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Thread: Camber or no camber, that is the chair question

  1. #1
    Suspended Andy's Avatar
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    Camber or no camber, that is the chair question

    Doing yet more planning for a new chair, and have room in my doorways to add a bit of camber to my chair. The chair I have now has 0° camber, so I have no experience with a chair that has it. My question is...do I really want it and why? If my experience with cars is any indication, negative camber just helps with tread contact in corners, but wrecks havoc on straight line tracking, so I am missing why I see so many chairs with camber, and copious amounts of it as well? I dont want the thing to go any direction but straight, am I missing something here?

  2. #2
    Senior Member canuck's Avatar
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    You get better side to side stability with camber, also with camber there will be less wheel contacting the ground making the chair roll easier. I'm going with 2 degree's on my ZRA. I have 0 & 3 on my A-4.

  3. #3
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    MUCH EASIER PUSH, AND LOWERS YOUR CG, TRACKS STRAIGHT MUCDH BETTER QAS WELL, I RUN BOUT 4-5 DEGREES, LOOKS COOL TOO

  4. #4
    I personally prefer no camber because its a pain to get through doors. I didnt notice that much of a difference with camber, except that it just looks better.

    Even if your body cannot move, you can still think and meditate ~Dalai Lama~

  5. #5
    What I did was measure the doorways in my house, and go with as much camber as I could without making the chair wider than the doorways. I have 4° I think, or maybe it's 6°. It makes the chair easier to turn and manouver.

    Some chairs have an optional adjustable camber tube. It's not something you can adjust on the fly, and I think it adds a bit of weight.
    _____
    Learn from the mistakes of others, you won't live long enough to make all of them yourself.

  6. #6
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    "Wider is Better". More stability, lower CG, easier to push especially if matched with lightweight rims and tires. Biggest drawback is overall width, so if your a larger person and want to get through narrower doorways, you'll probably not want too much camber. But even 2 degrees will be better than nothing. And with proper adjustment, the chair isn't going to track any worse than 0deg. I'm a small fry, my 15in wide TiLite has 4deg with 24" high flange hub rims and mtn. bike tires. and can just squeeze through a std 28" doorway with door not at 90deg open (so effectively 26"). If had narrow tires, it'd be even easier. This makes it nice since most places around here are built with 28"closet and bathroom doorways. Anything more than 8-10 degrees your going to run into serious doorway issues unless your like 12"wide.

    From what I've seen, most companies make you interchange the axle tube in order to change the camber. Quickie has an option (or used to) that had dual axle tubes that allowed you to just move the axle ass'y out, and put wheel into the other tube. No tools. But like jim mentioned, adds weight, like any option like that is going to.

    [This message was edited by strat on 01-18-04 at 07:15 PM.]

  7. #7
    Senior Member PB72181's Avatar
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    I want to meet that person who is 12" wide...heh.

    I have 4 deg...haven't tried 0 though, so I can't really tell you the difference, sorry. The laundry room door doesn't like me but that's the only one I have a problem with in the house. The best thing to do to calculate how much you can have, though would be to measure how much extra room in the doorway and how wide your chair is now, and then the diameter of your wheels, and then do the geometry thing to figure out what the missing angle is. Take it down a degree or two to be safe, and there you go. It gets a little complex in my mind because you have to deal with it in two halves to be able to do the equation (at least I do) but, it gets the job done...heh.

    Don't piss me off or I'll run over your toes.

  8. #8
    Kanuck, there isn't any less tire in contact with the floor/ground when you have camber set unless your tires have a flat surface on the tire to begin with. Most tires have a round profile so there's still the same amount of tire in contact.

    Camber, while adding to lateral stability, improves (reduces) turning effort. It effectively moves the force applied in turning the chair farther from the center of the turn. It's like using a longer lever to lift a rock.

    It also tends to give an improved angle for pushing. It's easier to push slightly away from your body that straight down with your elbows out a little.

    Camber only lowers the CG because the axle/chair junction is moved downward. Depending upon the chair it is possible to overdo the camber and create a problem with the angle of the caster stems. For optimum performance from the casters, the stems should be vertical. If they are tilted back at the top as they might be with a lot of camber, the front of the chair will seem to drop as you shift from forward motion to backing up. It really does drop and that means that you have to lift the front of the chair to transition to forward movement. If one of the stems doesn't turn freely you might find that caster not touch the floor.

    In cases where the chair won't track straight a common cause is one caster not contacting the floor. Sometimes due to the above--sometimes because the frame is bent.

    Andy, I would suggest that you consult with the manufacturer and see what happens to the caster stem angle as camber is added. Even a 1° change can impact the way the chair behaves.

    A lot of chairs these days have stem bearing housings that are welded to the frame. These cannot be adjusted with changes in camber as in some of the older designs such as Quickie's GPV.

    Another thing to look into is toe out. Unless some change can be made in the mounting of the camber tube, adding camber increases toe out. This makes the wheels want to roll away from each other increasing tire wear and pushing work. Most chairs have some provision for adjusting this. Way back when, Jim Martinson designed the Shadow. It was probably the first chair with a camber tube. Everybody else was attaching the axle to a plate (ala Quickie GP, GPV, Colours, etc). Unfortunately, It had mounting brackets welded to it so there was no adjusting the toe out. Kuschall came up with a rotating camber tube that had a small bubble level at the apex of the V to allow for correction of toe out. Most chairs have gone to the camber tube and most should allow the tube to rotate as needed.

    Toe out or in can be an issue if you change casters if the forks don't have different holes for different sized wheels.

    One last thing. Camber will mean you can't get as close to a cabinet or counter when sitting sideways. Your doorways might allow you to have more camber than you might want from the standpoint of working in the kitchen or whatever. Can you roll in close enough to reach something if the camber is increses.

    Sorry to babble. G'luck.

  9. #9
    I have always run zero camber on my chair. I have I think only once fallen over sideways and thats when I was sitting sideways on a steep hill. I find with any camber the wheels rub against the side of my pants unless I move the wheels further apart and if I do that I dont fit through the doors in my house. The other problem with adding camber for those that use folding wheelchairs is that when the chair is folded the wheels stick out further on the bottom and the chair is harder to get into a vehicle.

    I have tried adding camber a few times in the past and could really not tell much of a difference in the way the chair handles, so I really have no use for adding any camber. If I were using the chair to play basketball or tennis that would be a different story, under these circumstances camber is a must.

    "Life is about how you
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    soul dies".~Liz Fordred

  10. #10
    Suspended Andy's Avatar
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    Great replys guys, and thought provoking as well, lots of issues that I didnt think of. I think I will stick with 0 degrees for this next chair.

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