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  1. #1
    www.derbyrims.com
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    more mistaken 4-bar analysis

    I just discovered this doing a google search on suspension. Here's a link to some BMW motorcycle paralever (floating axle 4-bar) mistaken analysis, apparently authored by Anton Largiader:

    http://www.largiader.com/paralever/

    The common mistake is forgetting the driven wheel rotates around the axle, not the ground. The axle in both the monopivot and paralever example rotate around the same path with the fame (if truely a parallel 4-bar), so all the drive line effects are equal in geometry and tension balances. The housing the axle is mounted to may not rotate around as much, but the axle tracts the same path as the monopivot, aith a free wheel rotation. Any variation from an exact parallel foating axle linkage produces an altered path and incremental variation in drive train effects.

    In both a floating axle system or mono-swingarm system the chain effect is compared where the chain-line crosses the line perpendicular to the slope of the axle path (swingarm line).

    However, when braking the rear wheel from a floating brake link (or brake attached to a rear paralever housing) then the wheel does rotate with the brake-friction tensioned floating link (or paralever housing) about the frame about the virtual pivot described by the IC. When rear braking the floating rear link is extended to the ground including the rear wheel. So the wheel then also rotates around the ground since it can't rotate freely around the axle as it does when coasting or under power.

    The common mistake from those trying to differentiate floating drivetrains is imagining that wheel is attached to the floating link when there is no physical tension binding the wheel rotation with the floating link. Under frame mounted drive acceleration, there is a tension lock with the opposite link at the frame's pivot point of the driveline, exactly the same as a mono-swing arm system relates with frame mounted drive.

    It looks like the logic mistake has become a "fact" in layman popular mechanics writing, so no wonder it is repeated here.

    - ray

  2. #2
    No, that's not phonetic
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    Ray, with all due respect, the reason "misinformation" is repeated here despite your and other's ongoing public education programs is that your lessons are so utterly unintelligible that they are deflected off our thick skulls like so many ping-pong balls. The "wrong" stuff is not only generally presented in a digestible form, it is also often so seemingly logical in it's simplicity that we swallow it eagerly. By contrast, your counter-arguments are such an unpalatable plate of gibberish soaked in cod-liver oil it elicits an immediate gag-reflex.

    I used to really want to understand this stuff so I read your discussions with Steve regularly, slowly, and carefully. However, after repeatedly finding myself staring vapidly at a screen full of academic arguments versed in semi-technical (or fully-cryptic) jargon, without the slightest hint of recognition on my part and a trickle of drool running off my chin, I have given up.

    For instance, "when rear braking the floating rear link is extended to the ground including the rear wheel." WTF does that mean? Or, "under frame mounted drive acceleration, there is a tension lock with the opposite link at the frame's pivot point of the driveline, exactly the same as a mono-swing arm system relates with frame mounted drive." Huh?

    If you <i>really</i> want to set us free, please write short, concise sentences, in layman's terms and above all, IN ENGLISH. Oh yeah, lots of pictures.

    Thanks,
    tscheezy
    My video techniques can be found in this thread.

  3. #3
    The Ancient One
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    Quote Originally Posted by derby
    I just discovered this doing a google search on suspension. Here's a link to some BMW motorcycle paralever (floating axle 4-bar) mistaken analysis, apparently authored by Anton Largiader:

    http://www.largiader.com/paralever/

    The common mistake is forgetting the driven wheel rotates around the axle, not the ground. The axle in both the monopivot and paralever example rotate around the same path with the fame (if truely a parallel 4-bar), so all the drive line effects are equal in geometry and tension balances. The housing the axle is mounted to may not rotate around as much, but the axle tracts the same path as the monopivot, aith a free wheel rotation. Any variation from an exact parallel foating axle linkage produces an altered path and incremental variation in drive train effects.

    In both a floating axle system or mono-swingarm system the chain effect is compared where the chain-line crosses the line perpendicular to the slope of the axle path (swingarm line).

    However, when braking the rear wheel from a floating brake link (or brake attached to a rear paralever housing) then the wheel does rotate with the brake-friction tensioned floating link (or paralever housing) about the frame about the virtual pivot described by the IC. When rear braking the floating rear link is extended to the ground including the rear wheel. So the wheel then also rotates around the ground since it can't rotate freely around the axle as it does when coasting or under power.

    The common mistake from those trying to differentiate floating drivetrains is imagining that wheel is attached to the floating link when there is no physical tension binding the wheel rotation with the floating link. Under frame mounted drive acceleration, there is a tension lock with the opposite link at the frame's pivot point of the driveline, exactly the same as a mono-swing arm system relates with frame mounted drive.

    It looks like the logic mistake has become a "fact" in layman popular mechanics writing, so no wonder it is repeated here.

    - ray
    This is an excellent little article that gets at precisely the theoretical point that you, and KS, and others don't seem to be able to understand. It's what I was trying to explain the other day. (It's too hard to find the link with this damned new format but it's down the page somewhere.)

    The torque on the wheel locks it to the link on which the axle is mounted as far as the reactive force from the ground is concerned. That's true for both braking and drive acceleration. It's accepted in all writing about motor vehicles with suspension. Many of the people doing such writing are PhD.'s with specialties in vehicle dynamics. They are anything but laymen.

  4. #4
    The Ancient One
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    Quote Originally Posted by tscheezy
    "when rear braking the floating rear link is extended to the ground including the rear wheel." WTF does that mean? Or, "under frame mounted drive acceleration, there is a tension lock with the opposite link at the frame's pivot point of the driveline, exactly the same as a mono-swing arm system relates with frame mounted drive." Huh?

    Thanks,
    tscheezy
    I understand the first of these quotes perfectly. It means that the force acting on the contact patch of the wheel down on the ground affects the suspension the same as it would if the wheel were fused to the link at the axle. Imagine the bike with fused rear wheel being yanked across ice (slick tires, no studs) by a cable attached to the contact point and running along the ground. The yanking can be either forward or backward. The suspension will be affected the same as with a regular unfused axle and the wheel under torque and with good traction.

    What Ray doesn't understand is that this effect occurs for both braking torque and forward drive torque.

    The second of these quotes makes drool run down my chin too.

  5. #5

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    Quote Originally Posted by tscheezy
    Ray, with all due respect, the reason "misinformation" is repeated here despite your and other's ongoing public education programs is that your lessons are so utterly unintelligible that they are deflected off our thick skulls like so many ping-pong balls.
    I disagree.

    I think that the vast, vast, vast majority of riders is more concerned about having fun and riding bikes rather than obssessing about minutia that is critcally important to the pocket-protector mafia, but largelt unimportant when you're riding.

  6. #6
    Tonight we ride.
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    I'm not sure what the grease on your dirty BB spindle is doing, but I've been watching it for a good five minutes.

    I think I see a hand reaching out in an underhanded grab.

  7. #7
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    Sorry Ray but even I got a headache and gave up after about the third paragraph. Too many mental images running around and colliding with each other.

    I've got a new method which acheives equivalence between single pivots and linkages. It works for even the triple parrallelogram linkage which I guess is the true test.

    Remember, all acceleration forces come from the ground, that fact cannot be ignored like KS claims.

  8. #8
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    Quote Originally Posted by Pete
    I disagree.

    I think that the vast, vast, vast majority of riders is more concerned about having fun and riding bikes rather than obssessing about minutia that is critcally important to the pocket-protector mafia, but largelt unimportant when you're riding.
    Um, Pete, maybe you missed it but this is a tech-talk forum. If this stuff doesn't interest you then the passion forum might.

  9. #9
    only slightly broken
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    shaft drive vs chain

    Isn't the point of the above sited based on shaft drive motorcycles using
    the shaft as the swingarm? My hazy memory of such things is that the
    pinion tries to "climb" the ring gear under acceleration and the opposite
    under deceleration, the worst part being the sudden decrease in ground
    clearance when letting off on the throttle. The last paralever bmw I rode
    was MUCH better than pre-parlever bikes. Is this pertinent to chain drive
    push bikes? I have NO idea, I was an art major. -shrug-
    I would, though, be very careful about dissing Tony Foale....

    patrick, clueless, but not that worried about it.

  10. #10

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    Quote Originally Posted by tscheezy
    Ray, with all due respect, the reason "misinformation" is repeated here despite your and other's ongoing public education programs is that your lessons are so utterly unintelligible that they are deflected off our thick skulls like so many ping-pong balls.
    Reminds me of Richard Feynmann (RIP, genius physicist), who once remarked that if you can't explain something in plain English, then you most likely don't understand it yourself.

    Don't know if that's the case here, but the adage has always been accurate...

  11. #11

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    Quote Originally Posted by Dougal
    Um, Pete, maybe you missed it but this is a tech-talk forum. If this stuff doesn't interest you then the passion forum might.
    Key word:

    "minutia"

    Best of luck!

  12. #12
    The Ancient One
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    Good point to bring up the chain

    Quote Originally Posted by pffft
    My hazy memory of such things is that the
    pinion tries to "climb" the ring gear under acceleration and the opposite
    under deceleration
    That's one way of putting it. A more basic physics way of putting it would be to say that the shaft produces a torque on the wheel relative to the swingarm and simultaneously a torque on the swingarm relative to the wheel. The wheel rotates forward and the swingarm wants to rotate backward. This relationship locks the two together as far as the pushing force at the ground is concerned. That force tries to push the wheel down into the ground and thus jacks the pivot up.

    They use 4-bar linkages on shaft driven motorcycles in order to move the pivot point farther forward, making the virtual swingarm longer and making the wheel/link path more vertical. That reduces the jacking. If they used a truly parallel and level linkage, the virtual swingarm would be infinite and the wheel's path would be vertical and there would be no jacking at all.

