Does "Platform Dampening" = low-speed compression dampening?- Mtbr.com
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  1. #1
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    Does "Platform Dampening" = low-speed compression dampening?

    Many of the rear shocks now are available with some sort of "Platform Dampening". It seems to work and take away some of the bob associated with long-travel and single pivot suspension designs.

    But is "Platform Dampening" more than just and adjustable low-speed compression dampening circut?

    How else could/does it work?

    Diagrams and cut-aways appreciated!

    -Brad
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  2. #2
    MK_
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    Quote Originally Posted by Octane
    Many of the rear shocks now are available with some sort of "Platform Dampening". It seems to work and take away some of the bob associated with long-travel and single pivot suspension designs.

    But is "Platform Dampening" more than just and adjustable low-speed compression dampening circut?

    How else could/does it work?

    Diagrams and cut-aways appreciated!

    -Brad
    Essentially, a platform is low speed compression damping. The platform happes in the begning part of the stroke only, therefore it isn't a compression damping circuit which affects the full stroke of the shock.

    With SPV, you have a valve which is kept closed until enough oil pressure builds up to open it up, once it is open, oil pressure keeps it open, eliminating the platform.

    Similar thing happes with Propedal. At least on the DHX air and the 05 DHX (for the 06 the design has changed and little data is available about how thing work currently). I am not very familiar with the inner workings of Floats/RP3s. With the DHX, you have an oil metering valve which is kept closed by the air pressure in the boost chamber. In addition, propedal knob controls the preload on the spring which controls additional force on the valve (the spring either counteracts the air pressure or assists it, I am not positive about that one). So the valve is kept shut by the chamber pressure and the propedal spring, until the force of oil forces it open, much like SPV.

    I don't know much about the Romic or the 5th Element.

    Another way to create a platform is to have a fixed orifice in the shaft which is kept closed by the piston in the early part of the stroke and opened up at certain shaft position. The limited oil flow will give you a platform in the begining and once the second orifice is opened up, more oil flows through, reducing compression damping. That oil could then run through a shimmed circuit or through a fixed orifice circuit, which a the feature of the overall damper.

    _MK

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  3. #3
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    Quote Originally Posted by Octane
    Many of the rear shocks now are available with some sort of "Platform Dampening". It seems to work and take away some of the bob associated with long-travel and single pivot suspension designs.

    But is "Platform Dampening" more than just and adjustable low-speed compression dampening circut?

    How else could/does it work?

    Diagrams and cut-aways appreciated!

    -Brad
    You're right, most platform dampers are a bit more/different than standard compression dampers (like a shim stack). I think PUSH's platform mod for Fox shocks/forks involves a installing a dual-stage piston and a few other bits.

  4. #4
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    Thanks for your replys guys. Those are the answers I was looking for. I wish I could get a detailed cut-away of the Fox DHX Air (like the sweet cutaway of the CCDB that shows the oil paths).

    -B
    I get paid to ride shotgun.

  5. #5
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    Zero speed compression damping

    "Platform damping" is not really damping, it's nearly lock out on or off, preventing action damping. Shock action is the only time when damping occurs.

    There are detent air pressure or little coil platform specific spring loaded ball or piston valves (or an inertia activated valve), separate from the main suspension spring, that lock out the shock when there is low pressure on the suspension. (Inertia valves open with movement of a weighted piston valve from the whole shock's vertical direction movement). After enough pressure is applied to the suspension it opens the lock out valve against it's own platform spring pressure. And stays open as long as there is enough suspension action to keep the valve from springing closed (or resting the inertia piston closed). Advances in these automatic lockout "platform damping" has produces adjustable pressure threshold detent springs.

    Slow speed compression damping is different. It slows the fluid action while there is shock activation. The rate of slowing can be tuned to be slower while the shock is moving slowly, and reduce resistance, to reduce the situation of fluid flow "spike" or lockout (often by using flexible shims in the path of the fluid flow), when the shock is leveraged by the suspension to move faster.

    You'll need to do some research to find diagrams. I've heard that the Penski Shock site is very good for diagrams of non-platform shocks.

