Wheeled Mobility Device Database for Transportation Safety Research and Standards

31Technical Report #6

Technical Report #6

WHEELED MOBILITY DEVICE DATABASEFOR TRANSPORTATION

SAFETY RESEARCH AND STANDARDS

Prepared byGina Bertocci, M.S., Patricia Karg, M.S. and Doug Hobson, Ph.D.

Edited byAshli Molinero

April 1996Updated February, 1997


To address the issue of safely securing wheeled mobility devices (WMD) in vehicles, moreinformation characterizing production WMDs was needed. The University of PittsburghRehabilitation Engineering Research Center (RERC) on Wheelchair Technology has definedthe frame characteristics of wheeled mobility devices and developed a database containingcharacteristics relevant to securement. A representative number of WMDs have been surveyedto measure key characteristics, and have been recorded in the database. This report detailsthe development of the database and frame characterization scheme, the methods used tosurvey the production WMDs, and some descriptive statistics resulting from an analysis ofthe data. A discussion on how this information is being utilized in research aimed at developingtechnology and safety standards to ensure safe transportation is also included.

Abstract

RERC on Wheelchair Technology2

Introduction

Currently there are numerous sizes, shapesand configurations of wheeled mobilitydevices (WMD) available on the market. Thevariation is partly due to the differentmobility needs of individuals with variousdisabilities. These individuals should beafforded the same opportunities in vehicletransportation, regardless the type of WMDthey use. Unfortunately, as depicted by Figure1, the disadvantage to having this largeselection is realized in attempts to secure thevarious types of WMDs to the vehicle fortransportation. However, it remainsnecessary to provide equivalent safety,convenience and independence to those beingtransported while seated in their WMD,regardless of WMD size or shape.

To address the issue of safely securing WMDs,more information characterizing productionWMDs was needed. In addition, theinformation collected had to be relevant tothe issues involved in securing a WMD safelyand effectively in a vehicle during transport.To accomplish this, a survey data form wasdeveloped to record relevant WMDcharacteristics, and a database wasconstructed to maintain and organize theinformation. This information was firstsought to fill gaps in the informationnecessary for the RERC to perform researchinvolving the development of crashsimulation models used in transportationsafety research. It has also been used in thedevelopment of a transport wheelchairstandard, development of a surrogate

wheelchair for securement standards testing,and to initially define a common zone onWMDs for the placement of universaldocking interface hardware. The next sectiondetails the development of the surveyparameters and the frame characterizationscheme, the last section describes the surveymethods and shows the results of apreliminary analysis of the data collected.

Development of Survey Parameters and

Data Form

Factors considered relevant to the safe andeffective securement of a WMD include thecenter of gravity, weight, frame configuration,wheel configuration, and physicaldimensions. A data form was developed todefine the relevant parameters that neededto be measured and the contents of thedatabase. The data form developed iscontained in Appendix A. This data formrequired the surveyor to provideidentification information, frameclassification, physical dimensions, inertialproperties, material descriptions andlocations for potential securement points. Theform also served as the input template to thedatabase which recorded the values of theserelevant parameters.

Initially, it is useful to sub-divide WMDsbased upon their propulsion systems since inmost cases the form or frame structure isconfigured to accommodate the device’sfunctional operation[1]. For example, apowered device must have a frameconfiguration that is capable of supporting


the motor and drive train associated with thisspecific type of device. Therefore, as shownin Figure 2, WMDs were first categorized byeither manual or powered propulsion.Manual propulsion systems include bothstrollers, the traditional manual wheelchair,and the manual sport chair; while poweredsystems encompass scooters, powerbases andthe conventional powered wheelchair.Strollers, although not always thought of inthe traditional sense as WMDs, are in factcommonly found in transporting toddlerswith disabilities.

Since varying geometric and inertialproperties affect the response of a WMD in acrash[2], it is useful when analyzing andattempting to optimize factors influencingthis response to categorize WMDs basedupon characteristics that affect theseproperties. Accordingly, in addition toclassification of WMDs by their propulsionmethod, frame characteristics anddimensions are relevant to the securement ofthe WMD. Thus, a frame characterizationscheme was developed based upon a surveyof current production WMDs andincorporated into the data form. The framecharacterization scheme is outlined below foreach type of propulsion system. Althoughstrollers are one of the WMD classes, nofurther frame characterization was performedin this effort.

Frame Characterization Scheme

Manual and Sports Wheelchairs

Manual wheelchairs can be found having

frames that are rigid or that are capable offolding. As shown by Figure 3, rigid-framedmanual wheelchairs are most commonlyavailable in a 4-wheeled, box configuration,but can also be found in a cantilevered or a 3-wheeled, T–frame arrangement. T–frames aretypically used in the construction of sports-type wheelchairs. Wheelchairs employing thebox frame also have the option of a fixed orreclining seat, which may be removable.Frames which are foldable are found in eithera cross-brace or vertical-folding design.Cross-brace type frames are considered eitherfloating or contained, where a containedframe is one with the seat attached to theframe by more than just the cross-bracemember, as is the case in the floating styleframe.

