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  1. #1
    fc
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    Felt Equilink revealed...

    . Well not yet but I've taken it on a few rides and now I'm taking the suspension apart to analyze it. I'm learning a few things.

    Any ideas on how I should bench test it? As you can see, I'm taking pieces out to isolate their role in the system. Suggestions?

    Obviously, I'm going to take it out on a bunch of rides. But there might be something to be learned by tinkering in the garage too.

    francois
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    I don't think there is a lot you can do to isolate the various parts and their roles in the suspension behavior. Without the link connected the lower linkage is free to rotate around the pivot on the back of the BB and the wheelbase of the bike will be free to extend and compress as you pedal and brake.

  3. #3
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    I'd be careful about what you do there, since there is no pivot at the dropout, removing the red link (and shock) allows the upper and lower rockers to counter rotate under the weight of the bike, spreading apart the seat and chain stay - and it doesn't take much to push them past their elastic limit can cause permanent damage. There is a reason the red link is there - it limits this motion.

  4. #4
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    Axle path map?

    What I'd like to see is an actual axle path. Could you maybe put a pen thru the dropouts and show us what the axle path looks like? Don't know what other steeds are in your stable, but it'd be really nice to compare it to other bikes' axle paths. (VPP, single pivot, short link, etc.)

  5. #5
    Amphibious Technologies
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    Quote Originally Posted by itsdoable
    I'd be careful about what you do there, since there is no pivot at the dropout, removing the red link (and shock) allows the upper and lower rockers to counter rotate under the weight of the bike, spreading apart the seat and chain stay - and it doesn't take much to push them past their elastic limit can cause permanent damage. There is a reason the red link is there - it limits this motion.
    If you remove the red link, it will essentially be like a DW link with a differect IC but a DW-like linkage, in any case. My uninformed guess is, that red link is a design around the DW link. Though the absence of a rear triangle will cause what you describe.
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  6. #6
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    My uninformed guess is, that red link is a design around the DW link.
    that's an extremely uninformed guess.

    DW did NOT invent parallel linkage, therefore it is NOT a copy of the actual DW link.
    what would rainbow unicorn do?

  7. #7
    fc
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    Quote Originally Posted by itsdoable
    I'd be careful about what you do there, since there is no pivot at the dropout, removing the red link (and shock) allows the upper and lower rockers to counter rotate under the weight of the bike, spreading apart the seat and chain stay - and it doesn't take much to push them past their elastic limit can cause permanent damage. There is a reason the red link is there - it limits this motion.
    I hear ya. Just fyi, I'm not going to ride it like this. I'm just disconnecting it to understand what it does.

    I've learned a little bit already. Just removing the shock and seeing the travel path and action is interesting. Then seeing how the pedal load affects the suspension is interesting too. I'll take some videos later.

    fc
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  8. #8
    Amphibious Technologies
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    Quote Originally Posted by ferday
    that's an extremely uninformed guess.

    DW did NOT invent parallel linkage, therefore it is NOT a copy of the actual DW link.
    Perhaps but your argument is illogical or fallacious (non sequitur to be specific).

    Wasn't it Earl MacPherson then adopted by Horst Leitner for bicycles then designed around by other bike manufacturers?

    You should read my post carefully. I DID NOT say it is a copy; I said it's DW-like; there's a diference. But for argument's sake, let's assume DW did not invent the parallel linkage, which he evidently did not, it certainly does not mean the Equilink minus the "red link" and assuming a similar resulting IC is not DW-like in function; now does it?
    Last edited by SCUBAPRO; 02-02-2007 at 11:46 AM.
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  9. #9
    fc
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    Quote Originally Posted by coolhandluchs
    What I'd like to see is an actual axle path. Could you maybe put a pen thru the dropouts and show us what the axle path looks like? Don't know what other steeds are in your stable, but it'd be really nice to compare it to other bikes' axle paths. (VPP, single pivot, short link, etc.)
    I'll take a video of the axle path. There's a ton of horses on the stable. I just need a lot of beer to entertain me while wrenching.

    fc
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  10. #10
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    Quote Originally Posted by francois
    I'll take a video of the axle path. There's a ton of horses on the stable. I just need a lot of beer to entertain me while wrenching.

    fc
    fc, my sincere apologies for the slight derailment. I too am interested in what you come up with. Thanks, in advance, for the info.
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  11. #11
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    Quote Originally Posted by francois
    Any ideas on how I should bench test it? As you can see, I'm taking pieces out to isolate their role in the system. Suggestions?
    I for one would love it if you would remove the rear shock and go for a long, technical downhill ride.

  12. #12
    MK_
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    Quote Originally Posted by francois
    As you can see, I'm taking pieces out to isolate their role in the system. Suggestions?
    You can safely bolt the shock back on, isolating it out of the system would make it impossible to ride test. And we all know how those work, anyhow.

    Seriously, however, it would be interesting to add to coolhandluchs' idea of the pen in the dropout and to plot the axle path without the red link bolted in. Comparing it to a DW linkage bike would reveal whether Scuba's suspisions are grounded.

    _MK

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  13. #13
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    I would be interested in what the spring rate of the flex pivot in situ. The design is over constrained ( 6 pivots) so it has to flex at the stay(designed to flex). which is why it may look like DW but I realy think it is a different animal.

    so you could take the shock off and use a fish scale to pull the wheel up thru its travel. would interest me to see the spring curve. probably too hard for you to do with out a jig of some sort.

  14. #14
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    a few more pics of the Virtue 2


    no trail time in yet as we've got a little too much snow. The manufacturing is tight However, the first thing i noticed down at the chainstay yoke was the very tight toleraces between moving links. So tight that it has NO dirt or mud shedding abilities. My fear is that a rock or pebble can get logged and actually do damage.

    We'll see once we get her in the dirt.



    later, Chad
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  15. #15
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    Quote Originally Posted by SCUBAPRO
    Perhaps but your argument is illogical or fallacious (non sequitur to be specific).

    Wasn't it Earl MacPherson then adopted by Horst Leitner for bicycles then designed around by other bike manufacturers?

    You should read my post carefully. I DID NOT say it is a copy; I said it's DW-like; there's a diference. But for argument's sake, let's assume DW did not invent the parallel linkage, which he evidently did not, it certainly does not mean the Equilink minus the "red link" and assuming a similar resulting IC is not DW-like in function; now does it?
    Try this animation of a a 6-bar design. You can click and drag the pivot points around to change dimentions.

    http://www.igorion.com/_hf_files/_st...tephenson.html

    There was quite a look in the MTBR Interbike threads at the Felt path and it turns out to be more round and long radius within the travel range, more FSR like, than the dw-Link's more elliptically shorter to longer radius shaped path.

    DW may have borrowed the cantilevered type dropout from earlier parallel link design, but dw-Link is not a parallel link design, actually 70 - 90 degree away from parallel, and doesn't ride at all like one. (Yes, I've ridden the parallel link design Rocket-88 too, not very impressive other than for short travel sprint racer use).

    There are many designs now obviously closely following the dw-Link invention, but the Equilink is probably not one of them.

  16. #16
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    Quote Originally Posted by derby
    Try this animation of a a 6-bar design. You can click and drag the pivot points around to change dimentions.

    http://www.igorion.com/_hf_files/_st...tephenson.html
    Nice

    I have a question about the chainstay / seatstay connection near the dropout in the Equilink - is it rigid? If no and assuming there is no significant flex on the chainstay or seatstay I can see only two reasons they put red link there:
    1) durability,
    2) marketing/ patent issues.

    Sorry.

    Quote Originally Posted by derby
    DW may have borrowed the cantilevered type dropout from earlier parallel link design, but dw-Link is not a parallel link design,
    What do you mean by "parallel link design"? Parallel upper and bottom linkages? Imho it is not so important unless both links have the same length. In the later case we got a straight line axle path.

    I do not say it is DW-link copy but imo it is another Outland-like design.

    Cheers
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  17. #17
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    What the path should look like

    The picture below comes from my playing around with a Stephenson 6-bar linkage program. The pivot positions are not perfect but pretty close. The red line between the left hand red dot and the point of the black angle above it would be the Felt axle path approximately.

