HANS Dept. of Mechanical Engg. MESCE Kuttippuram 1 INTRODUCTION Only recently has the racing industry acknowledged that the number one cause of racing-related fatalities is basilar skull fractures from excessive head motions and neck loading. Racing legend Dale Earnhardt‟s death proved to the racing world and the general public that what appears to be a low impact crash can be fatal. Under development and extensively tested for over a decade, there is a device that can reduce the risk of serious injury or even death to the driver in such a crash. It is the Head And Neck Support (HANS) device. The HANS, head and neck support was invented by Dr. Robert Hubbard, a biomechanical engineering Professor at Michigan State University. Many debilitating or fatal head and neck injuries could be prevented using this system. The original HANS is shown in Figure 1 In 2000, compact versions of HANS (Figure 2) were developed for CART, IRL, F1, NASCAR, NHRA, ASA, Sports cars, Power Boating and many other racing series. Extensive testing has proven that HANS consistently reduces the injury potential from head motions and neck loads.
Transcript
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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INTRODUCTION
Only recently has the racing industry acknowledged that the number one cause
of racing-related fatalities is basilar skull fractures from excessive head motions and
neck loading. Racing legend Dale Earnhardt‟s death proved to the racing world and the
general public that what appears to be a low impact crash can be fatal. Under
development and extensively tested for over a decade, there is a device that can reduce
the risk of serious injury or even death to the driver in such a crash. It is the Head And
Neck Support (HANS) device.
The HANS, head and neck support was invented by Dr. Robert Hubbard, a
biomechanical engineering Professor at Michigan State University. Many debilitating or
fatal head and neck injuries could be prevented using this system. The original HANS is
shown in Figure 1
In 2000, compact versions of HANS (Figure 2) were developed for CART, IRL,
F1, NASCAR, NHRA, ASA, Sports cars, Power Boating and many other racing series.
Extensive testing has proven that HANS consistently reduces the injury potential
from head motions and neck loads.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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HANS….UP FOR SAFETY
The latest example of the engineers‟ efforts to make Grand Prix racing as safe as
possible is the new Head And Neck Support (HANS). The system is easy to use and
extremely effective. It prevents over-extension of the driver‟s neck region in the event
of extreme deceleration. It is designed to „complete‟ driver head protection, covering
the one aspect to be still exposed.
Forward movement of the head and neck has, until now, been the only
unrestrained area in driver impact safety. Extensive research and testing has resulted in
what experts now believe to be a practical solution to the issue.
HANS features a carbon fibre collar connected securely to the upper body, with
straps attaching it to the helmet. The four main parts of the system are:
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Dept. of Mechanical Engg. MESCE Kuttippuram
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1. Support brace- rests on shoulders.
2. Padding- is „fine tuned‟ for both comfort and fit.
3. Tethers-high strength Nomex tethers secure helmet to support brace.
4. Anchoring- complete system is secured by standard 75mm shoulder straps.
The fundamental purpose of the system is to effectively form a single „body‟ of
the head and torso.
By purposely directing the loads experienced following impact, the driver‟s
helmet is able to assist in dissipating the loads. HANS is intended to prevent driver‟s
head from being thrown forward in an accident, a common „whiplash‟ situation which
could lead to an over extension of the spinal column.
Drivers face theoretical deceleration stresses of up to 80 times the force of
gravity in an accident. In such a situation, the weight of the head and helmet increases
quickly from 7kg to as much as 560kg. HANS would help to absorb this strain, as well
as prevent the driver‟s head from hitting the steering wheel or front edge of the cockpit.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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BASIC CONCEPT
In a crash without HANS, the shoulder harness and seat restrain the driver‟s
torso, but only the neck restrains the head and helmet. The HANS device keeps the
driver‟s head from being pulled away from his upper body. With HANS, forces
stretching the neck are reduced to less than one-fifth in a frontal collision as slow as 41
mph. The HANS works in a simple and elegant manner.
A CFRP yoke is worn by the driver fitted around his neck and under the
shoulder belts. His helmet is loosely connected to this yoke by tethers ensuring free
movement of the head. In a frontal crash, these tethers restrain the head with forces that
directly counteract the head‟s forward movements while the torso and HANS are
restrained by the shoulder harness. By restraining the head to move with the torso in a
crash, the head motions and forces in the neck are dramatically reduced. The helmet
loading is also transferred from the base of the skull to the forehead- which is far better
suited in taking the force.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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RECENT HANS TESTING AND DEVELOPMENT
In 1997, DaimlerChrysler, Hubbard, and Downing started a cooperation to
develop and evaluate HANS prototypes suitable for the FIA Formula 1 environment.
