[Dirt rider]

ok i have been pondering the bb-7 and its pully. my thought is what wouold happen if the pully was on the piviot?. my first thoughts would be it woulnt work (and most likely it wont), as alot of chain would be affected in the procsees of cycling though its travel.

what do u think?


I am supremly bored!

 

[KonaDude]

It simply wouldn't pedal the same way as it does. Currently there are a few forces at work on that pulley, and because of the pulley. Those forces make it pedal pretty well, and they would be gone if the pulley was right on the pivot. In a way, you'd get a very slight compression effect if anything, which is very undesirable.

 

[evilbob]

It simply wouldn't pedal the same way as it does. Currently there are a few forces at work on that pulley, and because of the pulley. Those forces make it pedal pretty well, and they would be gone if the pulley was right on the pivot. In a way, you'd get a very slight compression effect if anything, which is very undesirable.

Perfect answer from KonaDude!

 

[dw]

Originally posted by KonaDude
Those forces make it pedal pretty well, and they would be gone if the pulley was right on the pivot. In a way, you'd get a very slight compression effect if anything, which is very undesirable.

If the pulley is larger than the cog that it is driving in the back, the chain pull will give compression. If the pulley is smaller than the cog driven in back, the chain pull effect will give extension.
This obviously doesnt take into effect the driving force acting on the swingarm at the axle. (hence i used the term chain pull)

The driving force at the axle, through the swingarm on the BB7 gives an extension component through most of the travel. The net forces must take into account both components. On the 2001 and 2002 BB7, the net affect will be less extension than presently in the system, but still extension.


dw

edit: spelling

 

[dw]

Originally posted by evilbob


Perfect answer from KonaDude!

see above

dw

 

[Steve from JH]

Originally posted by dw


If the pulley is larger than the cog that it is driving in the back, the chain pull will give compression. If the pulley is smaller than the cog driven in back, the chain pull effect will give extension.
This obviously doesnt take into effect the driving force acting on the swingarm at the axle. (hence i used the term chain pull)

The driving force at the axle, through the swingarm on the BB7 gives an extension component through most of the travel. The net forces must take into account both components. On the 2001 and 2002 BB7, the net affect will be less extension than presently in the system, but still extension.


dw

edit: spelling

The size of the pulley relative to the size of the cog in back is irrelevant. What matters is the relation of the chain line, in this case the line between top of pulley and top of cog, and the swingarm line, the line from axle through pivot.

The driving force is not measured at the axle but at the ground. It is only measured at the axle on cars with independent rear suspension. With rigid axle cars, or on bicycles or motorcycles, it is measured at the ground.

As far as putting the pulley at the pivot is concerned, a bike that would work perfectly well could be set up that way.

These ideas are not mine. They come from RACE CAR VEHICLE DYNAMICS by Milliken and Milliken and from MOTORCYCLE DESIGN AND TECHNOLOGY by Gaetano Cocco.

I have not taken into account the chain lengthening or kickback effect because, according to Balfa, the pulley is close enough to the pivot to make it negligible. If the pulley was at the pivot, there would of course be no chain lengthening effect at all.

 

[dw]

Originally posted by Steve from JH


The size of the pulley relative to the size of the cog in back is irrelevant. What matters is the relation of the chain line, in this case the line between top of pulley and top of cog, and the swingarm line, the line from axle through pivot.

The driving force is not measured at the axle but at the ground. It is only measured at the axle on cars with independent rear suspension. With rigid axle cars, or on bicycles or motorcycles, it is measured at the ground.

As far as putting the pulley at the pivot is concerned, a bike that would work perfectly well could be set up that way.

These ideas are not mine. They come from RACE CAR VEHICLE DYNAMICS by Milliken and Milliken and from MOTORCYCLE DESIGN AND TECHNOLOGY by Gaetano Cocco.

I have not taken into account the chain lengthening or kickback effect because, according to Balfa, the pulley is close enough to the pivot to make it negligible. If the pulley was at the pivot, there would of course be no chain lengthening effect at all.

