unit volume can be cut by
more than half below the "steel plateau" level. This decoupling
permits fuel-efficient cars to remain ultralight while combining
roomy interiors with ample crush length, which appears to improve
crash performance somewhat. Yet better materials and design can
also substitute for crush length.

Composites and other ultrastrong net-shape materials--many stronger
than the familiarly durable but lower-grade carbon-fibre fishing
rods, skis, etc.--would dominate in a hypercar. They would bounce
without damage in minor fender-bender collisions: most deformations
of carbon-fibre composite panels simply pop out again with little
or no damage. Under severe loads, composite structures fail very
differently than metal, so "totally different design concepts have
to be applied", and understanding of failure modes is not yet
mature. However, even under compressive loading--often considered
composites' weak point(72b,72a,)"Composite structural
elements...show high and in many cases better energy absorption
performance than comparable metal structures" (Kindervater 1991)
(73a,73b) Extensive aerospace experience is available from
designing all-composite structures and aircraft (like the Stealth
bomber and fighter) to withstand bird and stone strikes, landing
stress, etc.

Light metals would also be used where appropriate, such as in
sections of crushable light-metal foam or honeycomb for energy
management in a serious crash. These materials, available for two
decades (APS 1975), have a nearly perfect square-wave
response--they squash flat, absorbing enormous energy, before
transmitting crash accelerations--making them an ideal substitute
for ridedown length.

Other crash-energy-managing design options include buckling
members, down-deflecting heavy driveline components, filament-wound
or sheet-and-keel(74b,74a)cruciforms, and "impact beams(75a,75b)
Composite prototype and small-production cars and vans with
proprietary crash structures have in fact yielded some of the best
crash-test results ever recorded by a major automaker; some were
probably driveable after a 56-km/h barrier crash (P.H. Magnuson and
major-automaker experts, personal communications, March 1993;
Grosse 1992).

An ultralight car using ultrastrong materials, modern airbag
restraint systems, and crash-energy-managing design can weigh less
than half as much as today's platforms--as the Ultralite does--yet
be far safer than any car now sold. That is why racedrivers are
rarely killed nowadays when composite cars hit walls at 350 km/h:
as tens of millions of Americans saw on their 1992 tv news, the
composite car flies to bits, failing at "sections specifically
designed to initiate such breakaway and absorbing extensive crash
energy through controlled failure modes," but the "survival
capsule" remains intact and the driver generally limps away with
perhaps a broken foot. To be sure, ordinary drivers would lack the
racedriver's helmet, fitted foam restraints, spaceframe, etc., but
even in a head-on collision their lower speeds would imply
one-fourth the racedrivers' crash energy, and even if they were
more seriously injured, that would be a great improvement on their
fate in today's cars(76a,76b).

The main potential safety disadvantages(77b,77a)of the ultralight
hybrids described in section section 6-7 are that with their low
drag and low or absent engine noise, pedestrians may not hear them
coming unless a noisemaker is added that somehow warns without
being objectionable, and obstacles such as small trees, crash
barriers, and lampposts, against which a heavy car can dissipate
energy by breaking or deforming them, may instead stop a light car
or make it bounce off, increasing deceleration and perhaps
bounceback acceleration forces on passengers(78a,78b)

But beyond their general crashworthiness described above, such
"hypercars" also offer important safety features. The 2- or (with
series hybrids) 4-wheel switched reluctance drives offer full-time
antilock braking and antiskid traction, but with far greater
balance, response speed, and effectiveness than today's methods.

Hypercars' light weight means faster starts and stops; their stiff
shell, quicker and more precise handling.

Carbon-fibre designs can be so stiff and bouncy that an ultralight
car, if broadsided by a heavy lorry, could go flying--like kicking
an empty coffee-can. The very unfavourable momentum transfer would
go not into mashing the ultralight car but into launching it. Yet
occupants restrained by belts, bags, and headrests and protected
from intrusion into their protection space might well survive
unless accelerated by more than the often survivable ~40-60 g
range--in which case they'd be dead anyway in any car today, light
or heavy, steel or composite.

