The time has come to take the problem of shimmy out of the realm of myth and firmly into the world of science.
Background: When I started reading up on these forums a couple of years ago when I started cycling, I was amazed to find that the problem of shimmy (speed wobble, death wobble, harmonic vibration, whatever is it variously called) has not yet been explained in a rigorous mathematical way. Myths and anecdotes abound, but no solid math-based physical explanation is to be found anywhere. At best there are vague explanations involving a lot of hand-waving, but even these are either completely off target or too vague to be of real value.
I believe I have found the physical explanation to the phenomenon of shimmy. It is relatively straightforward to explain shimmy in broad math terms once you know the underlying mechanism; in rigorous details the math quickly becomes unwieldy far beyond its worth. To keep it simple, some simplifications have to be made which are perfectly acceptable but the ability to explain detailed cases mostly goes down the drain. My explanation differs markedly from what you can find on the web in the various FAQs, but I can write down equations or run a simulation that shows the effect.
So, to get forward in this problem I want to embark on a series of experiments to test various hypotheses about the cause of particular instances. For example, there is lots of talk about frame stiffness and about wheel stiffness. I want to put hypotheses like these to the test. I have figured out exactly how to test it. All I now need is time and equipment. If I am to obtain all the equipment myself, then it will obviously take a bit longer; however, if there are bike/frame builders or other interested parties who want to participate, specifically wrt experience and equipment, let me know. I am in Melbourne, Australia. My email address for expressions of interest is firstname.lastname@example.org. Just kill the noxious weed. I will provide a more direct email address to interested parties via that portal. If you know of potential interested parties that do not frequent these forums, please feel free to pass the word.
To recap, I already have the explanation down in broad math terms; I need to back that up with experiments for 2 reasons: One, to validate the details of explanation, and Two, to gain enough detailed understanding to provide answers to the question, "How can I cure my bike of shimmy?"
I am not associated with any academical insitution nor employed in the bicycle industry. I am just a curious individual who by happenstance encountered enough related details in my various jobs to realise what the explanation for shimmy is, and to have enough ability to write down that explanation in mathematical terms.
This will be a fairly long term project. One of the end results may be a technical paper, perhaps with a co-author if there are interested parties like graduate students. Hopefully the most important end result will be a widespread detailed understanding of the problem together with specific approaches of how to fix problems.
What I need off these forums are anecdotes of people who have encountered shimmy and have found various ways to counter it or who have performed repeatable experiments. One good example is by DannoXYZ who gives definite data about the effect of different wheels here. All these can be brought into the comprehensive explanation. What I don't need are posts about second-hand cases like "my friend's cousin's cat's fleas once had shimmy, very scary", because I may want to pose questions to gain further details, and first-hand info is more reliable.
Specifically there are two different cases of shimmy, one with riding hands OFF the handle bars and the other with hands ON the bars. It is the second case which I am focussing on, the first case I already understand in fairly fine detail. However, if you have anecdotes about case #1 in which you had repeatable experimental evidence on how you eliminated it by changing parts on the bike, please tell.
So, please post your anecdotes.