Steve,

I am well versed and understand fully the writings of Milliken and Cocco.

Re-read motorcycle design and technology. Page 73 should clear up all of your misconceptions. Gaetono clearly illustrates the moment pole calculation, WHICH IS DRIVEN BY SPROKET DIAMETERS FRONT AND REAR AND PIVOT LOCATION. These graphs clearly illustrate the concepts that I wrote about up top.

Ask yourself this, if the pulley is moved concentric to the main pivot (as we are speculating about here) what controls the location and vector of the chainline? A majic elf? nope. Its the SPROCKET PITCH DIAMETER.

I dont know what else to say man. Keep tryin.

dw

adding edit: keep in mind steve, we are talking about a concentric pivot swingarm here.

 

[MMike]

ahahahaaa... he quotes page numbers.....awesome.......

Originally posted by dw


Steve,

I am well versed and understand fully the writings of Milliken and Cocco.

Re-read motorcycle design and technology. Page 73 should clear up all of your misconceptions. Gaetono clearly illustrates the moment pole calculation, WHICH IS DRIVEN BY SPROKET DIAMETERS FRONT AND REAR AND PIVOT LOCATION. These graphs clearly illustrate the concepts that I wrote about up top.

Ask yourself this, if the pulley is moved concentric to the main pivot (as we are speculating about here) what controls the location and vector of the chainline? A majic elf? nope. Its the SPROCKET PITCH DIAMETER.

I dont know what else to say man. Keep tryin.

dw

 

[Steve from JH]

Originally posted by dw





adding edit: keep in mind steve, we are talking about a concentric pivot swingarm here.

I thought we were talking about the Balfa. If you made the pulley concentric with the pivot, then what you say is almost true. You could set it up so that the front pulley was only slightly larger than the rear cog and the pole of moments would be behind the axle and below the ground line. That would produce extension.

On a somewhat unrelated topic, do you know anything about this new Edge bike made in England? It appears to use a short parallelogram linkage with a solid triangle rear end so that the axle rotates exactly around the BB. The triangle does curvilinear translation rather than rotation. What's the point of using such a linkage instead of a simple swingarm?

My original point was that I could change the size of the front sprocket in the diagram on p.73 of the Cocco book and still produce the same initial pole of moments. Of course when the swingarm then is moved to a second position the second pole of moments is no longer the same.

 

[MikeD]

I was an art major!

:brainhurts:

 

[dw]

Originally posted by Steve from JH


If you made the pulley concentric with the pivot, then what you say is almost true.

Its more than almost true, its 100% true.

So if you now agree that this is true, then how can a pivot at the chainline give no extension? (as you have said before adamently) Ask yourself that one.

dw

 

[binary visions]

Originally posted by dw


Its more than almost true, its 100% true.

So if you now agree that this is true, then how can a pivot at the chainline give no extension? (as you have said before adamently) Ask yourself that one.

dw

Hm.

Lots of this suspension theory is over my head, though I'd like to learn more. dw: publish the book man! Aside from that, where would you suggest I go to learn more? I have what I think is a very good understanding of why and how certain suspension types work, but it's only a visual understanding: I see why pedal induced bobbing is caused, but have no terms or numbers to back it up. I understand why brake jack/dive happens, but can't explain it.

Also, I've learned one thing from watching these suspension discussions.. Arguing with dw over suspension theory is useless. He knows his stuff and backs it up very well: even if I don't understand all of it, I know a good backup proof when I see it!

 

[Steve from JH]

Originally posted by dw


Its more than almost true, its 100% true.

So if you now agree that this is true, then how can a pivot at the chainline give no extension? (as you have said before adamently) Ask yourself that one.

dw

It's easy to win an argument with someone if you attribute positions to them thay they do not have. I have not said any such thing, either adamantly or any other way.

