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#21
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UPGRADE 1970'S BIKES
datakoll writes:
bummmer...the greater or lesser trochanter ? yawl losing bone mass ? Not sure, maybe both. That is, the break was in the thicker part of the bone that connects the main part of the femur to the head (which makes up the hip joint). I've got osteoporosis (a result of genetics, maybe cycling, and malabsorption due to a major resection of the small intestine), so was pretty sure something had broken after the crash. It didn't hurt, I just couldn't move the leg. -- Joe Riel |
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#22
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UPGRADE 1970'S BIKES
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. (In the videos, it looks like the rider's toes are pointed down, too.) I'll get more serious than I was a couple posts ago (since nobody really repeals the law of gravity): To understand a bike being bunny hopped, I think it may help to think about how a skateboard is bunny hopped. The processes aren't the same (there's obviously no direct upward pull from the shoes on the skateboard) but I think there are some similarities. As I understand it, the skater jumps his own body mass upward. That's easy. And he'll soon lift his legs upward after his main body mass. But (nearly) simultaneously with the initial jump, he kicks down on the tail of the board. That levers the rest of the board upward, pivoting on the rear wheels. The board's center of mass is rising, so it's got upward inertia. It's also got rotational inertia, i.e. it's starting to do a backwards somersault. But a split second later, the skater's up-in-the-air foot applies downward force at the front half of the board to level it and stop that backwards rotation. So in that way, a pair of downward forces can produce upward motion of the board. So how much of this applies to jumping a flat pedaled bike? Certainly, the mass of the rider moves upward. But unlike the skateboard, he certainly applies a direct upward pull on the handlebars as his own body mass rises. That's easy to feel, and easy to see in the videos. But so far, all that's got us is a wheelie. Does the rider then push either forward on the bars (as Joe says) or downward on the bars (corresponding to the finish of the skateboard trick)? Seems either might work. And what, if anything, happens with the feet? It's raining pretty hard here right now, or I'd go out and play around trying to feel what I'm doing. But again, I'm hampered by simple lack of skill. I have to sense the forces during the brief duration of my tiny flat pedal bunny hop. Maybe someone more skilled can use their longer air time to analyze this? - Frank Krygowski Something I did a dozen years or so ago was to stand on two low sawhorses, one on each side of the bike, and from there test stategies for yanking on the bars. That made experimenting easy. Doing so showed me that it really wasn't practical to get the rear wheels off the ground with a uni-direction yank; our body really isn't designed to do that in the required direction. Nor was was yanking while applying a torque to the bars (something I'd heard) feasible, at least not for me. What did work was the lift and push. I just got on my bike and went out in the street Rode Bike! and *willed* the bike into the air. That's why I still sound uncertain when explaining it. That's why I get so incensed when Frank discounts what a rider "feels". "Those who can, do. Those who can't... " 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). Hate when that happens (losing the front end). 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. I used to be a flattrack motorcycle racer, so sliding sideways is a fish in water kind of thing, and as a kid on a bicycle spent about as much time sideways as wheelying. If traction was iffy in a turn, I'd bust the rear tire loose, at which point you're steering with the rear wheel, and forces that would compromise front end traction vanish. I *relished* slick turns. As a longer distance bicycle rider now, I have become more hung up on things like conserving momentum, so ride more conventionally "road style", and consequently feel the fear of losing the front end, and don't push it when I suspect iffy traction. I've lost the front end a couple of times on the road in recent years (once on frezzing fog - idiot! - and once on a what I will presume was a petroleum spill adjacent to a gas station). Another time I was coming down a hill, making a fast turn on the paved shoulder (there are paint markings on this turn that I avoid having slipped on them), hit some sand or something and the front end started to go, but luckily I had sort of panic braked - both brakes - and broke the rear wheel loose. This was quite the thrilling moment - clipped into my SPuDs w/ both wheels sliding as I passed a pickup truck on the inside. But I do take it easy a lot more in my old age, and worried that I was losing my skill or something, but just rode over to the baseball diamond a little bit ago and pitched the wheelie bike sideways a couple times in the dry dirt - (barefoot), no brakes, no problem. When I was a kid I would throw just about any bike sideways any time even on dry pavement - wide handebars help - which was in fact my braking technique on one bike with freewheel and no brakes. Ah, invincible youth :-) Cleanly broke the trochanter. Now I'm sporting a 10 inch rod in the femur with a four inch screw through trochanter. Have been walking with a cane for about two weeks now (that's better than using a walker). Need to do something for an aerobic workout, probably will be using the rowing machine for a awhile, though could try the turbo-trainer. Ouch! Sending out positive waves for a full recovery. |
