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#22
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Olmo
On 2017-07-07 08:01, wrote:
On Friday, July 7, 2017 at 7:17:19 AM UTC-7, Joerg wrote: On 2017-07-07 01:25, John B. wrote: On Thu, 6 Jul 2017 19:44:35 -0700 (PDT), wrote: On Thursday, July 6, 2017 at 10:35:24 AM UTC-7, Joerg wrote: On 2017-07-05 12:18, wrote: On Wednesday, July 5, 2017 at 11:51:51 AM UTC-7, Doug Landau wrote: Tom are Olmos any good Any chance this Olmo is a Basso? https://sacramento.craigslist.org/bik/6185998403.html Olmo's were as a rule were on a level of Basso or Colnago. I think that they are still made today. While that particular Olmo is VERY reminiscent of a Basso Gap, it is it's own maker. What was the big difference in frames back then? I know Italian ones were usually considered more fancy but my Dutch Gazelle frame looks nearly identical to this one. Ok, Reynolds steel instead of Columbus. The wheelbases and rake and trail were quite different and it makes a remarkable difference in feeling and ride. The difference between my Eddy Merckx Corsa Extra and the Basso Lotto is noticeable on the second pedal stroke. Yes, there could be minor differences in the dimensions which make a noticeable difference. On the photo they aren't visible. This is the same frame I ride, same color but larger geometry: https://www.lfgss.com/conversations/234710/ For some reason those still fetch good money at auction. I read an article about different handling between different bikes. The author and his buddy, a frame maker, even cobbled up a fork with adjustable trail. Anyway, they found that the Italian frames tended toward lower bottom bracket heights, in other words lower C/G, which they attributed to a more stable feeling bike. I can't imagine the BB to be even lower than on the Dutch frame I ride. Every time I switch back from the MTB (very high ground clearance) to the road bike I have to watch during dirt road stretches not to run into a pedal strike. If you compare your photo with https://www.google.com/search?q=Bass...t5ITOtNTl_igM: you can see a rather large difference in BB height. This difference is so dramatic that you have to learn to ALWAYS have your inside pedal up to keep it from dragging on the ground and possibly dumping you at speed. I'd say it is about the same. A few days ago I coasted and there was a rock not larger that the size of a small fist. Lower than the brick in the photo of the Basso Loto. Didn't pick up the pedal because I was sure it'll clear it. It didn't. But I didn't crash. -- Regards, Joerg http://www.analogconsultants.com/ |
#23
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Stability [ Olmo]
On 2017-07-07 09:24, wrote:
On Friday, July 7, 2017 at 9:10:54 AM UTC-7, Frank Krygowski wrote: On 7/7/2017 4:25 AM, John B. wrote: I read an article about different handling between different bikes. The author and his buddy, a frame maker, even cobbled up a fork with adjustable trail. Anyway, they found that the Italian frames tended toward lower bottom bracket heights, in other words lower C/G, which they attributed to a more stable feeling bike. As I've said many times, I'm far from being a connoisseur of bike handling. But it doesn't make sense to me that a lower center of gravity would make a bike feel more stable. First, the effect would seem to be minuscule if it existed. The center of mass of a bike+rider is generally somewhere around the saddle, i.e. maybe 40" high. I'd think lowering the center of mass by half an inch would make a tiny difference compared to other changes. But more important: To me, stability in a bike means it requires less frequent and energetic steering corrections to maintain balance. And in that respect, an "ordinary" or "high wheeler" is far, far more stable than a normal bike. Likewise, a recumbent is far less stable. The first time I road an ordinary, I was able to easily balance at 2 mph. The first time I rode a recumbent, I couldn't even balance. Someone had to run alongside and hold me up as I flopped left and right, until I could relax and let the bike work properly. The difference is polar moment of inertia about the axis along the ground between the two tire contact patches. With the "ordinary's" rider mass at about five feet or more, the sideways rotation needed for a fall begins much more slowly. There's plenty of time to correct even the tiniest deviation from vertical. By contrast, with a recumbent's center of mass at maybe 18", the sideways rotation initiates quickly. The same effect can be observed by trying to balance a yardstick (or meter stick) on its edge, vs. trying to balance a 6" (or 15 cm) ruler. Or trying to vertically balance a shovel or hammer with heavy side up vs. down. So if a higher center of mass is more stable for ordinaries, yardsticks and other objects, I don't see why it would be opposite for bikes. Well you're wrong. Firstly the saddle is also lower since the saddle height is measured from the pedal center. And in many high speed corners you put your weight on the outside pedal which is lower. Also the arc through which it passes is lower. There is about an inch difference in height and it is very noticeable believe me. I'll second that. My MTB doesn't corner nearly as well as my much lower CG road bike and the difference is not in the tires. I've tried with another MTB that the owner had equipped with slick road tires (he doesn't own a road bike), same thing. With MTB cornering often happens in a very different way, keeping the bike more straight up but leaning out and putting a leg out for skidding. Like dirt bikers sometimes do. -- Regards, Joerg http://www.analogconsultants.com/ |
