[Curb Hucker]

i havn't read the argument nor do i intend to, but i fully back Jm on this one

 

[Jm_]

ignore the rate stuff on the first picture, the only part important is the size of the arc

 

[thaflyinfatman]

ignore the rate stuff on the first picture, the only part important is the size of the arc

If that's supposed to be the "virtual pivot" (not sure whether you're referring to the IC or the CC here), it's way further forward than the CC of any FSR bike I've ever seen, and on the diagram doesn't match up with the IC. For example, Bighit compared to a pretty standard -placement singlepivot (roughly the same as a Turner DHR, I believe), note that the purple cross with "CC" labeled is the centre of curvature of the Bighit, the effective virtual pivot - and that it is BEHIND the BB. So, which one had the larger radius and more vertical axle path again? Now why don't YOU quit while you're behind... or at least drop the arrogance.

 

[thaflyinfatman]

i havn't read the argument nor do i intend to, but i fully back Jm on this one

That's pretty clever of you. I mean, if somebody tried to ram misinformation down my throat, I'd unconditionally back them too.

 

[Nately27]

If that's supposed to be the "virtual pivot" (not sure whether you're referring to the IC or the CC here), it's way further forward than the CC of any FSR bike I've ever seen, and on the diagram doesn't match up with the IC. For example, Bighit compared to a pretty standard -placement singlepivot (roughly the same as a Turner DHR, I believe), note that the purple cross with "CC" labeled is the centre of curvature of the Bighit, the effective virtual pivot - and that it is BEHIND the BB. So, which one had the larger radius and more vertical axle path again? Now why don't YOU quit while you're behind... or at least drop the arrogance.

How do you find the center of curvature for a 4-bar linkage? whats its relationship to the instantaneous center of rotation of the seatstay, and thus the wheel, at any time?

 

[RhinofromWA]

thaflyinfatman
Jm_

If I read those last few posts right..........you morons were agreeing with each other. Now you both agree that a design with the (CC,IC,VIrtual Pivot Point...whatever you dorks want to call it) farther in front of most single pivots will have a longer arc. The longer arc gives in the limited travel range of a bicycle a "more verticle" arc.

Any uneducated moron (like myself) can see that when the suspension compresses that that horst link elongates the effective chainstay length. The farther away from the rear axle and up and down from the chain stay line the more it elongates pushing out the rear axle....giving it a "more verticle" path of wheel travel. If the horst pivot is low enough the chain pulls the rear wheel forward and extends the suspension similiar to a higher single pivot under pedaling.

Now I know I don't have a bunch of computer aided drawings to make myself look and feel all important, but I would like to think I have a decent grasp on these relatively simple machines. (no offense to the work that goes into them)

I find it amazing that you two are insulting each other while talking about the same thing....

insert engi"nerd"ing techno-babble to split hairs of my post..........

NOW!

 

[Repack]

Make it stop! Please make it stop! Arghblawahahanooo!!!

 

[Jm_]

thaflyinfatman
Jm_

If I read those last few posts right..........you morons were agreeing with each other. Now you both agree that a design with the (CC,IC,VIrtual Pivot Point...whatever you dorks want to call it) farther in front of most single pivots will have a longer arc. The longer arc gives in the limited travel range of a bicycle a "more verticle" arc.

word..

 

[thaflyinfatman]

thaflyinfatman
Jm_

If I read those last few posts right..........you morons were agreeing with each other. Now you both agree that a design with the (CC,IC,VIrtual Pivot Point...whatever you dorks want to call it) farther in front of most single pivots will have a longer arc. The longer arc gives in the limited travel range of a bicycle a "more verticle" arc.

I disagree with Jm_ on principle

Basically what he's saying is that if the (virtual) pivot is further forward, the radius of the axle's arc will be larger. This is true. However, on FSR bikes, the IC (which is what some people call the virtual pivot, but it's only instantaneous and therefore doesn't give the whole picture at all, because it moves), moves down and back, giving the effect of changing the instantaneous pivot point, which in the vast majority of cases, gives you a circular axle path, the centre of which (aka centre of curvature) is JUST BEHIND the bottom bracket (not out in front of the BB, as Jm_ was saying). It is this that means that fsr bikes can have relatively little chain growth - and the radius of the curvature is about as short as you could get it with any singlepivot, if not shorter. This is where we're disagreeing.

 

[syadasti]

However, on FSR bikes, the IC (which is what some people call the virtual pivot, but it's only instantaneous and therefore doesn't give the whole picture at all, because it moves), moves down and back, giving the effect of changing the instantaneous pivot point, which in the vast majority of cases, gives you a circular axle path, the centre of which (aka centre of curvature) is JUST BEHIND the bottom bracket (not out in front of the BB, as Jm_ was saying). It is this that means that fsr bikes can have relatively little chain growth - and the radius of the curvature is about as short as you could get it with any singlepivot, if not shorter. This is where we're disagreeing.

I agree with what you are saying about the effective pivot point moving through the travel on a well designed FSR so that the chaingrowth is relatively minimal. This suspension geometry has been tuned by even specialized even within the same model (like the enduro) for certain trade offs - older ones pedaled better but were overly progressive, especially with an air shock.

Both FSR and single pivots will still be designed to function better in certain gear combos as the chain will change in relation to the pivots in different gear combos.

I also think you and JM have a pretty similiar visual idea of what is going on, but maybe you are just not explaining it well as you each are making some valid points...