Re: Great short distancer runners but Mother Nature left out the brains! - Page 3

 

Bob Myers wrote:


Publication, not necessarily a texbook.  Why, of course.  If it's not
published, it pretty much doesn't exist.  Life's tough.


It's from year 2000, so kinda late for such a revelation, isn't it?


http://socrates.berkeley.edu/~fajans/pub/pdffiles/SteerBikeAJP.PDF  

http://books.google.com/books?hl=en&lr=&ie=UTF-8&id=CPosYIEgag8C&oi=fnd&pg=PA176&dq=%22Lowell%22+%22The+Stability+of+Bicycles
%22+&ots=-ypSs4v3h6&sig=zxxeJL6m2iihRSrBDW2nphm15Y4

http://www.phys.lsu.edu/faculty/gonzalez/Teaching/Phys7221/vol59no9p51_56.pdf

I added links for people to easy find the actual texts.

I read through Jones' classic article in Physics Today, and sorry, but no
banana.  He made a really good effort, he managed to firmly exclude
gyroscopic forces as a main stabilizing agent, but didn't explain much.  A
lot of trial and error, recorded for posterity and a firm place in the
history, but not an explanation.  This article doesn't contain one single
equation FFS.

Lets see this 1982 thing.  I won't count it, even it it provides correct
models, because at this time I was going to an elementary school, so even
if the guys got it right this time around we can't expect that it would be
immediately thought in schools.  

This article is much better.  They almost figured contersteering by this
time and they definitely figured the mechanisms which make the bike
stable* , so pretty damn close to current level of knowledge, as
demonstrated in J. Fajans' article.  Though of course his article describes
the handling more accurately.  It wouldn't be published otherwise.

Now, you say that physicists "always knew" all the correct answers, were
never wrong and that only "those who call themselves teachers" were should
be blamed if I was thought in school the wrong model of bicycle handling.
At the same time you post a link where first hints that what is in
handbooks is probably wrong appear in 1970 (what, three hundred years after
first bicycles?), without really providing any answers, next article, after
12 years of research still isn't a really complete explanation, and it's
full of rather non-trivial math to boot, and most recent article from Y2000
quotes a number of relatively late papers where wrong gyroscopic model
still appears.  For the record, even recent models do not describe the
effects of tire profile on handling, AFAICT, so even now we may not have
the full picture.

If the problem of bicycle handling is so trivial, why all this confusion?
Why the guy who obviously spent some serious time making models and doing
computer analysis still didn't figure out any real answers? (Though he
recognized many problems, and is credited for it.)

*) The link to 1982 article by Lowell I found and provided above doesn't
contain full text, but what is there should suffice for the sake of our
discussion here.

--
Andrzej Rosa

 

Bob Myers wrote:


Some J. Fajans, it seems.  Polish name, btw.  
 

I know how those who call themselves teachers work.  I had plenty of them in
my family, and I assure you that you shouldn't blame those people.  They
have programs, books and all that which they simply follow, with or without
talent.


Just physicists weren't aware of it. ;-)

--
Andrzej Rosa

 

Scout wrote:

[...]

I consequently wrote, throughout the whole thread, that some amount of
steering is possible this way, and Keith Code wrote similar things too, so
are you paying attention?

Now, how much is what actually matters here.  In practice it takes quite an
amount of lean to counter for a very slight mishandling or an equally
slight slope on the road.  You don't even feel it on the bars, but
countering for it by body-steering is simply difficult.  What you can
achieve by body-steering is not a steering, not in my book.  Though I can
imagine that on a level surface this minute level of control it provides
may be just about sufficient.  I'll take your word for it, though.  

--
Andrzej Rosa

 

wrote:


umm, just yesterday you wrote:
"You just can't control your bike with your bodyweight.  It's
impossible."

--
Turby the Turbosurfer

 

Turby wrote:


Because it is.  Some amount of steering isn't control.

Anyway, just for kicks I tried your bodysteering ideas on a pushbike today.
Funny enough, it didn't work.  I was on a rather smooth dirt road, but
because it was a dirt road, people who maintained it introduced quite a lot
of convexity to it, to let the water drain easier, I guess.   So I was
trying to ride with hands off through it and I couldn't keep my pushbike
from riding off it.   Perfectly in the middle it worked, but once I rode a
meter to the side, no banana.  Full body weight on one pedal, plus a lean,
and still the bike tried to steer into the bushes.  

Hereby I confess to be totally unimpressed by the amount of control provided
by bodysteering, even on a pushbike.  Howgh.

--
Andrzej Rosa