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  1. #1
    illuminator82
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    leverage ratio on azure? need help DW

    i am trying to figure this out..
    need some serious help here;

    is a lower leverage ratio better for rear air shocks?
    all things being equal, ie same rear shock, good rear suspension design, etc...

    and if so, how would that apply to the ride characteristics of each design?
    ie single pivot versus faux bar versus horst link versus vpp versus dw link??

    and as the travel increases how is it affected?

    thanks in advance
    Last edited by brook_63@yahoo.com; 03-01-2007 at 09:12 AM. Reason: spelling error

  2. #2
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    double
    Last edited by clark; 03-01-2007 at 07:27 PM. Reason: double post

  3. #3
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    Quote Originally Posted by brook_63@yahoo.com
    i am trying to figure this out..
    need some serious help here;

    is a lower leverage ratio better for rear air shocks?
    all things being equal, ie same rear shock, good rear suspension design, etc...

    and if so, how would that apply to the ride characteristics of each design?
    ie single pivot versus faux bar versus horst link versus vpp versus dw link??

    and as the travel increases how is it affected?

    thanks in advance
    I'll try putting up a straw man. I don't know what leverage ratio is but what the hey.

    1) treat the shock as a linear spring F=kx

    2) loosen the stem on your Azure and lay it on a pine board or fir 4'x8' sheet

    3) trace it, paying special attention around the pivots.

    4) use aircraft plywood or aluminum sheet to model each of the pivots

    5) pin each pivot

    6) use an old slide rule to model the shock - glue the slider to a ruler

    now you can see exactly what happens as the suspension moves vertically. forget the square edge stuff for now, just look at vertical displacement of the rear axle... make a table showing with 4 columns: vertical wheel travel in even increments, incremental shock displacement for each wheel travel increment, incremental shock force for each wheel travel increment,

    Or, put both ends on scales. Use a block and tackle to pull down on the bottom bracket. Measure the bb height and weight as you pull the rope...

    If you look at the link where the shock is, you will see effort to make travel happen late in the cycle.

    I think. It hurts.

  4. #4
    www.derbyrims.com
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    Lower leverage ratio means there is relatively faster shock shaft speed for a given travel whether short or longer travel.

    The tradeoff is additional weight for longer shaft dampers, they are simply larger than a higher rate shock leverage is for the same wheel travel.

    Less damper fluid flow interruption is needed for equal travel resistance compared to higher leverage and slower damper shaft speed.

    The longer and faster the shaft speed then shorter the moment of friction, and direction change stiction transition is unstuck quicker.

    Lower leverage ratio damping resistance can have a wider range of tuning with finer adjustment.

    Another major factor of quality shock action is from lack of side loading of the damper shaft from suspension flex and lack of mounting pivot binding allowing the shock shaft to slide freely.

    The dw-link is one of the lowest leverage rear shock designs ever and is very much flex resistant. Other suspension designers jumping in quickly to follow and attempt to imitate DWs leading designs now.

  5. #5
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    Quote Originally Posted by derby
    Lower leverage ratio means there is relatively faster shock shaft speed for a given travel whether short or longer travel.

    The tradeoff is additional weight for longer shaft dampers, they are simply larger than a higher rate shock leverage is for the same wheel travel.
    Thank you for explaining this. In the interest not having all sorts of external references etc.

    The Azure uses a FOX FLOAT R AIR, 6.5"X1.5" to deliver 90mm of travel. The first number is eye to eye and the second number is travel. So the leverage ratio for the Azure is 90mm per 1.5 inches or 60mm/inch.

    Any bike that uses that shock and has 90mm of travel wll have the same leverage ratio? If leverage ratio varies with each incremental bit of travel - this seems important... does using the O-ring to estimate % sag work? Shock travel is not always? linear with susension travel..

    Quote Originally Posted by derby
    .... The dw-link is one of the lowest leverage rear shock designs ever and is very much flex resistant. Other suspension designers jumping in quickly to follow and attempt to imitate DWs leading designs now.
    How exclusive are the existing licensing agreements? Usually infringment results in additional licensees. Fine for inventors, but not so fine for existing licensees.

  6. #6
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    Quote Originally Posted by clark
    I don't know what leverage ratio is
    If the Azure has 3” / 76.2mm of travel and a 1.5” / 38.1mm shock your LR would be 2:1 or if it has 3.5" travel it would be 2.33:1

  7. #7
    www.derbyrims.com
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    Quote Originally Posted by clark
    Thank you for explaining this. In the interest not having all sorts of external references etc.

    The Azure uses a FOX FLOAT R AIR, 6.5"X1.5" to deliver 90mm of travel. The first number is eye to eye and the second number is travel. So the leverage ratio for the Azure is 90mm per 1.5 inches or 60mm/inch.

    Any bike that uses that shock and has 90mm of travel wll have the same leverage ratio? If leverage ratio varies with each incremental bit of travel - this seems important... does using the O-ring to estimate % sag work? Shock travel is not always? linear with susension travel..



    How exclusive are the existing licensing agreements? Usually infringment results in additional licensees. Fine for inventors, but not so fine for existing licensees.
    The 90mm trave to 1.5 inch shock shaft rate of the Azure would be overall or average shock leverage.

    The incremental change in leverage rate through travel produces rising or falling rate influence to the spring and damping rates of resistance in both directions of travel, compressing and rebounding.

    The better suspension designers do much dynamic testing to tune the incremental travel shock leverage rates to balance with the overall suspension inputs and reactions to handle a wide variety of terrain, rider power, and rider weight.

    DW is a rare bike suspension designer who uses advanced computer modeling to test designs as well as using pro rider testing feedback. The computer helps document precise changes in design. And by referencing pro rider feedback to specific design changes, meaningful comparisons and trends can be seen in correlation with physical design factors.

    I have no information on the licensing agreements. DWs business time is in very high demand and he appears to be moving forward with just a few partners with very careful caution.

  8. #8
    Just another FOC'er
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    Quote Originally Posted by clark
    The Azure uses a FOX FLOAT R AIR, 6.5"X1.5" to deliver 90mm of travel. The first number is eye to eye and the second number is travel. So the leverage ratio for the Azure is 90mm per 1.5 inches or 60mm/inch.

    Any bike that uses that shock and has 90mm of travel wll have the same leverage ratio? If leverage ratio varies with each incremental bit of travel - this seems important...
    Any bike with the same shock stroke and the same travel will have the same AVERAGE leverage ratio. Attached is a pic that shows the Azure's LR over its travel. I'm sure it's not completely accurate, but it's probably pretty close.

    It's a 'falling' leverage ratio making the suspension progressive. Harder to bottom out, but sensitive to the smaller stuff -- a good thing.
    Attached Images Attached Images

  9. #9
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    Thanks. That is a difficult standard to judge against... but it probably tells one fourth of the story. The easiest 4th.

  10. #10
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    another bump for epic dwlink knowledge

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