#24
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Olmo
On Wednesday, July 5, 2017 at 11:51:51 AM UTC-7, Doug Landau wrote:
Tom are Olmos any good Any chance this Olmo is a Basso? https://sacramento.craigslist.org/bik/6185998403.html think i need one of these http://www.ebay.com/itm/302364463733?ul_noapp=true |
#25
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Stability [ Olmo]
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#26
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Stability [ Olmo]
On Fri, 7 Jul 2017 12:10:51 -0400, Frank Krygowski
wrote: On 7/7/2017 4:25 AM, John B. wrote: I read an article about different handling between different bikes. The author and his buddy, a frame maker, even cobbled up a fork with adjustable trail. Anyway, they found that the Italian frames tended toward lower bottom bracket heights, in other words lower C/G, which they attributed to a more stable feeling bike. As I've said many times, I'm far from being a connoisseur of bike handling. But it doesn't make sense to me that a lower center of gravity would make a bike feel more stable. First, the effect would seem to be minuscule if it existed. The center of mass of a bike+rider is generally somewhere around the saddle, i.e. maybe 40" high. I'd think lowering the center of mass by half an inch would make a tiny difference compared to other changes. But more important: To me, stability in a bike means it requires less frequent and energetic steering corrections to maintain balance. And in that respect, an "ordinary" or "high wheeler" is far, far more stable than a normal bike. Likewise, a recumbent is far less stable. The first time I road an ordinary, I was able to easily balance at 2 mph. The first time I rode a recumbent, I couldn't even balance. Someone had to run alongside and hold me up as I flopped left and right, until I could relax and let the bike work properly. The difference is polar moment of inertia about the axis along the ground between the two tire contact patches. With the "ordinary's" rider mass at about five feet or more, the sideways rotation needed for a fall begins much more slowly. There's plenty of time to correct even the tiniest deviation from vertical. By contrast, with a recumbent's center of mass at maybe 18", the sideways rotation initiates quickly. The same effect can be observed by trying to balance a yardstick (or meter stick) on its edge, vs. trying to balance a 6" (or 15 cm) ruler. Or trying to vertically balance a shovel or hammer with heavy side up vs. down. So if a higher center of mass is more stable for ordinaries, yardsticks and other objects, I don't see why it would be opposite for bikes. I've always sort of wondered about bicycle design. The article I mentioned is indicative. They made up a special fork that allowed trail to be changed from several degrees of plus to several degrees of negative tail. They speculated on what the difference in BB height would cause. It appears to me that there are no, or people aren't familiar with, normal basic engineering studies of bicycle design versus the effects on stability and or handling. Witness your discussion of balancing a ruler. If you look into, say aircraft design there are innumerable studies of dimensional changes versus flight characteristics, or even velocity versus flight characteristics. Looking at automobile design there are innumerable studies or, say wheel camber versus degrees of under of over steer. Given that the bicycle probably came into common use long before either the auto or the airplane it seems odd there don't seem to be standards in design. Or perhaps studies on the effect of various changes in design versus stability, for example. Note the usual arguments about "Oooo Aluminum is so stiff". Good Lord! The effects of modifying the strength and elasticity of materials and angles making up a triangle have been known since the days of the early Greeks. Yet the use of a material with well known physical characteristics in a shape that has been known for 2000 years results in this jaw gapped evaluating of "Oh, so stiff". Sigh. But I suppose that the science the is applicable to a device who is protected by bright flashing beams of light is rather on the order of "Eye of newt and toe of frog, Wool of bat and tongue of dog". -- Cheers, John B. |
#27
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Stability [ Olmo]
On Fri, 7 Jul 2017 12:10:51 -0400, Frank Krygowski
