Static Mechanical Testing Of Wheelchair Seating Systems Engineering Essay

When in theodolite, the usage of the original maker ‘s vehicle seating and occupant restraint system should ever be recommended for usage by the residents whenever possible. In most instances this will supply the wheelchair resident with the greatest degree of protection from serious hurt. This is because the makers of the vehicle restraint systems have to follow with international and American Federal Torahs. However many wheelchair users are unable to reassign from their wheelchairs to a motor vehicle place for theodolite. These users must therefore rely on their wheelchair to map as a motor vehicle place during conveyance. While this attack has greatly facilitated mobility in the wheelchair community, it is known that the safety of wheelchair residents in theodolite is poorer than it is for residents going in the original maker seats. With the of all time increasing figure of people with disablements utilizing wheelchairs as motor vehicle seats wheelchair occupant safety in a clang and wheelchair crashworthiness is really of import.

A typical wheelchair siting system consists of separate seating and back units as shown in figure 1. These units are mounted to the wheelchair frame utilizing attachment hardware. The place and back pans are stiff surfaces and are normally made from aluminum, wood or plastics. Shock absorbers are placed on top of these surfaces and secured utilizing Velcro to finish a unit. Attachment hardware is normally designed to let for the quick and easy release of the place and back units. However old surveies have suggested that due to the loose adjustment of speedy release fond regard hardware with the wheelchair frame that they could execute ill when in a clang state of affairs ( Manary et al. , 2003 ) .

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Figure 1. A diagram of a typical wheelchair siting system constellation. ( Bertocci et al. , 2000 )

Motor vehicle place industries are required to execute extended proving to guarantee that their seats run into crashworthiness degrees outlined by the Federal Motor Vehicle Safety Standards ( FMVSS ) ( NHTSA. , 1993 ) in the U.S.A. They incorporate many safety design characteristics to protect the resident in the event of a clang. In contrast wheelchairs are designed to increase a handicapped individual ‘s mobility. In many instance the public presentation of a wheelchair siting system in a clang is unknown. However, when working as a motor vehicle place, the wheelchair siting system should supply the resident with a similar sum of protection as that provided by the maker ‘s original vehicle place.

There are two voluntary criterions which address the issues of the wheelchair design and public presentation for a wheelchair used as seating in a motor vehicle. ISO 7176-19 Wheelchairs ; Wheeled Mobility Devices for usage in Motor Vehicles ( ISO. 2000 ) and American National Standards Institute ( ANSI ) /Rehabilitation Engineering and Assistive Technology Society of North America ( RESNA ) WC-19 Wheelchairs Used as Motor Vehicle Seats ( ANSI/RESNA. 2000 ) measure the crashworthiness of a wheelchair and seating system. These criterions subject the frames to a assortment of trials, the most rigorous one likely being a 20g/48kph frontal impact sled trial ( ISO. 2008 ) ( RESNA. , 2000 ) . The criterions assess wheelchair unity, resident and wheelchair clang kinematics. Conformity of the wheelchair with the criterions is self certified by the industry.

Although ISO 7176-19 and ANSI/RESNA WC-19 are used to measure wheelchair crashworthiness there are many scenarios in which the enfranchisement can be invalidated. In many instances siting systems are frequently customized by clinicians to the single patients needs. This may affect an ISO 7176-19 certified wheelchair base been purchased and so a clinician may add a different seating system or fond regard hardware which was non tested with the frame. Therefore wheelchair siting systems may non in all instances be tested to ISO 7176-19 and WC-19 with the wheelchair frames that they are mounted to and this invalidates the enfranchisement. Despite there been a big assortment of siting merchandises commercially available, there is no general certification available to let comparing of different merchandise features and public presentation.