#23
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UPGRADE 1970'S BIKES
"Joe Riel" wrote in message ... 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. (In the videos, it looks like the rider's toes are pointed down, too.) I'll get more serious than I was a couple posts ago (since nobody really repeals the law of gravity): To understand a bike being bunny hopped, I think it may help to think about how a skateboard is bunny hopped. The processes aren't the same (there's obviously no direct upward pull from the shoes on the skateboard) but I think there are some similarities. As I understand it, the skater jumps his own body mass upward. That's easy. And he'll soon lift his legs upward after his main body mass. But (nearly) simultaneously with the initial jump, he kicks down on the tail of the board. That levers the rest of the board upward, pivoting on the rear wheels. The board's center of mass is rising, so it's got upward inertia. It's also got rotational inertia, i.e. it's starting to do a backwards somersault. But a split second later, the skater's up-in-the-air foot applies downward force at the front half of the board to level it and stop that backwards rotation. So in that way, a pair of downward forces can produce upward motion of the board. So how much of this applies to jumping a flat pedaled bike? Certainly, the mass of the rider moves upward. But unlike the skateboard, he certainly applies a direct upward pull on the handlebars as his own body mass rises. That's easy to feel, and easy to see in the videos. But so far, all that's got us is a wheelie. Does the rider then push either forward on the bars (as Joe says) or downward on the bars (corresponding to the finish of the skateboard trick)? Seems either might work. And what, if anything, happens with the feet? It's raining pretty hard here right now, or I'd go out and play around trying to feel what I'm doing. But again, I'm hampered by simple lack of skill. I have to sense the forces during the brief duration of my tiny flat pedal bunny hop. Maybe someone more skilled can use their longer air time to analyze this? - Frank Krygowski Something I did a dozen years or so ago was to stand on two low sawhorses, one on each side of the bike, and from there test stategies for yanking on the bars. That made experimenting easy. Doing so showed me that it really wasn't practical to get the rear wheels off the ground with a uni-direction yank; our body really isn't designed to do that in the required direction. Nor was was yanking while applying a torque to the bars (something I'd heard) feasible, at least not for me. What did work was the lift and push. 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. Now I'm sporting a 10 inch rod in the femur with a four inch screw through trochanter. Have been walking with a cane for about two weeks now (that's better than using a walker). Need to do something for an aerobic workout, probably will be using the rowing machine for a awhile, though could try the turbo-trainer. -- Joe Riel Joe Riel, Sorry to hear it. Hope you have a fast recovery, Kerry |
#24
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UPGRADE 1970'S BIKES
Not sure, maybe both. Your problem reinforces the Brandt Curve, where I should slow down another 5% |
#25
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UPGRADE 1970'S BIKES
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. (In the videos, it looks like the rider's toes are pointed down, too.) I'll get more serious than I was a couple posts ago (since nobody really repeals the law of gravity): To understand a bike being bunny hopped, I think it may help to think about how a skateboard is bunny hopped. *The processes aren't the same (there's obviously no direct upward pull from the shoes on the skateboard) but I think there are some similarities. As I understand it, the skater jumps his own body mass upward. *That's easy. *And he'll soon lift his legs upward after his main body mass. But (nearly) simultaneously with the initial jump, he kicks down on the tail of the board. *That levers the rest of the board upward, pivoting on the rear wheels. *The board's center of mass is rising, so it's got upward inertia. *It's also got rotational inertia, i.e. it's starting to do a backwards somersault. *But a split second later, the skater's up-in-the-air foot applies downward force at the front half of the board to level it and stop that backwards rotation. *So in that way, a pair of downward forces can produce upward motion of the board. So how much of this applies to jumping a flat pedaled