In a message dated 24/05/01 16:38:49 GMT Daylight Time, monkey37@bluemarble.net writes:
> Let's hear for some of the engineers on the list on this one. Through my
> personal experience I feel that bikes with lots of quick rake at the ends
> of the fork blades have a more comfortable front end. The only way I
> could think of it was like a leaf spring. I've hear all kinds of
> anicdotial information, but I want to see some science.
> enjoy,
> Branmdon"monkeyman"Ives
>
You are right that bicycle design is short on science and long on good
experience, anecdotal evidence and just plain rubbish. Even Mike Burrows'
book "Bicycle Design" is short on science, but he does debunk a lot of myths
and separates a lot of the nonsense from the sense. Cycle magazine road
tests and product reviews compound the problem by authoritatively pronouncing
complete rubbish -- a hilarious example of which is contained within the
latest issue or "procycling" which says of the Serotta Legend Ti Race Frame
that ".. an S-bend increases power transfer through the chainstays." -- may
sound convincing but is science fiction (or, to be more accurate, total
garbage).
That said, I am sorry to say that, as an engineer, I do not have the answers. I can say that my relaxed angle bikes with long fork rake ride comfortably and the forks appear to flex merrily as I ride over rough surfaces. My track and aluminum bikes appear "harsher" or less comfortable. But I seem to recall that Mike Burrows in his book provided data that showed that frame flex is negligible compared with tire flex, which I am almost prepared to believe. In which case, what we perceive as comfortable or uncomfortable may have more to do with the frequency, rather than amplitude, of vibrations experienced by the rider. There may be some good research on this topic, but I am not aware of it. The answers can only be found by carefully constructed experiments (which I should be delighted to design and carry out if appropriate funding were forthcoming).
Sorry I can't do better -- perhaps some of the other engineers have some good data they can share with us.
Hugh Thornton