|
|
Thread Tools | Display Modes |
#521
|
|||
|
|||
Steel frames and le Tour
On Jul 17, 4:10 pm, "Tom Kunich" cyclintom@yahoo. com wrote:
"Tuschinski" wrote in message ... And indeed when you look at the actual numbers of failures you find that a correctly built steel frame, even superlight ones, very seldom fail and when they do it is pretty plainly a workmanship or material error. Oh come on Tom, that's blatantly false. Back in the days, when we all raced Reynolds/Columbus we broke frames. Some of it by crashing, some by bad handling, some by bad manufacturers. And yes, we also broke Alu frames. And now we break CF frames *shrug*. Such is life ^^ I don't follow you here. Well built steel frames seldom fail. Well built AL frames (the super light ones) fail whether you take good care of them or not. I have personally observed quite a few carbon fiber failures and these bikes are EXPENSIVE. And the total savings a My Time VX costs almost 4 times more than my Basso Loto and they ride almost identically and weigh within a lb of each other. I used to have a Basso Ascot. It was my favorite bike ever. It died in a collision with a car and I didn't do too well either. It was a great frame, though. I think that it was the geometry that made the bike feel really nice. I don't know if your Lotto has the same geometry as my Ascot, but if it does, I know why you like it. I am sure that I will also be able to get a great ride with frames of different materials that have the same geometry as my Ascot. A lot of the times, a cyclist may like a bike more because the geometry makes it feel faster. I believe , like Carl, that the feeling is just that and your speed does not necessarily increase or decrease that much. However, it is great to ride on a bike that has "that" feeling. Andres |
Ads |
#522
|
|||
|
|||
Steel frames and le Tour
On Thu, 17 Jul 2008 23:08:40 -0600, Bret Wade
wrote: wrote: On Thu, 17 Jul 2008 14:13:43 -0600, Bret Wade wrote: wrote: The original question was whether a rider can _feel_ such tiny changes--that same old laughable "noticeably robust forward thrust." I wouldn't put it in those words but I have felt that sensation when switching from a 4 lb Ti frame to a 2.5 lb Al frame. It felt faster from the first pedal stroke. It was a team bike that I was somewhat skeptical of riding, so it wasn't just wishful thinking. Others on the team had similar experiences. I understand physics well enough to know that the sensation was misleading. Bret Dear Bret, Forgive a long-winded answer, but you're so refreshingly reasonable that I want to avoid any offense. What interests me is the idea that a 1.5 lb lighter frame "felt faster from the first pedal stroke"--possibly a generalization or even hyperbole, but it's what we have to work with. I don't know the actual weights, but it was a whole team, so a 150 pound rider and a 16.5 pound bike would probably be in the ballpark. That theoretical 166.5 pound bike and rider would drop to 165 pounds, about 0.9%. The bike itself would have dropped from 16.5 to 15.0 pounds, about 10%. The bike might twitch from side to side or heave forward 10% easier. But I gather that we agree that the speed and acceleration improvements are going to be so small that a calculator is necessary to see them. In fact, they don't show up on my first effort: http://bikecalculator.com/veloUS.html I tried 400 watts, a 150 pound rider, 15 and 16.5 pound bikes, tubulars, and drops. Because the calculator has only 2-decimal precision, both bikes went the same speed--27.85 mph. (A quick look at the time for 20 miles reassured me that the calculator is still grinding out infinitesimal details--43.08 minutes versus 43.09 minutes, a 0.01 minute lead, 0.6 seconds.) Let's send the bikes up the Alp d'Huez, which I have handy at 8.1% and 13.8 km (8.56 miles): http://en.wikipedia.org/wiki/Alpe_d'Huez The steep grade teases out a speed difference, but it's still nothing that a rider could detect. I get 41.03 minutes versus 41.33, a 0.3 minute or 18 second lead after almost 2500 seconds. That's ~1% faster. The speeds are 12.52 mph versus 12.43 mph. Raise the power to 500 watts, and the time and difference shrink to 34.04 versus 34.27, a little under 14 seconds, at 15.09 versus 14.99 mph. In other words, it takes the Alp d'Huez and a light, world-class rider to produce a tenth of a mile per hour and 14-second difference with a 1.5 pound lighter bike. So I'm glad that you understand the physics well enough to know that the impression was probably misleading. In unblinded testing, it's hard to tell which way our misperceptions will go. Just paying attention (because we're testing) distorts what we think we feel. Evil psychologists love to demonstrate how students will mis-measure the same lumber with the same measuring tapes, according to whether they've been told that it's important for the boards not to be too long, for them not to be too short, or that the measurement accuracy does (or doesn't) really matter. Cheers, Carl Fogel Dear Carl, No need to apologize, I understand that bad habits can be hard to break. The hardest thing I've done in my life is break a pack a day Marlboro habit. Anyway, I'll just point out that your very detailed analysis involves steady state aerobic climbing whereas most "Wow, this bike is fast!" moments will come during anaerobic accelerations. Not that I think the result would be much different. A small change in total mass won't affect either situation much. The bike weighed 16 lbs, rider was 165 lbs and max power was 1350 watts. Cheers, Bret Dear Bret, It doesn't much matter whether we talk about a momentary acceleration or steady-state cruising. Heck, it doesn't much matter whether we're talking about a grandmother setting off to