    If you use a chain instead of a shaft, all of the above is still true, but only if the chain line passes through the pivot point. Otherwise the chain's pull alters the amount of jacking. You can calculate the amount of jacking (or squatting in some cases) by finding the point where the chain line intersects the virtual swingarm line. You can then say that if you had a pivot at that point and a drive shaft the bike would behave the same.

    All this is leaving out kickback. Kickback doesn't exist with shaft drive. Because the shaft rotates in a plane at 90 degrees to the plane the suspension rotates in, movement of the suspension doesn't affect the drive shaft. But with a chain the upward movement of the wheel can cause the pedals to slow down by pulling back on the chain. The farther forward the point of intersection between chain and swing arm lines, the less the kickback.

    So, taking all this together, a chain driven 4-bar linkage with the chain line passing through the virtual pivot point (the instant center) and with that point well forward will behave very much like a shaft driven 4-bar.

  13. #13
    occupation : Foole
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    Cool-blue Rhythm Ummmm, ...well, ......

    LOL... I kinda sorta sometimes understand the most technical aspects of the suspension phyiscs shtuff that gets posted, and find it very interesting (in an abstract way...heh)

    And, on the other hand, I tend to agree with Pete, as well...in a practical way...especially after racking my feeble brain trying to figure out just what the bejeezuz my Fuel is - it ain't a 4-bar, for sure, but seems not quite a mono-pivot (flexing of rear stays...)...does it qualify as a faux-bar ??? Whatever, it works well, for me - which is what is important.

    Like I said, I love reading the high-tech, serious physics of what makes it all happen (or not), but, in the end, I just love riding, in general....don't have a lot of FS experience (outside of various limited demo rides, I have only extensively ridden my Fuel and my brother's Mantra, which is a very disturbing bike to ride, at least for me - he seems to enjoy it, however...)

    Keep the "suspension physics posts" coming..... I enjoy them (and try to make as much sense as I can of them...heh)

  14. #14
    The Ancient One
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    Quote Originally Posted by Pete
    Key word:

    "minutia"

    Best of luck!
    You have inspired me to adopt a new user title.

  15. #15

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    Don't play the game

    Quote Originally Posted by Steve from JH
    You have inspired me to adopt a new user title.
    You do realize that you are putting yourself down, don't you?

    Fairly or not, the prices of most FS frames are based on so-called "performance" of their suspension design. Knowing the features (BS or not) and differences (tiny or big) between these designs constitute good consumer information. Therefore, calling the details minor or trivial is misguided but mostly, it's a subjective judgement label so I ditto what Dougal said: if these things don't interest someone, there are other forums to go to. This is a tech forum after all.

  16. #16

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    Quote Originally Posted by Juramentado
    if these things don't interest someone, there are other forums to go to.
    Oh, these threads interest me all right.

    They are good for some laughs.

    p.s. There's a differece between discussing what bike to buy and obssessing over minutia. Check my previous posts if you're still struggling to understand the difference.

  17. #17
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    You got it!... The motorcycle article only looked at the position of the final drive housing, not at the full effect of the final drive couple with the drive shaft. The article concluded at the end that BMW compromised the full effect of a fully parallel drive train would produce. BMW actually just tuned the power-on no-squat they desired with the paralever suspension to be able to raise the gearbox output drive shaft for more ground clearance without increasing the power-on jack. Monopivot shaft drives need a lower pivot for the drive train to produce the same net no-squat power-on torque conversion. The paralever arraignment actually increases bump induced suspension input to the drivetrain jack (since the final drive cannot roll with the terrain as much), although the relatively heavy weight and low horsepower of the BMW's would feel the bump jack less than a greater power/weight bike.

    Bicycle suspensions would have a power-on 100% parallel paralever drive effect with a bottom-braket-concentric monopivot swingarm using equal sized cog and ring. Power-on squat effect would need to be tuned by path-pivot alignment with the suspended-mass inertia-input and tire patch. Bicycles however, have freewheel drive so there is no power-off compression effect to compensate for. It's interesting to note that the prototype factory motorcycles used in Moto-GP use freewheel drive too (this may be too dangerous for motorcycle street use).

    Needless to say it's no fun trying to read this compared to going out and riding various bikes, pedaled or moto’ed, to gain a feel for what fit's your own style of riding best.

    Side note for those without a headache yet: The paralever BMW drive shaft (or any multilink type suspension) must use a sliding drive shaft to couple with the final drive to compensate for the path's gain and loss in distance from the "effective pivot" (as dougle coined the term for the earlier term of "virtual pivot" of driven suspension effects). A monopivot drive shaft does not need a sliding couple, such as CV joint, and can use a fixed distance “U-joint”.

    - ray

  18. #18
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    I'd like to hear your new perspective.

    Actually sugar in the blood of the rider could be called the source of acceleration forces when riding. But I guess you could say that sugar comes from the ground too. Acceleration requires at least two masses when biking, the ground and the rider. You don't need a bike, it just makes it more interesting and fun

    I don't talk with KS very often, every few months or so. And we don't talk about bikes much since we don't agree easily sometimes. I try to listen to his gravity physics theories and how they compare with the leading physics thinking of existence theory (loop quantum, etc.) and the critiques he gets from those leading academic physicists. Of course the early critiques are "Say what!?! Impossible!". But later he's found published theory similar to his perspective and confirmation subsequently from the more established theorists. Perception is something that matures, individually and later culturally. There are no "new" ideas, there are simply discoveries and then the creative process of communicating and utilizing the perception of the discoveries.

    Path Analysis, as Dave Weagle commented a while back, is incomplete. There are only enough physics principles to debunk some magical advertising claims. PA doesn't (yet?) specifically analyze the suspended mass (90% rider) with the ground, only geometry in relation with basic principles of mass physics. It takes a rare, perhaps artistic sense, to "see" inertia. Since inertia cannot be drawn with fixed coordinates. I sense that you have this ability to "see" inertia. That is why you and KS agree in the principles, just not in the same language or with a spirit of patience and forgiveness of mistakes.

    I may be completely wrong in my perceptions of what I experience. I expect to make mistakes. I learn much faster by making mistakes, perceiving the mistakes, abandoning in them or correcting small errors, and moving forward. I may need to write a small book to better organize and clarify my perceptions. Some basic things seem so obvious to me which another person refutes without specifically and rationally describing the error, only repeatedly presenting some conclusion that is clearly impossible and that I cannot build upon because it makes no sense in ride time, geometry, or logic. Although the challenge of these obviously well intended and friendly critiques motivates me to pay attention and question my perspectives for confirming validation.

    Thanks for your comments.

    - ray

  19. #19
    The Ancient One
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    To each their own obsession

    Quote Originally Posted by Pete

    p.s. There's a differece between discussing what bike to buy and obssessing over minutia. Check my previous posts if you're still struggling to understand the difference.
    Some of us obsess over the minor details that make one bike, say a Truth, Id, or 5-Spot for example, different and quite likely better than some other bike.

    Some of us obsess over trying to be as offensive as possible.

  20. #20
    The Ancient One
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    According to your way of analysing, a shaft driven level swingarm system would behave the same as a shaft driven level parallel linkage. Not so. The first would have lots of jacking torque, the second none.

    If you replace the shaft with a parallel chain in the two above systems, they will behave the same under steady state acceleration. But with constantly fluctuating force such as you have with pedaling, you never have steady state acceleration. With each pedal stroke, the level swingarm with parallel chain will squat before accelerating, wasting a lot of rider energy; the level linkage with parallel chain will accelerate before squatting, wasting even less rider energy than a hardtail.

  21. #21

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    Oh, this tirade is so tiring

    Quote Originally Posted by Pete
    Oh, these threads interest me all right.
    They are good for some laughs.
    Sheesh. You're using a very tired retort in the face of logic, just to try to save face. For one thing, you keep coming back here in defence of your original post, when most have already had their say and are happy to move on. I think that's what's interesting, and funny.

    Quote Originally Posted by Pete
    p.s. There's a differece [sic] between discussing what bike to buy and obssessing over minutia. Check my previous posts if you're still struggling to understand the difference.
    What I'm struggling to understand is how you can think that anyone here is interested in your little namecalling games, and how you can believe that you can cover up your failed argument by claiming that your subjective judgements are objective. You obviously don't understand the "differece" between the two concepts. Here's an illustrative example: your posts are incredibly inane and utterly bereft of substance, but I admit it's an overall subjective view. Objectively, only the latter is true.

    When you don't understand what is being discussed, go to another forum rather than try to insult those who have the aptitude and intelligence to understand.

  22. #22

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    Quote Originally Posted by Juramentado
    Sheesh. You're using a very tired retort in the face of logic, just to try to save face.
    Save face? ROTFLMAO! Over what? Your suggestion that I go to Passion if I'm amused by obssessing over minutia?

    What kind of fantasy world do you live in?

    Quote Originally Posted by Juramentado
    For one thing, you keep coming back here in defence of your original post, when most have already had their say and are happy to move on. I think that's what's interesting, and funny.
    Defence (sic)? Interesting assumption, but way off base. I keep on coming back for the laughs and folks like you keep on providing them, albeit unintentionally.

    Quote Originally Posted by Juramentado
    What I'm struggling to understand is how you can think that anyone here is interested in your little namecalling games, and how you can believe that you can cover up your failed argument by claiming that your subjective judgements are objective.
    Well as far as whether anyone is interested question, perhaps you should look in the mirror and ask that question, since you seem to be interested, based upon your replies.

    "failed argument"? LOL again.