    In real life the path should be slightly more rearward. But this diagram shows how straight it is--straighter than any other design I think.

    The thing that sets the Equilink apart from other linkages is that you can't calculate the anti-squat from simply knowing the axle path. The red link acts to short circuit the transmission of forces from axle to frame so that the bike has much more accelerational anti-squat than the axle path angle would indicate.

    The design will pretty much eliminate squat from acceleration but does very little to reduce squat from rider bounce. Some riders will like this; some will not.
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  18. #18
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    Quote Originally Posted by Marcin J.
    What do you mean by "parallel link design"? Parallel upper and bottom linkages? Imho it is not so important unless both links have the same length. In the later case we got a straight line axle path.
    oops, my mistake - I mixed IC with CC. Radius of the rear axle path will be equal to the length of these links.

    Cheers
    marcin

  19. #19
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    Quote Originally Posted by Steve from JH
    The picture below comes from my playing around with a Stephenson 6-bar linkage program. The pivot positions are not perfect but pretty close. The red line between the left hand red dot and the point of the black angle above it would be the Felt axle path approximately.

    In real life the path should be slightly more rearward. But this diagram shows how straight it is--straighter than any other design I think.

    The thing that sets the Equilink apart from other linkages is that you can't calculate the anti-squat from simply knowing the axle path. The red link acts to short circuit the transmission of forces from axle to frame so that the bike has much more accelerational anti-squat than the axle path angle would indicate.

    The design will pretty much eliminate squat from acceleration but does very little to reduce squat from rider bounce. Some riders will like this; some will not.
    I agree with your assessment. There is a mechanical bias between low and high leverage torque rates when combined in the same mechanism. A higher torque leverage will override the influence of low leverage rate. The Equilink design’s cross-link has higher leverage torque during acceleration tension but a much lower leverage torque relation during bump activation.

    During pedal and acceleration there is more horizontal tension directed across the straighter aligned lower stay and lower frame link and so the cross-link would be a higher leverage factor binding the activity of the upper frame link against vertical movement. But vertical input from bumps or rider bob would direct leverage torque along the upper stay and upper frame link, and then the cross-link is in a low torque relation mainly keeping the system from collapsing and not binding the suspension so as when there is horizontal tension.

    Looking at Francois’s picture at the top with the shock and cross-link disconnect reveals the answer to the question I earlier had about spring rate. I had earlier thought there might be a falling rate spring tension from rather stiff flex stays. (falling rate springs or shock damping produces a pedaling platform effect). But it appears that the rear stays flex fairly easily so there would be very little spring rate influence within the travel range.

    So there is something special about the Equilink. I look forward to demo riding one hopefully at Sea Otter this April. I’m curious if low pedal bob comes at a cost of mush deadening pedal performance like platform shocks do for monopivots compared to the lively and snappier performance of a more purely path based high anti-squat suspension such as VPP and the exceptionally well balanced dw-Link. I’m expecting the Equilink pedaling is also very snappy when the shock has minimal platform damping.

  20. #20
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    Quote Originally Posted by SCUBAPRO
    Wasn't it Earl MacPherson then adopted by Horst Leitner for bicycles then designed around by other bike manufacturers?
    Not wanting to get into a pissing match or even sure this is relevant info, but...Horst Leitner didn't actually design the Horst Link, it was Karl Nicolai that came up with the idea while he was working for Horst. Horst merely put into production Karl's design and everyone started calling it the Horst Link.

  21. #21
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    Check this out...

    Felt's inspiration?

  22. #22
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    Kavik - I just read this too:

    http://thylacinecycles.com/wordpress/?p=50

    I felt a bit queasy afterward.

  23. #23
    TM1
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    I'm a little confused with this ...

    as far as I can tell, if you remove the red link you get a DW-link suspension. the same location of pivots and links.
    now, the DW-link do not have any flex in it when it comes to path movement. so the red link have NO part in the linkage or path.

    you can not say that the red link is responsible for the rotation of the links because they will rotate just the same without the red link.

    correct me if I'm wrong.

  24. #24
    The Ancient One
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    Quote Originally Posted by TM1
    as far as I can tell, if you remove the red link you get a DW-link suspension. the same location of pivots and links.
    now, the DW-link do not have any flex in it when it comes to path movement. so the red link have NO part in the linkage or path.

    you can not say that the red link is responsible for the rotation of the links because they will rotate just the same without the red link.

    correct me if I'm wrong.
    You're wrong.

    The two rear links, seatstay and chainstay, are carbon fiber and designed to flex. If you removed the red link, the mechanism would be unstable. The lower short link would be free to move without activating the shock as the rear stays flexed under the rider's weight or from hitting bumps.

    If you connect the red link the rear stays have to flex (or have an extra pivot as in the longer travel version) because the two rear pivots move apart and come together as the suspension cycles.

    If the rear end is rigid and there is no red link, then you do have a DW type linkage.
    "Don't criticize what you can't understand."

  25. #25
    Doesntplaywellwithmorons!
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    Steve and every other felt shill will of course conveniently continue to ignore the kavik evidence and the fact that felt blatantly ripped the design.
    I don't post to generate business for myself or make like I'm better than sliced bread

  26. #26
    conjoinicorned
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    Quote Originally Posted by DeeEight
    Steve and every other felt shill will of course conveniently continue to ignore the kavik evidence and the fact that felt blatantly ripped the design.

    from who? DW?

    umm...whatever.
    what would rainbow unicorn do?

  27. #27
    TM1
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    then, wrong I am NOT

    Quote Originally Posted by Steve from JH
    You're wrong.

    The two rear links, seatstay and chainstay, are carbon fiber and designed to flex. If you removed the red link, the mechanism would be unstable. The lower short link would be free to move without activating the shock as the rear stays flexed under the rider's weight or from hitting bumps.

    If you connect the red link the rear stays have to flex (or have an extra pivot as in the longer travel version) because the two rear pivots move apart and come together as the suspension cycles.

    If the rear end is rigid and there is no red link, then you do have a DW type linkage.
    felt is saying it is a special suspension design but basicaly, it is a DW with carbon rear.
    notice that any DW (or VPP for that mater) design has a bar that "closes" the rear triangle. in the felt design it is replaced with a red HOT link and 4 more pivots ...

    as I said. it's a DW.

  28. #28
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    Quote Originally Posted by TM1
    felt is saying it is a special suspension design but basicaly, it is a DW with carbon rear.
    notice that any DW (or VPP for that mater) design has a bar that "closes" the rear triangle. in the felt design it is replaced with a red HOT link and 4 more pivots ...

    as I said. it's a DW.
    Uhh there's a large difference between the DW vertical member that connects with the rear triangle behind the rocker and swing arms, with no pivots on the actual member, AND the felt design which has the vertical member pivoting on the rocker and swing links.

    Personally I like the DW design more, because it isn't relying on bending materials for the suspension to compress, that's just a retarded design. Save the conflicting geometry for the WalMart bikes (they do this crap too).

    Regardless of Science, once again does it ride good? Most of the reports I've read say is pedals well but doesn't absorb bumps very well. With conflicting geometry and bending carbon fiber uner compression it doesn't surprise me that it has no give on small bumps. In which case, I would rather have a lighter hardtail!

    My opinion would be completely different if there was a pivot in the triangle rather than bending chain and seat stays.

  29. #29
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    Quote Originally Posted by TM1
    felt is saying it is a special suspension design but basicaly, it is a DW with carbon rear.
    notice that any DW (or VPP for that mater) design has a bar that "closes" the rear triangle. in the felt design it is replaced with a red HOT link and 4 more pivots ...

    as I said. it's a DW.
    Nope. It's not.

    They were showing a proto with 6" of travel, and sporting an additional pivot near the dropout. Remove the red link on that bike and it becomes a noodle.

    BTW, you wrote "<i>as I said. it's a DW.</i>" Are you referring to the appearance? Or the function?