bike? Certainly, the mass of the rider moves upward. *But unlike the skateboard, he certainly applies a direct upward pull on the handlebars as his own body mass rises. *That's easy to feel, and easy to see in the videos. But so far, all that's got us is a wheelie. *Does the rider then push either forward on the bars (as Joe says) or downward on the bars (corresponding to the finish of the skateboard trick)? *Seems either might work. *And what, if anything, happens with the feet? It's raining pretty hard here right now, or I'd go out and play around trying to feel what I'm doing. *But again, I'm hampered by simple lack of skill. *I have to sense the forces during the brief duration of my tiny flat pedal bunny hop. *Maybe someone more skilled can use their longer air time to analyze this? - Frank Krygowski Something I did a dozen years or so ago was to stand on two low sawhorses, one on each side of the bike, and from there test stategies for yanking on the bars. *That made experimenting easy. *Doing so showed me that it really wasn't practical to get the rear wheels off the ground with a uni-direction yank; our body really isn't designed to do that in the required direction. *Nor was was yanking while applying a torque to the bars (something I'd heard) feasible, at least not for me. What did work was the lift and push. 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. *Now I'm sporting a 10 inch rod in the femur with a four inch screw through trochanter. *Have been walking with a cane for about two weeks now (that's better than using a walker). *Need to do something for an aerobic workout, probably will be using the rowing machine for a awhile, though could try the turbo-trainer. Wow, do they place an IM rod for a trochanter or did you break the femur too? The amazing thing is being on a cane in a couple of weeks after surgery. -- Jay Beattie. |
#26
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UPGRADE 1970'S BIKES
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. (In the videos, it looks like the rider's toes are pointed down, too.) I'll get more serious than I was a couple posts ago (since nobody really repeals the law of gravity): To understand a bike being bunny hopped, I think it may help to think about how a skateboard is bunny hopped. *The processes aren't the same (there's obviously no direct upward pull from the shoes on the skateboard) but I think there are some similarities. As I understand it, the skater jumps his own body mass upward. *That's easy. *And he'll soon lift his legs upward after his main body mass.. But (nearly) simultaneously with the initial jump, he kicks down on the tail of the board. *That levers the rest of the board upward, pivoting on the rear wheels. *The board's center of mass is rising, so it's got upward inertia. *It's also got rotational inertia, i.e. it's starting to do a backwards somersault. *But a split second later, the skater's up-in-the-air foot applies downward force at the front half of the board to level it and stop that backwards rotation. *So in that way, a pair of downward forces can produce upward motion of the board.. So how much of this applies to jumping a flat pedaled bike? Certainly, the mass of the rider moves upward. *But unlike the skateboard, he certainly applies a direct upward pull on the handlebars as his own body mass rises. *That's easy to feel, and easy to see in the videos. But so far, all that's got us is a wheelie. *Does the rider then push either forward on the bars (as Joe says) or downward on the bars (corresponding to the finish of the skateboard trick)? *Seems either might work. *And what, if anything, happens with the feet? It's raining pretty hard here right now, or I'd go out and play around trying to feel what I'm doing. *But again, I'm hampered by simple lack of skill. *I have to sense the forces during the brief duration of my tiny flat pedal bunny hop. *Maybe someone more skilled can use their longer air time to analyze this? - Frank Krygowski Something I did a dozen years or so ago was to stand on two low sawhorses, one on each side of the bike, and from there test stategies for yanking on the bars. *That made experimenting easy. *Doing so showed me that it really wasn't practical to get the rear wheels off the ground with a uni-direction yank; our body really isn't designed to do that in the required direction. *Nor was was yanking while applying a torque to the bars (something I'd heard) feasible, at least not for me. What did work was the lift and push. I just got on my bike and went out in the street Rode Bike! and *willed* the bike into the air. *That's why I still sound uncertain when explaining it. *That's why I get so incensed when Frank discounts what a rider "feels". *"Those who can, do. *Those who can't... " 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). Hate when that happens (losing the front end). 