DANGER: The things I build might kill me. If you build similar things, yours might kill you!
In particular, this blog talks about a power wheelchair that I built. If you really need a wheelchair, it is not a good idea to build one yourself. It is not easy, and it is not cheap. The savings in parts and materials are nothing compared to the cost in time spent. If you can’t justify the project on the basis of fun and education, don’t do it!
Some specific safety concerns are:
- Motors, gears, sprockets—The motors in my wheelchair are powerful enough to injure or kill if they aren’t kept under control. In particular, disconnect the battery before you handle any part of the drive train. Also disconnect the wiring to the motors whenever you work on the speed controller, and test the controller with a meter or scope before you connect the motors again. Try to rig up safety devices that will quickly disable the motors if you ever lose control of the chair.
- Electronics—The 24-V DC battery can deliver a severe shock or start a fire. Some components, such as the onboard charger, use high voltage AC that can injure or kill you. For electronics safety tips, review http://www.repairfaq.org/sam/safety.htm.
- Ergonomics and stability—My design follows the TLAR philosophy (“that looks about right”), with the understanding that I can fix anything that doesn’t work right (if I survive). But there are real engineering standards for wheelchairs that you should consider buying, especially if you are building a chair for someone besides yourself.
- Muscle Atrophy—When you stop using muscles, they lose strength rapidly. My biggest mistake when I started using my chair was to simply quit walking. I thought a short break would help my sore joints “catch up,” and in some ways it did. But after a few days I found it much harder than it had been before just to take a few steps with my walker. If you have to use a wheelchair, by all means get a doctor or therapist’s advice first, and follow it! Keep doing whatever you can do, as often and as vigorously as you can.