    Quote Originally Posted by Juramentado
    When you don't understand what is being discussed, go to another forum rather than try to insult those who have the aptitude and intelligence to understand.
    Tsk, tsk, tsk. Another assumption.

    I do understand what is being discussed.

    That doesn't preclude me from being amused by the folks that obssess over the minutia.

    Someone like you for example.

    Cheers!

    p.s. How can you possibly know that "most have already had their say and are happy to move on"? How can you possibly know what people's thread viewing habits are with such certainty that you would make that claim?

  23. #23

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    Quote Originally Posted by Steve from JH
    Some of us obsess over the minor details that make one bike, say a Truth, Id, or 5-Spot for example, different and quite likely better than some other bike.

    Some of us obsess over trying to be as offensive as possible.
    As an owner of all three bikes, the discussion relating to the differences between the ID, 5spot, and Truth is a perfect example of the minutia.

    Me obsess over being offensive?

    It's time for you to bust out a dictionary.

  24. #24

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    ROTFLMAO? Are you in a time lock?

    Quote Originally Posted by Pete
    Save face? ROTFLMAO! Over what? Your suggestion that I go to Passion if I'm amused by obssessing over minutia?
    No, over your assertion that a technical discussion of suspension design is minutia. Do you have comprehension disabilities? Wait, don't bother answering that one.

    Quote Originally Posted by Pete
    What kind of fantasy world do you live in?
    A much more productive one than yours!

    Quote Originally Posted by Pete
    Defence (sic)?
    Uh, that is a correct spelling. Do you have literacy disabilities? Wait, don't bother answering that one either.

    Quote Originally Posted by Pete
    Interesting assumption, but way off base.
    You and I know it's right on the mark. I won't tell anyone else, promise.

    Quote Originally Posted by Pete
    Well as far as whether anyone is interested question, perhaps you should look in the mirror and ask that question, since you seem to be interested, based upon your replies.
    Sure, I'm interested, if that will make you shut up.

    Quote Originally Posted by Pete
    "failed argument"? LOL again.
    Hmm, I can swear these little acronyms have not been in use since pimple-faced teens exchanged juvenile messages in pure text-based chatboards a couple of decades ago. Time locked, are we?

    Quote Originally Posted by Pete
    Tsk, tsk, tsk. Another assumption.
    I do understand what is being discussed.
    It's pretty obvious you don't understand it, and your pretending that you do is also too obvious. Anyone can "check your posts" and see the absolute lack of contribution there. Can't you try to do a bit better? For example, why don't you prove quantitatively that what you refer to as minutia is in fact that? Here's your chance, big boy!

    Quote Originally Posted by Pete
    That doesn't preclude me from being amused by the folks that obssess over the minutia.
    Do you really believe this retort actually works? Hint to Pete: this is a lose-lose comeback. If you do indeed get "amused" by these exchanges, there's a lot for people to feel sorry about with you. If you are merely using this as an attempt at an ascerbic reply (most likely case), sorry, you fail there too, by virtue of being too common to be cutting.

    Quote Originally Posted by Pete
    Someone like you for example.
    Why, I do believe I have a fan! Cheers indeed!

    Quote Originally Posted by Pete
    p.s. How can you possibly know that "most have already had their say and are happy to move on"? How can you possibly know what people's thread viewing habits are with such certainty that you would make that claim?
    Take a look... how many people are still responding to your posts? It's just you and I now, baby.

  25. #25

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    Quote Originally Posted by Juramentado
    You and I know it's right on the mark. I won't tell anyone else, promise.
    Hey, if that makes you feel better, have at it!

    Despite the fact that it's way off of the mark.

    Quote Originally Posted by Juramentado
    Sure, I'm interested, if that will make you shut up.
    So you asked yourself the question then? What was your answer?

    Quote Originally Posted by Juramentado
    Hmm, I can swear these little acronyms have not been in use since pimple-faced teens exchanged juvenile messages in pure text-based chatboards a couple of decades ago. Time locked, are we?
    Nope, but if they annoy the minutiamen mafia they can't be that bad, can they?

    Quote Originally Posted by Juramentado
    It's pretty obvious you don't understand it, and your pretending that you do is also too obvious. Anyone can "check your posts" and see the absolute lack of contribution there. Can't you try to do a bit better? For example, why don't you prove quantitatively that what you refer to as minutia is in fact that? Here's your chance, big boy!?
    "absolute lack of contribution" ROTFLMPWAO!

    Priceless! Thanks.

    Quote Originally Posted by Juramentado
    Do you really believe this retort actually works?
    Absolutely. The proof is in your replies!

    Quote Originally Posted by Juramentado
    Why, I do believe I have a fan! Cheers indeed!
    Fan? Not in the strict sense of the word.

    Are you a perfect foil? Pretty damn close.


    Quote Originally Posted by Juramentado
    Take a look... how many people are still responding to your posts? It's just you and I now, baby.
    Wow.

    That's amazing, and funny, yet you failed to answer the questions about your latest assumption. Here they are again:

    "How can you possibly know that "most have already had their say and are happy to move on"? How can you possibly know what people's thread viewing habits are with such certainty that you would make that claim?"

  26. #26
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    No disrespect to Tony Foele, by the way. He writes only about single pivot motorcycle design from what I've seen, and I've never seen anything to argue with in his single pivot perspective. Anton Largiader apparently wrote that BMW paralever article.

    - ray

  27. #27
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    It seems a shame that we can't even determine if the method for determining automobile roll center is applicable to the bicycle. This should be easy enough to do. Then, maybe, the discussion could move on to other contentious ideas.

    I think that you cannot apply it to bicycle suspension because the linkage is isolated from the wheel by a bearing. The torque applied through that bearing is minimal.

    Run your automobile roll center tests with a hinge between the wheel and the suspension upright. It doesn't work.

    Please forgive me, as I know I've disagreed with someone (s). I tend to get glassy-eyed, even though I do enjoy this stuff, and I can't keep the names and their respective theories straight. I mean no harm and think that we need some outside authority to help us with this.

    I know where Trevor Harris lives and I own a hopped up v8 powered datsun 510 that could be the ice-breaker...

  28. #28
    The Ancient One
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    We're dealing with pitch not roll

    Quote Originally Posted by D.F.L.
    It seems a shame that we can't even determine if the method for determining automobile roll center is applicable to the bicycle. This should be easy enough to do. Then, maybe, the discussion could move on to other contentious ideas.

    I think that you cannot apply it to bicycle suspension because the linkage is isolated from the wheel by a bearing. The torque applied through that bearing is minimal.
    You're wrong here. The BMW article linked by Derby at the beginning of this thread is right on and completely orthodox. Look in RACE CAR VEHICLE DYNAMICS by Milliken and Milliken. That's as good an authority as there is. In chap. 17 they discuss, among other things, how you would calculate percentage anti-squat for a rigid axle rear drive with twin parallel 4-bar linkages supporting the axle. You're not looking at roll from an end view of the car but at pitch from a side view. It's completely applicable to a bicycle or motorcycle, but only if they have a shaft drive. The chain complicates things.

    The basic assumption still applies, though. Even though the wheel is just as much isolated from the link by a bearing as on a bike, the wheel and link are treated as though they formed a single rigid body.

  29. #29
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    From axle friction?

    "The torque on the wheel locks it to the link on which the axle is mounted as far as the reactive force from the ground is concerned. That's true for both braking and drive acceleration."

    With braking it makes sense since there is no wheel rotation without rotating it's axle link the same (brake friction = braked link/wheel lock at some low speed, weight, etc).

    You should be able to explain the claimed perspective for drive tension, or site a reference with a clear explanation, if it's true. From what I notice the axle link remains unattached (except a minutia of friction)

    Is that minutia of increased friction what is being considered to be the wheel to link binding lock?

    I'm interested in the geometry and kinematics of the issue, not a-priori formulas or conclusions.

    Thanks for enabling my obsession with suspension.

    - ray

  30. #30
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    Quote Originally Posted by Steve from JH
    You're wrong here. The BMW article linked by Derby at the beginning of this thread is right on and completely orthodox. Look in RACE CAR VEHICLE DYNAMICS by Milliken and Milliken. That's as good an authority as there is. In chap. 17 they discuss, among other things, how you would calculate percentage anti-squat for a rigid axle rear drive with twin parallel 4-bar linkages supporting the axle. You're not looking at roll from an end view of the car but at pitch from a side view. It's completely applicable to a bicycle or motorcycle, but only if they have a shaft drive. The chain complicates things.
    The basic assumption still applies, though. Even though the wheel is just as much isolated from the link by a bearing as on a bike, the wheel and link are treated as though they formed a single rigid body.
    A bicycle doesn't have a live axle. And since it does not have a live axle, it also does not have a ring and pinion gear inside that live axle. If you've ever raced your Grabber Maverick out at the track, you know all about axle tramp (or hop) and you've installed Traction bars on your axle to reduce the spring wind-up , a result of having a crappy live axle with a ring and pinion inside of it. The axle housing wants to rotate in the opposite direction of the axle itself, and this is why the angles of the locating links is so important on a live axle. This doesn't happen on a chain driven bicycle.

    I think you're comparing apples to oranges and that the live axle theory doesn't apply. The same squat theory as regards an independent suspension with half shafts would be closer to applicable.

    Maybe Pete is right...

  31. #31
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    Here's a picture. If a driven rear wheel is attached to it's link it would have the same acceleration swingarm as the braking swingarm (multi-link or single swing arm).

    During travel the brake swing arm rotates around the ground point, the IC is the virtual pivot with the frame/chassis during braking. But during travel the axle swingarm rotates around a virtual pivot ("effective pivot" as Dougal calls it) with the frame/chassis at the radial center of the path (at the intersection of path slope change). This is consistent for both multi-link or single swing arm suspension.

