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Thread: Dump Question

  1. #1

    Dump Question

    I am currently using a chair with a 4" dump, 16" rear and 20" front. While this works fine, I'd rather have less. I need the 20" front for ground clearance, I'd actually like more ground clearance, but don't want to add dump. I have the rear down to 16" for my reach to the wheels, which are 25". If I went with 16.5" in the rear, would that raise my reach a full half inch...or maybe more? (I am not a geometry wizard.) I got to thinking about the dump length being carried over a 16" span (seat length) and wondered how much difference there would be.

    My current chair, with CAD, is here: http://sci.rutgers.edu/forum/showthr...=1#post1591233
    C5-6 Complete - 8/13/1982

  2. #2
    Keeping everything else the same, raising your RSH 1/2" would increase your reach about (13.5/16)*0.5 = 0.42" (slightly increasing your elbow angle).
    Chas
    TiLite TR3
    Dual-Axle TR3 with RioMobility DragonFly
    I am a person with mild/moderate hexaparesis (impaired movement in 4 limbs, head, & torso) caused by RRMS w/TM C7&T7 incomplete.

    "I know you think you understand what you thought I said, but what I don't think you realize is that what you heard is not what I meant."
    <
    UNKNOWN AUTHOR>

  3. #3
    With a higher RSH your elbow angle would be decreased

  4. #4
    I think how much dump you need should be determined more by your injury level than any sort of ground clearance desire. You can always start from your desired dump and get whatever ground clearance you need (I have played with this quite a bit w/ my Icon). But as a T8 if I don't have enough dump I feel unstable.

  5. #5
    With a higher RSH being the only thing changing, the elbow angle will increase:

    Name:  Wheelchair Elbow-Angle Range.JPG
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    --Pic won't load--

    Axle (pushrim) doesn't move, butt/shoulder move up, increasing distance between pushrim and shoulder, arm straightens a bit, elbow angle increases.

    According to VA research, optimum elbow angle for wheelchair propulsion is 110-130 degrees, which is approximated by the finger-tips-on-axle rule.

    Seat-Height propulsion effects highlighted.pdf

    --PDF won't attach - site's not working right . . .
    Last edited by chasmengr; 03-02-2015 at 10:36 PM.
    Chas
    TiLite TR3
    Dual-Axle TR3 with RioMobility DragonFly
    I am a person with mild/moderate hexaparesis (impaired movement in 4 limbs, head, & torso) caused by RRMS w/TM C7&T7 incomplete.

    "I know you think you understand what you thought I said, but what I don't think you realize is that what you heard is not what I meant."
    <
    UNKNOWN AUTHOR>

  6. #6
    chas,you are right,i had it wrong thinking the angle decreases when arm is less bent at elbow,
    its like you said;elbow angle will increase.

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