When we say in this discussion that extension is produced, neither of us is considering the reaction of the center of mass. An extending torque on the suspension can produce jack or squat or neither as the final result when you take the center of mass into account. The same bike ridden in the same gear by Shaquille O'Neale or some Munchkin could squat in the first case and jack in the second.

As for your statement being 100% true, I say not according to what Cocco is saying. On that same page 73 is a diagram in which compression is produced by having the pole of moments below the ground and in front of the rear axle. Likewise, although not shown, you could have extension if the pole of moments is behind the axle and below the ground. With a pivot concentric front sprocket, the first case would require the front sprocket to be smaller than the rear cog and the second case would require it to be larger.

 

[dw]

Originally posted by Steve from JH

It's easy to win an argument with someone if you attribute positions to them thay they do not have. I have not said any such thing, either adamantly or any other way.

When we say in this discussion that extension is produced, neither of us is considering the reaction of the center of mass. An extending torque on the suspension can produce jack or squat or neither as the final result when you take the center of mass into account. The same bike ridden in the same gear by Shaquille O'Neale or some Munchkin could squat in the first case and jack in the second.

As for your statement being 100% true, I say not according to what Cocco is saying. On that same page 73 is a diagram in which compression is produced by having the pole of moments below the ground and in front of the rear axle. Likewise, although not shown, you could have extension if the pole of moments is behind the axle and below the ground. With a pivot concentric front sprocket, the first case would require the front sprocket to be smaller than the rear cog and the second case would require it to be larger.

steve, you went off on this subject talking about the ellsworth frame the other day, where I corrected you. I let it die because I didnt feel that it was worth my time.

I am glad that you are beginning to understand the dynamics involved here. Moment pole is representation of the net effect of axle force and chain pull. YOu seem to be misunderstanding or not choosing to read completely my comments. We are speaking about chain pull here, not moment pole, two seperate entities.

As I have written above (3 times now)
On a concentric pulley suspension as we are discussing here, the CHAIN PULL with a smaller sprocket in front, and a lager sprocket in back. will give an extenesion force. Couple that with the axle force and you get the net force at the axle, which is graphically defined using the moment pole layouts.

IMPORTANT FOR YOU TO READ AND UNDERSTAND ----> As the suspension that we are discussing in this thread moves through its travel it can have a NET compression effect, but the chain pull will ALWAYS be contributing an extension force. Seeing as this is what the poster was asking....

Please stop trying to catch me in some kind of wrong statement. Its not going to happen, and honestly, this whole thing is becoming kind of tiring.

dw

 

[ohio]

Originally posted by Steve from JH
The same bike ridden in the same gear by Shaquille O'Neale or some Munchkin could squat in the first case and jack in the second.

You've made this statement in a couple of threads... are you saying this is true given the same power output from each rider or is it true regardless of power output.

Anyway, I think where a lot of your disagreements with DW (and in old threads here and on MTBR with me) stem from your treatment of chain effects and CoG effects collectively. For the purposes of designing bicycles, IMO there is little reason to incorporate CoG effects in performance under acceleration, because unlike a motorcycle the weight of the vehicle is somewhat negligeable and the position of the rider is highly variable. So the principles of design as described in a motorcycle chassis design text do NOT directly apply to bicycles, though they can be translated into use.

It makes these discussions much simpler if you treat the two seperately and then sum them after chain effects analysis on a case by case basis.

-ohio

 

[dw]

Originally posted by ohio


It makes these discussions much simpler if you treat the two seperately and then sum them after chain effects analysis on a case by case basis.

-ohio

yup, thats the way i do it at least.

dw

 

[FlipSide]

Originally posted by dw


Please stop trying to catch me in some kind of wrong statement. Its not going to happen, and honestly, this whole thing is becoming kind of tiring.

dw

 

[Steve from JH]

Originally posted by dw


steve, you went off on this subject talking about the ellsworth frame the other day, where I corrected you. I let it die because I didnt feel that it was worth my time.