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. I used to be a flattrack motorcycle racer, so sliding sideways is a fish in water kind of thing, and as a kid on a bicycle spent about as much time sideways as wheelying. *If traction was iffy in a turn, I'd bust the rear tire loose, at which point you're steering with the rear wheel, and forces that would compromise front end traction vanish. *I *relished* slick turns. As a longer distance bicycle rider now, I have become more hung up on things like conserving momentum, so ride more conventionally "road style", and consequently feel the fear of losing the front end, and don't push it *when I suspect iffy traction. *I've lost the front end a couple of times on the road in recent years (once on frezzing fog - idiot! - and once on a what I will presume was a petroleum spill adjacent to a gas station). *Another time I was coming down a hill, making a fast turn on the paved shoulder (there are paint markings on this turn that I avoid having slipped on them), hit some sand or something and the front end started to go, but luckily I had sort of panic braked - both brakes - and broke the rear wheel loose. *This was quite the thrilling moment - clipped into my SPuDs w/ both wheels sliding as I passed a pickup truck on the inside. But I do take it easy a lot more in my old age, and worried that I was losing my skill or something, but just rode over to the baseball diamond a little bit ago and pitched the wheelie bike sideways a couple times in the dry dirt - (barefoot), no brakes, no problem. When I was a kid I would throw just about any bike sideways any time even on dry pavement - wide handebars help - which was in fact my braking technique on one bike with freewheel and no brakes. *Ah, invincible youth :-) Cleanly broke the trochanter. *Now I'm sporting a 10 inch rod in the femur with a four inch screw through trochanter. *Have been walking with a cane for about two weeks now (that's better than using a walker). *Need to do something for an aerobic workout, probably will be using the rowing machine for a awhile, though could try the turbo-trainer. Ouch! *Sending out positive waves for a full recovery. http://www.youtube.com/watch?feature...14GN2_zNE&NR=1 Most of us aren't that skilled or aren't ready for the total loss of front wheel traction. Jay Beattie |
#27
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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: [In which Dan brags of glory days and tries to convey a *touch* of what it is to Ride Bike to poor hapless Frank... ] http://www.youtube.com/watch?feature...14GN2_zNE&NR=1 Most of us aren't that skilled or aren't ready for the total loss of front wheel traction. "... total loss of front wheel traction." Hate when that happens. It's all over. BTDT. Know the feeling. Got the t-shirt. Bled on it. |
#28
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UPGRADE 1970'S BIKES
Jay Beattie writes:
On Oct 7, 2:15Â*pm, Joe Riel wrote: Frank Krygowski writes: On Oct 7, 1:59Â*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. Â*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. Â*As I thought, I can get the rear wheel up just a little, maybe a couple inches, on a bike without clips. Â*That's my retro 3 speed. Â*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. Â*Then he fluidly but instantaneously transfers his body's inertia to the bike via the handlebars. Â*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? Â*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. Â*To verify that, stand in front of the bike and apply such an impulse; both wheels will leave the ground simultaneously. Â*Alas, applying the same impulsive force while riding the bike is quite awkward (try it, you'll see). Â*The way I believe it is done is in two steps: an upward pull, then a forward push. Â*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. Â*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. Â*I'm trying to understand that sensation. (In the videos, it looks like the rider's toes are pointed down, too.) I'll get more serious than I was a couple posts ago (since nobody really repeals the law of gravity): To understand a bike being bunny hopped, I think it may help to think about how a skateboard is bunny hopped. Â*The processes aren't the same (there's obviously no direct upward pull from the shoes on the skateboard) but I think there are some similarities. As I understand it, the skater jumps his own body mass upward. Â*That's easy. Â*And he'll soon lift his legs upward after his main body mass. But (nearly) simultaneously with the initial jump, he kicks down on the tail of the board. Â*That levers the rest of the board upward, pivoting on the rear wheels. Â*The board's center of mass is rising, so it's got upward inertia. Â*It's also got rotational inertia, i.e. it's starting to do a backwards somersault. Â*But a split second later, the skater's up-in-the-air foot applies downward force at the front half of the board to level it and stop that backwards rotation. Â*So in that way, a pair of downward forces can produce upward motion of the board. So how much of this applies to jumping a flat pedaled bike? Certainly, the mass of the rider moves upward. Â*But unlike the skateboard, he certainly applies a direct upward pull on the handlebars as his own body mass rises. Â*That's easy to feel, and easy to see in the videos. But so far, all that's got us is a wheelie. Â*Does the rider then push either forward on the bars (as Joe says) or downward on