Wheelchair armrest strength testing

There are about 1.4 million manual wheelchair users, 100,000 electric-power ed wheelchair users, and 60,000 electric-powered scooter users. The current study was undertaken to determine if the fasteners of a clamp-type armrest receiver were prone to failure. The first test was used to examine the pot ential misalignment of the armrest receiver components that attach it to th e frame. The second test was to evaluate the entire armrest using the Ameri can National Standards Institute/Rehabilitation Engineering and Assistive T echnology Society of North America armrest static strength standard. Finall y, we conducted three fatigue tests. The first fatigue test was performed b y repeating the static stability tests multiple times. The last two tests w ere a modified version of the double-drum wheelchair fatigue test used to a pply repeated loading and vibration simultaneously. A paired t-test showed that there is no statistically significant difference (p = 0.08), with a co nfidence of 95%, between critical alignment measurements. The armrest inclu ding the receiver passed the standard requirement of a force of 760 N being applied outward at 15 degrees. During fatigue testing, we found that armre sts did not exhibit any visible or functional damage. Upon completion of th e tests, the armrests and receivers functioned properly. At about 100,289 c ycles on a double-drum test machine, three bolts failed on each armrest rec eiver when the screws were loosened to have only five threads engaged prior to commencing the test. The design of the armrest tested was in compliance with existing national and international standards. Currently, both Intern ational Standards Organization and American National Standards Institute/Re habilitation Engineering and Assistive Technology Society committees are de veloping standards for seating systems that will include static, impact, an d fatigue strength testing of devices like lateral torso supports, lateral hip support, etc. Methods similar to those explored in this study should be considered. This study may help manufacturers when designing products and purchasers or regulatory agencies when attempting to evaluate the safety an d quality of armrest assemblies.