Powered Wheelchairs

Since many powered wheelchairs werederived by simply adding a motor and drivesystem to manual wheelchairs, it is notsurprising to find powered wheelchair frameconfigurations similar to those of manualwheelchairs. Like manual wheelchairs,powered units can first be sub-divided intofolding and rigid-box frames. Folding framesare typically found to have a cross-braceconfiguration, allowing the user to maintainthe convenience of portability throughfolding. Rigid-box frames used by poweredwheelchairs can be segregated by drivetype—either direct or belt drive. As in the caseof manual wheelchairs, powered unitsemploying a rigid-box frame are providedwith either a fixed or reclining seat. Figure 4summarizes the classification system for


powered wheelchairs.

Powerbases

Powerbases typically consist of a frameattached to the wheel suspension system andused to support the motor, drive system andbatteries. Differentiating the classes ofpowerbases is the method by which the seatis attached to the frame. One method employsa pedestal to mount the framed seat to thebase frame. The other method is moreindependent of the base frame, allowing theseat to “float” creating a less rigid couplingto the frame.

Scooters

Scooters are available in both 3-wheeled and4-wheeled configurations and can be groupedaccordingly. The method used by the motorto drive the wheels represents the next furthersubdivision within the scooter category.Three-wheeled scooters are available in eitherfront-wheel drive (fwd) or rear-wheel drive(rwd) versions, with both direct and belt drivemodels available in the rwd arrangement.Four-wheeled scooters are produced in rear-wheel belt driven and transaxleconfigurations. Figure 5 displays the scooterclassification system.

Survey Methods and Data Analysis Results

With the survey parameters defined and thedata form established, the next stepcomprised gathering data on relevantparameters for each of the WMD classes. Fieldsurveys of representative production WMDswere conducted using the WMD Data Form,

shown in Appendix A. A data form wascompleted for each surveyed WMD, with arepresentative number of devices beingsurveyed within each class. The informationgathered was recorded in a database formatto allow for data queries based uponspecifically defined fields and to provideinsight into the various parameter ranges,means, maximums and minimums, sorted byWMD class. Much of the data required by thisform parallels measurements andinformation necessary for complying with theANSI/RESNA and ISO WheelchairStandards [3,4,5]. Therefore, the field surveyprocess was simplified and measurementsverified by obtaining availablemanufacturers’ ANSI/RESNA or ISOReports. Field surveys were alsosupplemented with sales literature in an effortto provide a complete record on each WMD.It should be noted, however, that the methodsof measurement were unknown and mayhave varied from our own. Thus, the datawas evaluated separately and is noted in theresults.

A total of 77 WMD’s were recorded; 42powered and 35 manual WMDs. PoweredWMDs can be further subdivided into 19conventional power WMDs, 12 powerbasesand 11 scooters. The manual WMD samplingconsists of 21 conventional manual WMDs,and 14 sport WMDs. Following are surveymethods and results of analyses using thedatabase contents. First, select parameters arepresented based upon the propulsion classesof WMDs: Conventional Manual, SportsManual, Conventional Power, Powerbases


and Scooters. It is useful to analyze and utilizecertain data based upon the propulsion classes.The frame classes are useful when data isneeded for computer modeling and whenframe characterization is necessary, such as fordefinition of common clear zones for placementof docking system interface hardware. Analysismethods for each parameter, e.g., calculation ofstandard deviations or ranges, depended uponthe desired application of the results. Forexample, standard deviations of structuralparameters (e.g., seat-back intersection,wheelbase) were calculated for an effort toredefine the SAE/ISO surrogate wheelchair,which is used for dynamic testing in tiedownstandards [6,7], so that it is more representativeof production powered wheelchairs in it’sdynamic response. However, ranges wereevaluated for some parameters where only arepresentative value was sought.

Seating CharacteristicsANSI/RESNA and ISO Wheelchair Standardsobtain measurements using a reference loadergage for seating characteristics such as seatheight, seat width, seat back height and angle,and seat depth and angle. The techniques usedby this study to obtain these measurementswere conducted with an unoccupied WMD.Despite differences in testing procedures, datahas been combined since the needs of this studycan accomodate the variations in data acrossthe two methods. Furthermore, seatingcharacteristics data reported by this study aregenerally indicated as ranges and/or meanvalues.

Seat Height: Seat height data was obtained

by measuring the distance from the groundto the upper surface of the seating support atthe center of the seat’s front edge. Thesemeasurements were performed while the seatwas unoccupied. Maximum and minimumavailable seat heights were recorded basedupon available manufacturers’ productliterature, along with the actual seat heightof the WMD surveyed. Since a range of seatheights is typically available frommanufacturers for a given WMD, the upperand lower limits are shown in Figure 6 foreach adult WMD class. Additionally, themean value of seat heights of the surveyedWMDs is also shown in this figure. Mean seatvalues showed very little variation across thevarious classes, ranging from 18.5" to 20.3".Seat heights as high as 23" and as low as 14"were found to be available in adult WMDs.Numerical values for each class of WMD arepresented in Table 1.