the bars (corresponding to the finish of the skateboard trick)? Â*Seems either might work. Â*And what, if anything, happens with the feet? It's raining pretty hard here right now, or I'd go out and play around trying to feel what I'm doing. Â*But again, I'm hampered by simple lack of skill. Â*I have to sense the forces during the brief duration of my tiny flat pedal bunny hop. Â*Maybe someone more skilled can use their longer air time to analyze this? - Frank Krygowski Something I did a dozen years or so ago was to stand on two low sawhorses, one on each side of the bike, and from there test stategies for yanking on the bars. Â*That made experimenting easy. Â*Doing so showed me that it really wasn't practical to get the rear wheels off the ground with a uni-direction yank; our body really isn't designed to do that in the required direction. Â*Nor was was yanking while applying a torque to the bars (something I'd heard) feasible, at least not for me. What did work was the lift and push. I won't be attempting bunny hops any time soon. Â*A month ago the front wheel slid in a corner I've rounded a thousand times (downhill, slightly offcamber). Â*Don't know what I did wrong; I always go around the corner aggressively, but assumed I had a reasonable safety margin. Â*Apparently the margin was exceeded. Â*Cleanly broke the trochanter. Â*Now I'm sporting a 10 inch rod in the femur with a four inch screw through trochanter. Â*Have been walking with a cane for about two weeks now (that's better than using a walker). Â*Need to do something for an aerobic workout, probably will be using the rowing machine for a awhile, though could try the turbo-trainer. Wow, do they place an IM rod for a trochanter or did you break the femur too? The amazing thing is being on a cane in a couple of weeks after surgery. What's IM stand for? The main part of the femur didn't break. I'm pretty sure the rod in the femur is to support the screw/pin that goes through the trochanter (or whatever the part that connects to the ball joint is called). That screw is mechanically attached to the rod in the femur. There was also a secondary fracture of part of the trochanter that was left alone. From the X-rays I saw it seemed minor (i.e. not involved with support, etc). Yeah, my progress has been fairly quick, though am expecting a bit of a plateau soon enough. The acute rehab facility had me practice going up/down the fire-escape stairs using a cane less than a week after the crash; that was because I needed to learn to negotiate the stairs in my house which only have a handrail on one side. Stairs with handrails on both sides are trivial. Once home, I switched to a crutch for the stairs because it was more stable; used a walker otherwise. I can now walk without a cane, but it's not comfortable, too much compensation is required 'cause the glutes, etc, are too weak. With the cane, I can introduce a small torque that helps align the hips. -- Joe Riel |
#29
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UPGRADE 1970'S BIKES
On Oct 7, 9:43*pm, Joe Riel wrote:
Jay Beattie writes: 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.. (In the videos, it looks like the rider's toes are pointed down, too..) I'll get more serious than I was a couple posts ago (since nobody really repeals the law of gravity): To understand a bike being bunny hopped, I think it may help to think about how a skateboard is bunny hopped. *The processes aren't the same (there's obviously no direct upward pull from the shoes on the skateboard) but I think there are some similarities. As I understand it, the skater jumps his own body mass upward. *That's easy. *And he'll soon lift his legs upward after his main body mass. But (nearly) simultaneously with the initial jump, he kicks down on the tail of the board. *That levers the rest of the board upward, pivoting on the rear wheels. *The board's center of mass is rising, so it's got upward inertia. *It's also got rotational inertia, i.e. it's starting to do a backwards somersault. *But a split second later, the skater's up-in-the-air foot applies downward force at the front half of the board to level it and stop that backwards rotation. *So in that way, a pair of downward forces can produce upward motion of the board. So how much of this applies to jumping a flat pedaled bike? Certainly, the mass of the rider moves upward. *But unlike the skateboard, he certainly applies a direct upward pull on the handlebars as his own body mass rises. *That's easy to feel, and easy to see in the videos. But so far, all that's got us is a wheelie. *Does the rider then push either forward on the bars (as Joe says) or downward on the bars (corresponding to the finish of the skateboard trick)? *Seems either might work. *And what, if anything, happens with the feet? It's raining pretty hard here right now, or I'd go out and play around trying to feel what I'm doing. *But again, I'm hampered by simple lack of skill. *I have to sense the forces during the brief duration of my tiny flat pedal bunny hop. *Maybe someone more skilled can use their longer air time to analyze this? - Frank Krygowski Something I did a dozen years or so ago was to stand on two low sawhorses, one on each side of the bike, and from there test stategies for yanking on the bars. *That made experimenting easy. *Doing so showed me that it really wasn't practical to get the rear wheels off the ground with a uni-direction yank; our body really isn't designed to do that in the required direction. *Nor was was yanking while applying a torque to the bars (something I'd heard) feasible, at least not for me.. What did work was the lift and push. 