Previous testing of wheelchair siting systems has highlight that some commercially available fond regard hardware may non be able to defy the forces associated with a 20g/48kph frontal impact ( Bertocci et al. , 2001 ) . The unity of the seating system and fond regard hardware must be maintained during a clang. Without a stable support surface for the resident a restraint system will non be able to supply effectual protection ( Bertocci. 2009 ) . Failure of siting systems has been shown to increase the hazard of occupant submarining, which has been linked to several internal hurts of variety meats in the abdominal part ( Leung et al. , cited in Bertocci et al. , 2003 ) . Submarning can be defined as when the lap belt restraint faux pass over the iliac crest to the abdominal soft tissues of the resident. A wheelchair siting system should supply a degree of safety for the individual with a disablement that is equal to that of a individual sitting in a vehicle place utilizing the vehicle restraint system. Therefore, the customized wheelchair siting constituents in usage must be evaluated to find their crashworthiness.

Wheelchair User Demographics

In The U.S.A. as of 2003 there are between 2.3 million to 2.7 million approximative wheelchair users ( La Plante. 2003 ) ( U.S Census Bureau. , 2002 ) . This is estimated to hold grown to between 3.8 million to 5.2 million by 2009 ( Flagg et al. , 2009 ) . The figure of existent wheelchair users in Europe is hard to accurately find. It is estimated that there are approximately 1.2 million wheelchair dependent persons in England ( NHS. 2004 ) . In Ireland it is estimated that a lower limit of 700 wheelchair users take at least 5000,000 route trips yearly staying in their wheelchairs during theodolite ( Simms et al. , 2009 ) . The most common conditions which cause disablements in people taking to the demand of a wheelchair are arthritis ( 13 % ) , stroke ( 11 % ) , multiple induration ( 5 % ) , palsy and orthopedic damages are besides other common causes ( Salipur. 2005 )

As populations grow and life anticipation additions, the figure of the wheelchair users will besides increase. Due to the increased Numberss of the wheelchair community traveling, there will be an addition in the sum of people utilizing wheelchairs as vehicle seats. This will hence take to more people being at hazard of serious or fatal hurts.

Reappraisal of transit criterions

Wheelchair users who are unable to reassign to a motor vehicle during theodolite may be at higher hazard to injury in the event of a clang. Over the past twosome of decennaries big paces have been made in the development of wheelchair transit criterions.

Wheelchair transit safety can be divided into three chief classs ;

Wheelchair securement and occupant restraint systems.

Wheelchair crashworthiness.

Wheelchair Seating.

Wheelchair securement and occupant restraint systems

Wheelchair securement and occupant restraint systems are covered by the International Standards Organization ( ISO ) standard 10542 ; wheelchair tie-downs and occupant restraint systems ( WTORS ) ( ISO. 2004 ) . In the United States of America the country is covered by the Society of Automotive Engineers ( SAE ) J2249 ; Wheelchair tie-down and Occupant Restraint Systems ( WTORS ) ( SAE. 1999 ) .

ISO 10542 is split into five parts ;

Requirements and trial methods for all systems.

Four-point strap type tie-down system.

Docking-type tie-down system.

Clamp type and tie-down system.

Systems for specific wheelchairs.

The ISO 10542 criterion specifies the demands for instructions and warning labelling, design demands every bit good as the public presentation demands for WTORS. ISO 10542 requires that the WTORS must be able to procure an 85 kilogram alternate wheelchair and keep a fiftieth percentile male trial silent person during a 20g/48 kilometers per hour frontal impact trials ( ISO. 2004 ) . The standard for the frontal impact trials include keeping the silent person and the wheelchair in an unsloped place, keeping the WTORS unity and forestalling tie-down separation from the wheelchair, restricting wheelchair jaunts, every bit good as leting remotion of the silent person and trial wheelchair subsequent to the trial without the usage of tools ( ISO. 2004 ) . However the criterion does non necessitate any rear impact proving to find the crashworthiness of the WTORS, which may bring forth different lading to frontal sled trials.