    - ray
    Attached Images Attached Images
    Last edited by derby; 01-26-2004 at 11:06 PM.

  32. #32
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    This looks like a diagram for an independent suspension. On a rigid axle suspension, which is what is analogous to a bike, the accelerating swing arm and the braking swing arm are identical. See chap. 17 of Milliken and Milliken.

  33. #33
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    For a drive shaft the explanation is found in your BMW article as follows:

    Our model will be a motorcycle with the rear wheel locked to the rear hub. This is a realistic example because in operation, it's that link between the wheel and hub that transmits the forces involved, so for a given moment in time we can assume that they are a solid unit. After all, removing that link is the same as coasting, and the effects that interest us occur under acceleration and braking (when torque is transmitted from the hub to the wheel).

    Now with a chain it's more complicated. The drive shaft is anchored at the hub, but the chain is not. But the chain can be thought of as acting on the swing arm, which the hub is part of, at the point of intersection of chain line and swing arm line--the pole of moments or instant centre of forces. You can't make something rotate unless it rotates against something. The chain makes the wheel rotate against a virtual swing arm defined by the pole of moments. The reactive torque coming back on to the swing arm is proportionate to the torque on the wheel in the ratio of distance to pole of moments/radius of cog. This is the torque on the swing arm when we do not consider the force at the ground--i.e. when the wheel is spinning freely with no traction.

    When we add in traction at the ground we can consider the wheel to be locked to the swingarm in the same way as and for the same reason as given in the BMW article. Without the locking the wheel would be coasting.

  34. #34
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    In what way doesn't a bicycle have a live axle? As I understand it a dead axle would be for example the front axle.

    The chain makes the wheel and axle rotate against resistance at the hub. The reaction goes back into a virtual swing arm defined by the point where the chain line intersects the swing arm line. The swing arm wants to rotate in the opposite direction of the wheel.

    Anti-squat with independent suspension is calculated using the thrust at the axle instead of the ground because the half axles rotate in a plane at ninety degrees to the plane of the rotation of the wheel. Not applicable to bikes.

  35. #35
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    Its a great point on a motorcycle forum, just how does this compair to a human powered bicycle? The chain torque has always been an issue for dirt bikes, but tring to compair a 40 horsepower bike's chain torque at about 8000 rpms to that of a mountain bike, doesnt work for me. Its a different issue, chain related problems are so much more greater on a motorcycle than on a bicycle, plus one thing that the motorcycle world does not yet use are the stable platform shocks that iliminate most of the problems that mountain bikes have. Try as you must to rule the mtb world with a FSR link bike and down playing any other SP or multilink systems really kinda sucks, I say that becuase many times I have seen someone asking for advice about there newly perchased bike, the responce they get is: your bike sucks! That would wipe me out! Coming from the dirtbike world I have learned technics to properly ride a motorcycle, and I find that most of these technics work on a mountainbike as well. I have found that perhaps the only place that a FSR link bike might be an atvantage is climbing very steep and technical rocky slopes, BUT, before my single pivot bike ever gives up, my legs give up, so does it really make a difference? I dont think so. The whole braking thing is kinda lame, learn how to ride a bike properly, you shouldnt be dragging your rear brake while desending anyway, learn to use the front brake more, brake before a turn, dont brake in the turn, and why is there a problem braking going uphill? To most people out there riding a mountain bike having fun, there is no problems, they wouldnt know of any problems untill they go to mtbr forums an get slammed for buying a single pivot bike, some of you guy's do every thing possible to get your point out, like compairing motorcycles to bicycles,
    Sorry, rant over

  36. #36
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    Quote Originally Posted by Steve from JH
    In what way doesn't a bicycle have a live axle? As I understand it a dead axle would be for example the front axle.

    The chain makes the wheel and axle rotate against resistance at the hub. The reaction goes back into a virtual swing arm defined by the point where the chain line intersects the swing arm line. The swing arm wants to rotate in the opposite direction of the wheel.

    Anti-squat with independent suspension is calculated using the thrust at the axle instead of the ground because the half axles rotate in a plane at ninety degrees to the plane of the rotation of the wheel. Not applicable to bikes.
    A bicycle does not have a live axle driven by a shaft with ring and pinion. Imagine the chain driven live axle, supported by bearings at the elliptical springs supporting it, or at the upright links attached to the trailing links. The only portion of this arrangement that resembles the axle housing is the outer race of the bearings, and there is no way for the rotational forces to be transferred to that outer race.

    And further:

    Imagine a 4 bar rear suspension. bike faces to the right. The swingarm rotates about the BB shell. The swingarm and seatstay (upright link) both pivot at a point 1mm forward of the rear axle. The shock is driven by the swingarm.

    Imagine that the upper link is placed at such an angle that it causes the seatstay (upright) to rotate greatly counterclockwise as the susp compresses.

    Is it not true that, according to your theory, when one pedals this design through bumpy terrain, the rider would experience noticable pedal feedback, despite the fact that there is negligible chain growth? Because there is chain force, attached to the ground, the wheel has to be locked to the upright link. If it is locked to the upright link during the instant of your calculations, how could it not be locked the whole time the rider is applying force to the chain?

  37. #37
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    New question here.

    Don't you people work?? Sheesh.

  38. #38
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    Quote Originally Posted by D.F.L.
    A bicycle does not have a live axle driven by a shaft with ring and pinion. Imagine the chain driven live axle, supported by bearings at the elliptical springs supporting it, or at the upright links attached to the trailing links. The only portion of this arrangement that resembles the axle housing is the outer race of the bearings, and there is no way for the rotational forces to be transferred to that outer race.

    And further:

    Imagine a 4 bar rear suspension. bike faces to the right. The swingarm rotates about the BB shell. The swingarm and seatstay (upright link) both pivot at a point 1mm forward of the rear axle. The shock is driven by the swingarm.

    Imagine that the upper link is placed at such an angle that it causes the seatstay (upright) to rotate greatly counterclockwise as the susp compresses.

    Is it not true that, according to your theory, when one pedals this design through bumpy terrain, the rider would experience noticable pedal feedback, despite the fact that there is negligible chain growth? Because there is chain force, attached to the ground, the wheel has to be locked to the upright link. If it is locked to the upright link during the instant of your calculations, how could it not be locked the whole time the rider is applying force to the chain?
    As far as the kickback goes, it has nothing to do with the force at the ground. You seem to be interpreting me as saying the wheel is actually locked to the floating link. I said that you can consider the rotating wheel and the link to which it is attached to respond to force at the ground as though they were locked.

    Between my replies to you and those to Derby I've pretty well used up my explanations. I will just attach some diagrams from my motorcycle book, MOTORCYCLE DESIGN AND TECHNOLOGY by Cocco. These illustrate the pole of moments method of calculating torque on the suspension. Tony Foale uses the same method in his book. This method is generally accepted in the motorcycle world. You should be able to see that if the 4-bar drive shaft cycle had a chain instead and if the chain line passed through the P of M point, which is the instant center, then the torque would be the same as for the drive shaft cycle. This method assumes the point at issue--that the wheel and link can be considered as a unit.
    Attached Images Attached Images

  39. #39

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    You've shown yourself to be quite the lightweight!

    Quote Originally Posted by Pete
    Nope, but if they annoy the minutiamen mafia they can't be that bad, can they?
    So there it is, your sole reason for posting the rubbish that you do? You're a sad case indeed. Minutiamen mafia? Do you also suffer from paranoid schizophrenia?

    Quote Originally Posted by Pete
    "absolute lack of contribution" ROTFLMPWAO!
    Amazing. You manage to repeat yourself, and at the same manage to refrain from contributing anything of substance at all. It does take practice, that's for sure.

    Quote Originally Posted by Pete
    Priceless! Thanks.
    What, your utter lack of substance? Hey, you're doing the job all by yourself!

    Quote Originally Posted by Pete
    Fan? Not in the strict sense of the word.
    But a fan nevertheless. I'll try not to disappoint you, okay?

    Quote Originally Posted by Pete
    Are you a perfect foil? Pretty damn close.
    Oooh, dirty talk might turn you on, but it does nothing for me, I'm afraid.


    Quote Originally Posted by Pete
    Wow.

    That's amazing, and funny, yet you failed to answer the questions about your latest assumption. Here they are again:
    "How can you possibly know that "most have already had their say and are happy to move on"? How can you possibly know what people's thread viewing habits are with such certainty that you would make that claim?"
    And because you're not very bright at all, here is the answer again:
    Look at the response to your posts, and see that most have already ignored you. They have moved on to discuss the details of the original post, as well as contributing their own analyses.

    You, on the other hand, failed to answer a simple question, and instead tried to divert attention from your absolute lack of knowledge of the subject you so despise. Here it is again:

    Why don't you show quantitatively that your claim of suspension design analysis of bicycle frames is minutia? Show everyone here the facts and figures that you've based your insults and hysterical proclamations on. Show that you have at least a basic comprehension of the subject matter.

    Being the little lightweight that you are though, I wouldn't at all be surprised if you try to divert attention from your lack of knowledge yet again.

  40. #40
    Cleavage Of The Tetons
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    KTM has been using a stable platform shock for years!

    And curiously, the reason why they went that technology close to a decade before bicycles was to eliminate the dogbone linkage(roughly 4 bar, but not quite), in order to make a lightweight, single pivot swingarm work, while having the performance and suppleness of a dogbone. As someone state above, "there are no new ideas", well, there are new ideas, but Stable platform shock valving certainly is not one of them.

  41. #41
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    PS, steve...