A progression of HANS prototypes were made and evaluated in many impact
sled tests to develop a HANS (Figure 2) that is much smaller than the original device
(Figure 1). This smaller HANS fits reclined driving positions, as is the norm in F1,
CART, and IRL. Also, the smaller HANS devices have worked spectacularly well for
drivers in upright seating positions such as NASCAR, ASA, TransAm, and the German
Touring Car Series.
The results shown in Table 1 are from testing by DaimlerChrysler, and provide a
summary of HANS‟s performance in frontal crashes. These tests were run with a
dummy to simulate a reclined driver with a crash sled acceleration of 45 G‟s. Figures 3
through 5 show the extreme forward motions of the helmet.
The results of the baseline test without HANS are shown in Table 1 relative to
published injury thresholds used for passenger cars. Without HANS, the dummy‟s head
swung forward, hitting the steering wheel. The resultant load in the neck (the
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Dept. of Mechanical Engg. MESCE Kuttippuram
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combination of the tension and shear loading of the neck) exceeded the injury threshold.
Neck loading of this magnitude leads to fractures of the base of the skull (basilar skull
fractures) that are the most common cause of death in racing drivers.
The HANS provided a dramatic reduction in injury potential. With HANS, the
head was less likely to strike surfaces of the cockpit. The Head Injury Criterion (HIC)
was used to assess the severity of direct head impacts. In most cases with HANS, the
HIC were not applicable. Even so, HIC was reduced with HANS. Without HANS the
head swung forward and, as will be discussed below with Figure 6, head accelerations
due to head swinging without HANS were higher than with HANS where head
swinging was restrained. With HANS, the forward motions and rebound of the head
were reduced. Also, the neck loads were dramatically reduced, decreasing the potential
for basilar skull fractures. Chest deflections were also reduced. As the dummy was
pushed against the shoulder belts, the HANS device distributed some of the force to the
shoulders and away from the chest.
Frontal Impact:
Figures 3 through 5 show the extreme forward positions of the helmet during
each test without and with HANS. In Figure 5, the HANS restrained the helmeted head
to move with the torso (the driver‟s upper body).
First, the torso slid forward under the belts and HANS until the HANS tethers
were pulled straight by the forces of the helmeted head. Next, the frontal portion of the
HANS (its yoke) and torso were restrained by the shoulder belts.
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Dept. of Mechanical Engg. MESCE Kuttippuram
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In a frontal test without HANS (Fig. 3), the dummy‟s helmeted head hits with
the steering wheel. This amount of movement may seem remarkable, but drivers‟
helmets often hit their steering wheels in actual crashes. The largest head accelerations
and neck loads without HANS (Table 1) occurred in these tests before the impact of the
steering wheel and exceeded safe limits. These excessive loads cause basilar skull
fractures, which is life threatening.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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With an original HANS device (Fig. 4), head motion was reduced, and head
impact with the steering wheel contact was just avoided. The head accelerations and
neck loads (Table 1) were significantly reduced, which is the main reason that HANS
users have had no head or neck injuries.
The HANS prototype for reclined drivers (Fig. 5) reduced forward head motion
by 7.5 inches compared to no HANS (Fig. 3) and by 3.3 inches compared to the
original HANS (Fig. 4). This was achieved with the added benefit that head
accelerations and neck loads were reduced. With HANS (Fig. 4 and 5), the helmet
alignment is controlled by the tethers so the helmet stays in position on the driver‟s
head.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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Figure 6 shows typical results from crash test with crash sled accelerations of 45
G‟s. It is a graphical summary of typical test results without and with HANS. The
arrows from the top of the neck indicate the magnitudes of the components of forces
that pull the head and neck apart. These arrows are drawn to scale to illustrate how
much the HANS reduced these forces.
Without HANS, the head pulls the neck forward with a shearing load that
slightly exceeds the injury threshold limit. The neck tension (pull) is much larger than
the injury threshold limit because the head swings violently forward. Neck shear and
tension combine for a total neck load that is nearly twice the injury threshold value.
These large neck loads are the cause of basilar skull fractures that are the most common
cause of race driver death. In crash tests without HANS, head accelerations, like neck
loads, are largest due to the swinging motion of the head. The HIC injury without
HANS nearly doubles that of safe levels while remaining well below them with HANS.
These values of HIC are significant because without HANS, the head often strikes parts
of the cockpit.