The American criterion SAE J2249 ; Wheelchair tie-down and Occupant Restraint Systems ( WTORS ) is really similar to that of the ISO 10542 criterion. It besides has design demands, demands for instructions, certification and labelling every bit good as the public presentation demands for WTORS. The testing besides includes a frontal impact trial of 20g/48 kilometers per hours utilizing a 50th percentile male trial silent person ( SAE. 1999 ) . This criterion besides does non necessitate any rear impact testing of the WTORS.

The criterions are comparable, with the difference between them being J2249 applies WTORS that are used with kids aged six old ages and supra every bit good as with grownups, where ISO 10542 applies WTORS to adults merely.

The standard lineations countries of usage for WTORS.

For usage with forward confronting wheelchairs in vehicles,

It includes all different types of wheelchair securement systems,

Belt – type occupant restraint systems,

Both riders and drivers,

For usage in both public and private vehicles,

For usage with all wheelchairs including scooters, and powered wheelchairs.

Wheelchair crashworthiness

The 2nd country that wheelchair transit safety can be broken into is wheelchair crashworthiness. This is covered internationally under the ISO standard 7176-19 ; wheelchairs used as motor vehicle seats standard ( ISO. 2008 ) . In America wheelchair crashworthiness is covered by the American National Standards Institute/Rehabilitation Engineering Society of North America ( ANSI/RESNA ) WC-19 ; Wheelchairs used as Motor Vehicle seats standard ( ANSI/RESNA. , 2000 ) . ISO 7176-19 and ANSI/RESNA WC-19 trial wheelchairs unity and besides the resident and wheelchair kinematics in the event of a clang.

These criterions outline the lower limit design demands and public presentation demands of a wheelchair when it is being used as a motor vehicle place if the vehicle is involved in a clang or if sudden alteration of way takes topographic point. A major design demand of both criterions is the inclusion of four securement points on the wheelchair frame. Both criterions detail the same design demand with respect to the type and figure of securement locations. Each of the securement points location, form and size are specified in the criterion, with each point been compatible with end adjustments of strap-type tie-down securement systems. The criterions give somewhat different standards for the size and form of the securement zones. ISO 7176-19 provinces each must be 50mm or longer in length and 25mm or wider in breadth. WC-19 provinces each point must be between 50mm-60mm in length and 25-30mm in breadth. This means that all fluctuations of WC-19 securement point geometries would follow with ISO 7176-19, nevertheless non all ISO 7176-19 would non follow with WC-19 demands.

For conformity with ISO 7176-19 ; wheelchairs used as motor vehicle seats and WC-19 ; Wheelchairs used as Motor Vehicle seats standard trial topic must be subjected to a frontal sled impact trial. This testing process subjects the trial wheelchair frame to a 20g/48kph fontal impact sled trial. The process requires the usage of a ISO 7176-7 mention silent person which represents the fiftieth percentile male ( ISO. 2007 ) . In the trial the topic wheelchair is secured and the fiftieth percentile male silent person is restrained utilizing a foster wheelchair tie-down and securement system. ISO 7176-19 allows for the usage of commercially available four point tie-down securement system in the testing process. In comparison WC-19 provinces that a foster four point securement system must be used during the frontal sled impact proving. The RECRC – WTS replies to often asked inquiries high spots several differences between the two criterions in respect to the public presentation required during the frontal impact trials ( Hobson. 2003 ) . These are listed below ;

WC-19 requires that detachable siting systems must non divide from the wheelchair base frame at any attachment points, while ISO 7176-19 does non foreground the country.

WC-19 requires that distortion of wheelchair securement points does non forestall detachment of any tie-down maulerss, while ISO 7176-19 is soundless on this subject.

ISO 7176-19 requires that remotion of the silent person from the wheelchair after the trial shall non necessitate tools ( other than hoist ) , while WC-19 is soundless on this point.

WC19 does non let the wheelchair to do partial or complete failure of any portion of the tie-down or restraint system, while ISO 7176-19 is soundless on this demand.

