Nothing About Us Without US Part Four Chapter 39 1 of 3 http www dinf ne jp doc english global david dwe001 dwe00150 htm part4chap39 Nothing About Us Without Us Developing Innovative Technologies For By and With Disabled Persons PART FOUR WHEELS TO FREEDOM 253 CHAPTER 39 A One Hand Drive Wheelchair for Che A Challenge for Mart n CHE was a policeman until the fateful night he was shot He and his drinking buddies had decided to play Russian Roulette a deadly game where men point a six shooter pistol with just one bullet in it at each other s head pull the trigger and see who gets shot first Che lost The bullet left him paralyzed on the left side of his body hemiplegic Luckily Che s mind and speech were unaffected He was given a standard wheelchair But with the use of only one arm he needed assistance to go anywhere Che spent months at PROJIMO for rehabilitation and to learn new skills A commercial one arm drive wheelchair from the United States had been donated to the program Che loved it and tried to go everywhere in it But it kept breaking down Commercial one arm drive wheelchairs always break Factory made hemiplegic one arm drive wheelchairs are very expensive and seldom seen in poor countries They have design problems which limit their usefulness They are built for smooth hospital floors not village paths On rough terrain they repeatedly break and are hard and costly to fix This commercial design is nothing like Osvaldo s one arm drive chair made at PROJIMO see page 249 In the commercial chair the rider delivers power to both rear wheels with one hand The two hand rims one next to and slightly smaller than the other are mounted on one side of the chair One rim is fixed to the wheel on that side The other is connected by a central axle transverse rod to the opposite wheel To move straight ahead the rider grips both hand rims at once To make a turn he pushes just one hand rim The weakness of the commercial chair is that the axle that transfers power from one side to the other is too thin It passes on ball bearings through the center of the wheel hub on the near side and is welded to the hub on the far side Unfortunately the axle cannot be replaced by a thicker stronger one because of the small hub hole it goes through When modestly stressed the fragile axle breaks Need for a Rugged Low Cost One Hand Drive Wheelchair PROJIMO sees a lot of persons who need a one hand drive wheelchair These include folks who have had a stroke or suffered a head injury like Che and children with hemiplegic cerebral palsy Osvaldo s chair with front wheel steering allowed him to move about town independently and helped him to recover self direction and the will to live The design was simple low cost 2 17 2007 9 33 PM Nothing About Us Without US Part Four Chapter 39 2 of 3 http www dinf ne jp doc english global david dwe001 dwe00150 htm part4chap39 and fairly easy to make But that chair had one big disadvantage Like hand driven tricycles it took up a lot of space Indoors it was cumbersome There was a need for a one arm chair that was cheap road worthy and compact 254 Mart n P rez Designs a Stronger One Arm Drive Wheelchair MART N the paraplegic wheelchair builder whose gurney is featured in Chapter 37 was aware of the need for a reliable one arm drive wheelchair Time and again he had welded and tried to strengthen the weak axle of Che s commercial chair He also realized that if the power transfer mechanism broke while the rider was climbing a steep ramp or trail it could be dangerous During Mart n s visit to California while recovering from surgery he stayed in the home of wheel chair designer Ralf Hotchkiss When Ralf was away teaching Mart n used Ralf s workshop which is beautifully adapted for working from a wheelchair see page 195 One day Mart n began to design and build a one arm drive wheelchair that would be compact and low cost yet strong In building the wheelchair frame Mart n followed Ralf s basic Whirlwind design For the one arm drive mechanism he used features from the commercial design but with a much thicker and stronger transverse rod axle to transfer power from a hand rim on one side of the chair to the wheel on the far side Testing the strength of the new mechanism When the chair was done Mart n and Ralf tested the strength of the one arm drive mechanism They hooked a spring scale to the far wheel and with a block and tackle put increasing force on the hand rim that powered it To their joy Mart n s heavy duty axle rod withstood over 200 pounds of force before it broke This is much stronger than the commercial hemiplegic system which breaks at about 30 pounds of force Go back to the CONTENTS Nothing About Us Without Us Developing Innovative Technologies For By and With Disabled Persons by David Werner Published by HealthWrights Workgroup for People s Health and Rights Post Office Box 1344 Palo Alto CA 94302 USA 2 17 2007 9 33 PM Nothing About Us Without US Part Four Chapter 39 3 of 3 http www dinf ne jp doc english global david dwe001 dwe00150 htm part4chap39 Copyright 1998 by David Werner 2 17 2007 9 33 PM