Seat Width: Seat width measurementsrepresent the distance between the centers ofthe horizontal frame members supporting theseating system. Recorded data includes themaximum and minimum available seat widthfor each WMD model (from manufacturers’literature), as well as the seat width of thesurveyed WMDs. All measurements wereconducted using an unoccupied seat. Rangesof available seat widths for each of theproduction classes are presented in Figure 7and Table 1. The mean values of seat widthsof the surveyed WMDs are also indicated byFigure 7 and Table 1. There was very littlevariation in mean seat widths across thedifferent WMD classes, ranging from 15.9" to


17.5". For all WMD classes, the maximumavailable seat width for the surveyed WMDsis 20".

Seat Back Height and Angle: The evaluation ofeach WMD also included measurements ofthe seat back height and seat back angle. Seatback height was evaluated by measuring thedistance from the unoccupied seating surfaceat its rearmost location, to the top edge of thebackrest. Seat back angle was defined as theangle between the seat back plane andvertical. The mean seat back height for eachof the WMD classes is shown in Figure 8. Themean seat back height values and seat backangles are presented in Table 1. Based uponthe survey results, powerbases were foundto have the highest mean back height at 20.5".Conversely, sports manual WMDs aretypically found to have the lowest back heightat a mean of 13.5". The mean seat back angleswere largest for the scooter population (12.4°)and smallest for powerbases (4°).

Seat Depth and Angle: The depth of each ofthe sample WMDs was assessed bymeasuring the distance from the front edgeof the seat to the intersection with the backrestplane. Seat angle was represented as the anglebetween the seating surface plane andhorizontal. Figure 9 and Table 1 provide meanseat depths for each WMD class. Again, onlya slight variation (16.5" to 18.6") was foundacross the various classes of WMDs surveyed.Powerbases were found to have the greatestmean seat depth at 18.6". Figure 10 and Table1 also provide mean seat angles for each ofthe WMD classes. Manual sports WMDs were

found to have the steepest mean seat angleat 11°. Conversely, powerbases have onlyslight seat angles as evidenced by a mean seatangle of 4°.

Seat Position Relative to Rear Wheel Axle: Toadequately model the physical structure of aWMD it is necessary to identify the positionof the seating system relative to the WMDframe. This was quantified by measuring boththe vertical and horizontal distance from therear axle to the intersection of the seat andseat back. In many cases the rear axle positionis adjustable for manual WMDs. When thistype of configuration was encountered therange of adjustability was recorded. Inaddition to the range of adjustment, the actualvertical and horizontal measurements wererecorded as the survey WMD was previouslysetup. Mean values were calculated basedupon the actual rear axle configurations at thetime of evaluation.

The mean vertical distances between the seat-seat back intersection and rear axle, alongwith the standard deviation, for each WMDclass have been calculated and are presentedin Figure 11. Horizontal distances andstandard deviations are shown in Figure 12.Positive values reflect a seat-seat backintersection that is located forward and abovethe rear axle. Upon review of the verticaldistances between the rear axle and seat-seatback intersection, scooters appear to presentthe largest mean distance at 18.6". Manualsports WMDs typically have their seat-seatback intersection located closer to the rear axlethan any other single class with a mean


vertical distance of 7.3". Mean horizontaldistances are generally less than the verticalcomponents, with the largest mean horizontaldistance (5.9") occurring in powerbasestructures. Scooters typically were found tohave their seat-seat back intersections closeto vertically aligned (1" mean) with the rearaxle.

Wheel Characteristics

Front and Rear Wheel Diameters: Front and rearwheel diameters where also measured as apart of the WMD assessment process. Thefindings are reported in Figure 13 and Table2. As expected, rear wheel diameters werefound to be the largest (approximately 24")for the conventional manual and sportsmanual classes. Scooters and powerbasessurveyed had generally smaller diameter rearwheels (8.8" and 11.6", respectively) than themean diameter of rear wheels used onconventional power WMDs (mean = 15.6").Smaller variations, 5.5" to 8.3", were found infront wheel diameters across the variousclasses of WMDs.

Front and Rear Wheelbase Widths: Wheelbasewidth for the front and rear wheels wasmeasured between the centerlines of the tires.Figure 14 and Table 2 indicate the meanvalues of the measurements for each of theWMD classes. Only slight variation was seenacross the surveyed classes for both the frontand rear wheelbase widths. Front wheelbasemean widths varied from 17.1" to 19.5", whilerear mean widths varied from 20.3" to 22".

Wheelbase Length: Wheelbase length wasmeasured for each of the surveyed WMDs byrecording the distance between the front andrear axles. Figure 15 and Table 2 indicate themean values of wheelbase length for eachWMD class. Also, since wheelbase length isof particular concern for predictingmaneuverability in vehicles, standarddeviations were also calculated for eachWMD class wheelbase length and are shownin Figure 15 and Table 2. Of the surveyedWMD classes, scooters were found to havethe largest mean wheelbase length at 31.6".Within one standard deviation, the scooterswere found to have up to as large as a 36.8"wheelbase length. Sports manual WMDs,conversely, have the smallest mean wheelbaselength of 17.9", permitting a tighter turningradius.