The upper limit allowed rearward caput jaunt in WC-19 is 450 millimeter for the 50the percentile grownup male silent person, while it is 400mm in ISO 7176-19.

ISO 7176-19 provinces that locking mechanisms of tilt siting systems shall non demo marks of failure after a trial, while WC-19 does non specifically refer to lean locking mechanisms but instead includes this demand under the demand that “ primary burden carry parts ” shall non demo marks of failure.

The consequence of these differences is that the frontal impact trials for WC-19 are by and large greater than those of the ISO 7176-19. This is due to the sum of rearward caput jaunt allow by be each criterion. The base on balls and neglect standards are the same for each criterion.

ISO 7176-19 ; wheelchairs used as motor vehicle seats standard and WC-19 ; Wheelchairs used as Motor Vehicle seats standard have largely been harmonized. There are nevertheless two chief exclusions which stops them from been to the full harmonized. First the standards for rearward caput jaunt of the trial silent person and secondly the allowed sidelong spacing of wheelchair securement points ( Hobson. 2003 ) . Conformity with ISO 7176-19 ensures conformity with WC-19, nevertheless non all WC-19 would non follow with ISO 7176-19 demands.

There are two chief differences between the two criterions. First difference is down to the range of each. ISO 7176-19 does non presently cover the testing of pediatric wheelchairs. The other chief difference is associated with the securement of the wheelchair during the frontal sled impact trial. ISO 7176-19 requires the wheelchair frame to be tested, be secured utilizing a commercially available WTORS which complies with ISO 10542. In contrast ANSI/RESNA WC-19 stipulates that a foster four point tie-down system is used to procure the wheelchair to be tested.

Wheelchair siting

ISO 16840-4 Wheelchair seating ; Seating systems for usage in motor vehicles ( ISO. 2008 ) specifies trial methods and demands for design and public presentation, for instructions and warnings and for merchandise marker and labelling of siting systems intended to be used as a forward confronting place in a motor vehicle when fitted to a manual or powered wheelchair. ISO 16840-4 provides a agency of proving the crashworthiness of usage or after market wheelchair siting systems.

As specified in Annex C ; wheelchair siting system – Inactive trial method, the wheelchair place and endorse support are evaluated based on an estimated burden associated with a 20g/48kph frontal impact. The system to be tested is evaluated utilizing a alternate frame. The foster trial frame eliminates distortion that may happen in a wheelchair frame. If the seating system to be tested does non come provided with attachment hardware foster fond regard hardware should be used to prove the place or back.

In ISO 16840-4 the seating system is required to defy a force of 16,680N and a back support system is required to defy 10,188N. The tonss are transmitted to the system to be tested utilizing an ISO 7176-7 ( ISO. 2007 ) mention stevedore gage ( RLG ) . The mention stevedore gage represents a fiftieth percentile grownup male and is designed to imitate the dimensions and mass distribution of the human organic structure ( ISO. 2007 ) . There are two subdivisions to the RLG, the underside subdivision which simulates the natess and legs and the dorsum subdivision which simulates the weight distribution of the bole of a individual. Tonss are transmitted through the Centre of gravitation of the RGL which is positioned otherwise depending on which surface is to be tested.

ANSI/RESNA WC-20/4 ; Seated Devices for usage in Motor Vehicles ( ANSI/RESNA. , 2010 ) is an American criterion which was developed from the ISO 16840-4 criterion. The standard specifies the design, public presentation, demands and trial methods for wheelchair siting systems for usage by grownups or kids over 22 kilograms when frontward confronting theodolite in any type of motor vehicle.

WC-20/4 requires dynamic proving which is representative of a 48kph/20g frontal impact. The trial is carried out utilizing a foster wheelchair base. The usage of a foster wheelchair base for proving is indispensable to set up the worst instance scenario burden of a seating system associated with the 48kph/20g frontal impact. Foster 4-point tie-downs are used to procure the base during proving. A 3-point resident restraint system is used to keep the resident during proving. The resident is represented by an anthropomorphous trial device ( ATD ) , who ‘s weight and dimensions are chosen based on the maker ‘s guidelines.