    Regarless of our stances on Dirt Bikes/Mt. Bikes, I actually admire your dedication to the minutia of suspension. Someone here's gotta do it. I have learned as much as I have needed on certain topics in your posts. Kudos. PPS, We are supposed to get 8" to 10" tonight, don't worry, I can't stand snowmobiles, see ya' on the pass!

  42. #42

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    Quote Originally Posted by Juramentado
    So there it is, your sole reason for posting the rubbish that you do?
    That's another one of your assumptions.

    Quote Originally Posted by Juramentado
    You're a sad case indeed. Minutiamen mafia? Do you also suffer from paranoid schizophrenia?.
    A sense of humor helps immensely.

    Quote Originally Posted by Juramentado
    Amazing. You manage to repeat yourself, and at the same manage to refrain from contributing anything of substance at all. It does take practice, that's for sure.
    Once again:

    "Anyone can "check your posts" and see the absolute lack of contribution there."

    ROTFLMPWAO!


    Quote Originally Posted by Juramentado
    Oooh, dirty talk might turn you on, but it does nothing for me, I'm afraid.
    That has nothing to do with you being the perfect foil.

    Quote Originally Posted by Juramentado
    And because you're not very bright at all, here is the answer again:
    Look at the response to your posts, and see that most have already ignored you.
    Nice projection!

    Nah, the one who obviously isn't very bright is the one that makes enormous assumptions about people's viewing habits based opn replies. Since you seem to be truly struggling with this simple concept, here's a hint for you:

    "viewing habits"

    Best of luck!

    p.s. This should help you with your search for proof of minutia. Apparently you you shose to ignore this part:

    Quote:
    <TABLE cellSpacing=0 cellPadding=6 width="100%" border=0><TBODY><TR><TD class=alt1 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">Originally Posted by Steve from JH
    Some of us obsess over the minor details that make one bike, say a Truth, Id, or 5-Spot for example, different and quite likely better than some other bike.

    Some of us obsess over trying to be as offensive as possible.
    </TD></TR></TBODY></TABLE>
    <!-- END TEMPLATE: bbcode_quote -->As an owner of all three bikes, the discussion relating to the differences between the ID, 5spot, and Truth is a perfect example of the minutia.

  43. #43
    conjoinicorned
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    forgive me for oversimplifying...

    but isn't a live axle one which attaches to both the wheel and the rest of the vehicle, as well as powering the wheel?

    that sounds like an MTB hub to me, i can't intuitively come up with a good reason that an axle needs a housing, the power is transferred in a different way on a bike. a shaft would more closely mimic a shaft drive (or even a diff), but there doesn't seem to be a reson why the housing would need rotational torque.

  44. #44
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    WRX front suspension ...Yes I should have mentioned I swiped this picture form someone's Subaru WRX front suspension. It's a Mac Strut (virtual floating axle 4-bar), but the concept is directly related.

    A solid axle rear differential housing attached by parallel bars has the same drive train and drive suspension relation (although less friction) as a differential housing with side to side independent suspension. The continuously solid mounted drive shaft translates gearbox twist without pulling across the chassis like a common chain drive does. (CV joints are used for any drive line distance growth due to suspension path also with no vertical component.)

    It doesn’t matter if the drive shaft differential housing is mounted to the frame or axle link, the vertical component from drive line to the wheel is the same (zero), unlike chain drive.

    There of coarse is acceleration rate and gear component to chassis jack. Any twisting of the suspension is due to unsecured shear stress flex (hardware spring action).

    I think I finally realized today why car guys use the IC as and acceleration pivot too. I'm pretty sure drive shafts translate the drive tension from the gearbox output, across drive pivot(s), to the axle's final drive housing unit IN-LINE in solid (or low unwanted flex) housings with the suspension pivots.

    If a chain drive (of a bike) could pull and turn the gears in line from suspension pivot(s) to axle we could use the IC as pivot too.

    If we could just use one cog and a chain guide attached to the floating link to wrap the chain down around that cog to maintain 100% chainline alignment with the swing arm pivot(s) then the IC could be the actual effective pivot like a shaft drive. This might make an interesting looking single-speed suspension, but there would be a lot of added friction and weight. Some well-designed chain tension changes through travel can be designed for beneficial effect.

    However chainline through axle and pivot(s) is highly impractical, and wouldn’t produce any extra benefit, so it’s not useful in bikes. So when including chain drive effects, the inline dynamic path crossing radial pivot ("effective-pivot") of a floating axle 4-bar must be used as a virtual chain-drive suspension pivot for consistent calculations when comparing the geometry of the parallelogram 4-bar and the monopivot effect.

    Steve, the chain guide attached to the floating link to produce a solid rear differential housing with the chain line tracking the swingarm (and through pivot) would give you the trajectory you imagine through the IC. But it would increase pedal kickback due to the additional pivot to track. It’s really not entirely possible with chains and rollers, but shafts and CV joints can do it.

    Ouch! That hurt my head!!

    - ray

  45. #45
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    A solid axle rear differential housing attached by parallel bars has the same drive train and drive suspension relation (although less friction) as a differential housing with side to side independent suspension.

    No. The solid axle rotates in the same longitudinal plane as the wheels rotate in when the suspension moves up and down. The half axles of an independent suspension rotate in a plane at 90 degrees. In the first case there is direct torque feedback to the suspension pivot from the ground. In the latter case not.

    Do like I did. Go to a local library and get Milliken's book RACE CAR VEHICLE DYNAMICS on interlibrary loan if necessary. Read chap. 17 in particular. A racing engineer for Toyota e-mailed me a couple of years ago and told me this book was the bible. It has been recently revised.

  46. #46
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    I'm afraid my Pass days are over

    Quote Originally Posted by rideit
    Regarless of our stances on Dirt Bikes/Mt. Bikes, I actually admire your dedication to the minutia of suspension. Someone here's gotta do it. I have learned as much as I have needed on certain topics in your posts. Kudos. PPS, We are supposed to get 8" to 10" tonight, don't worry, I can't stand snowmobiles, see ya' on the pass!
    I'm going to need new knees to do any more skiing. I could get the artificial replacements but I'm sure they would tell me not to ski--voids the warranty or something. They'd probably tell me not to mountain bike either.

    In my day I used to go up on the pass probably 50 times a winter. I was one of the first guys to revive the telemark turn up there. Back in 1980 I wrote a column on XC and telemark skiing for the Jackson Hole Guide. I got some of the same reaction I get on here. Too technical. What is he talking about? Just go ski.

    My position on both dirt bikes and snowmobiles is that the places they can go freely off road should be designated. The places should be chosen not to interfere with game and other reacreational users and should be far enough away from houses not to be seen, heard, or smelled.

  47. #47
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    Thanks for the correction... The diff on a solid live axle does rotate with the axle (and the wheels) disregarding motor torque, and only considering static tension with a non-turning motor. While the independent diff rotates with the chassis (frame and motor), it has a monopivot final drive. A chain drive doesn't have a differential nor shaft drive, it is unique in character to the other two.

    The chain creates a variable tension between the chassis (the frame) and wheel (not swingarm) that could be considered an odd (telescoping) link between frame and wheel (not concentric with the axle) added to either a mono-pivoting or multi-pivoting suspension.

    A drive shaft system produces tension that is connected by housing to the rest of the suspension and axle, unlike chaindrive (unless housed in pivoting units, such as URT or hardtail). The chain drive is a suspension modifier, it is not one with the suspension. Chain drive sustem modifies the suspension compliance between the motor torque and ground line. A drive shaft system is axle concentric, unlike a chain drive, and does not modify the suspension compliance between the motor torque to the ground line.

    Shaft drive is concentric with the motor (and frame pivot) AND axle, chain drive is not. There in lies the mistake of considering the two drive systems equivalent.

    (You’re welcome!)

    - ray

  48. #48
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    Supertracking theory.

    Until recently ordinary suspension theories were widely regarded as sufficient, since any phenomenon could be explained in terms of it by a sufficiently skilled theorist. This is not good enough however. Here we introduce the concept of supertracking, superbalancing, superrotating, superbraking theory of suspension design ("Supertracking theory") which has the attribute that it possesses all properties whatsoever. With this theory, any phenomenon can be explained by a theorist of arbitrary skill. There is no better suspension design theory. Also, it is natural.

    (...to be continued)

    (from G. Wow-mann)

  49. #49
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    Sorry tscheezy... I can tend to ramble, proof reading my stuff hurts me too! I've never been good at the cute sound bite conclusions. I do get some nice complements behind the scenes, so I guess it's usually entertaining.

    Even if I'm wrong a lot, it brings out others with corrections, and we all learn a little more. I really enjoy the learning process. Sorry for the run on sentences (and fragments). Technical stuff has so many pieces that run tightly together.

    I'll have to add pictures. Until recently I've been too busy with work to learn about drawing with the computer and developing a picture library. Maybe I'll get the time and motivation now that I finally got laid off from my 9 year programming job. Looks like the industry has gone deep into competition saturation, and I'm not a smooth and macho self salesman (obviously), so I may have to retire for a season and start up serving something different. A new suspension design bike business? I wish! That would shut me up...

    Nah!

    - ray

  50. #50

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    Quote Originally Posted by Pete
    That's another one of your assumptions.
    Yes, and you must admit I'm hitting home runs with every one of them.

    Quote Originally Posted by Pete
    Once again:

    "Anyone can "check your posts" and see the absolute lack of contribution there."

    ROTFLMPWAO!
    What a surreal response. You're "ROTFLMPWAO" with your absolute lack of contribution? I guess this is the "sense of humor" you mentioned you must have.

    Quote Originally Posted by Pete
    That has nothing to do with you being the perfect foil.
    You keep flattering yourself as well. Is there a disorder you don't have?