In the rare accidents so severe as to crush the composite shell
(usually in hammer-and-anvil fashion), the occupants would be far
less likely to be injured than by intruding torn metal edges in a
steel car; with any potentially intruding carbon-fibre shards
overlain by or interwoven into fracture-masking aramid or
polyethylene cloth, the crushed composite sections can become
relatively innocuous.

Victims' extrication would be much faster (a crucial element of
critical medical care--most victims not dead on the spot can be
saved if brought to hospital within an hour): the doors are
likelier to function, the composite shell can provide easier
access(79,79a) cutting it with a rotary wheel is quick and makes no
sparks to ignite fuel vapours, and breakaway energy-absorbing main
components would no longer impede access to the passenger
Ultralights' decoupling of mass from volume makes it
straightforward to maintain a wide track and long wheelbase for
rollover resistance.

Hydroplaning risk should not rise and may fall, because the car
weighs less but has narrower tires.

The small powertrain volume and raked bonnet are consistent with
improved visibility and, as Dr Michael Seal suggests, with
headlamps behind the bottom of the windscreen (so they are cleaned
by the same wipers). The hidden headlamps are also exceptionally
powerful and can cause road markers and certain textiles to

With careful design, composites', especially foamcore composites',
excellent attenuation of noise and vibration could yield an
extremely quiet ride--important because road noise is no longer
masked by engine noise(80a,80b) This plus the virtually complete
absence of wind noise should make driving less fatiguing,
potentially boosting driver alertness.

"The whole car is so simple, reliable, corrosion-resistant,
fault-tolerant, and failsafe-designable that dangerous mechanical
failures are far less likely."

For all these reasons, the design approach described here could
yield substantially improved safety. Hypercars could also offer
ample comfort, unprecedented durability and ease of repair,
exceptional quietness (sound-deadening materials, no wind noise, no
squeaks), beautiful finish and styling while retaining significant
stylistic flexibility, impeccable fit and weatherproofness, high
performance (light weight means faster acceleration), unmatched
reliability, and--as we shall see next--probably low cost.

One caveat is in order, however. Especially in the litigious United
States, innovation is deterred by the threat that makers of new and
hence initially "unproven" technologies may have to pay damage
claims even for accidents in which they are blameless. Some experts
fear that such potential liability might add exposure up to several
thousand ECU or $ per car-year, especially for manufacturers large
enough to invite lawsuits but not large enough to defeat them.
Absent tort reform, removing this important barrier to market entry
may require some government indemnity or coinsurance to makers of
hypercars meeting a national safety standard, at least until
actuarial experience has field-validated their theoretical ability
to match or exceed the safety of today's cars(81a,81b).


67a Historic data must be interpreted with care. Until 1985, the
U.S. accident population was only ~15% restrained by belts and
airbags, rising to ~50% in 1990 (D. Friedman, personal
communications, March 1993). Although admirably extensive analyses
of mass vs. safety have been performed (e.g., Evans 1991), the
higher crash death rates observed in the average of today's light
cars (but certainly not in all models) are for a fleet all built
with broadly similar methods and materials, and hence cannot be
used to predict the safety of the completely new kinds of cars
proposed here.

68b Such effects are almost impossible to measure because, for
example, larger cars (which tend to be heavier with currently
dominant designs) tend to drive more miles, carry more people, and
be driven in less urban settings (hence at higher speeds) and in
riskier ways, while smaller cars tend to have younger drivers who
are more crash-prone but survive better (Evans 1991, pp. 75-76)

69a A car-design variable strongly correlated with risk is
acceleration--a fact unmentioned since Detroit intensified its
marketing of muscle cars.

70a,70b As Evans (1991) states,"When a crash occurs, other factors
being equal[:] The lighter the vehicle, the less risk to other road
users. The heavier the vehicle, the less risk to its occupants "
The opposite should therefore also be true.

71A,71B And light trucks and sports utility vehicles. In the United
States these were exempted from safety requirements, and their
crash-test performance shows it.

72A,72B This varies with composition: the ratio of strength in
tension to that in compression is approximately 1 for most carbon
fibre, 3-4 for aramid, and up to 10 for high-performance
polyethylene. Among many proofs of the right composites'
suitability for compressional loads, a carbon/epoxy unmanned
minisubmarine exhibited no fibre breakage at pressures equivalent
to 7 km depth (G.M. Wood and D.A. Waters, personal communication,
26 March 1993).