All types of siting systems are included in this criterion. WC-20/4 defines a seating system as a place pan, place back and attachment hardware. WC-20/4 lists demands for a seating system that when met is intended to be used with a wheelchair frame which meets the demands of WC-19. This frame is so intended to be secured utilizing an SAE J2249 approved wheelchair tie-down and occupant restraint system.

Wheelchair Securement and Occupant restraint Systems ( WTORS )

As stated antecedently, whenever it is possible, people who use wheelchairs for personal mobility should reassign out of their wheelchair and into the vehicle place and hive away the wheelchair individually when going in a motor vehicle. Use of the maker ‘s original seating and restraint systems provides the resident with the highest degree of safety in the event of a clang or exigency tactic of the vehicle. Therefore the best manner to cut down the hazard to the resident is to forestall or understate the possible contact with the inside of the vehicle. This is possible through the proper usage of motor vehicle restraint systems. Large paces have been made in motor vehicle occupant restraint systems over the last twosome of decennaries. However due to many wheelchair users been unable to reassign to vehicle siting they are unable to avail of this addition in safety. It was for this ground wheelchair secrurement and occupant restraint systems were developed ( WTORS ) .

Research has shown that the chief cause of disabling and life endangering hurts is impact of the resident with the vehicle inside or in the event of expulsion or partial expulsion from the vehicle, with objects outside of the vehicle ( Schneider. 2007 ) . Betocci G. , et al 2000 survey utilizing computing machine clang simulations and limited sled proving concluded that the greatest forces experienced by a seating system are those associated with a frontal impact. It is for this ground that the criterions developed for wheelchair tie-down and occupant restraints are designed for public presentation with the wheelchair seated occupant confronting frontward ( Digges et al. , 1993 ) .

Wheelchair Securement

The securement of wheelchairs in motor vehicles while in theodolite is a really of import country for occupant safety. Methods of securement have greatly changed over the last twosome of decennaries with the apprehension of the kinematics involved in a clang. Previous methods of securement have included low tech methods such as bungee cording the wheelchair to the interior of the vehicle and utilizing wheel clinchs ( Bertocci et al. , 2009 ) . Current methods of wheelchair securement include ; four point tie-downs, docking systems and clamp type securement.

When utilizing a wheelchair as a motor vehicle place an ISO 7176-19 or WC-19 certified wheelchair frame should be used when possible. Although these are voluntary criterions they meet the design and public presentation demands that enable them to last a 20g/48kph frontal hit. The certified frames have four clang tested securement points where tie-down straps and maulerss are attached to ground the frame. The design demands of the criterions enable fast and easy fond regard of the hardware. A WTORS that has been certified by ISO 10542 or J2249 should besides be used to procure a wheelchair when in theodolite.

Four-Point Tie-down system

The four-point tie-down system shown in figure 2 is the most common type of WTORS in usage today. It is a system of straps with terminal maulerss which attach to the wheelchair at four securement points and attach to the vehicle at four different fond regard countries. This method of securement is really effectual and can be used with a broad assortment of wheelchair frames non merely those certified by ISO 10542 or J2249.

When procuring a wheelchair utilizing a four point tie-down system there are a few guidelines which should be observed. First the wheelchair and resident should ever confront towards the forepart of the vehicle. Attach the securing straps to the four procuring points on the ISO 7176-19 or WC-19 certified frame. If a ISO 7176-19 or WC-19 certified frame is non been used the straps should so be attached to a welded junction on the frame or where the frame is secured utilizing hardened steel bolts. The straps should ne’er be attached to a movable portion of the wheelchair i.e. wheels. The rear ground tackle points in the vehicle should be located such that they are straight behind the rear securement points on the wheelchair. The front vehicle ground tackle points should be positioned such that they are wider apart than the breadth of the wheelchair.