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. *Now I'm sporting a 10 inch rod in the femur with a four inch screw through trochanter. *Have been walking with a cane for about two weeks now (that's better than using a walker). *Need to do something for an aerobic workout, probably will be using the rowing machine for a awhile, though could try the turbo-trainer. Wow, do they place an IM rod for a trochanter or did you break the femur too? The amazing thing is being on a cane in a couple of weeks after surgery. What's IM stand for? *The main part of the femur didn't break. *I'm pretty sure the rod in the femur is to support the screw/pin that goes through the trochanter (or whatever the part that connects to the ball joint is called). *That screw is mechanically attached to the rod in the femur. *There was also a secondary fracture of part of the trochanter that was left alone. *From the X-rays I saw it seemed minor (i.e. not involved with support, etc). Yeah, my progress has been fairly quick, though am expecting a bit of a plateau soon enough. *The acute rehab facility had me practice going up/down the fire-escape stairs using a cane less than a week after the crash; that was because I needed to learn to negotiate the stairs in my house which only have a handrail on one side. *Stairs with handrails on both sides are trivial. *Once home, I switched to a crutch for the stairs because it was more stable; used a walker otherwise. I can now walk without a cane, but it's not comfortable, too much compensation is required 'cause the glutes, etc, are too weak. *With the cane, I can introduce a small torque that helps align the hips. IM stands for intermedullary -- within the marrow cavity of a bone. So they drill out the marrow cavity and drive in a rod or "nail," usually to stabilize a fracture, but in your case, it sounds like they used it as some sort of anchor for the the screw through the trochanter. People with leg fractures usually spend months on crutches, so you're doing great. Now you have to go back to the scene of the crime and figure out what happened. 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. 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. -- Jay Beattie. |
#30
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UPGRADE 1970'S BIKES
Jay Beattie writes:
On Oct 7, 9:43Â*pm, Joe Riel wrote: Jay Beattie writes: On Oct 7, 2:15Â*pm, Joe Riel wrote: Frank Krygowski writes: On Oct 7, 1:59Â*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. Â*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. Â*As I thought, I can get the rear wheel up just a little, maybe a couple inches, on a bike without clips. Â*That's my retro 3 speed. Â*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. Â*Then he fluidly but instantaneously transfers his body's inertia to the bike via the handlebars. Â*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? Â*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. Â*To verify that, stand in front of the bike and apply such an impulse; both wheels will leave the ground simultaneously. Â*Alas, applying the same impulsive force while riding the bike is quite awkward (try it, you'll see). Â*The way I believe it is done is in two steps: an upward pull, then a forward push. Â*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. Â*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. Â*I'm trying to understand that sensation. (In the videos, it looks like the rider's toes are pointed down, too.) I'll get more serious than I was a couple posts ago (since nobody really repeals the law of gravity): To understand a bike being bunny hopped, I think it may help to think about how a skateboard is bunny hopped. Â*The processes aren't the same (there's obviously no direct upward pull from the shoes on the skateboard) but I think there are some similarities. As I understand it, the skater jumps his own body mass upward. Â*That's easy. Â*And he'll soon lift his legs upward after his main body mass. But (nearly) simultaneously with the initial jump, he kicks down on the tail of the board. Â*That levers the rest of the board upward, pivoting on the rear wheels. Â*The board's center of mass is rising, so it's got upward inertia. Â*It's also got rotational inertia, i.e. it's starting to do a backwards somersault. Â*But a split second later, the skater's up-in-the-air foot applies downward force at the front half of the board to level it and stop that backwards rotation. Â*So in that way, a pair of downward forces can produce upward motion of the board. So how much of this applies to jumping a flat pedaled bike? Certainly, the mass of the rider moves upward. Â*But unlike the skateboard, he certainly applies a direct upward pull on the handlebars as his own body