    I demoed the Three, but had some setup issues that I couldn't resolve in the time I had available. It is an active rear end, and it climbed well, but I have no idea how the shock was set up, the fork was soft and my cockpit was too far forward, so I had a rather unpleasant ride.
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  30. #30
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    Quote Originally Posted by DeeEight
    Steve and every other felt shill will of course conveniently continue to ignore the kavik evidence and the fact that felt blatantly ripped the design.
    The dude should have made the Felt guys sign an NDA. I obviously don't know if he did or did not, but if he didn't, then he pretty much screwed up and that's that. The world's a tough place.

  31. #31
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    Quote Originally Posted by ferday
    from who? DW?

    umm...whatever.
    No...god... the equilink is NOT a ripoff of the DW-link... its a ripoff of a Kavik design shown at Interbike FOUR years ago and which Felt sent people to investigate and then claimed "they weren't really interested in".

    This link... http://www.tsunamirock.com/images/se...t/link_ani.htm shows the Kavik suspension actuation including the wheel path of the axle and the original frame shown at Interbike.

    Or read this... http://thylacinecycles.com/wordpress/?p=50
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  32. #32
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    Quote Originally Posted by DeeEight
    No...god... the equilink is NOT a ripoff of the DW-link... its a ripoff of a Kavik design shown at Interbike FOUR years ago and which Felt sent people to investigate and then claimed "they weren't really interested in".
    whew....thanks d8. you of all people i didn't think was on the DW bandwagon, that guy's followers are freaking zealots.

    nice link btw, i wonder why no-one else is making the kavik design? looks neat, i like the lower link better than the one on the felt.
    what would rainbow unicorn do?

  33. #33
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    Quote Originally Posted by DeeEight
    No...god... the equilink is NOT a ripoff of the DW-link... its a ripoff of a Kavik design shown at Interbike FOUR years ago and which Felt sent people to investigate and then claimed "they weren't really interested in".

    This link... http://www.tsunamirock.com/images/se...t/link_ani.htm shows the Kavik suspension actuation including the wheel path of the axle and the original frame shown at Interbike.

    Or read this... http://thylacinecycles.com/wordpress/?p=50
    Word

  34. #34
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    Quote Originally Posted by DeeEight
    Steve and every other felt shill will of course conveniently continue to ignore the kavik evidence and the fact that felt blatantly ripped the design.
    That's the guerilla marketing of felt and another company steve from jh supports as well.

  35. #35
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    Quote Originally Posted by ferday
    nice link btw, i wonder why no-one else is making the kavik design? looks neat, i like the lower link better than the one on the felt.
    Because Kavik's genius, got out of the bike industry a few years ago (let's face it, a genius welder/fabricator can scrape by in the bike world, or support a major family in another field of work) and didn't really pursue the design himself. If you look at the bike pic shown at Interbike, you'll see the dropouts are VERY nice looking. Kavik dropouts were used by several other framebuilders (like Peyto Cycles) because with one dropout design/mount standard, you can alter a frame to different configurations in a couple minutes (singlespeed, track, disc compatible, etc). Kavik's leaving the bike world cost these other framebuilders these amazing dropouts. Oddly enough, another brand ripped the design for the dropouts and marketed them as their own invention.
    I don't post to generate business for myself or make like I'm better than sliced bread

  36. #36
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    where is kavik now and what is he doing?

  37. #37
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    The pivot structure that extends beneath the bb reminds me of the early Outland designs. Clearly not a VPP, but the point is even though they have similar rocker and tension links, the lower pivot structure fairly different...different enough to make an arguement with really good legal representation... and in this business sometimes that's all it takes.

    That does not change what's right or how who got what idea. But since when does what's right have anything to do with law?
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  38. #38
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    Quote Originally Posted by Fat Elvis
    The dude should have made the Felt guys sign an NDA. I obviously don't know if he did or did not, but if he didn't, then he pretty much screwed up and that's that. The world's a tough place.
    The dude was showing his design. He didn't have to disclose squat for them to take a few photos and replicate. It probably took them this long to reverse engineer it. NDA would not help a whole lot. But yes, the world is a tough place and biking industry is particularly viscous. Take the formidable Horst Link for example. If the rumors are true it wasn't even invented by Horst Leitner, simply brought to American from Germany and patented here, then stolen over and over.

    _MK

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  39. #39
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    Nicolai

    Quote Originally Posted by MK_
    The dude was showing his design. He didn't have to disclose squat for them to take a few photos and replicate. It probably took them this long to reverse engineer it. NDA would not help a whole lot. But yes, the world is a tough place and biking industry is particularly viscous. Take the formidable Horst Link for example. If the rumors are true it wasn't even invented by Horst Leitner, simply brought to American from Germany and patented here, then stolen over and over.

    _MK
    Not really brought "here", but close. Nicolai http://www.nicolai.net/ was working for Horst when he developed the "Horst" link.
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  40. #40
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    Quote Originally Posted by DeeEight
    No...god... the equilink is NOT a ripoff of the DW-link... its a ripoff of a Kavik design shown at Interbike FOUR years ago and which Felt sent people to investigate and then claimed "they weren't really interested in".

    This link... http://www.tsunamirock.com/images/se...t/link_ani.htm shows the Kavik suspension actuation including the wheel path of the axle and the original frame shown at Interbike.

    Or read this... http://thylacinecycles.com/wordpress/?p=50
    Yes, the Felt design works very similar to how the Kavik animation shows. It is a 6-bar 7 pivot suspension design (not including axles as pivots).

    If Kavik has a prior patent it might be infringing, depending on the description of what is claimed. The angle of the lower link is so different I wouldn’t call it a copy, the Kavik probably has more acute semi-active torque sensitive effect.

    The Felt and Kavik produce chain torque sensitive platform effect. It is another type of semi-active suspension, in that it semi-locks-out compression compliance only when there is pedal torque.

    The dw-Link and all 4-bar/4pivot designs are for the most part path based acceleration squat balanced (not so well balanced in most cases).

    The Kavik and Felt designs are about as far in contrast from dw-Link as possible. Dw-Link is classified as fully active the Felt is in a class of semi-active designs, including hign pivot swingarm, URT, and semi-URT (iDrive/Maverick) types.

  41. #41
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    Lets call it like it is... A ripoff.

    Quote Originally Posted by marcus_dukakis
    http://thylacinecycles.com/wordpress/?p=50

    I felt a bit queasy afterward.
    Me too. Thats straight up FUCT, whether Felt managed to slip under the "10% rule" or not. I was kind of curious about the Equilink myself. Now, not so much.

    I hate biters and ripoff artists.
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  42. #42
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    Quote Originally Posted by benja55
    Me too. Thats straight up FUCT, whether Felt managed to slip under the "10% rule" or not. I was kind of curious about the Equilink myself. Now, not so much.

    I hate biters and ripoff artists.
    Is making the link red constitute 10%? Come on Felt! Make it right.

  43. #43
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    Quote Originally Posted by Davide
    Not really brought "here", but close. Nicolai http://www.nicolai.net/ was working for Horst when he developed the "Horst" link.
    once again, davide bends the truth.

  44. #44
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    Disagree

    Quote Originally Posted by derby

    The Felt and Kavik produce chain torque sensitive platform effect. It is another type of semi-active suspension, in that it semi-locks-out compression compliance only when there is pedal torque.

    The dw-Link and all 4-bar/4pivot designs are for the most part path based acceleration squat balanced (not so well balanced in most cases).

    The Kavik and Felt designs are about as far in contrast from dw-Link as possible. Dw-Link is classified as fully active the Felt is in a class of semi-active designs, including hign pivot swingarm, URT, and semi-URT (iDrive/Maverick) types.
    I see nothing in the Felt or Kavik design that would make them be "semi-active". Through the first half or so of the travel path there would be much less pedal feedback than on a DW link. And it's pedal feedback that reduces compliance on regular rear suspension bicycles. On URT's and semi-URT's it's the rider's weight on the swingarm that reduces compliance.