With HANS, the head is restrained to move with the torso and not to violently
swing forward. Neck loads are all reduced (illustrated by the reduced length of the
arrows) and the neck tension component due to head swinging is reduced the most.
Head accelerations are also reduced primarily due to reductions in head swinging. HIC
values are typically reduced with HANS (HIC is not applicable without helmet or head
impact, and helmet impacts are typically infrequent with HANS).
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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Figure 7 shows frames from high-speed videos of crash sled tests from GM run
at Wayne State University in 2000 to simulate a NASCAR cockpit. The sled
acceleration was 45 G‟s. As in other tests without HANS, the helmet and head move
forward and strike the steering wheel. Although it is not readily apparent in this frame
from the high-speed video without HANS, the dummy head rotated forward inside the
helmet so that the chin of the dummy was well below the bottom of the helmet. In all
cases without HANS where the helmet only is in contact with the head, the head rotates
toward the direction of impact and the helmet follows the head so that the helmet tends
to rotate away from the impact relative to the head. In frontal impact, the head moves to
expose the face and the top of the helmet eye port moves toward the top of the head.
With HANS, the helmet is restrained by the tethers, which are placed below and
behind the centre of the helmet and head. Once the HANS tethers hold the helmet, the
head is restrained by contact with the forehead and the helmet and head are restrained
from swinging. That is, HANS helps hold the helmet and head so that they tend to stay
in the normal positions.
In Figures 5 and 7, it can be seen that HANS holds the helmet and head to stay
over the shoulders and the head does not swing forward as is does without HANS.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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Angled Impact:
In 300angled impacts, head motions (Fig. 8) and injury measures are similar to
those in frontal impacts except that without HANS the helmet hits the side of the
cockpit. This impact with the cockpit suddenly rotates the helmet and the dummy‟s
head, which could cause head and neck injury. With HANS, the motions of the head
and the impact with the cockpit edge are reduced, and the HANS tethers effectively
counteract the rotation of the helmet and head. This restraint of helmet rotation would
also be effective in impacts with other objects like tires or tire barriers. There is no
commonly accepted threshold for head rotation, yet sudden head rotations are known to
cause injury in racing. HANS reduces these head rotation injuries.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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Rear Impact:
In a rear impact, the back of the driver‟s helmet hits the cockpit padding behind
the helmet with a high force as his body is pushed up the seatback (Fig.9). The friction
between the helmet and the padding restrains the back of the helmeted head from
moving with his body. The driver‟s head is forced to rotate backwards (see illustration).
His neck is compressed. This combination of unprotected neck bending and
compression is typical of neck fractures that occur with rear impacts.
With the HANS on, its collar, rather than the helmet, impacts the pad. The
friction forces are diverted onto the HANS and driver‟s shoulders. Also, the HANS
supports the rear edge of the helmet, reducing rotation. In rear impacts, the injurious
forces and head rotation are reduced with HANS. Further, the HANS covers the back
of the neck, which is otherwise exposed.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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WHY NOT AIRBAGS?
Daimler-Chrysler carried out a broad based review of systems capable of
preventing the driver‟s head impacting the steering wheel or cockpit rim, while at the
same time relieving his neck of tension and shear forces generated when it attempts to
decelerate his head and helmet, weighing together about 15 lbs .the two most promising
technologies were an airbag that deployed from the rim of the cockpit, and was pulled
across the steering wheel prior to being inflated, and the HANS device.
Theories abound concerning the viability of using airbags in the cockpit. Experts
believe, however, that the triggering could be effectively controlled. But while the
incredibly high speeds necessary to deploy airbags are achievable, there are key
„failings‟ that make them unsuitable as a sole method of restraint.
They can be put down as:
1. They cannot be reused.
2. They contain rocket propellant.
3. Airbag can only confine movement of head itself.
4. The centre of steering wheel is level with driver‟s chin. Airbag would therefore
contact chin first, rotating the head.
The HANS system was selected as it is a totally passive system, and doesn‟t
require electronics, pyrotechnic devices, or the extensive development that would be
required to prove the systems in a race environment
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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HANS PERFORMANCE SUMMARY
The key points of the HANS performance are:
1. In frontal impact with HANS system, the head moves with the torso to help
reduce injurious head motions, accelerations, and neck loads.
2. With HANS, helmet position is controlled on driver‟s head.
3. Sudden head rotation is reduced.
4. HANS improves head restraint if a driver‟s helmet is struck.
5. Driver restraint is improved while accelerating, braking, in a roll-over, or rear
impact.