    Quote Originally Posted by Pete
    Nice projection!
    Uhh, actually, it's rather obvious evidence. Obvious, that is, to everyone except you.

    Quote Originally Posted by Pete
    Nah, the one who obviously isn't very bright is the one that makes enormous assumptions about people's viewing habits based opn replies. Since you seem to be truly struggling with this simple concept, here's a hint for you:

    "viewing habits"
    Sorry, this doesn't succeed in deflecting attention from your ignorance and utter lack of knowledge of the issue (and of anything else, for that matter). What a terribly weak response. It's not even slightly humorous, so I can't really even say "ROTFLMPWAO". The proof is right there, it's been explained to you in simple, common everyday words! Look again, little id!iot... how many people have the "viewing habits" you proclaim? Hint: It's a number less than two. I'm the only one suffering you, and that's only because you're a fan of mine.

    Quote Originally Posted by Pete
    p.s. This should help you with your search for proof of minutia. Apparently you you shose to ignore this part:

    Quote:
    <TABLE cellSpacing=0 cellPadding=6 width="100%" border=0><TBODY><TR><TD class=alt1 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">Originally Posted by Steve from JH
    Some of us obsess over the minor details that make one bike, say a Truth, Id, or 5-Spot for example, different and quite likely better than some other bike.

    Some of us obsess over trying to be as offensive as possible.
    </TD></TR></TBODY></TABLE>
    <!-- END TEMPLATE: bbcode_quote -->As an owner of all three bikes, the discussion relating to the differences between the ID, 5spot, and Truth is a perfect example of the minutia.
    I "shose" to ignore it? No, rather, that embarrasingly shallow "qualitative" (as opposed to quantitative: get a dictionary) observation of yours served only to support my clear observations, which are as follows:

    1. You bullshat insults to those who discussed matters beyond your comprehension.
    2. You had no hope of even beginning to understand the subject.
    3. You bullshat some more to try to deflect attention to the fact that you knew nothing about bike suspension design, in the vein of "if I crap on long enough, no one will notice I'm an ignoramus".
    4. You've been challenged twice to show "quantitatively" that what you bullshat had some substance, but twice you bullshat some more, squirming and wriggling away because you know nothing, you have nothing, and you don't have a hope of ever getting any understanding of the subject.
    5. Finally, you tried to pass off your shallow, qualitative and incredibly inane statement about being the "owner of all three bikes" (wow, by the way) as quantitative data. Incredible. The scientific and engineering community must heed and write that into books on bike suspension design.

    You're an intellectual lightweight, Peter, not even good at poking fun or mischief at people and subjects you don't understand. You did all the work in showing all these as facts, and I've enjoyed seeing you scramble desperately for cover when challenged.

    Now, as your other intellectual superiors have done, it's time to find out how effective the Ignore feature is on this new forum. Good luck with your crap!

  51. #51
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    What bike?

    Since this topic is about motorcycles and suspension and now proper motocross technique I figured I'd pose this question. Anyone know what bike Johnny O'Mara rides? Here is a pic.
    Attached Images Attached Images
    M

  52. #52
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    Blur?

  53. #53
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    eagle eye

    Are you taunting me or do you really see something that indicates he's on a Blur?
    M

  54. #54
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    Educated guess? I figured it might even be you(not kidding). Hell, "once a racer aways a racer"..i aways say. I raced mx for 15 or so years. Raced support class when Marty Smith and Hannah came to town(Burnt Hickory in N Ga)were fighting it out in the 125 class Nationals. 7-8yrs ago, I used to see Marty Tripes 6 times a year since he works for Scott Goggles as they sponsored the Pro paintball team I played for over 3 or so years until we changed over to a JT Racing factory deal. He was actually THE first person to dominate Stadium cross on the ol 1973-4 silver and green 250 Elsinores(God I'm old). Hes like 350lbs now man. You wouldn't believe it even. Nice dude tho.

  55. #55
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    That pic really is Johnny O'Mara. I don't remember much from his day, but he is one fast dude on an MTB. Here are some times from a recent race at Southridge in Fontana, which by the way is also host to paintballers (makes me nervous when the practice DURING the race - 'hey look a moving target'). The first set are the winners in their category for reference, the second set is the expert men 35-44 (I "race" expert men 27-34). O'Mara was fastest by over 4 minutes.

    713 B SEMIPROM R MERRICK 1 1:57:59
    358 F EM19-26 T KADY 1 1:51:16
    724 G EM27-34 T TUBBS 1 2:03:28

    712 H EM35-44 J O'MARA 1 1:47:08
    718 H EM35-44 M HILEMAN 2 1:51:39
    8H H EM35-44 R O'BRYAN 3 1:58:52
    1H H EM35-44 E ARNET 4 2:04:54
    720 H EM35-44 B MCCALL 5 2:05:15
    714 H EM35-44 D ANDREWS 6 2:07:05
    2H H EM35-44 R BONNIN 7 2:08:43

    Anyway, my point is that although I like understanding the mechanics of mtb suspesion it is important to keep in mind that speed is really based on training and skill development. In sport class I thought I had both, moving to expert has proved me so wrong. Suspension truly is important in freeriding and downhill, but oddly those riders can get short shrift in these threads.
    M

  56. #56
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    Agree 100%. An old racer saying...."no matter how fast you are, theres always somebody thats faster"...is always a constant. O'Mara is showing hes a true champion, as he again excels in his new chosen media. Good for him. Had no idea, and seeing that kinda stuff inspires me even more. At 45 I feel lucky to have rediscovered racing..long after otherwise I'd put it down and was thru with it all. I love it now more then ever.

    Oh, by the way..I think your "on your left" is cool as hell. Wish i'd thought of it. Damn even. I just have those damn duck legs.

    Good luck this season.

    duck

  57. #57
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    Yeah, those avitars are neat. At first I had a picture of my kids, but seeing that I realized, hey, this is an MTB site nobody cares how cute my kids are. So, WTF is with the duck thing anyway. FWIW, I like it - very enigmatic. Also, it is so interesting how varied the body types are in racing. There's the skinny legged spinners (like ducks - their legs paddling ferocioiusly under the water) and the big strong guys who look like they could break a chain peddling one-legged.

    You have a good season too. See you on the shave weight forum.
    M

  58. #58
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    [QUOTE=Motivated]Yeah, those avitars are neat. At first I had a picture of my kids, but seeing that I realized, hey, this is an MTB site nobody cares how cute my kids are. So, WTF is with the duck thing anyway. FWIW, I like it - very enigmatic."...

    Nothing mysterious here...my last name includes the word Duck... Sooooo..I've always been called Duck by just about everyone, especially since my long time best friend and sometimes team mate, has the same first name as I(Jeff)so this only encouraged the use of the duck thing. In my long mx days(71 to 84 off and on), everyone in the pits called be Duck-bill, like the then common snap on helmet visor assembly.

    Ball Ground MX park during a National. Old pic at 24yrs of age. The bike was the 2nd generation of watercooled tech for the Honda CR125 pic'd. 1983, as it was a revamped 82 i raced that year. I would say i wish i was again strong and invincvable still at that age, but alas..I'd had my left knee operated on twice by this pic. I was already fragile by then. Sitting on my Dads old 1965 Ford F100 truck. Bought it new for Gods sake.

    Was JUST(days even)married in that pic now that I think about it, and my wife was pissed off that i'd gone racing.....

    <img src="http://www.fototime.com/ftweb/bin/ft.dll/standard?pictid={0D7327CE-20AD-4D7E-9DB7-174ED87C280A}">

  59. #59
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    Just saw this. Goes with the "on your left"..man...Note the 2 words on my tail section. Thats my Branch Mgr from work trying to helpThe pits 1 hour before the start of the Invitational 1987 WERA Grand National finals at Road Atlanta that Nov. Novice 750 Superbike class final that is. Arrogent as hell..eh? Good thing I won that day LOL!. Fabian Cortez(Vance and Hines factory stroked 850cc GSXR ride)finished in my draft. He was an ******* anyway. Hope he never forgets reading that as he crossed the finish line.

    Duck

    <img src="http://www.fototime.com/{9D354B31-4D35-4701-90B0-F355DF10DDBF}/picture.JPG">
    Last edited by Duckman; 02-03-2004 at 05:28 PM.

  60. #60
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    Cool pics and stories

    Enjoyed reading that - you've got quite a history on 2 wheels. You could probably school a lot of us on braking, turning and general bike control.
    M

  61. #61
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    (Edit-1, underlined) To wrap this topic up …. Steve, I tried to find Race Car Vehicle Dynamics by Milliken, William F. It’s only at UC Berkeley and Stanford’s Libraries in the SF Bay area. And it is checked out until February 19 in both places (maybe the same book). I’m unemployed currently and can’t justify buying Milliken’s book now for $99 from Amazon (maybe someone can post Chapter 17 for academic review and non-commercial use without violating copyright privilege).

    So I’ve been thinking about the mystery of the idea Steve presents that with a bicycle’s rear suspension that “the wheel and link are treated as though they formed a single rigid body” during pedaling a bike or chain driven motorcycle (even though we agree this is true when the link mounted rear brake pads grabs the wheel’s rotor). I seriously doubt this is taken from a quote from any previous vehicle dynamic theorist, so I suspect this is Steve’s individual interpretation of Milliken’s writing about single or multi-link suspension. And I don’t see any similarity in bicycle drive and a live-axle drive (except when URT or hardtail drive).

    Either stop reading now, or take a couple of aspirin, or your favorite headache remedy now! Here’s my analysis:

    I agree 100% that a live axle system, where the shaft drive input angle (and differential gear angle) rotates with the axle’s directly attached suspension link. It acts as if the motor was directly attached to the link the axle is mounted to.