    I know, I know, you can't feel the feedback on your DW-link. But I'm not talking about perception here; I'm talking about mechanically measurable reverse rotation of the cranks accompanying suspension travel. If I rub my finger around the inside of the toilet bowl, I can't perceive any bacteria on it. But theoretical considerations alone are enough to keep me from then sticking that finger in my mouth!
    "Don't criticize what you can't understand."

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    Quote Originally Posted by Steve from JH
    I see nothing in the Felt or Kavik design that would make them be "semi-active". Through the first half or so of the travel path there would be much less pedal feedback than on a DW link. And it's pedal feedback that reduces compliance on regular rear suspension bicycles. On URT's and semi-URT's it's the rider's weight on the swingarm that reduces compliance.

    I know, I know, you can't feel the feedback on your DW-link. But I'm not talking about perception here; I'm talking about mechanically measurable reverse rotation of the cranks accompanying suspension travel. If I rub my finger around the inside of the toilet bowl, I can't perceive any bacteria on it. But theoretical considerations alone are enough to keep me from then sticking that finger in my mouth!
    get your royalty check from Felt yet?

  46. #46
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    Self defense

    I haven't been posting much recently. The main reason is that I'm fed up with the way what I intend to be purely intellectual discussions keep turning into personal attacks.

    D-8 has called me a "shill". Thylacine says the thread I started last year about the Felt bike was "guerilla marketing". Both of these accusations imply that I'm benefitting financially somehow from promoting Felt's product.

    Well first, I'm not promoting it. I'm simply trying to analyze how it ought to work theoretically. For all I know it might ride like crap.

    Second, I never have, do not now, and undoubtedly never will, benefit financially from any aspect of the bicycle business. Neither Thylacine nor D-8 can say the same. I'm simply a daily mountain bike rider who has an arm-chair interest in suspension theory. I've been studying it for the last 7 years or so.

    I didn't know anything about the Kavik bike until the last few days. It does indeed look like he had the idea first.

    You can go back through all the posts I've made on this subject and substitute "Kavik" for "Felt Equilink". It's fine by me.
    "Don't criticize what you can't understand."

  47. #47
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    Quote Originally Posted by benja55
    Me too. Thats straight up FUCT, whether Felt managed to slip under the "10% rule" or not. I was kind of curious about the Equilink myself. Now, not so much.

    I hate biters and ripoff artists.
    That's jumping a bit fast to conclusions, if you ask me. What if Felt was already working on a similar design concept as Kavik when they first met? It's perfectly possible. Certainly, if they found out a competitor was working in the same area, they would patent their work as quickly as possible to protect themselves.

  48. #48
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    Quote Originally Posted by Steve from JH
    I haven't been posting much recently. The main reason is that I'm fed up with the way what I intend to be purely intellectual discussions keep turning into personal attacks.

    D-8 has called me a "shill". Thylacine says the thread I started last year about the Felt bike was "guerilla marketing". Both of these accusations imply that I'm benefitting financially somehow from promoting Felt's product.

    Well first, I'm not promoting it. I'm simply trying to analyze how it ought to work theoretically. For all I know it might ride like crap.

    Second, I never have, do not now, and undoubtedly never will, benefit financially from any aspect of the bicycle business. Neither Thylacine nor D-8 can say the same. I'm simply a daily mountain bike rider who has an arm-chair interest in suspension theory. I've been studying it for the last 7 years or so.

    I didn't know anything about the Kavik bike until the last few days. It does indeed look like he had the idea first.

    You can go back through all the posts I've made on this subject and substitute "Kavik" for "Felt Equilink". It's fine by me.
    I really dig the tech discussions. Steve, remember, suspension theory and thrashing on the trail will nearly always produce a conflicting result. Throw in opinions, and the pure science gets all muddied up. Stay on track, you are getting there.

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    Quote Originally Posted by Fat Elvis
    That's jumping a bit fast to conclusions, if you ask me. What if Felt was already working on a similar design concept as Kavik when they first met? It's perfectly possible. Certainly, if they found out a competitor was working in the same area, they would patent their work as quickly as possible to protect themselves.
    Their time table, according to their press releases and issue of patent, aren't early enough. I have no doubt they had looked at a lot of designs...

  50. #50
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    Quote Originally Posted by Steve from JH
    If you connect the red link.......
    Don't you mean the silver link?

    No longer member of the bike industry nor society, so don't hassle me.

  51. #51
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    Quote Originally Posted by Thylacine
    Don't you mean the silver link?

    Yes. Change "red" to "silver", as well as changing "Felt" to "Kavik" in all my posts.
    "Don't criticize what you can't understand."

  52. #52
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    Quote Originally Posted by Kavik
    Their time table, according to their press releases and issue of patent, aren't early enough. I have no doubt they had looked at a lot of designs...
    Sure, but what about their internal documentation, such as invention disclosures? I'm not saying I think that this is the case, I'm just saying it's possible. Independant companies work on similar design concepts all the time. Hell, there's only so many ways to suspend the rear wheel of a bicycle.

  53. #53
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    Quote Originally Posted by Steve from JH
    Second, I never have, do not now, and undoubtedly never will, benefit financially from any aspect of the bicycle business. Neither Thylacine nor D-8 can say the same.
    Are you serious? You think attempting to do the right thing and stand up for people I respect has financial benefits?

    I'm an Industrial Designer. IP is my life, and my livelyhood. Whenever anyone disregards the ethics of ideas, that's the largest dis' you can give someone of my profession.

    Brian is a friend and colleague. Whenever anyone disregards that, that's the largest dis' you can someone who considers themselves their friend and colleague.

    So, if you wanted to know my motivation for bringing this to everyone's attention, there they are.
    No longer member of the bike industry nor society, so don't hassle me.

  54. #54
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    Quote Originally Posted by Fat Elvis
    Sure, but what about their internal documentation, such as invention disclosures? I'm not saying I think that this is the case, I'm just saying it's possible. Independant companies work on similar design concepts all the time. Hell, there's only so many ways to suspend the rear wheel of a bicycle.
    Anything is possible. However, you have a company that has no suspension engineers, has no history designing suspension, actually went out to Arizona after seeing the Kavik at Interbike, and then you have the timeframe of three years to play catch-up before releasing a bike that have a VERY unique linkage configuration that has no precedent.

    How many other companies have come out of nowhere with a distinctive and unique suspension design, without mentioning or crediting a suspension designer? How many have done so with a design with such compelling prior art?
    No longer member of the bike industry nor society, so don't hassle me.

  55. #55
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    Quote Originally Posted by Thylacine
    Are you serious? You think attempting to do the right thing and stand up for people I respect has financial benefits?
    I didn't mean that. I simply meant you're in the bike business and I'm not.

    If Brian came up with the idea first--and it looks like he did--he should get the credit.
    "Don't criticize what you can't understand."

  56. #56
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    Quote Originally Posted by Steve from JH
    I haven't been posting much recently. The main reason is that I'm fed up with the way what I intend to be purely intellectual discussions keep turning into personal attacks.

    D-8 has called me a "shill". Thylacine says the thread I started last year about the Felt bike was "guerilla marketing". Both of these accusations imply that I'm benefitting financially somehow from promoting Felt's product.

    Well first, I'm not promoting it. I'm simply trying to analyze how it ought to work theoretically. For all I know it might ride like crap.



    I didn't know anything about the Kavik bike until the last few days. It does indeed look like he had the idea first.

    You can go back through all the posts I've made on this subject and substitute "Kavik" for "Felt Equilink". It's fine by me.
    Hey Steve,

    What was the title of the thread that you put up in NO LESS THAN FOUR FORUMS, which necessitated all being merged into one? What was the name of the thread you put up?

    How many different threads devoted to the equilink have you now put up?
    Last edited by Jerk_Chicken; 04-17-2007 at 05:27 PM.

  57. #57
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    Quote Originally Posted by Jerk_Chicken
    Hey Steve,

    What was the title of the thread that you put up in NO LESS THAN FOUR FORUMS, which necessitated all being merged into one? What was the name of the thread you put up?
    From my perspective I find great irony in the title of this thread.