I am glad that you are beginning to understand the dynamics involved here. Moment pole is representation of the net effect of axle force and chain pull. YOu seem to be misunderstanding or not choosing to read completely my comments. We are speaking about chain pull here, not moment pole, two seperate entities.

As I have written above (3 times now)
On a concentric pulley suspension as we are discussing here, the CHAIN PULL with a smaller sprocket in front, and a lager sprocket in back. will give an extenesion force. Couple that with the axle force and you get the net force at the axle, which is graphically defined using the moment pole layouts.

IMPORTANT FOR YOU TO READ AND UNDERSTAND ----> As the suspension that we are discussing in this thread moves through its travel it can have a NET compression effect, but the chain pull will ALWAYS be contributing an extension force. Seeing as this is what the poster was asking....

Please stop trying to catch me in some kind of wrong statement. Its not going to happen, and honestly, this whole thing is becoming kind of tiring.

dw

Hey I'm not going to stop until I get tired myself or until I get banned.

Remember these are not my ideas but Gaetano Cocco's. You are not using "chain pull" the same way he is. The section of the book we've been discussing is called EFFECT OF THE TRANSMISSION OF DRIVING FORCE TO THE GROUND. In parentheses it says, "known as CHAIN PULL effect in the motorcycle world."(p. 71) Note that nothing is said about force at the axle.

CHAIN PULL ANGLE is defined on p.72: The angle formed by the straight line passing from the PofM to the point on the ground P[the ground contact point] and the surface of the ground is called the CHAIN PULL ANGLE.

The greater the chain pull angle, the more extension. On p.73 we find figure 6.6 called "negative chain pull angle". The text says, "If we gave completely free play to our imagination, we could create a transmission system that tends to compress the suspension during acceleration." The diagram shows the PofM below the ground line so that the angle is negative. The front sprocket is smaller than the rear. It's not a pivot concentric setup but it just as well could be.

The way you are using the term would apply when there is no traction--with the wheel suspended in the air for example.(p.74-75) There the relevant angle is that between the swingarm line and the chain line. Your statement about cog size for a concentric pivot would then always be true since there is no ground line to consider.

It seems to me that it's important to keep clear this distinction between what happens with traction and without. I've noticed in other posts of yours that you do not seem to do so.

 

[Steve from JH]

Originally posted by ohio


You've made this statement in a couple of threads... are you saying this is true given the same power output from each rider or is it true regardless of power output.

Anyway, I think where a lot of your disagreements with DW (and in old threads here and on MTBR with me) stem from your treatment of chain effects and CoG effects collectively. For the purposes of designing bicycles, IMO there is little reason to incorporate CoG effects in performance under acceleration, because unlike a motorcycle the weight of the vehicle is somewhat negligeable and the position of the rider is highly variable. So the principles of design as described in a motorcycle chassis design text do NOT directly apply to bicycles, though they can be translated into use.

It makes these discussions much simpler if you treat the two seperately and then sum them after chain effects analysis on a case by case basis.

-ohio

The Shaquille reference was meant to pertain to height of CofG.

I think I am always careful to be clear whether or not I am considering the CofG.

DW does not seem to be clear in distinguishing the chain pull effect when there is traction from when there is not. Or perhaps he believes there is no difference.

 

[ohio]

Originally posted by Steve from JH
[B
It seems to me that it's important to keep clear this distinction between what happens with traction and without. I've noticed in other posts of yours that you do not seem to do so. [/B]

I believe all of DW's cases are assuming traction, though I haven't read back through EVERYTHING...

With a bicycle, there is almost no reason to consider the case with no traction, since the rotational inertia of the wheel itself is so low that it's acceleration has a negligeable effect on the suspension.

 

[dw]

Originally posted by Steve from JH

Hey I'm not going to stop until I get tired myself or until I get banned.