    Platform shocks are relatively new and produce an enhanced a static-friction like effect which earlier "more primitive" sticky and higher friction shocks provided to earlier short travel suspension preventing wallowing and over active lightly loaded suspension such as during pedaling. Platform damping has enhanced most longer travel designs that were too freely active to pedal well for any use other than downhilling. And many of the less efficient accelerating shorter travel designs such as low monopivot and ICT are noticeably enhanced to accelerate with better efficiency and handle with better stability without using as much slow and medium speed damping as needed before to accelerate well, and freeing up damping for better higher speed control, but at the cost of loosing some small bump smoothness.



    - ray

  6. #6
    MK_
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    Quote Originally Posted by derby
    "Platform damping" is not really damping, it's nearly lock out on or off, preventing action damping. Shock action is the only time when damping occurs.
    ray, but another way to look at the near lockout of the platform is to see it as lockout that works only at very low shaft speeds, therefore low speed compression damping would technically still apply. Since damping is shaft speed control, the platform keeps the shaft speed at nearly zero. But this is splitting hairs.

    Nice overall description of platforms.

    _MK

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  7. #7
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    After a few rides on my FOX Float Propedal, I realized that my 1996 Marzocchi XC500 was way ahead of his time. No suspension at all unless you hit a big rock!
    Too bad this Propedal was called static friction (and lack of negtive spring)!!

    fab.

  8. #8
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    Quote Originally Posted by MK_
    ray, but another way to look at the near lockout of the platform is to see it as lockout that works only at very low shaft speeds, therefore low speed compression damping would technically still apply. Since damping is shaft speed control, the platform keeps the shaft speed at nearly zero. But this is splitting hairs.

    Nice overall description of platforms.

    _MK

    It's like 100% compression damping, untill the threshold is reached.

    I've been saying the same thing as derby for a while, when talking about shaft movement and low speed compression damping/platforms. I definitely agree with what he said.
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  9. #9
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    Quote Originally Posted by MK_
    Essentially, a platform is low speed compression damping. The platform happes in the begning part of the stroke only, therefore it isn't a compression damping circuit which affects the full stroke of the shock.

    With SPV, you have a valve which is kept closed until enough oil pressure builds up to open it up, once it is open, oil pressure keeps it open, eliminating the platform.

    Similar thing happes with Propedal. At least on the DHX air and the 05 DHX (for the 06 the design has changed and little data is available about how thing work currently). I am not very familiar with the inner workings of Floats/RP3s. With the DHX, you have an oil metering valve which is kept closed by the air pressure in the boost chamber. In addition, propedal knob controls the preload on the spring which controls additional force on the valve (the spring either counteracts the air pressure or assists it, I am not positive about that one). So the valve is kept shut by the chamber pressure and the propedal spring, until the force of oil forces it open, much like SPV.

    I don't know much about the Romic or the 5th Element.

    Another way to create a platform is to have a fixed orifice in the shaft which is kept closed by the piston in the early part of the stroke and opened up at certain shaft position. The limited oil flow will give you a platform in the begining and once the second orifice is opened up, more oil flows through, reducing compression damping. That oil could then run through a shimmed circuit or through a fixed orifice circuit, which a the feature of the overall damper.

    _MK

    I may be splitting hairs here, but when you say

    The platform happes in the begning part of the stroke only, therefore it isn't a compression damping circuit which affects the full stroke of the shock.


    and

    Another way to create a platform is to have a fixed orifice in the shaft which is kept closed by the piston in the early part of the stroke and opened up at certain shaft position.

    I am reading that as saying that platforms are position sensitive. Perhaps I am misreading what you wrote, but they are not really position sensitive. The platform works the same throughout the whole stroke assuming the shock is at rest. The platform happens wherever in the stroke the shock has come to rest. That's why you can run 15% sag or 40% sag and still have a platform. If anything, the platform becomes stronger as the shock is set deeper in it's travel because most platform shocks use air chamber pressure to adjust the platform, and that pressure increases as the shock is compressed.

  10. #10
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    I'm a visual guy, so here are some pictures. The one graph shows the effect of platform damping.

    More platform = a greater initial force required before the shims 'snap' open and allow oil to start flowing (ignoring all bumps that don't create enough force to open the preloaded shims).


    More low-speed compression = taller 'nose' of the compression damping curve, but initial force to start damping crosses at zero force so it starts working under even really small bumps.


    Hopefully, they are worth a million posts... Graphs stolen and modified from Penske, so hopefully they are right.
    Last edited by bikerx40; 03-15-2006 at 06:36 PM.
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