    However, it was not started by Steve. It was started buy a guy who is stoked about his new ride. These fellas are just trying to demystify the way the linkage interacts with all of the forces imposed on it.

    If bike tech were boring, and the bike business was a walk in the park, then all this site would talk about is cool trails and fitness.

    Felt has done a fine job with their execution. The bike looks good. It is a shame they missed some pretty important elements in their final revision, but I'm sure they'll figure it out...

  58. #58
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    Actually, several months ago, steve was so stoked about a design, he posted all over the board in spambot fashion. The title proudly proclaimed the equilink the "holy grail" of mountain biking.

    His credibility is questionable at the very least. He argues incorrect points to the end, mystifying people with ******** to get the suspension flavor of the week out there.

  59. #59
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    "Holy Grail" was meant ironically.
    "Don't criticize what you can't understand."

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    Okay people, let's not scapegoat Steve here. He might be a Patsy, but he's not the Perp.
    No longer member of the bike industry nor society, so don't hassle me.

  61. #61
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    Quote Originally Posted by Steve from JH
    I see nothing in the Felt or Kavik design that would make them be "semi-active". Through the first half or so of the travel path there would be much less pedal feedback than on a DW link. And it's pedal feedback that reduces compliance on regular rear suspension bicycles. On URT's and semi-URT's it's the rider's weight on the swingarm that reduces compliance.

    I know, I know, you can't feel the feedback on your DW-link. But I'm not talking about perception here; I'm talking about mechanically measurable reverse rotation of the cranks accompanying suspension travel. If I rub my finger around the inside of the toilet bowl, I can't perceive any bacteria on it. But theoretical considerations alone are enough to keep me from then sticking that finger in my mouth!
    Active suspensions do not increase in compression resistance (or “stiffness”) when pedaling hard. Semi-active designs do increase in compression resistance when pedaling hard.

    The dw-Link neither increases nor decreases in stiffness when seated, there is no “feedback” because the suspension doesn’t move from seated pedaling. And it only softens in resistance very slightly from standing and stomping the pedals, but relaxes completely from bump-induced compression (if the commonly over-damped shocks these days allow). From riding comparisons the dw-Link is noticeably better balanced for any trail condition, smooth or rough, than any other design.

    The Felt and prior Kavik design are torque sensitive. The horizontal direction of gear and chain linked torque between the BB and rear axle squeezes the linkage. And the torque “load” tension bias across the lower links and acute angle of the lower short link line crossing the line of torque tugs the coupling-link (Felt calls “Equilink”) preventing the lightly tensioned upper short link from rotating forward from downward directional input at the pedal surface. This is classic semi-active pedal induced suspension stiffening. There is also no pedal feedback since the suspension doesn’t move from pedaling.

    The largest difference in efficiency is in the bumps. The semi-active 6-bar design remains compression resistant when maintaining or increasing pedaling cadence, however the active balanced dw-Link relaxes compression resistance to nil when pedaling in bumps. DW-link Pedal feedback is softer than a hardtail or URT in bumps. I haven’t tested the Felt, the semi-active stiffer suspension in bumps may produce no more momentum in bumps.

    These 6-bars are clever designs, like URT in effect but turned sideways.

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    let me cite from felt's patent...


    What is claimed is:

    1. A suspension system comprising: a) a front frame; b) a rear frame; c) an upper link pivotably attached to the front frame at a front upper pivot point and the rear frame at a rear upper pivot point, the front and rear upper pivot points defining an upper base line; d) a lower link pivotably attached to the front frame at a front lower pivot point and the rear frame at a rear lower pivot point, the front and rear lower pivot points defining a lower base line; and e) a tie link pivotably attached to the upper link at a top pivot point and the lower link at a bottom pivot point, the top and bottom pivot points disposed between the upper base line and the lower base line.

    ...more claims to come
    the way that claim is written it does not interfere with kavik's system. i have not been a supporter of felt's marketing, but this time i believe they just did what almost everybody in the bicycle industry does. they got their inspiration from one design and thought about what they could make from that inspiration without infringing the original idea. finally they came up with their own design.

    in the end their design differs from kavik's design like let's say vpp differs from ict. nobody claims vpp was stolen from fsr even though both systems share the number of four suspension members. with kavik/felt it's the exact same situation, only now we are talking about six suspension members. i am sure we are going to see more designs with six bar linkages in different layouts in the future.

  63. #63
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    Quote Originally Posted by Thylacine
    Anything is possible. However, you have a company that has no suspension engineers, has no history designing suspension, actually went out to Arizona after seeing the Kavik at Interbike, and then you have the timeframe of three years to play catch-up before releasing a bike that have a VERY unique linkage configuration that has no precedent.
    You don't necessarily need engineers on staff to come up with a new design. They could very well have sub-contracted the design out, and bought out all IP rights. Hell, there are plenty of starving grad students out there, I'm sure that if you waved $20K or so in front of their noses you could get someone to come up with a new design. Again, I don't necessarily believe that this is the case, but I'm not a huge fan of jumping to conclusions when I don't have all the information, or the available info is lacking. I also do not like all the nonsense being said about SfJH. The dude is a mountain biker who likes to geek out on suspension technology. There's nothing more to it than that. He's been posting here forever, and his debates with Derby et. al. can be pretty entertaining, even if, like me, you have no idea what the hell they are talking about.

  64. #64
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    Quote Originally Posted by Thylacine
    Okay people, let's not scapegoat Steve here. He might be a Patsy, but he's not the Perp.
    So he's the lee harvey oswald of felt's marketing machine ?
    I don't post to generate business for myself or make like I'm better than sliced bread

  65. #65
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    Quote Originally Posted by Fat Elvis
    I also do not like all the nonsense being said about SfJH. The dude is a mountain biker who likes to geek out on suspension technology. There's nothing more to it than that. He's been posting here forever, and his debates with Derby et. al. can be pretty entertaining, even if, like me, you have no idea what the hell they are talking about.
    That pretty well sums it up.

    Although I usually understand what I myself am talking about, I often have trouble with Derby.
    "Don't criticize what you can't understand."

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    Quote Originally Posted by DeeEight
    So he's the lee harvey oswald of felt's marketing machine ?
    PERHAPS. These companies hope someone like Steve comes around to tout their new tech before he, or anyone else has had a chance to ride the designs, re: Felt Equilink the Holy Grail.

  67. #67
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    Quote Originally Posted by Jerk_Chicken
    PERHAPS. These companies hope someone like Steve comes around to tout their new tech before he, or anyone else has had a chance to ride the designs, re: Felt Equilink the Holy Grail.
    I seriously doubt that any company could survive if they're marketing plan was to hope that some dude somewhere out there on a message board would praise their technology. That is just absurd.

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    Nor did I say that.

    There are lots of bike companies out there that have great businesses based on word of mouth, however.

    One can't underestimate the power of the internet. To discount it would make an advertising exec obsolete because they would be stuck in the 80's.

  69. #69
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    Quote Originally Posted by Steve from JH

    The thing that sets the Equilink apart from other linkages is that you can't calculate the anti-squat from simply knowing the axle path. The red link acts to short circuit the transmission of forces from axle to frame so that the bike has much more accelerational anti-squat than the axle path angle would indicate.

    Hey Steve, I hate being the guy that always corrects you on this stuff, it is really not my intent to keep doing this to you, nothing personal, just trying to keep the facts straight.

    If you know axle path, then you CAN calculate anti-squat. There is no magic in the system. The axle path is what it is, and if you know it then you can calculate anti-squat.

    I just read about the Kavik thing, that's sad.
    dw★link
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  70. #70
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    Me 2...

    Quote Originally Posted by Steve from JH
    I often have trouble with Derby.
    I'm smarter then the average bear, but periodically I still get lost in Derby's tomes.

    Still, I appreciate all the info and knowledge that gets dropped these boards.

    As for the Kavik/Felt thing.... Yeah, that still seems too close for comfort. I know thats how much of business gets done but its still weak IMHO. My respect goes out to those who actually design their own shitt. Even more so to those who design and then BUILD IT.
    - -benja- -

  71. #71
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    Quote Originally Posted by _dw
    Hey Steve, I hate being the guy that always corrects you on this stuff, it is really not my intent to keep doing this to you, nothing personal, just trying to keep the facts straight.