Frame Characteristics

Securement Point Separation:

In the dynamic modeling of a secured WMD,the location and angles of the tiedowns arecritical in determining the crash response ofthe WMD. Additionally, since ADA requiresthat a 48" long area be allocated to a WMDsecurement station, tiedown floor anchoragesare typically longitudinally spaced 48"-54"apart. WMDs having an excessive lengthcould cause tiedowns to be rendered uselessif the tiedowns’ minimum lengths are toolong due to hardware constraints. Therefore,as a part of the survey, the longitudinaldistances between potential securementlocations were recorded for those WMDshaving accessible structure. Measurements


were made between the center of the rearvertical structural member to the center of thefront vertical structural member, indicated byframe dimension, L, on the data form inAppendix A. It is anticipated that these framemembers would serve as securement pointswhen using a 4-point belt tiedown system.In the case of scooters, which typically havetheir structures enclosed by a moldedhousing, the tiller and seat structure wereidentified as potential securement locations,assuming that manufacturers wouldstructurally reinforce these components.

The results of these measurements, presentedas means and their standard deviations, areshown in Figure 16. Table 3 provides thenumerical values of these results for eachadult WMD class. The survey has shown thatscooters as a class have the largest separationbetween securement points with a mean of36.6". Such a result can be anticipated sincescooters typically have the greatest lengthsof all WMDs. Consequently, scooters, attimes, present problems when tiedowns areunable to be shortened to accommodate thewide separation in securement points.Conventional manual WMDs have thesmallest securement point separationdistance at a mean of 17.6".

Physical Characteristics

Weight

As a part of the survey, WMD weights wererecorded using either manufacturers’literature, or by weighing the surveyedWMD. The weight of WMDs is an issue in

securement since the weight is proportionalto the load imposed on the securementsystem. Some commercially availabletiedowns have been found through sledtesting to be capable of handling WMDsweighing approximately 200 lbs or less in a30mph/20g crash. Therefore, a statisticaldistribution of the surveyed WMDs is usefulin identifying the segment of WMDs that mayexceed the capabilities of commerciallyavailable tiedowns in a 20g crash. Such adistribution is provided in Figure 17, ahistogram of adult powered WMD weightsbased upon class. To further analyze thisweight data for powered WMDs, a box plotwhich indicates percentile distributions isprovided in Figure 18. A key for interpretationof this diagram is also provided and indicatesdesignations for 90th, 75th, 50th, 25th and10th percentile populations, as well as themean. As shown by Figure 18, which groupsall powered WMDs, a 260 lb WMD representsthe 90th percentile of powered WMD weights.The mean weight of all powered classes(scooters, powerbases and conventionalpowered) was 180 lbs. A similar statisticalbreakdown for each individual powered classis shown in Figure 19. This figure clearlyshows that powerbases have the largestweight, with a mean weight of 222 lbs.Manual class WMDs weights were alsoevaluated using the same statistical approachwith the resulting box plots shown in Figure20. It was found that the conventional manualWMDs had a mean weight of 34 lbs, whilesports manual WMDs have a lower meanweight of 28.0 lbs. A histogram combining alladult classes of WMDs for comparison by


weight of the entire sampled population ispresented in Figure 21. As shown, themaximum weight WMD of the entiresampled population weighs 320 lbs and theminimum weighs 21 lbs. The calculated meanweight for the WMD sampling was 116 lbs.

Center of Gravity

Also important when modeling the dynamicbehavior of a WMD in a crash is the locationof the center of gravity (CG). Therefore, aneffort was made to identify center of gravitydata for the surveyed WMD. This data werecollected following either of twoconfigurations: (1) defining the CG of theWMD alone, or (2) determining the CG of thecombination of the WMD and a 220 lbanthropomorphic test dummy (ATD). Centerof gravity data were generated using thestability or tip angle of the WMDs in theforward and sideward directions. SinceANSI/RESNA and ISO WheelchairStandards require manufacturers to measurethe tip angles of WMDs while occupied withan ATD, this data was used to determine thecombined WMD and ATD CG [3,4,5].Although information regarding the ATD’sphysical characteristics such as CG andmoments of inertia is available, it is notpossible to separate the WMD and ATD intotwo separate components for calculation ofWMD CG since the exact position of the ATDin the seat is unknown. When possible,sample WMD tip angles were determinedwithout the use of an ATD while followingthe ANSI/RESNA stability test protocol sothat the CG of the WMD alone could be

computed. Tip angles where measured usinga tilt platform with the WMD facing bothupward and sideward on the slopedplatform. Otherwise, ANSI/RESNA data onstability angles, as measured bymanufacturers when using an ATD occupiedWMD, was requested. In both configurations,CGs were computed using physicaldimensions of the WMD and decomposingforce vectors for the given tip angles. It is alsoimportant to note that WMDs with adjustablerear wheel axle positions will have varyingCG locations that depend upon the positionof the axle. For each of the surveyed WMDs,tip angle measurements were performed withthe axle in the position to which the chair waspreviously set.