Remember these are not my ideas but Gaetano Cocco's. You are not using "chain pull" the same way he is. The section of the book we've been discussing is called EFFECT OF THE TRANSMISSION OF DRIVING FORCE TO THE GROUND. In parentheses it says, "known as CHAIN PULL effect in the motorcycle world."(p. 71) Note that nothing is said about force at the axle.

CHAIN PULL ANGLE is defined on p.72: The angle formed by the straight line passing from the PofM to the point on the ground P[the ground contact point] and the surface of the ground is called the CHAIN PULL ANGLE.

The greater the chain pull angle, the more extension. On p.73 we find figure 6.6 called "negative chain pull angle". The text says, "If we gave completely free play to our imagination, we could create a transmission system that tends to compress the suspension during acceleration." The diagram shows the PofM below the ground line so that the angle is negative. The front sprocket is smaller than the rear. It's not a pivot concentric setup but it just as well could be.

The way you are using the term would apply when there is no traction--with the wheel suspended in the air for example.(p.74-75) There the relevant angle is that between the swingarm line and the chain line. Your statement about cog size for a concentric pivot would then always be true since there is no ground line to consider.

It seems to me that it's important to keep clear this distinction between what happens with traction and without. I've noticed in other posts of yours that you do not seem to do so.

wow, diggin deeper and deeper arent we...

i most certainly do incorporate traction into everything.. It should be completely clear to you that ths is the case. how could one perform such an analysis and not??? at this point you seem to be just babbling.

Seriously. You are totally misunderstanding what you are reading in the written references you cite. Gaetono Cocco's book is not meant to be a motorcycle design guidebook, it is a reference for riders to understand what is happening with their bike. It is not a complete engineering work.

I cant help you any further in this matter. I was trying to be a nice guy and help you out, but you dont want to hear it. Despite what you state here, chain pull is not the only force at work on the suspension. At least that should be clear to te lay person.

forget it Steve, you spin this any way that you want. Some day, if you learn more and open your eyes to the fact that you are not correct, youre going to read this all again and say, " wow, dw was/is spot on"

Ill ask you again, please stop spreading misinformation on these boards. I am telling you straight up, you do not see the full picture here. This isn't me being cocky, this isn't me giving a care at all whether you figure it out eventually or not. This is me, fully understandding the principles we speak of, not wanting the general public to read what you have written and become misinformed.

dw

 

[EBasil]

I forgot: which of you two guys is Horst Leitner?

 

[dw]

Originally posted by EBasil
I forgot: which of you two guys is Horst Leitner?

maybe a better question is "which one of you guys has built suspension frames that work as well as or better than bikes based on an old design by horst leitner"???

'hrmmmmmm

 

[ohio]

Wowee. Remind me not to get on DW's bad side while he's scrambling to get ready for Interbike!

Dave, your chainguides are a farce and you stole the Imperial design from Pacific! And you spec'd inferior cotton for your Evil T-shirts! According to my FEA, the optimum thread fabric is 125 tpi, 200g organic egyptian combed cotton. I challenge you to prove otherwise!


Ican'tbelieveI'mstillatwork...grumblegrumble...

 

[EBasil]

Originally posted by dw


maybe a better question is "which one of you guys has built suspension frames that work as well as or better than bikes based on an old design by horst leitner"???

Whoa! I posted something about you earlier. I had no idea Gary Fisher, himself, posted here! I didn't know you welded, though...



Okay, okay: Which one of you guys has designed suspension frames that work better than bikes based on an old design by Horst Leitner ? Examples would be nice. Oh, and Gary, if you list the URT bikes I'm gonna throw away all my printouts of this thread!

 

[dw]

im sorry.

i am coming down hard on our man steve here and it is not my place.