wrote: On 7/7/2017 4:25 AM, John B. wrote: I read an article about different handling between different bikes. The author and his buddy, a frame maker, even cobbled up a fork with adjustable trail. Anyway, they found that the Italian frames tended toward lower bottom bracket heights, in other words lower C/G, which they attributed to a more stable feeling bike. As I've said many times, I'm far from being a connoisseur of bike handling. But it doesn't make sense to me that a lower center of gravity would make a bike feel more stable. First, the effect would seem to be minuscule if it existed. The center of mass of a bike+rider is generally somewhere around the saddle, i.e. maybe 40" high. I'd think lowering the center of mass by half an inch would make a tiny difference compared to other changes. But more important: To me, stability in a bike means it requires less frequent and energetic steering corrections to maintain balance. And in that respect, an "ordinary" or "high wheeler" is far, far more stable than a normal bike. Likewise, a recumbent is far less stable. The first time I road an ordinary, I was able to easily balance at 2 mph. The first time I rode a recumbent, I couldn't even balance. Someone had to run alongside and hold me up as I flopped left and right, until I could relax and let the bike work properly. The difference is polar moment of inertia about the axis along the ground between the two tire contact patches. With the "ordinary's" rider mass at about five feet or more, the sideways rotation needed for a fall begins much more slowly. There's plenty of time to correct even the tiniest deviation from vertical. By contrast, with a recumbent's center of mass at maybe 18", the sideways rotation initiates quickly. The same effect can be observed by trying to balance a yardstick (or meter stick) on its edge, vs. trying to balance a 6" (or 15 cm) ruler. Or trying to vertically balance a shovel or hammer with heavy side up vs. down. So if a higher center of mass is more stable for ordinaries, yardsticks and other objects, I don't see why it would be opposite for bikes. I'm not sure that you are using the correct formula. Generally the width/length of the object and the effective movement of the C/G versus the width as the object is tilted is used isn't it? The classic triangle on it's base versus the triangle on it's apex. In one case the C.G. is raised as the object is tilted in the other it is lowered. -- Cheers, John B. |
#28
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Stability [ Olmo]
On Friday, July 7, 2017 at 9:00:55 PM UTC-4, John B. wrote:
On Fri, 7 Jul 2017 12:10:51 -0400, Frank Krygowski wrote: On 7/7/2017 4:25 AM, John B. wrote: I read an article about different handling between different bikes. The author and his buddy, a frame maker, even cobbled up a fork with adjustable trail. Anyway, they found that the Italian frames tended toward lower bottom bracket heights, in other words lower C/G, which they attributed to a more stable feeling bike. As I've said many times, I'm far from being a connoisseur of bike handling. But it doesn't make sense to me that a lower center of gravity would make a bike feel more stable. First, the effect would seem to be minuscule if it existed. The center of mass of a bike+rider is generally somewhere around the saddle, i.e. maybe 40" high. I'd think lowering the center of mass by half an inch would make a tiny difference compared to other changes. But more important: To me, stability in a bike means it requires less frequent and energetic steering corrections to maintain balance. And in that respect, an "ordinary" or "high wheeler" is far, far more stable than a normal bike. Likewise, a recumbent is far less stable. The first time I road an ordinary, I was able to easily balance at 2 mph. The first time I rode a recumbent, I couldn't even balance. Someone had to run alongside and hold me up as I flopped left and right, until I could relax and let the bike work properly. The difference is polar moment of inertia about the axis along the ground between the two tire contact patches. With the "ordinary's" rider mass at about five feet or more, the sideways rotation needed for a fall begins much more slowly. There's plenty of time to correct even the tiniest deviation from vertical. By contrast, with a recumbent's center of mass at maybe 18", the sideways rotation initiates quickly. The same effect can be observed by trying to balance a yardstick (or meter stick) on its edge, vs. trying to balance a 6" (or 15 cm) ruler. Or trying to vertically balance a shovel or hammer with heavy side up vs. down. So if a higher center of mass is more stable for ordinaries, yardsticks and other objects, I don't see why it would be opposite for bikes. I've always sort of wondered about bicycle design. The article I mentioned is indicative. They made up a special fork that allowed trail to be changed from several degrees of plus to several degrees of negative tail. They speculated on what the difference in BB height would cause. It appears to me that there are no, or people aren't familiar with, normal basic engineering studies of bicycle design versus the effects on stability