Data is presented in both formats (WMDalone and WMD with ATD) for each adultWMD class. Figures 22 and 23 show themeans and standard deviations of the verticaland horizontal location of the CG, for anunoccupied WMD. Horizontal CGs arereported relative to the rear wheel axle, whilevertical CGs are taken relative to the ground.As shown by Figure 22, conventional manualWMDs have the highest mean vertical CG at15" above the ground. Additionally, the onestandard deviation calculations of this classof WMDs shows a wide range of vertical CGs,ranging from 13" to 17". Sports manualWMDs have a mean vertical CG slightly lessthan the conventional manual class at 13.1".Conventional powered WMDs andpowerbases have mean vertical CGs that varyonly slightly from each other at 11.4" and11.6", respectively. Scooters were found to


have the lowest mean vertical CG at only 7.5"above the ground.

Horizontal CGs for each of the WMD classesvary less across the different classes than verticalCGs. As shown in Figure 23 scooters were foundto have their horizontal CG the furthest forwardfrom the rear axle than any other WMD class ata mean of 8.2". As with the vertical CG,conventional powered WMDs and powerbaseswere found to have only slight differences intheir mean horizontal CGs at 5.6" and 6",respectively. Combined WMD and ATD verticaland horizontal CG data is presented in Figures24 and 25, respectively. This data was notavailable for scooters.

Width and Length

When accessing vehicles and manueveringinside of vehicles, the overall width and lengthof the WMD must be considered. Vehicle layoutdesigns should be capable of allowing freeaccess to lifts, through doorways and ramps,as well as to WMD securement stations.Previously, ANSI/RESNA and ISO WheelchairStandards have identified maximum values ofoverall width and length to be used whenmanufacturing WMDs complying with thesestandards [3,4,5]. Thess standards have limitedoverall width to 27.5" and overall length to47.25".

Measurements of overall width and length forsampled WMDs were obtained either throughmanufacturers’ literature or directmeasurement following the ANSI/RESNA andISO Wheelchair Standards guidelines [3,4,5].Measurements of overall length were obtained

with footrests. In the case of folding WMDs, theWMD was opened fully and the measurementwas taken to the furthest points on each side ofthe WMD. WMD widths were measured witharmrests installed on the WMD. The histogramsin Figures 26 and 27 show a distribution ofoverall widths and lengths, respectively, for theWMDs in the sample population. Overallwidths of the sampled WMD populationranged from 18" to 31", with a mean value of24". Three of the WMDs were wider than theANSI/RESNA and ISO width limitation.Overall lengths of the sampling ranged from18" to 56", with a population mean of 40". SixWMDs exceeded the ANSI/RESNA and ISOlength limitation.

Turning Radius

An additional measurement critical to accessingvehicle layout and securement stations is theWMD turning radius. This WMD characterisiticrepresents the smallest space in which theWMD can turn in a circle. A WMD with atighter, or smaller, turning radius can negotiatesharper turns than one with a larger turningradius. Determination of the turning radius istypically a function of wheelbase length andwidth, along with the overall width and lengthof the WMD. A population distribution ofturning radii for all types of adult WMDs ispresented by a histogram in Figure 28. Of thesampled WMDs having this informationavailable, the maximum turning radius is 56"and the minimum is 27". A turning radius meanof 38" was found for this sample. Incomparisons, it is common to find scooters tohave larger turning radii than conventionalmanual and sports WMDs.


References

1. Trefler, E., Hobson, D., Monahan, L., Shaw,G., and Taylor, S, Seating and Mobility forPersons with Physical Disabilities, Tucson,Arizona: Therapy Skill Builders,1993, pp. 281.

2. Hunter–Zaworski, K. and Ullman, D.“Mechanics of Mobility Aid Securement andRestraint on Public Vehicles”, TransportationResearch Record 1378, pp. 45–51.

3. American National Standards Institute/Rehabilition Engineering and AssistiveTechnology Society of North America, ANSI/RESNA Wheelchair Standards Parts 01-15,December 1996.

4. Axelson, P. Minkel, J. and Chesney, D. AGuide to Wheelchair Selection: How to Usethe ANSI/RESNA Wheelchair Standard toBuy a Wheelchair , Washington, D.C.:Paralyzed Veterans of America, 1994.

5. The International Organization forStandardization , ISO 7176, Parts 01-16,Wheelchair Standards, 1996.

6. Society of Automotive Engineers, SAEJ2249 Wheelchair Tiedowns and OccupantRestraints for use in Motor Vehicles,Warrendale, PA.: SAE, 1996.

7. The International Organization forStandardization , ISO/CD 10542 Wheelchairtiedown and occupant restraint for motorvehicles, Draft Standard, Sept 1996.

