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UPGRADE 1970'S BIKES



 
 
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  #31  
Old October 8th 12, 04:34 PM posted to rec.bicycles.tech
Dan O
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Default UPGRADE 1970'S BIKES

On Oct 7, 7:18*pm, Jay Beattie wrote:
On Oct 7, 6:22*pm, Dan O wrote:









On Oct 7, 2:15 pm, Joe Riel wrote:


Frank Krygowski writes:
On Oct 7, 1:59 am, Joe Riel wrote:
Dan O writes:
On Oct 6, 4:09 pm, Frank Krygowski wrote:
On Oct 6, 3:01 pm, Jay Beattie wrote:


On Oct 6, 10:53 am, Frank Krygowski wrote:


I usually have my straps set at a sort of compromise length, loose
enough to flip into very quickly, but tight enough to provide just a
bit of security against foot slips. *They're tight enough that I can
bunny hop, which is good enough for me.


Based on all the trick riding I see, you don't need to be clipped in
to bunny hop the bike -- but I find it hard to do on a road bike
without clips, so I must be a flounder...


I just tried it, to be sure of my memory. *As I thought, I can get the
rear wheel up just a little, maybe a couple inches, on a bike without
clips. *That's my retro 3 speed. *I seem to be pushing a bit rearward
on the pedals to do it, which seems to be the same thing I see in
videos likehttp://www.youtube.com/watch?v=Z19zFlPah-o


Look at ~2:00. See how his weight goes way back to lift the front end,
then, springing off the pedals, he leaps into the air, chasing the
front end with his body mass, until the handlebars are in his lap.
The rear wheel is still on the ground. *Then he fluidly but
instantaneously transfers his body's inertia to the bike via the
handlebars. *See how his elbows and knees - fully extended a fraction
of a second before - are bent at the top and the bike has come up
underneath him? *There's no lifting it by the pedals.


I don't know if I've really got it figured out, but for me I think
it's almost all through the handlebars.


An impulsive force applied to the handlebars and in a direction directly
away from the center of mass of the bike will do the trick. *To verify
that, stand in front of the bike and apply such an impulse; both wheels
will leave the ground simultaneously. *Alas, applying the same impulsive
force while riding the bike is quite awkward (try it, you'll see). *The
way I believe it is done is in two steps: an upward pull, then a forward
push. *Those can be efficiently applied and since the average direction
of the two force is through the CoM the result is nearly the same.


That sounds like a possibility to me. *However, when I do it on a flat
pedal bike, I certainly get the impression my feet are pushing a bit
backward on the pedals, and sort of trying to claw them upward, with
my toes pointed downward. *I'm trying to understand that sensation.

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  #32  
Old October 8th 12, 05:22 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
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Default UPGRADE 1970'S BIKES

On Oct 7, 5:15*pm, Joe Riel wrote:

I won't be attempting bunny hops any time soon. *A month ago the front
wheel slid in a corner I've rounded a thousand times (downhill, slightly
offcamber). *Don't know what I did wrong; I always go around the corner
aggressively, but assumed I had a reasonable safety margin. *Apparently
the margin was exceeded. *Cleanly broke the trochanter.


Wow. Sorry to hear it.

- Frank Krygowski
  #33  
Old October 8th 12, 05:52 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
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On Oct 7, 4:17*pm, AMuzi wrote:
On 10/7/2012 2:34 PM, Frank Krygowski wrote:


https://www.youtube.com/results?sear...ny+hop+a+bicyc....

or

http://preview.tinyurl.com/99p39s2


Ah, good!

Looks to me like that verifies a lot of what Joe and I were saying.
He pulls up on the bars. But he doesn't jump up at the beginning;
instead, he gets his weight "as far back as you can," sort of kicking
his center of mass downward and backwards with respect to the bike
just before pulling the front wheel up. (That's a lot easier with a
short wheelbase BMX bike and low saddle.)

As the front wheel begins rising, he jumps his center of mass upward.
You can see his legs straighten.

Then comes the "scoop with your feet" that he mentions, the toes-down
action I described that helps kick the rear of the bike upward. He
also mentions a "J motion" of the hands, which corresponds to what Joe
was saying.

Oddly, he doesn't seem to mention that he "*willed* the bike into the
air." Since he's trying to _teach_ people, maybe he thought such
hocus-pocus language wasn't particularly helpful?

- Frank Krygowski
  #34  
Old October 8th 12, 06:18 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
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On Oct 8, 10:23*am, Jay Beattie wrote:

Sort of OT, but I was descending a familiar hill and slid out and
crashed and broke a few ribs but no major bones. *A week or so later I
felt good enough to go riding, and while descending yet another hill,
I developed a huge shimmy -- so bad, I had trouble steering he bike to
a stop. *This was on a bike that had never had a shimmy and on a hill
I had ridden hundreds of times. *It was all due to nerves.


That's really interesting. It seems very likely that a person's
shaking or trembling from nervousness would be within range of a
bike's resonant frequency for lateral vibration. Talk about a
feedback loop! Nervousness inducing shimmy, shimmy inducing more
nervousness...

Apart from
your physical rehab, it takes a little while to get over the
psychological effect of crashing. *I'm doing a lot of riding with a
guy who was hit by a car in an intersection in spring, and apart from
recovering from having his clavicle resected, he is nervous around
cars now -- particularly at intersections. *He has a tendency to jam
on his brakes at odd moments, making drafting a little challenging.


Fear can be terrible. One of my good friends experienced a near crash
on a long, fast downhill. As he told it (I wasn't there), his front
tire blew out but stayed on the rim. He panicked and locked up his
rear, which also blew out. He skidded across the oncoming lane and
stopped upright on the shoulder. No crash, but he never recovered
psychologically. Afterwards he was unable to descend at more than
about 10 mph; he was literally slower downhill than uphill. He gave
up riding soon after.

But that brings up another feedback loop. I recall from my mountain
biking days that there were obstacles I'd try to "clean" (in the
observed trials sense) that were impossible unless I committed to
taking the risk of a fall. I think a more cautious person couldn't
pull it off at all, and the failure to pull it off would lead to more
nervousness.

I can envision that phenomenon working in lots of different
situations, everything from giving a speech to controlling a narrow
lane.

- Frank Krygowski
  #35  
Old October 8th 12, 11:11 PM posted to rec.bicycles.tech
Dan O
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Default UPGRADE 1970'S BIKES

On Oct 8, 10:18*am, Frank Krygowski wrote:

snip


But that brings up another feedback loop. *I recall from my mountain
biking days that there were obstacles I'd try to "clean" (in the
observed trials sense) that were impossible unless I committed to
taking the risk of a fall.


And I find some things I try to do involve significant risk of falling
out of bed ;-)

*I think a more cautious person couldn't
pull it off at all, and the failure to pull it off would lead to more
nervousness.

I can envision that phenomenon working in lots of different
situations, everything from giving a speech to controlling a narrow
lane.


La vida loca!

  #36  
Old October 9th 12, 05:59 AM posted to rec.bicycles.tech
Joy Beeson
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Posts: 1,162
Default UPGRADE 1970'S BIKES

On Mon, 08 Oct 2012 08:34:12 -0700, Joe Riel wrote:

Would the paramedics bring the bike to the hospital?


A deputy took my bike, after establishing that no other vehicle had
been involved. My spouse retrieved it from the sheriff's sub-station,
and was annoyed that they didn't ask for proof that he was my spouse.
--
Joy Beeson
joy beeson at comcast dot net
 




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