and or handling. Witness your discussion of balancing a ruler. If you look into, say aircraft design there are innumerable studies of dimensional changes versus flight characteristics, or even velocity versus flight characteristics. Looking at automobile design there are innumerable studies or, say wheel camber versus degrees of under of over steer. Given that the bicycle probably came into common use long before either the auto or the airplane it seems odd there don't seem to be standards in design. Or perhaps studies on the effect of various changes in design versus stability, for example. Note the usual arguments about "Oooo Aluminum is so stiff". Good Lord! The effects of modifying the strength and elasticity of materials and angles making up a triangle have been known since the days of the early Greeks. Yet the use of a material with well known physical characteristics in a shape that has been known for 2000 years results in this jaw gapped evaluating of "Oh, so stiff". Sigh. But I suppose that the science the is applicable to a device who is protected by bright flashing beams of light is rather on the order of "Eye of newt and toe of frog, Wool of bat and tongue of dog". -- Cheers, John B. There have been many attempts to mathematically understand bicycle stability. It turns out that it's a marvelously complicated topic. The mathematics researchers generate is beyond what I'm willing to try to understand; and I've done a lot of mathematics. Look up the work of Jim Papdopoulos, for example. http://www.nature.com/news/the-bicyc...matics-1.20281 Fortunately, in this discussion I'm not attempting to deal with the general problem. I'm examining only one tiny aspect: the influence of the height of the center of mass. I'd say that's pretty easy to understand. - Frank Krygowski |
#29
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Stability [ Olmo]
On Friday, July 7, 2017 at 9:19:23 PM UTC-4, John B. wrote:
On Fri, 7 Jul 2017 12:10:51 -0400, Frank Krygowski wrote: On 7/7/2017 4:25 AM, John B. wrote: I read an article about different handling between different bikes. The author and his buddy, a frame maker, even cobbled up a fork with adjustable trail. Anyway, they found that the Italian frames tended toward lower bottom bracket heights, in other words lower C/G, which they attributed to a more stable feeling bike. As I've said many times, I'm far from being a connoisseur of bike handling. But it doesn't make sense to me that a lower center of gravity would make a bike feel more stable. First, the effect would seem to be minuscule if it existed. The center of mass of a bike+rider is generally somewhere around the saddle, i.e. maybe 40" high. I'd think lowering the center of mass by half an inch would make a tiny difference compared to other changes. But more important: To me, stability in a bike means it requires less frequent and energetic steering corrections to maintain balance. And in that respect, an "ordinary" or "high wheeler" is far, far more stable than a normal bike. Likewise, a recumbent is far less stable. The first time I road an ordinary, I was able to easily balance at 2 mph. The first time I rode a recumbent, I couldn't even balance. Someone had to run alongside and hold me up as I flopped left and right, until I could relax and let the bike work properly. The difference is polar moment of inertia about the axis along the ground between the two tire contact patches. With the "ordinary's" rider mass at about five feet or more, the sideways rotation needed for a fall begins much more slowly. There's plenty of time to correct even the tiniest deviation from vertical. By contrast, with a recumbent's center of mass at maybe 18", the sideways rotation initiates quickly. The same effect can be observed by trying to balance a yardstick (or meter stick) on its edge, vs. trying to balance a 6" (or 15 cm) ruler. Or trying to vertically balance a shovel or hammer with heavy side up vs. down. So if a higher center of mass is more stable for ordinaries, yardsticks and other objects, I don't see why it would be opposite for bikes. I'm not sure that you are using the correct formula. Generally the width/length of the object and the effective movement of the C/G versus the width as the object is tilted is used isn't it? The classic triangle on it's base versus the triangle on it's apex. In one case the C.G. is raised as the object is tilted in the other it is lowered. The base width is a factor in the case of a stable object with three or more contact points with the ground. It doesn't apply in the case we're discussing, where the axis relevant to stability is the ine connectin two tire contact points. When viewed from the front or back, the bike is effectively balancing on an edge. When lateral tipping begins, the bike+rider center of mass does not rise. - Frank Krygowski |
#30
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Stability [ Olmo]
On Fri, 7 Jul 2017 21:10:57 -0700 (PDT), Frank Krygowski