    If you know axle path, then you CAN calculate anti-squat. There is no magic in the system. The axle path is what it is, and if you know it then you can calculate anti-squat.

    I just read about the Kavik thing, that's sad.
    And I hate to be so presumptious as to correct you, but I will.

    On other designs, including yours, you can calculate the absolute amount of anti-squat if you know three things: the location of the rear contact patch, the extended chain line, and the axle path normal or perpendicular line.

    To get the anti-squat expressed as a percentage you also need to know the height of the center of mass and the wheel base. But you know all this.

    On the Felt design (and presumably on the Kavik original but I haven't worked it out yet) the above is not true. There will be much more anti-squat than would be indicated by knowing the above three things.

    That's what makes it interesting.

    I predict that some day you will come to agree.
    "Don't criticize what you can't understand."

  72. #72
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    Bold!

    Quote Originally Posted by Steve from JH
    I predict that some day you will come to agree.
    Hmmmm... Don't bring a knife to a gun fight!
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  73. #73
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    Quote Originally Posted by Thylacine
    Anything is possible. However, you have a company that has no suspension engineers, has no history designing suspension, actually went out to Arizona after seeing the Kavik at Interbike, and then you have the timeframe of three years to play catch-up before releasing a bike that have a VERY unique linkage configuration that has no precedent.

    How many other companies have come out of nowhere with a distinctive and unique suspension design, without mentioning or crediting a suspension designer? How many have done so with a design with such compelling prior art?
    Well 3 companies easily come to mind who have blatantly copied prior design and claimed it as original.

    Ellsworth’s copy of Turner Suspension prior production design. And BMC’s and Giant’s copies of prior production DW-LINK design.

  74. #74
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    Quote Originally Posted by derby
    Well 3 companies easily come to mind who have blatantly copied prior design and claimed it as original.

    Ellsworth’s copy of Turner Suspension prior production design. And BMC’s and Giant’s copies of prior production DW-LINK design.
    Chumba's EVO looks like falling into the ICT patent... however, the shock position is completely different.
    Check my Site

  75. #75
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    Quote Originally Posted by Warp
    Chumba's EVO looks like falling into the ICT patent... however, the shock position is completely different.
    By my analysis the chain line does run through the IC at squat in a 32/20 gear combination. But to fall within the ICT patent it would have to stay quite close to that with travel, and it doesn't.
    "Don't criticize what you can't understand."

  76. #76
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    Is this the Kona guy?

    Quote Originally Posted by Jerk_Chicken
    once again, davide bends the truth.
    Does anybody knows who this idiot is? Is he the same guy who sold is Turner for a Kona?

    Can he maybe please tell everybody what is "the truth" regarding the development of the Horst?
    Last edited by Davide; 04-18-2007 at 08:45 PM.

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    1. Don't have a Spot, thanks.
    2. Love my RFX. It's my dreambike.
    3. It's got the non-horst rear end
    4. I came off a Horst rear end and elected to go with the non-horst.

    And Davide, if you're forgetting already, you can't tell the correct story on the development of the Horst Link.

  78. #78
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    actually it's quite simple:

    -- the equilink system has a fixed axle path, i think we all agree on this.

    so now let's leave consensus...

    -- whenever there is a fixed axle path, that path will reflect all parameters of any kinematical system that connects the rear axle to the main frame
    -- since the equilink also has a fixed axle path, any effects the red link has on the system will also be inherited in the wheel path, therefore making it impossible that this link can later additionally affect the system


    steve, if you took the effort to perform actual force calculations on the stephenson linkage that the equilink is, you would easily find out that, just as with any other system, only forces perpendicular to the axle path will not move the system.
    to be more precice, in the particualar implentation of bicycle suspension, the force component parallel to the axle path would have to be constant even with varying chain force, in order not to induce squat.

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    Quote Originally Posted by igorion
    actually it's quite simple:

    -- the equilink system has a fixed axle path, i think we all agree on this.

    so now let's leave consensus...

    -- whenever there is a fixed axle path, that path will reflect all parameters of any kinematical system that connects the rear axle to the main frame
    -- since the equilink also has a fixed axle path, any effects the red link has on the system will also be inherited in the wheel path, therefore making it impossible that this link can later additionally affect the system


    steve, if you took the effort to perform actual force calculations on the stephenson linkage that the equilink is, you would easily find out that, just as with any other system, only forces perpendicular to the axle path will not move the system.
    to be more precice, in the particualar implentation of bicycle suspension, the force component parallel to the axle path would have to be constant even with varying chain force, in order not to induce squat.
    The axle path is not the only thing that is under influence of forces...

  80. #80
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    Quote Originally Posted by Steve from JH
    And I hate to be so presumptious as to correct you, but I will.
    Steve, what are you talking about? You're talking in circles... Here we go again, yay!

    Quote Originally Posted by Steve from JH
    On other designs, including yours, you can calculate the absolute amount of anti-squat if you know three things: the location of the rear contact patch, the extended chain line, and the axle path normal or perpendicular line.

    To get the anti-squat expressed as a percentage you also need to know the height of the center of mass and the wheel base. But you know all this.
    Welll sort of. This is basically the fundamental physics on which everything that I have developed is based.

    I have no clue what you are talking about as "absolute anti-squat". Anti squat can only be quantified as a percentage, and in order to have any idea how much anti-squat you have you need to know center of mass location, vehicle angle in relation to gravity, wheelbase, in addition to driving force, chain force, and contact patches. On a side note, I find it hilarious that you now preach this when 4 years ago you fought me tooth and nail on these very forums saying that this wasn't the case. Glad to see that you have it somewhat worked out.

    Quote Originally Posted by Steve from JH
    On the Felt design (and presumably on the Kavik original but I haven't worked it out yet) the above is not true. There will be much more anti-squat than would be indicated by knowing the above three things.

    That's what makes it interesting.
    You are completely mistaken on this point. How you are arriving to this conclusion is beyond me, but I suggest taking a college level class in kinematics. The analysis is not beyond what a first year student would know after a smemster of study.

    Quote Originally Posted by Steve from JH
    I predict that some day you will come to agree.
    Not likely unless there is some cataclysmic change that happens in the universe which completely changes all areas of physics. At that point I think we'll have bigger things to worry about.

    I am done with this. Good luck Steve, glad to see that you've come part way in the last couple years.

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  81. #81
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    Quote Originally Posted by Kavik
    The axle path is not the only thing that is under influence of forces...
    Yes, in essence it is, although I would word the statement differently to more accurately describe the situation. Anyways, for what its worth, I know pretty well what you must be feeling right now.
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  82. #82
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    Quote Originally Posted by igorion
    actually it's quite simple:

    -- the equilink system has a fixed axle path, i think we all agree on this.

    so now let's leave consensus...

    -- whenever there is a fixed axle path, that path will reflect all parameters of any kinematical system that connects the rear axle to the main frame
    -- since the equilink also has a fixed axle path, any effects the red link has on the system will also be inherited in the wheel path, therefore making it impossible that this link can later additionally affect the system


    steve, if you took the effort to perform actual force calculations on the stephenson linkage that the equilink is, you would easily find out that, just as with any other system, only forces perpendicular to the axle path will not move the system.
    to be more precice, in the particualar implentation of bicycle suspension, the force component parallel to the axle path would have to be constant even with varying chain force, in order not to induce squat.
    Listen to this man. He speaks the truth.
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    Quote Originally Posted by _dw
    Anyways, for what its worth, I know pretty well what you must be feeling right now.
    Thanks Dave.

    The Felt design (specifically their lower link configuration) differs from mine, and so does the resulting function. I built mine to address forces that theirs does not. I don't want to give away too much information, because the armchair analysis of this stuff is fascinating.