Figure 2. Four-Point Tie-down system, ( Hobson et al. , 2008 ) .

This method of securement requires that the wheelchair resident have person else with them to procure the wheelchair to the vehicle. However is holds many advantages over other manners of securement. It is able to attach to most wheelchair frames and provides stableness under clang, exigency and normal drive conditions ( Bertocci et al. , 2009 ) .

Docking Tie-Down Systems

Docking tie-down systems shown in figure 3 are another manner of procuring a wheelchair while in theodolite. This is a method which is non widely used in public subdivision and is preponderantly used in the private sector. This is chiefly due to the demand to modify the wheelchair frame to do it compatible with docking systems. Docking systems consist of a lock pin located on the wheelchair which inserts into a locking fixture located on the vehicle floor. Docking occurs automatically. When the vehicle has stopped and the resident of the wheelchair wishes to detach from the system they merely need to press a handily placed release button. The docking system can be located at the rear or straight underneath the wheelchair. This manner of securement allows the wheelchair resident to secure and let go of their ain wheelchair without the demand for aid.

Figure 3. A docking Tie-down System, ( Hobson et al. , 2008 ) .

Docking tie-down systems are designed with a twosome of in build safety steps ;

For safety grounds the lockup system will non withdraw a wheelchair while the vehicle ignition is turned on. This eliminates the hazard of the resident or another rider been injured if the release button is pressed by chance.

If the wheelchair is non firmly locked into place by the moorage system a warning signal will be heard. The warning sound will non halt until the wheelchair has been docked firmly.

The moorage system is advantages as the resident does non necessitate aid. However the system has disadvantages in relation to other securement methods. It is more dearly-won than a four-point tie-down system and due to the excess equipment required it increases the weight of the wheelchair.

Clamp Type Securement Systems

Clamp type securement systems should non be used to procure a wheelchair in theodolite. They have no met the standards set out by the ISO 10542 or J2249 criterions. They hence do non supply the wheelchair resident with the needed sum of protection in the event of a clang or an exigency tactic.

Occupant Restraint System

In add-on to procuring a wheelchair during theodolite it is of import that the resident of the wheelchair is provided with an effectual restraint system. An effectual restraint system is critical to protecting the resident in a clang. The restraint system used in vehicles normally consists of a lap and shoulder belt. Restraints systems which have passed the needed testing of ISO 10542 and SAE J2249 should ever be used. Proper adjustment and placement of the lap and shoulder belt are critical to supply complete protection to the resident. The lap belt should be placed low across the pelvic girdle. The belt should non be placed across an occupant venters as this could do life endangering hurts in a clang ( Bertocci et al. , 2009 ) . The lap belt should be positioned between 45-75 grades to the horizontal when viewed from the side as shown in figure 4 below.

Figure 4. How to place a lap belt, ( Hobson et al. , 2008 ) .

The shoulder belt should diagonally bisect the trunk and connect to the lap belt at the hip of the resident. In some instances the 3-point lap and shoulder system may non be sufficient and extra restraints are required due to hapless postural stableness of the resident. In this instance, the excess restraints used should besides be 1s that have passed the needed trials detailed under ISO 10542 and SAE J2249. If restraints are used which are non certified by ISO 10542 and SAE J2249 so they will supply the resident with an unknown degree of protection.

Review of Previous Related Studies

In this subdivision diaries related to project subject will be discussed.