wrote: On Friday, July 7, 2017 at 9:00:55 PM UTC-4, John B. wrote: On Fri, 7 Jul 2017 12:10:51 -0400, Frank Krygowski wrote: On 7/7/2017 4:25 AM, John B. wrote: I read an article about different handling between different bikes. The author and his buddy, a frame maker, even cobbled up a fork with adjustable trail. Anyway, they found that the Italian frames tended toward lower bottom bracket heights, in other words lower C/G, which they attributed to a more stable feeling bike. As I've said many times, I'm far from being a connoisseur of bike handling. But it doesn't make sense to me that a lower center of gravity would make a bike feel more stable. First, the effect would seem to be minuscule if it existed. The center of mass of a bike+rider is generally somewhere around the saddle, i.e. maybe 40" high. I'd think lowering the center of mass by half an inch would make a tiny difference compared to other changes. But more important: To me, stability in a bike means it requires less frequent and energetic steering corrections to maintain balance. And in that respect, an "ordinary" or "high wheeler" is far, far more stable than a normal bike. Likewise, a recumbent is far less stable. The first time I road an ordinary, I was able to easily balance at 2 mph. The first time I rode a recumbent, I couldn't even balance. Someone had to run alongside and hold me up as I flopped left and right, until I could relax and let the bike work properly. The difference is polar moment of inertia about the axis along the ground between the two tire contact patches. With the "ordinary's" rider mass at about five feet or more, the sideways rotation needed for a fall begins much more slowly. There's plenty of time to correct even the tiniest deviation from vertical. By contrast, with a recumbent's center of mass at maybe 18", the sideways rotation initiates quickly. The same effect can be observed by trying to balance a yardstick (or meter stick) on its edge, vs. trying to balance a 6" (or 15 cm) ruler. Or trying to vertically balance a shovel or hammer with heavy side up vs. down. So if a higher center of mass is more stable for ordinaries, yardsticks and other objects, I don't see why it would be opposite for bikes. I've always sort of wondered about bicycle design. The article I mentioned is indicative. They made up a special fork that allowed trail to be changed from several degrees of plus to several degrees of negative tail. They speculated on what the difference in BB height would cause. It appears to me that there are no, or people aren't familiar with, normal basic engineering studies of bicycle design versus the effects on stability and or handling. Witness your discussion of balancing a ruler. If you look into, say aircraft design there are innumerable studies of dimensional changes versus flight characteristics, or even velocity versus flight characteristics. Looking at automobile design there are innumerable studies or, say wheel camber versus degrees of under of over steer. Given that the bicycle probably came into common use long before either the auto or the airplane it seems odd there don't seem to be standards in design. Or perhaps studies on the effect of various changes in design versus stability, for example. Note the usual arguments about "Oooo Aluminum is so stiff". Good Lord! The effects of modifying the strength and elasticity of materials and angles making up a triangle have been known since the days of the early Greeks. Yet the use of a material with well known physical characteristics in a shape that has been known for 2000 years results in this jaw gapped evaluating of "Oh, so stiff". Sigh. But I suppose that the science the is applicable to a device who is protected by bright flashing beams of light is rather on the order of "Eye of newt and toe of frog, Wool of bat and tongue of dog". -- Cheers, John B. There have been many attempts to mathematically understand bicycle stability. It turns out that it's a marvelously complicated topic. The mathematics researchers generate is beyond what I'm willing to try to understand; and I've done a lot of mathematics. Look up the work of Jim Papdopoulos, for example. http://www.nature.com/news/the-bicyc...matics-1.20281 Fortunately, in this discussion I'm not attempting to deal with the general problem. I'm examining only one tiny aspect: the influence of the height of the center of mass. I'd say that's pretty easy to understand. - Frank Krygowski What you seem to be saying is that a bicycle 100 feet tall would be far more stable then one 1 foot tall and I'm not sure that is correct. If this logic is applied then it would be easier to stand on a one inch broomstick 10 feet tall rather then a 1 inch broomstick 1 inch tall. Re the papdopoulos problem I think (without any great effort being expended) is that the problem is trying to analyze an object with a number of forces acting on it simultaneously by considering each separate force, when, I suggest, the results are the results of a combination of forces. The dihedral of an aircraft wing, for example, tends to keep the wings level..... as long as the wing is moving forward through the air. -- Cheers, John B. |
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