  84. #84
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    Quote Originally Posted by _dw
    I have no clue what you are talking about as "absolute anti-squat". Anti squat can only be quantified as a percentage, and in order to have any idea how much anti-squat you have you need to know center of mass location, vehicle angle in relation to gravity, wheelbase, in addition to driving force, chain force, and contact patches. On a side note, I find it hilarious that you now preach this when 4 years ago you fought me tooth and nail on these very forums saying that this wasn't the case. Glad to see that you have it somewhat worked out.
    Here's what I meant by "absolute anti-squat". If you didn't know the location of the center of mass or the length of the wheelbase but did know the three things I listed, you could still calculate what percentage of the thrusting force at the contact patch would produce downward force at the axle. I'm assuming a bike on level ground.

    At the time I first argued with you (on Ridemonkey and I was right by the way) I had already come to accept all the kinematic principles we agree on. So your statement is either a lie or a mistake.


    You are completely mistaken on this point. How you are arriving to this conclusion is beyond me, but I suggest taking a college level class in kinematics. The analysis is not beyond what a first year student would know after a smemster of study.
    Kavik doesn't think I am completely mistaken. As he says below, "The axle path is not the only thing that is under the influence of forces..." In particular, the connecting link itself is influenced by the force at the axle as that force is transferred to the frame.

    While I never had a course in kinematics, I was in the honors math program at Stanford long ago. I find your tone insulting as it has consistently been in our few encounters. I don't want to continue arguing with you anymore either. I'm old enough to be your grandfather and don't need the aggravation.
    "Don't criticize what you can't understand."

  85. #85
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    The "SfJH Link"

    Oh wait, Steve doesn't work, but makes a career of going up against established engineers with actual degrees and inventions behind them.

  86. #86
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    Oh wait, Steve doesn't work, but makes a career of going up against established engineers with actual degrees and inventions behind them.
    and you have zero knowledge about anything SfJH is talking about, so maybe it's time to shut your fat phocking mouth, or enter into the technical argument and actually prove a point.
    what would rainbow unicorn do?

  87. #87
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    Quote Originally Posted by ferday
    and you have zero knowledge about anything SfJH is talking about, so maybe it's time to shut your fat phocking mouth, or enter into the technical argument and actually prove a point.
    Actually, you'd be surprised at how much I might understand, when one considers your statement, then compares it with the reality of the situation.

    I have view Steve's nonsense here for a while. He baffles people with bs, and as evidenced by your response, he has some fans that believe in his ramblings.

    Sorry, mr internet armchair engineering discussion wizard. You sound closer to a Limp Bizkit/Linkin Park fan who has just been told how much those bands suck.

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    Am I correct in saying that the Felt design works just like a high single pivot in the top of travel and then dips down lower as the suspension compresses?

    One part of their claim to reduced pedal bob seems like it comes from bending the rear traingle. Bending carbon fiber MUST have some form of resistance to the motion of the suspension, thus adding to the mix of pedal bob reduction.

    It appears to me that they calculated which parts of the travel would benefit from the bending and designed it so there is carbon resistance in some parts of travel but not in others.

    I would think that maximum resistance in the top parts of travel would reduce pedal bob and brake squat. Then if the carbon resistance lowers through more travel, you get compliance to larger hits.

    Based on where the Equilink sits, it seems like it is there to provide proper constraints and to bend the rear traingle in just the right way.

  89. #89
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    LOL


    i'm not defending SfJH or davide or anyone else, but your fanboy comment is funny. you may very well understand perfectly, hell you may design suspension systems for all i know.

    but all you've ever offered the mtbr forums is caustic non informative psuedo-opinions. and that of course is my psuedo-opinon.
    what would rainbow unicorn do?

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    Quote Originally Posted by Steve from JH
    Kavik doesn't think I am completely mistaken. As he says below, "The axle path is not the only thing that is under the influence of forces..." In particular, the connecting link itself is influenced by the force at the axle as that force is transferred to the frame.
    I apologize. My train of thought does not place high importance on the wheel path. Yes, it is a result of the entire system. Yes, it is a fixed path. However, to analyze only forces along the path is like only seeing whats on the right side of the = sign. There are some forces on the front linkages that change under different riding dynamics that affect not the axle path, but it's ability to move along this path.

    BTW - I am biased, because I tend to compare the two rather than purely accepting Felt's claims.

  91. #91
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    Quote Originally Posted by ferday
    LOL


    i'm not defending SfJH or davide or anyone else, but your fanboy comment is funny. you may very well understand perfectly, hell you may design suspension systems for all i know.

    but all you've ever offered the mtbr forums is caustic non informative psuedo-opinions. and that of course is my psuedo-opinon.
    then you might need to go through my post history. Dig a bit deeper (hint, look not only at my post history, but look below ).

  92. #92
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    Quote Originally Posted by ferday
    and you have zero knowledge about anything SfJH is talking about, so maybe it's time to shut your fat phocking mouth, or enter into the technical argument and actually prove a point.
    That's not a problem since SfJH has no idea what he's talking about. He makes this **** up as he goes along.
    I don't post to generate business for myself or make like I'm better than sliced bread

  93. #93
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    Quote Originally Posted by MudMuncher
    Am I correct in saying that the Felt design works just like a high single pivot in the top of travel and then dips down lower as the suspension compresses?
    That's a better description of how the DW link works.

    One part of their claim to reduced pedal bob seems like it comes from bending the rear traingle. Bending carbon fiber MUST have some form of resistance to the motion of the suspension, thus adding to the mix of pedal bob reduction.

    It appears to me that they calculated which parts of the travel would benefit from the bending and designed it so there is carbon resistance in some parts of travel but not in others.

    I would think that maximum resistance in the top parts of travel would reduce pedal bob and brake squat. Then if the carbon resistance lowers through more travel, you get compliance to larger hits.
    You're putting too much importance on the flexing carbon stays. That was just a choice they made just as Trek did with I think it was the Fuel. They could have used rigid stays with a pivot just above the axle. In fact they market a longer travel version of the Equilink called the Redemption that is built that way. Kavik's original design seems to have a pivot just above the axle.

    Based on where the Equilink sits, it seems like it is there to provide proper constraints and to bend the rear traingle in just the right way.
    What the red link does on the Felt bike is turn the force acting on the axle into force acting on itself. You could have a chain line that was actually trying to pull the axle up along its path where the net effect would be to move the red link downward relative to the frame, pulling the axle down with it.

    At sag the path of the Equilink's axle would be similar to that of a low single pivot bike. But much more anti-squat, which is downward extending force designed to resist the squat produced by acceleration, would be generated than with a low single pivot.
    "Don't criticize what you can't understand."

  94. #94
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    What the red link does on the Felt bike is turn the force acting on the axle into force acting on itself. You could have a chain line that was actually trying to pull the axle up along its path where the net effect would be to move the red link downward relative to the frame, pulling the axle down with it.
    this is turning ridiculous.

    steve, just like i wrote in my last post, would you please sit down and draw some vectors and forces into a hypothetical 6-bar linkage!
    after you have that worked out you will easily be able to see your misperception concerning this subject.

  95. #95
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    Quote Originally Posted by igorion
    this is turning ridiculous.

    steve, just like i wrote in my last post, would you please sit down and draw some vectors and forces into a hypothetical 6-bar linkage!
    after you have that worked out you will easily be able to see your misperception concerning this subject.
    Actually, during the winter I spent quite a bit of time drawing vector diagrams using the picture from the Felt site and the Paint function on my computer. I don't have any software that will handle six-bar stuff. It was difficult and tedious to do it that way and the diagrams aren't much good.

    I'm attaching three of them anyway. The first one has the chain in the highest possible gear. It's the clearest of the diagrams. The other two are of the middle gear combo and the lowest gear. They are full of mistakes and corrections.

    What I did was take as a unit vector the line from the axle to the rear lower pivot directly ahead of the axle. For each different gear combination I then determined the length of chain line that would represent the force to produce that unit vector. I then could establish a vector for the force from axle to upper pivot (rear pivot on the rocker arm). I was assuming that the flex in the stays is equal and doesn't favor the top or bottom of the linkage.