mass rises. Â*That's easy to feel, and easy to see in the videos. But so far, all that's got us is a wheelie. Â*Does the rider then push either forward on the bars (as Joe says) or downward on the bars (corresponding to the finish of the skateboard trick)? Â*Seems either might work. Â*And what, if anything, happens with the feet? It's raining pretty hard here right now, or I'd go out and play around trying to feel what I'm doing. Â*But again, I'm hampered by simple lack of skill. Â*I have to sense the forces during the brief duration of my tiny flat pedal bunny hop. Â*Maybe someone more skilled can use their longer air time to analyze this? - Frank Krygowski Something I did a dozen years or so ago was to stand on two low sawhorses, one on each side of the bike, and from there test stategies for yanking on the bars. Â*That made experimenting easy. Â*Doing so showed me that it really wasn't practical to get the rear wheels off the ground with a uni-direction yank; our body really isn't designed to do that in the required direction. Â*Nor was was yanking while applying a torque to the bars (something I'd heard) feasible, at least not for me. What did work was the lift and push. I won't be attempting bunny hops any time soon. Â*A month ago the front wheel slid in a corner I've rounded a thousand times (downhill, slightly offcamber). Â*Don't know what I did wrong; I always go around the corner aggressively, but assumed I had a reasonable safety margin. Â*Apparently the margin was exceeded. Â*Cleanly broke the trochanter. Â*Now I'm sporting a 10 inch rod in the femur with a four inch screw through trochanter. Â*Have been walking with a cane for about two weeks now (that's better than using a walker). Â*Need to do something for an aerobic workout, probably will be using the rowing machine for a awhile, though could try the turbo-trainer. Wow, do they place an IM rod for a trochanter or did you break the femur too? The amazing thing is being on a cane in a couple of weeks after surgery. What's IM stand for? Â*The main part of the femur didn't break. Â*I'm pretty sure the rod in the femur is to support the screw/pin that goes through the trochanter (or whatever the part that connects to the ball joint is called). Â*That screw is mechanically attached to the rod in the femur. Â*There was also a secondary fracture of part of the trochanter that was left alone. Â*From the X-rays I saw it seemed minor (i.e. not involved with support, etc). Yeah, my progress has been fairly quick, though am expecting a bit of a plateau soon enough. Â*The acute rehab facility had me practice going up/down the fire-escape stairs using a cane less than a week after the crash; that was because I needed to learn to negotiate the stairs in my house which only have a handrail on one side. Â*Stairs with handrails on both sides are trivial. Â*Once home, I switched to a crutch for the stairs because it was more stable; used a walker otherwise. I can now walk without a cane, but it's not comfortable, too much compensation is required 'cause the glutes, etc, are too weak. Â*With the cane, I can introduce a small torque that helps align the hips. IM stands for intermedullary -- within the marrow cavity of a bone. So they drill out the marrow cavity and drive in a rod or "nail," usually to stabilize a fracture, but in your case, it sounds like they used it as some sort of anchor for the the screw through the trochanter. People with leg fractures usually spend months on crutches, so you're doing great. Now you have to go back to the scene of the crime and figure out what happened. It was a block away from home---I was returning from a ride. I've walked by it several times recently and didn't learn anything. That day was hot (+95F), with high humidity. On the ride I felt sporadic rain drops, but never saw any moisture on the road and doubt that was an issue. A cyclist next door suggested that the heat could have softened the tar strip used to repair a crack in the road, however, that runs across the road, so I would have been crossing it (it's less than two inches wide)---seems unlikely to be a factor. My current hypothesis was rider error. I was riding the Moulton, and, while I've been around that corner on the Moulton many times, most were a few years ago when returning from a daily commute. Now most of my riding [and hard cornering] is done on a regular road bike, and the handling is significantly different; the Moulton responds much faster. I still haven't made a serious inspection of the Moulton---it appears to have just cosmetic damage to the right side bar tape where the bike slid. 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. 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. Yeah, that will be interesting, seeing how I deal with it. I was wondering what would have happened if I crashed further from home. That is, a woman in the neighborhood stopped, called 911, and later dropped my bike off at my house. What is the usual protocol when on the road? Would the paramedics bring the bike to the hospital? Seems unlikely, but leaving/losing it would have added insult to injury (I was riding alone). -- Joe Riel |
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