6. HANS provides improved load spreading of shoulder belt forces in driving
and in crashes.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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RECENT RESEARCH
CART mandated HANS use starting in 2000. Since CART had thoroughly
documented crash injury outcomes and crash dynamics with measured chassis
accelerations for several years, it was possible to study crashes without and with HANS
use.
The HANS has been found to be clinically as effective in reducing the incidence
of head and neck injury as hypothesized on the basis of previously reported laboratory
findings. The overall experience with HANS in CART through the 2001 season was
very positive with HANS reducing injuries compared to similar crashes without HANS.
This positive experience with HANS contributed significantly to mandating HANS use
for all CART drivers, in all series, and all driving including testing, practice, and racing.
With the recent increase in HANS use, other head and neck restraints have been
offered as alternatives to HANS. Such alternatives typically use straps that come
vertically up from the racer‟s back and attach to the helmet. Such vertical straps do not
directly resist that forward motion of the racer‟s helmet and head, which leads to the
injuriously large loads in the neck. These alternative head and neck restraints do share
and slightly reduce the neck loading as the head swings forward, while HANS directly
resists that forward motion that cause injurious neck loads and substantially reduce
these loads.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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In the first independent
study of alternatives to HANS it
was tested a baseline of no head
and neck restraint, and the D-Cel,
Hutchens, and HANS devices. The
crash sled test conditions were:
stock car cockpit, belts, and seat
with a 300right front impact
direction and 35 mile per hour
velocity change and a peak crash
acceleration of 50 G‟s.
Pictures at the left (Figure
10) show how far forward and
down the helmet and head go.
With the D-Cel and Hutchens
devices, the helmet and head
motions are essentially the same as
with no head and neck restraint.
With a HANS head and
neck support (bottom), the
swinging motion of the head is
effectively limited so the head
stays in place on the shoulders and
is much less likely to impact
something in the cockpit.
Excessive loading of the
head through the neck causes fatal
basilar skull fractures.
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Dept. of Mechanical Engg. MESCE Kuttippuram
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The table below compares the loading on the neck for different head neck
restraints.
It was found that the HANS device proved to give consistently excellent results
in controlling neck tension forces and forward head excursions at the crash severity
used in the tests. The other devices provided borderline performance in controlling neck
tension forces and no significant reduction in forward head excursion at the crash
severity used in the tests. These results show that HANS is the only head and neck
restraint that is really effective.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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IMPLEMENTATION
Since the early 1990‟s, the original HANS has been used in diverse forms of
racing including open wheel, sports, stock, and sprint cars, monster trucks, and power
boats. The smaller and revised HANS shape, developed with the cooperation of
DaimlerChrysler has made HANS acceptable to drivers in an even broader range of
cockpits. Several HANS shapes have been made with different collar angles and yoke
shapes to fit diverse drivers and cockpits. CART, NASCAR, and FIA F1 and other
sanctioning bodies have cooperated to make drivers in all of their series comfortable
with HANS in preparation for mandatory use Work to make HANS acceptable to
drivers continues and is essential to broadening use of HANS.
HANS devices are mandatory in several racing series and being considered for
others worldwide. Throughout the spread of HANS use, the makers have cooperated
with sanctioning bodies, sponsors, teams and drivers to integrate HANS into the diverse
cockpits and to make HANS devices acceptable and desirable to the racers. In this
diverse implementation of HANS, HANS could always be used once appropriate
accommodations were made to fit HANS into the cockpit and onto the racer. In some
cases these accommodations required constructive feedback and cooperation with racers
and their teams. This cooperation has resulted in a broad selection of HANS sizes and
shapes and padding systems.
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Dept. of Mechanical Engg. MESCE Kuttippuram
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CONCLUSION
Only after many years of research, development and testing was the unique
revolutionary system of supporting the neck from sudden impacts. And this has
consistently and effectively reduced the injury potential from head motions and neck
loads.
The potential of the HANS system is clear and has been recognized by racing
safety and medical experts and by sanctioning body officials. Thus the head and neck
support system has been made mandatory by the FIA for the 2003 Formula-1 season.
Researches are being carried on for bringing a simplified, compact version of HANS
into passenger cars.
HANS
Dept. of Mechanical Engg. MESCE Kuttippuram
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REFERENCES
1. “Development of the HANS-Head and Neck support for Formula 1”, Society of
Automotive Engineers, SAE Publication 1998
2. “Biomechanical performance of a Head and Neck Support”, p-236, SAE