    However, DFL posting above was correct in stating that a chain drive system does not have or act like a live axle. There is never 100% translated torque of the frame-mounted motor to the axle’s link as there is with a live-axle.

    The chain-drive system only has a torque lock with the motor (or rider and crank-set) output sprocket on the frame. The chain could be viewed as welded to the frame at a moment of acceleration when the motor is 100% fixed to the frame. (Although a rider as a motor is never 100% fixed to the frame, but for argument’s sake we can pretend for a moment in analysis she is.) There is a physical lock of the chain with the wheel also at any moment, like a solid link from the frame to the top of the cog at any moment. But there is no physical or conceptual lock of either the chain or the wheel with the link the wheel’s axle is mounted to.

    DFL is also correct that the chain-drive is more closely associated with the independent rear suspension, rather than a live-axle drive system. But it is not the same. The independent rear suspension pictured earlier in a graphic I posted of a Subaru WRX rear drive, shows that the differential is attached to the frame. And a telescoping driveshaft virtually transfers the motor output from the frame directly to the wheels in the horizontal direction of the frame with the ground, and with no torque influence from the suspension rotations, much like a moment of the line of a chain-drive direction to the wheel. A shaft-driven independent suspension acts as if the motor is attached to the frame inline with the driven wheel’s axle, having a concentric drive without any vertical tension from the motor to the axle mounted suspension link. The motor and independent shaft-drive input to the wheel produces only frame rotation tension in opposition to the motor’s acceleration axis direction (consider the different frame movement when either side-wider or in-line mounted motors when they rev up), while the suspension alone produces all the frame anti-squat or anti-roll.

    The difference between a chain-driven wheel and independent shaft-driven wheel is a bit complicated and practically never the same, due to the rare and then fleetingly horizontal to ground chain-drive, while the independent shaft drive being in line with the frame is always horizontal to ground (on average). But chain-drive is always a mutually dependent combination of the frame and a percent of the wheel’s edge, and independent of the axle’s link, never acting like a live-axle shaft-drive.

    Shaft-drive with live-axle suspension is as if the motor was mounted to the axle link and directly driving the wheel’s axle. The effective motor drive-line is virtually a dot or line between the wheels spinning with the center of the live-axle bound wheels. The drive-train from the actual chassis mounted motor is translated without any vertical or horizontal tensions by a telescoping shaft-drive (if designed to avoid binding and resulting axle tramp) to the differential input of the live-axle, whether the suspension is multi-link or monopivot. For example of the net effect: if the motor was electric, it would be like the armature and shaft of the motor was the axle and the outer shell set of magnets of the motor was welded into the suspension link (whether floating link or monopivot, a simple leaf-spring is a type of mono-pivot). The live-axle drive produces an axle concentric, circular radiating “centrifugal” inertia of acceleration torque with the swingarm or link the live-axle differential is mounted to. And has a circular torque path with the swingarm/link around the axle and rotates the suspension so the effective IC with acceleration (or PofM, where the drive torque crosses the swing-arm) is wherever the physical swingarm monopivot is, or IC of a floating link live-axle is, at any moment.

    The live-axle drive is similar to braking system dynamics of a monopivot or a floating brake link, with any type of drive-line system. The wheel is one with the axle and the link the axle is mounted to when braking rotates with the wheel. The live-axle link the axle is mounted rotates with accelerating the motor in direct correlation with the wheel, faster than the wheel if front drive, slower than the wheel when rear drive. The live-axle driven suspension activates the frame at suspension’s monopivot, or IC of a floating drive-link with the frame. A front driven live-axle compresses the frame at the suspension IC or monopivot, rear drive extends the frame at IC or monopivot. Like when braking, the effective swingarm of a live-axle is from the wheel’s ground patch to monopivot or IC of a floating link with the frame, at any moment.


    Shaft-drive with fully independent suspension has a drive-line with vertical frame pitch tension in polar alignment with the frame’s pitch, at the height of the shaft-drive output from the frame. Without a live-axle differential, the independent suspension produces an IC with acceleration (or PofM, drive-line crossing swing-arm) wherever the axle’s path about the frame’s physical monopivot or virtual path pivot is at any moment.

    The chain-line is the drive-line of chain-drive. Where the chain-line crosses the swing-arm line is where the PofM is at any moment. Like a shaft-drive independent suspension, it doesn’t matter if the axle is mounted to a mono-pivot or multi-link.

    Comparing the acceleration line from the ground through the PofM against the alignment of the inertia of the CM (excluding unsprung mass) can compare the relative behaviors between various suspension-plus-drive configurations. There are only PofM vs. CM inertia tuning variances to balance bump compliance and traction vs. acceleration efficiencies. Between various configurations of suspensions and drive trains, if the PofM angle is the equal angle and varies in angle during travel at equal rate, and if the variation of CM inertia is also equal, then the acceleration effects are equal between the various linkage and drive systems.

    It doesn’t matter for bicycle suspension acceleration whether there is a monopivot or multi-link design if the PofM vs. suspended CM inertia is tuned the same. Differences in shock tuning and other frictions, and differences in the unsprung mass of the rear wheel and linkage, will vary the effects too.

    When the net inertia of the suspended CM is aligned with the acceleration line from the ground through PofM there is no suspension activity. Balanced CM inertia is variously fleeting with bicycle suspension, but the wavering imbalances are smoothed by shocks. Slower damping smoothes inertia imbalances more than fast and less restrictive damping. The most efficient accelerating and braking suspensions can use relatively fast damping and still be stable and well balanced with hard use (and can use slower damping too for more extremely hard input use such as landing jumps).

    - ray
    Last edited by derby; 02-07-2004 at 09:33 AM.

  62. #62
    ccm
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    why do you consider platform shocks work better with single pivot?

    why do you consider platform shocks work better with single pivot? or what did you say?

  63. #63
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    Sorry to hear about your job, Ray.

    Here's some basic physics:

    Consider a plain old fashioned rigid bike. If you create a torque on the rear wheel by pedaling, the rotational force that causes it has to have an equal and opposite rotational reaction. Where does that reaction go? It goes to the whole frame. The frame is made to rotate backwards around the wheel..

    This torque relationship locks the wheel to the frame and makes the bike behave as though it were one rigid body as far as the reactive thrust at the ground is concerned. If you fused the rear wheel to the frame and then provided the same thrusting force acting on the ground contact point as occurs when pedaling, the bike would come just as close to flipping over backward from the reaction up at the center of mass in either case.

    Now let's add a rear suspension. There are two basic kinds, now that independent suspension on cars has been added to the argument. In an independent suspension the point at which the torque action/reaction interchange occurs, the differential, is anchored to the frame, just as the hub is anchored to the frame on a rigid bike. It does not move with the suspension. The reaction thus goes back to the frame and the thrusting force at the ground produces a reaction at the center of mass just as on a rigid bike. If there is any anti-squat, it will be because of the thrusting force at the wheel center acting below the pivot point for the longitudinal component of the suspension's movement. That would apply to your MacStrut example.

    For rigid axle cars, drive shaft or chain driven motorcycles, and bicycles, the point at which the torque interaction occurs is part of the suspension, it moves with the virtual swingarm that the linkage system defines. The rotational force on the wheel produces a reaction on the link to which the axle is attached and a torque lock occurs between the wheel and virtual swingarm. You seem to understand this for drive shafts or for chain driven URT's, but you have a problem with a regular chain drive with BB on the main frame. Well, look back at the original example--a rigid bike. The reactive force acting through the chain pulls the frame back around the wheel. If you add a pivot point somewhere the frame can flex at that point like it was hinged. But the reactive torque still goes into the part of the frame immediately connected to the wheel and the wheel will be torque locked to that part. Then the forward force at the ground produces a backward reaction at the pivot point analagous to the backward reaction at the center of mass on the rigid bike. The wheel and virtual swingarm behave as though they formed one rigid body, just as the wheel and rigid frame behave that way. It's important to keep in mind the meaning of "as though". Of course in neither case are they really rigid bodies.

    The pole of moments theory is a way of adding the influence of the chain pull angle into the analysis. What a chain does that a drive shaft does not do is pull the main frame and rear axle towards each other. Because the chain can pull at different angles it can alter the over all torque produced. Basically the pole of moments is the point through which the ground force would have to pass in order for all the forces, proactive and reactive, working through the drivetrain to produce no net torque on the suspension. If all the forces converge at a single point, there is no force couple and thus no torque. The reaction runs into the action, so to speak.

    The pole of moments is in no way a pivot. It is a calculation device. In order to see how the forces passing through the suspension system from the ground affect the center of mass you still have use the line from ground through instant center. It's just that the amount of torque or anti-squat you get will be determined by the pole of moments. There could be none, or the anti-squat could be reversed into pro-squat.

    By the way, if you accept the pole of moments theory then you are already conceding that the wheel is torque locked to the virtual swingarm. Otherwise you would use the thrusting force at the axle and you would never draw a diagram that included the contact patch in any way.

  64. #64
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    Another mistaken 4-bar analysis.

    Another mistaken 4-bar analysis. This time it’s my mistake. I’m abandoning my mistaken notion that when braking a rear wheel with a floating brake that there is any extending action form IC’s when forward of a front wheel. IC’s do no act like independent pivots. The path pivot tracks with the swing of the IC when rear braking tensions the link and wheel the brake is attached to. I have more to think about to understand what happens when the IC is below the ground horizon, in front and behind the rear wheel.

    IC is not a pivot either, just like the PofM isn’t. They are both mapping points for combined angles of trust from real physical pivots and real rotation path slopes and tangents. The paths associated among real pivots are what really matter. The IC’s can map for us what real pivots are doing in combination.