    Next I calculated the vector for the force acting on the two rear pivots, top and bottom in a direction rotational around the pivots at the ends of the connecting link. That's the key step and that's how you have to do it. If you jump past these pivots to the frame pivots, you will be analyzing something close to a DW link and will not be taking into account the role of the connecting link in determining either the force transmission or the axle path.

    The next step is to calculate the vectors acting on the end pivots of the connecting link in a direction rotational around the frame pivots.

    The last step is to calculate the vectors acting upward through the connecting link pivots at the top and downward at the bottom.

    Except for the highest gear combination where the forces are balanced, the downward force always exceeds the upward force.

    You now factor in the contribution of the thrusting force at the ground acting horizontally through the axle, increasing somewhat the downward force on the connecting link and causing an upward force on the axle from load shift slightly smaller than the thrusting force itself (the height of the center of mass is assumed to be slightly smaller than the wheel base.).

    It turns out that the extending force on the linkage and the squatting force from load shift are approximately balanced in almost all gears. That vindicates Felt's basic claims.

    What you, DW and others are not seeing is the following: The chain force translated to the axle can be broken down into two components. One acts on the axle tangent to the axle's path. The second acts at 90 degrees to the first. This second component is trying to pull the axle toward the frame. The exact angle of the pull will of course depend on the choice of gears. This second component is always much larger than the first.

    Now on ordinary FS bikes, those with a single pivot and swingarm, whether or not they have extra links, and true four bars, this second component can produce no movement of the suspension because no part of the linkage system has a degree of freedom that would allow it to be influenced by the force. All the force can do is cause compressive and bending stress on the linkage members.

    That is not true of the six-bar Kavik/Felt designs. The connecting link, not directly attached to either the wheel or the frame, is put under tension by the forward pull on the axle and that tension can be unbalanced to favor downward movement.

    Since the second component of chain force is much larger that the first, it's perfectly possible for the component acting tangent to the axle's path to be pulling the axle upward but be overbalanced by the other component pulling the connecting link downward. That would happen, for example in the next to highest gear on the Felt, by my calculations.
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  96. #96
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    Model of behavior

    Well when in doubt, build a model. So I did with cardboard and thumbtacks.

    Like I’ve previously done with 4-bars, I build a 6-bar. It’s easy to do. Just get some stiff cardboard like beer can case cardboard. Cut it into about 1-inch strips, and tack these struts together with thumbtacks, using a large piece of cardboard as the frame link.

    By pinching the cardboard frame with my right thumb and finger where a pivoting BB would be, and pinching a point on the rear stay where the pivoting axle would be, the action of the frame link in relation to tension between the rear axle and BB can be felt. (OUCH! pardon the pun!)

    So after a few different configurations of links and frame, similar to both the Kavik and Felt interpretations of 6-bars, some conclusions are very noticeable.

    It was quickly obvious that, just like every other suspension design, the axle path is all that matters as far as chain tension reactivity is concerned. This is easily felt by rotating the links while adding tension between the “axle” and BB”.

    Of course on suspension bicycles the shock spring and damping rate matters a lot, and alters the rate of activity but not the direction. But I’m removing that variable to feel only the mechanical direction of rotation action under tension.

    And every other component of these 6-bar designs other than the linkage configuration is in common with any other design, monopivot or 4-bar configuration.

    So as igorion and _dw have clarified here, there is no difference in path defined “virtual swingarm pivot” (where there is a moment intersecting the perpendicular projection line to the path) with the 6-bar designs than other multi-link configurations which prescribe a fixed (non-flexible) wheel path under tension.

    The Felt design seems to produce a more rearward biased path then Kavik’s. Kavik’s is more similar to dw-Link which is rearward at the top end of travel and rotating more rapidly past vertical to forward during compressing travel.

    Perhaps dw learned his most balanced path from Kavik!

    But dw-Link was sold first in 2003 which preceded Kavik’s Interbike show of his design by a year…..hummm?! Then could Kavik have learned the optimized anti-squat path by first riding the dw-Link??


    Edit added:
    /////////////////////

    Modeling Braking tension action:

    I sensed a fairly large difference by modeling braking tension to the rear stays. Small differences in link configuration made a big difference in the braking “virtual swingarm” pivot with the frame.

    Braking reactions are more difficult to explain in words. So the conclusion is that the Korvick emulates a monopivot very closely while the Felt configuration is more ideally suited for trail riding traction and stability dw-Link or Horst link in braking reactivity.

    Background (for anyone really interested):

    Like 4-bar floating brake systems, the 6-bar floating brake system produces a different “virtual swingarm” pivot with the frame than the virtual pivot produced from pedaling tension inputs. Because unlike chain tension’s single direction input at the axle, braking input binds the wheel with the caliper-link to rotate around the rear axle with the bound rear wheel rotation. Furthermore, the frame rotates around both the virtual swingarm pivot and the real pivot of the front axle (excluding braking reactions from rider weight shift and front brake reactions, both of which are extending).

    While braking, the direction of input to the caliper link's connecting multi-links are in opposite directions, the upper pivot to the connecting link is forward and the rearward pivot is relatively rearward in direction to the CM and frame. While unlike braking, with chain tension the axle's floating link's directional input is not connected by friction to rotate with the wheel, only the path matters and the swing links all move the frame forward.

    Monopivot braking (and pedaling) reactivity is the same as floating axle multi-link systems, except the monopivot (really a double-link system including both the swing and frame links) is physical and can be seen, unlike floating multi-link braking systems which require mapping virtual and momentary pivot positions.


    I simulated the tension pickup points like I did with chain tension modeling at the rear axle and BB, but for braking I pinched locations for the rear axle and front axle. The rear and front axle are where suspension braking reaction rotates primarily around.

    The Kavik seems more acutely compressive in braking reactivity than the Felt. My moving my hold of the front axle more rearward the compressive leverage was relaxed. It was as if the linkage produces very similar reactivity as a virtual monopivot.

    The Felt 6-bar configuration was compressive but moderately less. It felt like it has a virtual monopivot somewhere between the seat tube and head tube, much like a Horst Link or DW-Link.

    In general for braking, a mild to moderate compression with a virtual or real frame pivot between the BB and half way toward the head tube produce the easiest to modulate traction and handling, and most stable braking for trail use bikes. Only very rear end weighted downhill specific bikes can benefit from a virtual pivot closer to the front wheel or a head of the bike.

    I would conclude from modeling that the Felt has overall better linkage geometry for handling and braking. But the Kovik has better pedaling reactivity closer to the ideal that was established by the DW-Link.

    The DW-Link combines ideal pedaling action and also has ideal trail braking link geometry. Niether the Kovik or Felt combine to balance both trail riding requirements as well, but the Kovik is closer.
    Last edited by derby; 04-23-2007 at 09:05 PM.

  97. #97
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    No longer member of the bike industry nor society, so don't hassle me.

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    steve, i am sorry to say, but your approach is completely wrong!

    you are evaluating "upward" and "downward" forces within the red link. then you end up with with the "downward" force exceeding the "upward" force.

    this is not how it is done!

    EQUAL force will ALWAYS be acting on BOTH the top and bottom pivots of the red link. this is a fundamental principle in statics (i know it is a dynamic system, but for evaluating forces, statics will do).




    i don't want to be somebody to just criticize others work so i have written a little app to illustrate a more correct approach:



    START APP (FLASH): http://www.igorion.com/_equilink_force/

    you can drag and drop the starting point of the input force acting on the axle. doing that you can see that the force on the damper will disappear if the input force aligns with the path normal, no matter how much input force is applied. in that state the system is balanced (this is what i have been trying to make clear to you through all my posts). force input at any different angle will cause the damper to be stressed. you can also see how the equilink does NOT equalize any other state than the one described above.

    maybe this can clarify some of the points i have been trying to make. if you want i can describe the calculations in my app more precisely in another post.

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    geez igorion you are my hero

  100. #100
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    I think I speak for most when I say I'd love to see a comparison between the Kavik and the Felt!

    Maybe in a new thread?
    No longer member of the bike industry nor society, so don't hassle me.

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