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Thread: cantilever tippyer?

  1. #1

    cantilever tippyer?

    Hi,

    If you have 2 chairs with the same spec apart from frame style, one box frame and one cantilever is the cantilever tippyer as I have read that on a forum before and wondered if that is true?

  2. #2
    Yep. Having a greater proportion of the frame's mass above the axle will make it tippier. Little adjustments have a greater effect on stability, and when it flips, it goes quickly.


  3. #3
    Senior Member SuprSi's Avatar
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    I think if you had a very heavy box-frame chair it would have more weight at the front, but you can compensate for this by simply moving the axle forwards.

    Check out some posts by TotoL1, he designs and builds some very impressive box-frame designed chairs. Actually they don't resemble a box at all, but they don't fall under the cantilever category. Personally I like the look of a very minimalistic cantilever chair, I've got my Kuschall set very tippy with quite a lot of camber and I absolutely love how well it responds, it's like an extention of myself.
    T11 Asia A after near-fatal bike crash.. Just happy to still be here

    No, I didn't loose my mind... It got scared and ran away!!

  4. #4
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    Quote Originally Posted by SuprSi View Post
    ...Personally I like the look of a very minimalistic cantilever chair...
    Ditt O

  5. #5
    Is it just the greater proportion of the frame's mass above the axle will make it tippier? My current chair is a box frame but the two extra thin titanium tubes that aren't on a cantilever frame musn't weigh much at all, so this would only be a small decrease in weight at the front of the chair, would this still make a noticeable difference in tippyness?

  6. #6
    Senior Member SuprSi's Avatar
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    Probably wouldn't make much difference.
    T11 Asia A after near-fatal bike crash.. Just happy to still be here

    No, I didn't loose my mind... It got scared and ran away!!

  7. #7
    That's what I was thinking , is the extra tippyness I see written about cantilever frames more when going over uneven ground, where the extra flex in this type of frame when hitting a eg bump or stone, causes it be more tippy?

  8. #8
    Senior Member SuprSi's Avatar
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    If you hit bumps or stones in any type of chair you could potentially fall out forwards, not backwards, larger casters and 'frog leg' forks and softroll wheels will help avoid this. But if your chair is set up fairly tippy it is easier to flick the casters over bumps/stones or backwheel ballance over grass, gravel etc. But this just comes down to basic wheelchair skills, a skillful wheeler could get around pretty well in a really crap chair.
    T11 Asia A after near-fatal bike crash.. Just happy to still be here

    No, I didn't loose my mind... It got scared and ran away!!

  9. #9
    Apples to apples a cantilevered frame will tip back more easily. Only the lower 1/3 to 1/2 portion of the front frame tubing is located below the axle. That means that once the balance point is surpassed, there is less mass that must rotate up and over the rear axle as the chairs flips back. This difference is mostly negligible until the chair actually tips.

    As other's have alluded to, cantilevered frames do pose more of a risk to endo should the front casters stop abruptly, and this tendency is noticeable in the real world. A primary reason is that the lower frame rail helps to disperse energy throughout the frame and buttresses the caster housing during impacts. The cantilevered frame can only direct energy up the front frame and some compression/rebound occurs in the vicinity of the bend. The rebound that occurs after the initial contact can add to the forward momentum of the chair. That is why weight distribution and caster selection become important issues on this type of frame.



    http://sci.rutgers.edu/forum/showthr...t=91333&page=4


  10. #10
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    Quote Originally Posted by SCI_OTR View Post
    [I]... As other's have alluded to, cantilevered frames do pose more of a risk to endo should the front casters stop abruptly, and this tendency is noticeable in the real world. A primary reason is that the lower frame rail helps to disperse energy throughout the frame and buttresses the caster housing during impacts. The cantilevered frame can only direct energy up the front frame and some compression/rebound occurs in the vicinity of the bend. The rebound that occurs after the initial contact can add to the forward momentum of the chair. That is why weight distribution and caster selection become important issues on this type of frame.
    Boy have you got the engineering right. I was one of your poster boys.

    What a perfect explanation of my completely-by-surprise, in-a-millisecond launch into space about 3 months ago.

    Front end tuned and ZR physics now understood, my next crash should be no surprise.

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