    As I mentioned in my last thesis above, of live-axle drive, verses independent-drive and chain-drive, I agree 100% that hardtail bikes, URT, and live axles act the same under power. But independent suspension doesn’t and chain-drive is even something different (not fully independent, but not live axle, else they would act the same in all moments of travel). The motor mounted on the frame with a live-axle can twist the frame along the axis of a longitudinal mounted motor. But any vertical tension to the live-axle driven suspension (other than mass and friction reactions to acceleration) originate in the live-axle, as if the motor was mounted sidewinder to the axle housing and it’s attached link. If a UTR had two swing arms to the frame it would have the exact same effect of a live axle link with two swing-arms to the frame. A URT with a monopivot acts the same as a live-axle with a monopivot suspension, such as single pivot leaf spring. Are you saying that all bikes or maybe just ICT bikes act like URT suspensions? I don’t think that is true, although ICT bikes do emulate live-axle PofM action in one special gear set, but that’s a handicap in the goal to achieve bump compliance with stability, so ICT requires slow damping for the same reason that low-monopivots do for pedaling.

    I’ll re-read you pole of moment comments again, I didn’t follow that.

    - ray

  65. #65
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    Aw hsit, here we go again

    ...as if bike geeks, geeking out over bike gear is an unusual occurance, or a bad thing.

    I have had extended conversations like 'nipples: alloy or brass?' myself. Heh, bike geeks (like me) like to geek out over this stuff. It's part of the territory. That does not make us bad people.

    kill me now

  66. #66
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    Quote Originally Posted by derby
    A bunch of stuff that gives Steve a headache.
    It's simple really. The chain rotates the wheel with respect to the frame. Simultaneously it rotates the frame with respect to the wheel. That's Newton's law of action/reaction applied to torques. The action/reaction ties the wheel to the part of the frame it is immediately connected to.

    The pole of moments could be said to determine a length of virtual swingarm corresponding to the distance from axle to intersection of chain line and swingarm line. But whatever the length of the virtual swingarm the wheel is always torque locked to the link where the axle is mounted. That causes the wheel and link to form what your BMW article calls the rear drive unit. I like that terminology. I'm going to start using it.

    The instant center of rotation is most definitely the actual pivot point for the movement of the rear drive unit, whether you like it or not.

  67. #67
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    Chain-drive is different than both live-axle and independent suspension. Chain-drive can emulate either when using very limited chain-line/gear variables.

    The effect of a live-axle is pretty simple to understand if you use the electric motor attached to axle-mounted-link example. Bicycles only act like that, when hardtail, or standing and pedaling on a URT bike, or in one (high squat, low torque) gear set of ICT.

    A ring concentric monopivot with a 1:1 gear is fully independent suspension. But that's rather impractical for good pedaling stability without very slow damping and limiting travel (or possibly a two stage chain-drive we've seen on experimental heavy DH bikes).

    The PofM is another significant IC alignment point to consider. Strong-Like-Bull calls it the “Instant Center of Forces” which is more descriptive of the effect. The PofM angle from the ground is handy to compare various drive and suspension systems for similarities. Some non-live-axle suspensions can emulate live-axles, track the PofM angle similarities between vehicles to see, if the PofM angle is the same during travel, they have the same effect. The effects of the suspension are what matter.

    Chain-drive has the potential to emulate shaft-drive independent suspensions and the designs possible with live-axle. Chain-drive can also do what neither other system can do with possible improvements in stable bump compliance the shaft drives can't do, such as exaggerating or reducing and altering the rate of the bump compliance kick-back/kick-forward effects to the motor that any drive system transfers through gear rate travel.

    There is no advantage I see in emulating live-axle, else F1, rally cars, sports cars, dune buggies, motorcycles (except for the heavy BMW's and Moto-Guzzi's), would use or emulate live-axle. It seems to me that BMW's and Moto-Guzzi use a live-axle drive (with mysterious patent claims and trademarks) to create sales attention buzz. If live-axle was so great it would be winning races. Sound familiar?

    - ray
    Last edited by derby; 02-11-2004 at 07:10 PM.

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    But that's not when I expect my suspension to work most

    Okay so the suspension is compromised by braking and pedaling forces, but isn't four bar suspension more effective when your not braking?

    The point is when I'm pedaling I'm generally not going as fast and don't need the full benefit of the suspension. More importantly, I brake in front of the bad stuff and try to estimate a good speed to coast through it. I'm sure there are exceptions to this but I'm guesstimating that they are in a minority of situaltions.


    Quote Originally Posted by Steve from JH
    This is an excellent little article that gets at precisely the theoretical point that you, and KS, and others don't seem to be able to understand. It's what I was trying to explain the other day. (It's too hard to find the link with this damned new format but it's down the page somewhere.)

    The torque on the wheel locks it to the link on which the axle is mounted as far as the reactive force from the ground is concerned. That's true for both braking and drive acceleration. It's accepted in all writing about motor vehicles with suspension. Many of the people doing such writing are PhD.'s with specialties in vehicle dynamics. They are anything but laymen.

  69. #69
    The Ancient One
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    Have your cake and eat it

    Quote Originally Posted by DrGlen51
    Okay so the suspension is compromised by braking and pedaling forces, but isn't four bar suspension more effective when your not braking?

    The point is when I'm pedaling I'm generally not going as fast and don't need the full benefit of the suspension. More importantly, I brake in front of the bad stuff and try to estimate a good speed to coast through it. I'm sure there are exceptions to this but I'm guesstimating that they are in a minority of situaltions.
    The claim for four bars is that they can be set up to compromise the suspension less when braking than single pivots. In other words there's less difference between coasting suspension performance and rear braking suspension performance. This lets you brake later and harder before the bad stuff and to use some rear brake while going through the bad stuff to keep your speed down and still be able to steer safely.

    You can also get the effect with a single pivot and a floating brake linkage.

  70. #70
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    Quote Originally Posted by DrGlen51
    Okay so the suspension is compromised by braking and pedaling forces, but isn't four bar suspension more effective when your not braking?

    The point is when I'm pedaling I'm generally not going as fast and don't need the full benefit of the suspension. More importantly, I brake in front of the bad stuff and try to estimate a good speed to coast through it. I'm sure there are exceptions to this but I'm guesstimating that they are in a minority of situaltions.
    I have a different perspective. When I pedal, I need my suspension the most. It's usually over a rocky sketchy climb or a long rough rock garden where I want/need to keep my speed up. If my suspension were to stiffen there, would loose climbing traction and spin out on the climbs, and have the rear bounce and kick on the runs making it difficult to pedal as well as maintain a line.

    IMO if you are racing a brown-paved NORBA trail, this is almost a non-issue, It's not needed. But on rough technical terrain, it's an amazing benefit.

    All this is in addition to the breaking benefis, which if would also be a big deal for my needs but not necessarily for everyone.

    Faster is better, even when it's not.

  71. #71
    Jm.
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    No doubt, there is nothing more annoying when you are trying to climb up a grade and having the suspension try to compress from a rock or a root, only to have your chain-torque cause it to "lock out" and get much stiffer, causing you to loose traction and spin out. This is what many mid-high pivot single pivot bikes do, and what's worse is that the effect is exaggerated in the granny gear.

    I've ridden a lot, I'd rather have a little bob with a fully active system, than no bob and something that won't suck up the bumps on the climb.

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    funny funny funny

    I agree completely with Pete on this one. You guys just mangle intellectual constructs by pretending to know what bike is "best" at suspension effectiveness. There's no provable "best," you know.

    Some people like to discuss theory. That's fine, and even admirable **if** one knows what one's doing.

    Theorists who can't explain their point, and rely on graphs and charts and "data", are exactly what your excellent Feynmann quote applies to. I too like Richard Feynmann's thinking and brilliance.

    However, this nonsensical malarkey reminds me of the Meatheads who think that knowing professional/collegiate sports "statistics" makes them somehow equal to the great minds debating whether the human genome should be patentable, or whether there is an ethical reason to support gene manipulation.

    And I believe that most of the "suspension theory" prattled about in this forum is equal to that sports fan "genius" that is nothing like genius at all.

  73. #73
    mtbr member
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    Quote Originally Posted by rideit
    And curiously, the reason why they went that technology close to a decade before bicycles was to eliminate the dogbone linkage(roughly 4 bar, but not quite), in order to make a lightweight, single pivot swingarm work, while having the performance and suppleness of a dogbone. As someone state above, "there are no new ideas", well, there are new ideas, but Stable platform shock valving certainly is not one of them.
    huh? what the heck does linkage-less motorcycle suspension have to do with stable platform? ktm (and a few other small mfrs) went to a linkless suspension because they believed modern valving and progressively wound springs would work as well as a rising-rate linkage to make a bike supple on small hits while still providing bottoming resistance. last i heard, stable platform was the latest marketing hype for counteracting sloppy pedaling technique.

    seems to me ktm lost the linkage around '99, but it might have been earlier. at any rate, the suspension didn't actually get good stock until '03, and better in '04.

    what amuses me is constant argument over which frame design is better when by far the most important part of the equation (on modern frames, which almost all pretty much work) is the shock valving. sure, the suspension on my motorcycle (02 ktm) was lame, but i revalved the fork, and had the shock revalved by a professional, and now the suspension (same components) is pretty sweet. hmmmmmm. likewise, my only complaint with my Superlight was the crappy air shock. an adjustable coil shock would have made that bike perfectly satisfactory. but by the time you buy a new shock, you might as well sell the old bike and buy a new one.
    mw
    mark weaver
    kuna, id

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