Evaluation of wheelchair siting system crashworthiness

Before the debut of ISO 16840-4, wheelchair seating ; siting system for usage in motor vehicles an early survey ( Bertocci et al. , 2000 ) used computing machine simulations and biodynamic computations to develop a trial standard to measure wheelchair back support crashworthiness. The survey evaluated the crashworthiness of five combinations of back support and fond regard hardware utilizing a inactive testing process which simulated lading conditions. Tonss were applied that were associated with a 20g/48kph frontal impact. A antecedently validated theoretical account found these tonss to top out at 2,280 pound ( Bertocci. 1999 ) . The Study featured a alternate wheelchair frame with 1 inch ( 25.4mm ) placed 18 inches ( 457mm ) apart which simulates the dimensions of a typical wheelchair frame. The wheelchair back support surfaces were mounted to this and tonss were applied through the Centre of gravitation of the upper trunk unit of an ISO 7176-7 mention stevedore gage. Tonss were applied utilizing an Instron 4204 series proving machine.

Consequences show that none of five tried wheelchair supports could defy the tonss applied. Each of the tried pieces failed at less than 50 % of the applied force ( Bertocci et al. , 2000 ) . The research concluded that if subjected to the tonss associated with a frontal impact the fond regard hardware would neglect. The writers discussed the deductions of these consequences bespeaking that this type of failure could take to inordinate rearward occupant jaunt. This type of jaunt has been shown to increase the hazard of secondary caput impact with the interior vehicle surfaces ( Warner et al. , 1991 ) . Back support failure besides increases the hazard of cervical spine hurt every bit good as expulsion from the place due to the resident restraints being rendered uneffective ( Saczalski. 1989 ) ( NHTSA. 1997 ) . The paper highlighted the fact that wheelchair fond regard hardware is designed for speedy release to let for speedy folding of the wheelchair. However due to this design the hardware does non supply full gaining control of the frame and may non execute good under clang conditions ( Bertocci et al. , 2000 ) . The survey concluded that none of the commercially tested hardware could defy the forces that may be encountered during rear impact or recoil associated with a 20g/48kph frontal impact. The writers besides noted that if the hardware passed this trial it would non needfully connote a crashworthy wheelchair siting system.

A survey by Bertocci et al set out to measure the crashworthiness of commercially available bead hook place fond regard hardware ( Bertocci et al. , 2001 ) . The survey proposed a inactive trial method with forces tantamount to those associated with a 20g/48kph frontal impact. The trial process assumed the usage of a fiftieth percentile male in conformity with ANSI/RESNA WC-19. The survey relied on computing machine simulations and sled proving to set up the proving standards. The lading degree used was 16.680N which is the degree associated with a wheelchair secured with rear tie-downs and aligned with the wheelchair Centre of gravitation in a 20g/48kph frontal impact. Consequences showed that none of the seating hardware tested was able to defy the needed force. Failure was defined as component break or inordinate distortion of the portion which would take to it been unable to supply a stable seating platform. All the bead hooks tested failed below 50 % of the 16,680N applied burden due to inordinate distortion or straightening of the hook part. The writers concluded that bead hook siting attachment hardware may non be able to supply a stable seating surface for the wheelchair resident in the event of a clang.

A paper by Bertocci et al set out to set up a wheelchair siting system trial standards for frontal impacts with the usage of computing machine simulations and sled trials ( Bertocci et al. , 2001 ) . The survey relied on computing machine simulations and sled trials tonss associated with a 20g/48kph frontal impact and 50th percentile male resident were estimated to develop the trial standard ( Bertocci et al. , 2001 ) . The computing machine simulations used the ISO 10542 alternate wheelchair to look into lading during impact ( Bertocci et al. , 1996 ) and another one used a powered wheelchair to look into the influence of different siting features ( Bertocci et al. , 2000 ) . The trial apparatus used a foster wheelchair frame. This isolated the hardware to be tested from the other seating constituents. It eliminated the distortion that could happen in a wheelchair when subjected to the tonss. Five different types of bead seats were tested each made from different stuffs i.e. wood plastic. The consequences from the research showed that two different types of bead maulerss met the needed criterion. The writers noted that extra proof of the testing process would be required. However the survey suggests that some bead place stuffs may non be capable of defying the tonss associated with a clang. The writers concluded that bead seats utilizing tough stuffs that yield under lading conditions may be better suited to prolong crash burden conditions ( Bertocci et al. , 2001 ) .