Steve. I am not posting a novel here. I have adressed small parts of a much greater system. I can tell you that I am 100% confident in my work. It is not of my own creation in full. Everything that I know, I have learned, and I have been damn sure to back up what i have learned with lots of my own work, design and testing. Met with many people with more experience than I in the mechanical arts. I am happy to share what I kow with the people. This is why I dedicated myself to writing my bok a couple years ago. It is to much to type a complete answer on a forun every time that someone like yourslef, with some knowledge, but maybe not the total knowledge comes in. I can see that you are a smart guy, and I am confident that you will see things as I do at some point with the addition of more of your attention.

dw

 

[evilbob]

IMO most people who post suspension questions here do not have the schooled, read or applied knowledge to understand the full technical response given by some of the experts. While I find the technical experts to be competent (DW is very) and the conversation is enlightening (sort of), it is beyond the need of most posters. In an effort to supply the right answer perspective gets lost as to the questions real need. This one turned into a match of who's therory or book interpretation is bigger and there by loses value to most who are curious about a simple explenation/answer. Not saying anyone here can't take details but Dirt Riders question was simple enough and KonaDude did good with a simple explanation. DW your awesome, say it once if the simple answer is wrong and get out, anything further is a waste of your time. Steve.....moto stuff has other issues bikes do not so some of the book examples do not apply to bikes in the larger since of same examples. Keep it simple enough for the general population and you will help them more. Spray the turf and you guys start losing credibility. This is a bad thing as most people need the experts to come up with fun toys and to be able to clear the high level technical mumbo jumbo into easy comprehensable answers. Tech wars (shared learning opportunities)are better waged on the side, please.

 

[dw]

Originally posted by EBasil



Whoa! I posted something about you earlier. I had no idea Gary Fisher, himself, posted here! I didn't know you welded, though...

Okay, okay: Which one of you guys has designed suspension frames that work better than bikes based on an old design by Horst Leitner ? Examples would be nice. Oh, and Gary, if you list the URT bikes I'm gonna throw away all my printouts of this thread!

i believe that there was and AS WELL AS OR BETTER in there

I would never come out and say straight up better. Not my style.

I put down the welding torch and got on the analysis horse in 1998. I let the welders spend their time wleding, and I do the design work. Look around e basil, if you really care to see examples of what I have designed. I have plenty more coming too E No URT's here, heh

dw

 

[dw]

Originally posted by evilbob
IMO most people who post suspension questions here do not have the schooled, read or applied knowledge to understand the full technical response given by some of the experts. While I find the technical experts to be competent (DW is very) and the conversation is enlightening (sort of), it is beyond the need of most posters. In an effort to supply the right answer perspective gets lost as to the questions real need. This one turned into a match of who's therory or book interpretation is bigger and there by loses value to most who are curious about a simple explenation/answer. Not saying anyone here can't take details but Dirt Riders question was simple enough and KonaDude did good with a simple explanation. DW your awesome, say it once if the simple answer is wrong and get out, anything further is a waste of your time. Steve.....moto stuff has other issues bikes do not so some of the book examples do not apply to bikes in the larger since of same examples. Keep it simple enough for the general population and you will help them more. Spray the turf and you guys start losing credibility. This is a bad thing as most people need the experts to come up with fun toys and to be able to clear the high level technical mumbo jumbo into easy comprehensable answers. Tech wars (shared learning opportunities)are better waged on the side, please.

yeah, you are right. I just cant leave well enough alone sometimes. I will work on the one time answer and leave it at that. You would think after I have been thorough this 20 times I would learn that.

dw

 

[evilbob]

yeah, you are right. I just cant leave well enough alone sometimes. I will work on the one time answer and leave it

Desire and habit I do it all the time, trying not to but very hard when you just want to help.
If we all had the time to meet and constructivly work this stuff, man what could be learned and the results that would follow.

 

[binary visions]

Originally posted by dw


yeah, you are right. I just cant leave well enough alone sometimes. I will work on the one time answer and leave it at that. You would think after I have been thorough this 20 times I would learn that.

dw

Well, I think we all want to set straight people who are talking about the subjects we know a lot on. Even if it doesn't matter, even if you're not changing their mind, it's pretty natural to want to talk about what we know best.