Summary

The information contained within thisdatabase has several potential applications inresearch, design and standards development.To date, it has largely been used to supportthe development of wheelchairtransportation standards and thedevelopment of dynamic models used forcrash simulations. In keeping with thegrowing transportation needs of the disabledcommunity, continual efforts will be made bythe authors to update and add WMDs to thedatabase. Statistical analyses of thisinformation will be made available to assistthose designing devices, conducting researchand developing standards for WMDtransportation.


FIgure 1 Universal Interface Concept

Personal WheeledMobility Devices

Public and PrivateTransport Vehicles

Universal Interface Concept

SCOOTERS

POWER BASES

CONVENTIONALPOWER

WHEELCHAIR

CONVENTIONALMANUAL

WHEELCHAIR

STROLLERS

POWERED PROPULSIONMANUAL PROPULSION

WMD CLASSES

SPORTS

Figure 2 WMD Classification System- Propulsion System Categories


MANUAL WMDs

FOLDING FRAME RIGID FRAME

VERTICAL FOLDING CROSS BRACE

FLOATING CONTAINED

OVER CENTER LOCK-OUT & SIDE LINK

SLIDE FRONTTELESCOPIC POST

T-FRAME(3 WHEEL)

CANTILEVER

FIXED SEAT RECLINING SEAT

REMOVABLE SEAT

NONREMOVABLE SEAT

BOX FRAME(4 W HEEL)

Figure 3. Manual WMD Categories

POWERED WMDs

FOLDING FRAME RIGID BOX FRAME

CROSS BRACE BELT DRIVE DIRECT DRIVE

FLOATING CONTAINED

Figure 4. Powered WMD Categories


SCOOTERS

3 WHEEL 4 WHEEL

REAR WHEEL DRIVE REAR WHEEL DRIVE,TRANSAXLE

REAR WHEEL DRIVE,BELT OR CHAIN

DIRECT DRIVE

BELT OR CHAIN DRIVE

FRONT WHEEL DRIVE,BELT OR CHAIN

Figure 5 Scooter Categories

Seating Conventional Powerbase Scooter Conventional Manual

Characteristic Power WMD Manual WMD Sports WMD

Seat Height - Mean 20 18.5 20.3 19.5 18.9

Seat Height - Low* 17.6 16 17 15.8 14

Seat Height - High* 20.8 23 22 21.4 21

Seat Width - Mean 17 17 17.5 15.9 16

Seat Width - Low* 14 12 14 11 12

Seat Width - High* 20 20 20 20 20

Seat Back Height - Mean 17.2 20.6 15.5 16.4 13.5

Seat Back Angle - Mean 7.9 4 12.4 8.1 6

Seat Depth - Mean 17 18.6 16.5 16.7 16.9

Seat Angle - Mean 4.4 3.6 6.2 4.8 11.2

Seat-Back to Rear Axle-Horiz-Mean 3.4 5.9 1 1.3 2.2

Seat-Back to Rear Axle-Horiz-Std Dev 1.5 4.2 1.7 1.9 1.4

Seat-Back to Rear Axle-Vert-Mean 10.7 11.9 17.5 6.2 5.7

Seat-Back to rear Axle-Vert-Std Dev 2.9 2.4 1.1 2.8 1.6* Values taken from manufacturer’s literature

Table 1. Seating Characteristics of Adult WMDs(all linear measurements in inches and angles in degrees )


B

B

BB

B

H

H

H

H

H

J

J

J

JJ

Conv Power Powerbase Scooter Conv Manual SportsManual

10

12

14

16

18

20

22

24

Sea

t Hei

ght (

in)

Adult WMD Class

High

Low

Mean

Figure 6 Adult WMD Seat Height Meansand Ranges

B B B B B

H

H

H

H

H

J JJ

J J


10

12

14

16

18

20

22

24

Sea

t Wid

ths

(in)

Adult WMD Class

Figure 7 Adult WMD Seat Width Means and Ranges

Low

Mean

High


B

B

BB

B


0

5

10

15

20

25

Mea

n S

eat B

ack

Hei

ght (

in)

Adult WMD Class

Figure 8 Adult WMD Mean Seat Back Heights

B

B

BB

B


13

14

15

16

17

18

19

20

Sea

t Dep

th (

in)

Adult WMD Class

Figure 9 Adult WMD Seat Depth Means


KK

K

K

KK

K

K

KK

B

B

B

BB


0

2

4

6

8

10

12

14

16

18

20

Rea

r A

xle

to S

eat-

Bac

k In

ters

ectio

n (in

)

Adult Power WMD Classes

Figure 11 Adult WMD Vertical Distance fromRear Axle to Seat-Back Intersection; Means

and Standard Deviations

Ver

tical

Dis

tanc

e

Std Dev

Std Dev

Mean

B

B

B

B

B

ConvPower

Powerbase Scooter ConvManual

SportsManual

0

2

4

6

8

10

12

Sea

t Ang

le (

Deg

rees

)