Ha investigated the crashworthiness of wheelchair catapulting place and catapulting back systems ( Ha et al. , 2002 ) . The survey tested three manners of catapulting dorsums and catapulting seats utilizing a inactive trial process. Previously validated theoretical accounts were used to develop the trial standard. Loads associated with a 20g/48kph frontal impact for catapulting dorsums were found to be 2290lb ( Bertocci et al. , 1999 ) and for the sling seats 3750lb ( Bertocci et al. , 1999 ; Bertocci et al. , 2000 ) . The consequences for the survey show all but two of the catapulting back passed the trial standards and all but two of the catapulting seats passed besides. Most of the failures occurred at the seams of the gaps. The writers concluded that although most test specimen passed the trial standard this does non intend that they needfully crashworthy.

Frontal Impact Sled Trials

Before ISO 16840-4 Bertocci et al conducted frontal sled trials of wheelchairs which were to be used as motor vehicle seats ( Bertocci et al. , 2001 ) . The end of the research was to supply industries with counsel for the design of crashworthy constituents. The trials measured the burden of the place during a 20g/48kph frontlet sled impact. An resident was represented utilizing a 50th percentile male silent person. Two different rear securement constellations were measured. The consequences revealed downward tonss ranged from 17,019N to 18,682N and shear forces ranged from 4424N to 6717N. The writers noted that the burden predicted in old documents utilizing computing machine simulations ( Bertocci et al. , 1996 ; Bertocci et al. , 2000 ) were similar to the tonss measured in this paper. The paper concluded that manufactures must take into history both downward and shear forces when planing siting constituents.

A paper by Manary et al set out to develop design and public presentation demands for theodolite wheelchair criterions ( Manary et al. , 2003 ) . The aim of the survey was to develop a alternate wheelchair frame which could be used to prove wheelchair siting systems independent of their frames. Data was collected from 259 frontal sled impact trials. The consequences from the paper showed that when siting failure occurs during a clang it is normally consequences from attachment hardware failure ( Manary et al. , 2003 ) . The writers noted that many of the fond regard hardware tested that failed did non to the full lock with the wheelchair frame. They suggested that if the hardware were redesigned to to the full lock with a frame it could supply better crashworthiness.

Bertocci et Al used computing machine simulations to understand place and place back lading in frontal clang state of affairss ( Bertocci et al. , 2000 ) . The survey used a antecedently validated computing machine theoretical account ( Bertocci et al. , 1996 ) which used a powerbase wheelchair and 50th percentile male silent person been subjected to a 20g/48kph frontal impact. Modeling package Dynaman was used to imitate clang conditions. The consequences from the trial showed that lading conditions was really dependent on surface stiffness. The stiffer the surface stuff the higher the burden experienced. Load values peaked at 2, 525 pound. The place back angle was besides found to be a factor. As the seat-back recline angle increased from the perpendicular the tonss experience decreased. The writers concluded that siting surface stiffness and place back angle affected the tonss, and hence industries should take this into history when design wheelchair constituents.

Wheelchair Seating Stiffness

A survey by Bertocci et Al. investigated the effects of wheelchair place stiffness and energy soaking up belongingss on the hazard of occupant submarining during a 20g/48kph frontal impact. A antecedently validated computing machine theoretical account ( Bertocci et al. , 1996 ) was used to carry on analysis on the consequence of place stiffness and energy soaking up belongingss on wheelchair seats in a frontal impact. The consequences of the writers show that place stiffness and the energy soaking up belongingss of the place do influence resident kinematics during a clang. Therefore influence the hazard of occupant submarining. It was noted that old surveies by Leung et Al. highlighted that lap belt burden was a critical factor in foretelling the hazard of occupant submarining ( Leung et al. , 1982 ) . The survey concluded that the hazard of occupant submarining is influenced by the place stiffness and energy soaking up features.



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