Or maybe it's just me. 'Cause I do it all the time. It's just really frustrating when you spend so much time understanding and learning something, dedicating so many hours to having a full understanding, and someone is spreading information that you know to be wrong (and please, Steve, don't take this as a slam: I don't even know which one of you is right!).

Oh well. Keep arguin', just make sure there's no blood

 

[KonaDude]

Originally posted by dw


If the pulley is larger than the cog that it is driving in the back, the chain pull will give compression. If the pulley is smaller than the cog driven in back, the chain pull effect will give extension.
This obviously doesnt take into effect the driving force acting on the swingarm at the axle. (hence i used the term chain pull)

The driving force at the axle, through the swingarm on the BB7 gives an extension component through most of the travel. The net forces must take into account both components. On the 2001 and 2002 BB7, the net affect will be less extension than presently in the system, but still extension.


dw

edit: spelling

Agreed on that, I was providing a super general answer, since I didn't want the discussion to elevate to this (as much as I love technical discussion). Now that it has, I guess it's too late. hah.

Sometimes I find it difficult to follow these discussions not because of a lack of understanding, but because my mind goes beyond my education. I can look at a design and figure out which forces are at play and in which directions, but I have trouble explaining it in your terms.

Besides, as I've become more busy, I have trouble making my typical ultra-long posts or even thinking much about bikes beyond getting these darn prototypes done.

If you and Steve could sit down in a room for awhile and talk in person, you may not disagree this much because you would be better able to communicate the technicalities you are getting stuck on right now.

Relax.

 

[Thylacine]

*shyly puts hand up as a maker of idler pully based bike*

Okay your honor, I'm guilty as charged. Now before I say anything, I would like to point out that I'm not an engineer - I'm an industrial designer - which is kind of like an bad engineer with an ego, but less boring, err, I mean focussed. And to be honest, I looked at Coccos book, but I saw nothing about suspension, only stuff about how to make clothes - which didnt help me make a bike, but I got some great ideas for a team jersey!

So anyway, to explain my rationale in a way that wont alienate most people. On my frame I put the idler pulley where it is to help isolate chain loads from the suspension equation. All single pivot bikes have this problem of chain torque induced 'bobing', and after riding my design and others, I'm a believer that what myself, Balfa and others are doing is a viable solution. Now, theres no denying from what I understand that idler size and location relative to the pivot loaction has an effect on the performance of the design. Do I think that it was more important to have a decent size idler to take the loads and not wear quickly, rather than compare it to a motorbike which has different requirements? Yeah, absolutely. Do I think that locating the idler ON the pivot rather than offset like I have would make a big difference? No, not at all.

So it sucks to see this kind of flame war happening. Its not really constructive, and it doesnt make the BB7 any better or worse a bike, just makes everyone look petty and stupid. I think the BB7 is a pretty nice bike personally, and like I said, the idler pulley concept DOES work. How do I know? I built one. I ride one thats done over 1000kms since last December with no damage except a worn out pully and a few snapped chains ( Damn that Shimano 9sp! ). I've even leared a few things along the way that werent obvious even after my 18 months of research, my consultant engineers and I hate to think how many hours infont of a computer.

Anyway, thats just my 2 cents. Idler bikes are cool in my book, and I say if you want one, go for it. In the meantime, fingers crossed in the not to distant future I'll be able to offer mine up for sale, and hopefully we'll all put those sh!tty pseudo four bar bikes in their place!

 

[dw]

Originally posted by Thylacine
*shyly puts hand up as a maker of idler pully based bike*

Okay your honor, I'm guilty as charged. Now before I say anything, I would like to point out that I'm not an engineer - I'm an industrial designer - which is kind of like an bad engineer with an ego, but less boring, err, I mean focussed. And to be honest, I looked at Coccos book, but I saw nothing about suspension, only stuff about how to make clothes - which didnt help me make a bike, but I got some great ideas for a team jersey!

