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#31
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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
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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
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UPGRADE 1970'S BIKES
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
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UPGRADE 1970'S BIKES
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
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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
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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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