73,73B For example (Kindervater 1991), in "fracture dominated
crushing modes of carbon or hybrid [carbon-aramid] composite
tubes[,] specific energies over 100 kJ/kg [with nearly 100% crush
force efficiency AE, i.e., nearly ideal plastic energy absorption]
could be obtained compared to 60 kJ/kg...in the best aluminium
configurations." Specific energy absorption equal to that of
aluminium tubes, at comparable or somewhat lower AE, can also be
obtained from sinewave-beam composite assemblies. For such reasons,
composites are predicted within the next ten years to be used "for
up to 80 percent of the structural weight of a helicopter." To be
sure, "Pure carbon fibre reinforced laminates under compression
loading can have extremely high energy absorption capability but
disintegrate completely into small laminate fragments," but
"Hybridization with tougher fibres such as Kevlar or high
performance polyethylene [stacked or in intraply weaves]...provides
post crash structural integrity" with lower stiffness but also
perhaps lower weight, since polyethylenes like Dyneema SK60 have
specific gravity below unity.

74A,74B Such a cruciform using hybrid composites to resist
longitudinal crushing (of, say, an aircraft subfloor supported by
cruciform pillars) absorbs ~3.25x the kJ/kg of an aluminium
cruciform (Kindervater 1991); comparable U.S. automakers' findings
are ~4.

75A.75B Kdser (1992), of the Institute for Lightweight Structures
at the Swiss Federal Institute of Technology (Z|rich), shows that
a foam- or honeycomb-filled, nearly rectangular beam wrapped around
a light car (500-600 kg curb weight, 2,5-2,8 m overall length) can
decelerate ~250-kN mean impacts at ~48 mean g without intrusion.
"Higher impact forces and decelerations can be obtained with small
modifications without significant increase of weight."

76A,76B Given such an ultrasafe family car, you could in principle
make it even a little safer in two-car collisions (albeit less able
to maneuver to avoid them, and more hazardous to other cars) by
using more mass, including more of those same safety-producing
materials. But you may not want to, because the marginal cost
would be relatively high, the marginal benefit relatively low, and
the performance penalty from mass compounding possibly substantial.
However, the better the regenerative braking, the smaller the mass
penalty--hybrids scale up well--so some extra mass yielding
potentially large increments of safety could be accommodated if
desired. Our conclusions therefore do not depend on extrapolating
our qualitative safety conclusions to the extremely lightweight
frontiers of the 400-kg Ultima.

77A,77B Minor ones might also exist, such as post-crash
high-voltage conduction by uninsulated carbon fibres.

78A,78B Such artificial barriers can be redesigned, but must still
withstand natural forces.

79a,79b The Ultralite's clamshell doors, for example, open up the
entire side of the car at once, giving simultaneous full access to
both the front and rear of the whole passenger compartment. Yet the
thin carbon-fibre door, light enough to be lifted by a small child,
is so strong that it provides adequate side impact resistance with
no B-pillar.

80a,80b Active noise cancellation works much better for engine
noise than for road noise, but a tire tread has been proposed whose
halves make out-of-phase sounds that tend to cancel at some
frequencies (P. MacCready, personal communication, 4 March 1993).
Interior quietness need not require much weight: some modern
aircraft, for example, selectively filter out annoying frequency
ranges with "inhomogeneous layers of polyimide foam."

81a,81b AeroVironment (Monrovia, California) is coordinating a
systematic exploration of the many public policy issues raised by
integrating a new kind of vehicle, the electric "SubCar" into
innovative transportation systems. Like anything different,
including hypercars, the SubCar raises a host of issues from
emissions to liability and insurance. For example, Consulier's
2,59-meter-long, 5,9 l/100 km [40 mi/gal] "Ram-Chop" urban
commuter-vanlet design, seating four abreast ahead of a >1,4-m3
over-engine cargo area, is so short that two can be parked
end-to-end or side-by-side in one U.S. parking space, like Fiat's
even shorter (2,1-m) 3-passenger Downtown (Autoweek 1993); but
would that be legal?

Christopher Gronbeck - June 10, 1994
Center for Renewable Energy and Sustainable Technology
Please address comments to www-content@crest.org

Yeah, I was just making it all up....

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