So anyway, to explain my rationale in a way that wont alienate most people. On my frame I put the idler pulley where it is to help isolate chain loads from the suspension equation. All single pivot bikes have this problem of chain torque induced 'bobing', and after riding my design and others, I'm a believer that what myself, Balfa and others are doing is a viable solution. Now, theres no denying from what I understand that idler size and location relative to the pivot loaction has an effect on the performance of the design. Do I think that it was more important to have a decent size idler to take the loads and not wear quickly, rather than compare it to a motorbike which has different requirements? Yeah, absolutely. Do I think that locating the idler ON the pivot rather than offset like I have would make a big difference? No, not at all.

So it sucks to see this kind of flame war happening. Its not really constructive, and it doesnt make the BB7 any better or worse a bike, just makes everyone look petty and stupid. I think the BB7 is a pretty nice bike personally, and like I said, the idler pulley concept DOES work. How do I know? I built one. I ride one thats done over 1000kms since last December with no damage except a worn out pully and a few snapped chains ( Damn that Shimano 9sp! ). I've even leared a few things along the way that werent obvious even after my 18 months of research, my consultant engineers and I hate to think how many hours infont of a computer.

Anyway, thats just my 2 cents. Idler bikes are cool in my book, and I say if you want one, go for it. In the meantime, fingers crossed in the not to distant future I'll be able to offer mine up for sale, and hopefully we'll all put those sh!tty pseudo four bar bikes in their place!

your bike should work, it makes a lot of sense why it would!

i think your bike's supension design looks pretty sweet myself.

you know whats crazy, i got so fed up with this thread when it was going that this is the first time that I actually came back to techtalk board since my last post in it...

dw

 

[Jm_]

yeah, I've watched Grizza(thylacine)s design take off, really neat to see him design it, get the required parts produced, and assembled, I know he's proud and it's a big accomplishment.

BTW, I probably wont ride a bike designed by Steve from JH.

 

[Thylacine]

Originally posted by Jm_
yeah, I've watched Grizza(thylacine)s design take off, really neat to see him design it, get the required parts produced, and assembled, I know he's proud and it's a big accomplishment.

BTW, I probably wont ride a bike designed by Steve from JH.

Thanks for the praise Jm - I feel all warm and fuzzy inside Seriously though, I love this bike, I just hope that people warm to the X-Trials and the sweet steel hardtail XCSL enough for me to be able to produce the FS bike, and the FR design I have on the drawing board some time in the future. I'm a big believer in the 'single pivot bikes with a twist', so hopefully things going to plan I'll be able to step up and put these puppies into production within the next 12 months. Thats my dream and gawddamnit, I'm gonna live it!

 

[MikeD]

Jm...

You an old empty beerer? Few Monkeys know the Grizza....!

MD

 

[partsbara]

who is this evil , evil cat grizza you speak of ?

empty beer, for sure, i m off to the fridge to get another becks !

 

[Thylacine]

Mate, I've had my share of evil for a lifetime today. Turns out my nice fabricator 'friend' is a cross between Gordon Gecko and Satan, but dressed like Forest Gump ( post shrimp fishing days, you know, when he had heaps of cash ) so I'm looking for a new fabricator or 5. I'm sure he's reading this coz he has his computer hooked up to search for anything on the net that says Thylacine, and lemme tell ya, its not because hes a fan. *waves*

Ah well, back to square one. Time to go looking for some good people. If I got as much support in my professional life as I do from you guys and my Japstralian buddies, they're be no limit to what we could accomplish.

As a great man, Mr Marui from Tioga once said....

"*brushes hands together like removing dirt from them* Move On!"

 

[MikeD]

Hey, if ya need to hire a Thylacine Drug Against War, get me my Down Under Green card and I'll be down to do your dirty work when ya need it...

Would it piss him off more if I had some stickers?

MD

Sorry to hear it all, bro...I'd hoped things had gotten better. It's astounding what people can do.