The shimmy article was OK. In general, I'm not a fan of every BQ article I read, but BQ is the only publication I read cover to cover every time.
FWIW the two fender articles alone make buying a copy worthwhile. On Dec 10, 2:07 pm, William <[email protected]> wrote: > Jan > > I'm extremely flattered at your almost instant reply. I don't know if > that means you regularly read the list or if somebody you know does. > I admire your work deeply and endorse your publication > enthusiastically. Every copy of BQ I've seen has had something > astonishing for me. This issue was no different. I am pleased to be > a subscriber. > > Regarding shimmy, it's possible that my expectations were > unrealistic. I thought I'd learn some conclusive, empirically > testable conclusions, and I didn't get that. That being the state of > things, I'm motivated now to experiment myself. I'm certain that you > encourage that, and your article actually has helped urge me to do > that which I think is a positive outcome. > > The things that 100% can agree upon is that shimmy is an oscillation. > For that reason, it is easy to assume that there should be a spring > +mass+damper model that can be used to understand the system. > Whatever that system is, we can also agree, I think, that there exists > some excitation force is acting on that system and making it > oscillate. The missing piece in the few articles I've read prior to > yours is a failure to establish and define what any of these things > even are. What is the spring? You argue that it is the flexing > torsion of the frame, but then concede that both the stiff frames you > hate nor the flexy frames you love both don't shimmy. You imply that > tire flex has something to do with the system, but it's not clear to > me whether you think it's part of the spring, the mass, the damper, > the exitation force, a combination, or all four. What is the mass? > Some suggest that it is only the steering parts, others state it is > everything including rider and the rear part of the bike. What's the > damper? You argue that it's the stuff that hinders rotation: headset > plus riders hands, and indirectly the riders leg squeezing the top > tube. J. Brandt says tire tread is also a significant damper. > Regarding the excitation force, there is no consensus of what it is or > where it comes from. Sheldon(RIP) said it came from the back end of > the bike, J. Brandt says it comes from the spinning wheel and > sometimes from the natural frequency of human shivering. You, I > think, allow it to be anything, since it is the amplifying or > attenuating property of the system that is important, hence the > artificial whacking the top tube to get it going. If there isn't even > consensus on what the system is, then there is no hope to formally > construct a comprehensive understanding of that system. > > It very well may be that shimmy is just a property of a bike+rider > system that is the unknown functional combination of numerous > unmeasurable variables. If that's the real answer, then maybe you're > recommendation is the only one that works: > > If your bike shimmies, change something > If it got better, be happy or change the same thing even more > If it got worse, change the same thing in the other direction > If it stayed the same, change something else > > Again, my opinions about whether or not your article not meets my > expectations does not reflect on the quality of your contributions to > the cycling world. I hoped that your article starts a dialogue that > gets the topic driven to a more satisfying scientific understanding. > It all strikes me as voodoo right now. With all due respect, this > needle bearing headset thing, especially, strikes me as voodoo. > > Bill > > On Dec 10, 10:29 am, Jan Heine <[email protected]> wrote: > > > William, > > > I am sorry you are disappointed with our article on shimmy. We tried > > to offer summary of the factors that appear to cause or exacerbate > > shimmy. After all, we know that some bikes rarely shimmy (heavy tubes, > > long trail, no load, skinny tires). It appears that shimmy is a multi- > > faceted problem with more than one cause and more than one solution. > > To provide a complete picture, we presented other opinions on the > > issue, which may help you in your own research... I find it > > fascinating what people thought about these things 50 or 70 years ago. > > > Most of all, we felt the need to publish this article, because we very > > much like bikes with optimized handling, wide supple tires, relatively > > flexible tubing, etc. The one downside of these bikes is a greater > > tendency to display shimmy. Of course, your Sam Hillborne shows that > > even bikes that are very different also can display persistent shimmy. > > And none of our favorite bikes shimmies a lot, so low trail, front > > loads, wide supple tires and relatively flexible tubing don't > > automatically result in a bike that shimmies. I am beginning to > > believe that all bikes have a tendency to shimmy, and depending on a > > number of factors, the oscillations either are dampened or self- > > reinforce. > > > For your bike, if you don't already have a needle-bearing headset, I'd > > give it a try. That is the only thing we have found to work > > consistently in "curing" shimmy or at least reducing it so that it > > appears only rarely. You may also try to switch to narrow, stiff > > tires, but there are downsides to that. If you are carrying a load on > > your bike, you could try using a backpack (with its own downsides). > > It's hard to change the tubing or geometry of your bike... > > > I don't know what you expected in the article, but I would like to > > remind you that we offer a money-back guarantee for the unused portion > > of your subscription. And if your experiments yield something > > conclusive, please let us know. We'd love to publish your experiences > > as an additional piece to the puzzle. > > > Jan Heine > > Editor > > Bicycle Quarterlyhttp://www.bikequarterly.com > > > Follow our blog athttp://janheine.wordpress.com/ > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. 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