Adult WMD Classes

Figure 10 Adult WMD Mean Seat Angle


K

K

KK

K

K K

K K

K

B

B

BB

B


-2

0

2

4

6

8

10

12

Rea

r A

xle

to S

eat-

Bac

k In

ters

ectio

n (in

)


Hor

izon

tal D

ista

nce

Figure 12 Adult WMD Horizontal Distancefrom Rear Axle to Seat-Back Intersection;

Means and Standard Deviations

Std Dev

Std Dev

Mean

Table 2. Wheel Characteristics of Adult WMDs (all units in inches)

Wheel Conventional Conventional Manual

Characteristic Power WMD Powerbase Scooter Manual WMD Sports WMD

Front Wheel Diameter - Mean 7.2 7.8 8.3 7.1 5.5

Rear Wheel Diameter - Mean 15.6 11.6 8.8 23.8 24.1

Front Wheelbase Width - Mean 18.3 19.5 18.8 17.6 17.1

Rear Wheelbase Width - Mean 22 20.5 21.3 20.3 21.7

Wheelbase Length - Mean 22.1 19.9 31.6 19.2 17.9

Wheelbase Length - Std Dev 2 3.6 4.1 2.5 2.9


B

B

B

B B

JJ J

J

J


0

5

10

15

20

25

Whe

el D

iam

eter

(in

)

Adult WMD Class

B Rear Wheel

J Front Wheel

Figure 13 Adult WMD Mean Front and RearWheel Diameters

B

BB

B

B

JJ

JJ J


0

5

10

15

20

25

Whe

elba

se W

idth

(in

)

Adult WMD Class

B Rear Wheel

J Front Wheel

Figure 14 Adult WMD Mean Front and RearWheelbase Widths


K

K

K

KK

K K

K

K KB

B

B

BB

Conv Power Powerbase Scooter Conv Manual Sports Manual0

5

10

15

20

25

30

35

40

Whe

elba

se L

engt

h (i

n)


Figure 15 Adult WMD Wheelbase Length; Means and Standard Deviations

Table 3. Frame Characterisitcs of Adult WMDs (all units in inches)

Frame Conventional Conventional Manual


Securement Point Separation - Mean 18.7 22.4 36.6 17.6 21.4

Securement Point Separation - Std Dev 2.6 4.4 4.1 1.6 2.3


KK

K

K

KK

K

K

K

K

B

B

B

B

B

Conv Power Powerbase Scooter Conv Manual Sports Manual0

5

10

15

20

25

30

35

40

45

Secu

rem

ent P

t Sep

arat

ion

(in)

Adult WMD Classes

(N=8) (N=8)(N=5) (N=16) (N=7)

Figure 16 Adult WMD Front-to-Rear Securement Pt Separation Distance;Means and Standard Deviations

Physical Conventional Conventional Manual


Weight - Mean 162 222 152 34 28

25th Percentile Weight 125 205 140 30 21

75th Percentile Weight 180 243 165 40 36

CG Vertical - WMD - Mean 11.4 11.6 7.5 15 13.1

CG Vertical - WMD - Std Dev 0.6 0.4 0.8 2 0.6

CG Horizontal - WMD - Mean 5.6 6 8.2 7.9 6.1

CG Horizontal - WMD - Std Dev 1.9 1.8 0.2 1.5 0.4

CG Vertical -WMD/ATD† - Mean 31.7 29.1 28.4 28.2

CG Vertical - WMD/ATD† -Std Dev 1.6 5.6 3.5 1.7

CG Horizontal - WMD/ATD† - Mean 9.7 10.3 5.8 6.3

CG Horizontal - WMD/ATD† - Std Dev 1.1 4.2 1 1.4

† ATD weight = 220 lb

Table 4. Physical Characterisitcs of Adult WMDs (all units in inches)


Figure 17 Adult Powered WMD WeightDistribution (Conv Power, Powerbases &Scooters)

<0

[0,5

0)

[50,

100)

[100

,150

)

[150

,200

)

[200

,250

)

[250

,300

)

[300

,350

)

[350

,400

)

≥400

0

2

4

6

8

10

12

Num

ber

of W

MD

s

Weight (lb)

B

0

50

100

150

200

250

300

Wei

ght (

lb)

Adult Powered WMDs

90th %tile

75th %tile

Mean

50th %tile

25th %tile

10th %tile

Figure 18 Adult Powered WMD Weight Distribution(Conv Power, Powerbases and Scooters)


B

B

B

Conv Manual Sports Manual All Manual Classes0

5

10

15

20

25

30

35

40

45

Wei

ght (

lb)

Manual WMD Class

Figure 20 Adult Manual WMD Weight Distribution

B

BB

B

Powerbases Scooters Conv Power All PowerClasses

0

50

100

150

200

250

300

350

Wei

ght (

lb)

Power WMD Class

Figure 19 Adult Powered WMD Weight Distribution


Figure 21 All Adult WMD Weight Distribution

<0

[0,2

5)[2

5,50

)[5

0,75

)[7

5,10

0)[1

00,1

25)

