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Info on leverage ratios etc

Discussion in 'Downhill & Freeride' started by rentawench, Jan 27, 2008.

  1. rentawench

    rentawench Chimp

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    Well I did a few searches and couldnt really find what I am looking for so here goes. Basically I am just wanting to read up on things to do with suspension, mainly calculating the leverage ratio a frame has in regards to pivot location etc.

    I've spent a while googling it, but got nothing particularly useful to mountain bikes from what I could work out. So does anyone have any links to articles etc.

    I have the linkage software but Im more interested in the theory behind it as opposed to letting that do it for me

    Thanks

    Mike
     

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  2. DirtyMike

    DirtyMike Turbo Fluffer

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    The ratio itself is pretty easy, knwoing the total travel vs shock stroke. Its figuring the progression that can be tricky. Never been able to find anything myself as far as a dedicated website on how to calculate it, I just always contacted the Manf when the questions have come up in the shop
     
  3. davep

    davep Turbo Monkey

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    The average legerage rate is just the wheel travel divided by the shock stroke...th epivot placement has nothing to do with it.

    Now to find the instantaneous leverage rate is more difficult and not something you could do with out having an equation that described the wheel path and the shock compression.

    I think you would end up with a second order differential equation to solve that would give you the instant. leverage rate curve (too buisy to really work this out).
    Either way, you dont have that equation to start with..the linkage software tries to interpolate the wheel curve and shock movement and come up with some equation..but it is far from perfect.
     
  4. Curious_George

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    it wouldnt be a differential equation it would just be the constantly changing equation of the tangent line
     
  5. jcook90

    jcook90 Turbo Monkey

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    I think it could be accomplished with a combination of both. Lot of rate of change equations and such. When dealing with a singlepivot (morewood, orange, etc no extra 4-bar linkage), it can be thought of as a lever and balance the torques/distances moved. If the rear wheel moves z-degrees about the central pivot, the shock pivot moves the same amount about the pivot. I can't really explain this completely online. I'll probably try to figure it out in calc tomorrow.