[125

,150

)[1

50,1

75)

[175

,200

)[2

00,2

25)

[225

,250

)[2

50,2

75)

[275

,300

)[3

00,3

25)

[325

,350

)≥3

50

0

5

10

15

20

25

Num

ber

of W

MD

s

Weight (lb)

Min = 21 lbMax = 320 lbMean = 116 lbN = 71

K K

K

K

K

KK

K

K K

B B

B

B

B


6

8

10

12

14

16

18

Ver

tical

CG

Loc

atio

n (in

)

Adult WMD Class

Figure 22 Adult WMD Vertical CG Location - Means andStandard Deviations (Relative to Ground)


KK

K

K

K

KK

K

KK

BB

BB

B


2

4

6

8

10

12

14

Hor

izon

tal C

G L

ocat

ion

(in)

Adult WMD Class

Figure 23 Adult WMD Horizontal CG Location - Meansand Standard Deviations (Relative to Rear Axle)

KK

K

KK

KK

K

B

BB B

Conv Power Powerbase Conv Manual Sports Manual6

11

16

21

26

31

36

Ver

tical

CG

Loc

atio

n (in

)

Adult WMD Class

Figure 24 Adult WMD w/ 220 lb ATD Vertical CG -Means and Standard Deviations (Relative to Ground)


Figure 26 All Adult WMD Overall Width Distribution

<14

[14,

16)

[16,

18)

[18,

20)

[20,

22)

[22,

24)

[24,

26)

[26,

28)

[28,

30)

[30,

32)

[32,

34)

≥34

0

5

10

15

20

25

30

Num

ber

of W

MD

s

Overall Width (in)

Min = 18"Max = 31"Mean = 24"N = 64

K

K

K

K

K

K

K K

BB

BB

Conv Power Powerbase Conv Manual Sports Manual4

6

8

10

12

14

16

Hor

izon

tal C

G L

ocat

ion

(in)

Adult WMD Class

Figure 25 Adult WMD w/ 220 lb ATD Horizontal CG -Means and Standard Deviations (Relative to Rear Axle)


Figure 28 All Adult WMD Turning RadiusDistribution

<10

[10,

15)

[15,

20)

[20,

25)

[25,

30)

[30,

35)

[35,

40)

[40,

45)

[45,

50)

[50,

55)

[55,

60)

[60,

65)

[65,

70)

≥70

0

1

2

3

4

5

6

7

8

9

10

Num

ber

of W

MD

s

Turning Radius (in)

Min = 27"Max = 56"Mean = 38"N = 26

Figure 27 All Adult WMD Overall Length Distribution

<10

[10,

15)

[15,

20)

[20,

25)

[25,

30)

[30,

35)

[35,

40)

[40,

45)

[45,

50)

[50,

55)

[55,

60)

≥60

0

5

10

15

20

25

Num

ber

of W

MD

s

Overall Length (in)

Min = 18"Max = 56"Mean = 40"N = 64


Appendix A- Survey Data Form


Amigo FWDAmigo RWD DeluxeBruno Regal Model 55Celebrity PrideE & J QuestE & J MagnumE & J XcaliburE & J MXE & J Kid PowerE & J Vision NitroE & J Premier Xtra DutyE & J LancerE & J MarathonE & J SprintE & J EZ LiteE & J EpicE & J TempestE & J Mobie II PremierEagle Hurricane 7VEagle Hurricane JrElectric Mobility Rascal #250Excel Mobility BalderFortress 2001 LXFortress 655FSFortress 2000FSFortress Legend JrFortress 720Fortress 770Genus - Invacare Cat 3W ScooterInvacare Action Power 9000Invacare 9000 Dual Axle ModelInvacare 9000 TallInvacare PatriotInvacare 2000 Series (2016 AD)Invacare Action TigerInvacare Action A4Invacare Action A4 PediatricInvacare Action JrInvacare Rocket

WMD Database Listing

Appendix B- WMD Database Listing

Invacare Tracer LX (14)Invacare Tracer LX (20)Invacare Action MVPInvacare Ranger X Storm SeriesInvacare Action XTInvacare RangerInvacare ArrowInvacare Power PremiereInvacare Action XtraInvacare Rolls 1000Invacare Ride Lite 9000Invacare JaguarKuschall Champion 1000Kuschall Champion 3000Levo LCM/N/44/52/6 StandingOrthokinetics Pony IIPermobil ChairmanPermobil HexiorPride ShuttleQuickie P200Quickie P110 - ChildQuickie RXQuickie P110 - AdultQuickie RevolutionQuickie GPVQuickie ZippieQuickie Quickie 2 - 13x14 SeatQuickie Quickie 2 - 11x10 SeatQuickie Quickie 2 - 16x16 SeatQuickie Quickie 2 - 17x17 SeatQuickie BreezyQuickie 1Quickie GPQuickie P100Quickie P300Quickie P500Wheelchairs of Kansas BCW PowerXL Wheelchairs Pacer


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