the grocery store or a pro suddenly giving everything he's got up the Alp d'Huez. The mistaken belief that Newton's world changes dramatically for really powerful riders or really steep hills keeps coming up in this thread, so forgive me for ploughing through the same old stuff again. *** 160 + 16.0 = 176.0 lbs = 72.727 kg + 7.273 kg = 80.000 kg 160 + 17.5 = 177.5 lbs = 72.727 kg + 7.955 kg = 80.682 kg 177.5/176.0 = ~1.008, so acceleration should increase 1% in the real world. Sprint acceleration calculator: http://www.analyticcycling.com/DiffE...n500_Page.html First, let's see how much faster the 1.5-lb-lighter bike accelerates from a standing start at 1350 watts up a convenient 8.1% stretch of the Alp d'Huez. Use max power 1350, avg power 1349.9, slope 0.081, and do it for a distance of 10 meters (the very last field). Then do it again for a max power of 100 watts and an average of 99.9. 1350 watts 100 watts 176.0 177.5 176.0 177.5 meters time time time time 1.0 0.3 0.3 1.1 1.1 2.5 0.6 0.6 2.4 2.4 5 1.2 1.2 4.2 4.2 10 2.1 2.1 7.6 7.6 15 2.8 2.8 10.9 11.0 20 3.3 3.3 14.3-14.4 25 3.9 3.9 17.6-17.8 50 6.4 6.4 34.4 34.7 100 10.6 10.7* 68.0 68.6 150 14.6 14.6 101.7 102.5 200 18.4 18.4 135.4 136.5 250 22.0-22.1 169.2 170.6 300 25.7-25.8 203.1 204.8 * shows how rounding can affect things In other words, a 1.5-lb acceleration difference takes a long time up an 8.1% grade to show up on a calculator that reads in tenths of a second. It takes 250 meters for a ~0.5% time difference to show up reliably on a 0.1 second stopwatch for the powerful rider. Neither rider is going to notice an off-the-line ~1% acceleration increase with the seat of his pants. If he's extrapolating from the change in how he can heave the 10% lighter bike around, then he must have an impressive calculator inside his head. *** For steady-state cruising up the same hill, the speed differences are even less than the acceleration differences. Use 1350 watts, 8.1% grade, rider 160, bikes 16 and 17.6 lbs, tubulars, hoods he http://bikecalculator.com/veloUS.html I get 27.99 mph versus 27.90 mph, 99.678% as fast. Once you accelerate to cruising speed, the high speed wind drag effect reduces the ~1% idealized mass difference to ~0.3%. Now try grandma at 100 watts up the same 8.1% grade. She goes 3.15 versus 3.17 mph. *** As has been suggested, something besides the 1.5 lb frame difference might account for the faster-from-the-first-pedal impression. All of the technical possibilities (stiffer frame, different tires, better aero, and so on) are dwarfed by the stubborn psychological effect of trying a new bike. Even the same thing with a different paint scheme will feel "different" if we're told "go ahead and try this new [fill in the blank]." Trying something with an eye toward comparing it puts us in an entirely different position than just using something familiar. Cheers, Carl Fogel |
#523
|
|||
|
|||
Steel frames and le Tour
On Fri, 18 Jul 2008 02:43:30 -0700, "Paul M. Hobson"
wrote: wrote: Dear Scott, It's easy to lose track of such insignificant figures, so pardon this correction. In this sub-thread, the weight penalty was only 1 kg, 2.2 lbs, for an imaginary elite rider putting out 400 watts up a 10% grade. It produces a 0.18 km/h speed penalty, not the claimed 6 km/h. My point was that the wildly exaggerated claim that 1 kg would slow a pro down 6 km/h was absurd (and, as usual, presumably made in good faith). To slow someone like that imaginary pro down 6 km/h with extra weight on that climb, you have to perch an imaginary 50 kg podium girl on his handlebar. Carl: What about another rider and bike? http://tinyurl.com/6qo82g g \\paul Dear Paul, Nice photos! The terrible thing is that Horner and his passenger would have passed the likes of me up that hill. Cheers, Carl Fogel |
#525
|
|||
|
|||
Steel frames and le Tour
wrote in message
... On Jul 17, 4:10 pm, "Tom Kunich" cyclintom@yahoo. com wrote: And the total savings a My Time VX costs almost 4 times more than my Basso Loto and they ride almost identically and weigh within a lb of each other. I used to have a Basso Ascot. It was my favorite bike ever. It died in a collision with a car and I didn't do too well either. It was a great frame, though. I think that it was the geometry that made the bike feel really nice. I don't know if your Lotto has the same geometry as my Ascot, but if it does, I know why you like it. I am sure that I will also be able to get a great ride with frames of different materials that have the same geometry as my Ascot. A lot of the times, a cyclist may like a bike more because the geometry makes it feel faster. I believe , like Carl, that the feeling is just that and your speed does not necessarily increase or decrease that much. However, it is great to ride on a bike that has "that" feeling. I had a Basso Gap as my first high end bike and it was a great bike after I replaced the new Dura Ace headset with a new Campy headset that didn't have a high speed wobble... I'm tall - 6'4" and ride a 61 or 62 cm bike and some other VERY famous bikes ride like crap in these sizes. I've had a large collection of increasingly expensive bikes and yet none of them are any better than the Basso. Though some of them are just as good. The Bassos have always been good to me. |
#526
|
|||
|
|||
Steel frames and le Tour
On Jul 18, 3:57*pm, Lou Holtman wrote:
'...... anaerobic accelerations.....' Geezes what crap is that? Are you retarded? If someone goes from a "cruise" of say 100W, then up to an unsustainable peak of 1350W, and with any reasonable probability the speed increased, what would you like to call it? |
#527
|
|||
|
|||
Steel frames and le Tour
Lou Holtman wrote:
wrote: On Thu, 17 Jul 2008 23:08:40 -0600, Bret Wade wrote: wrote: On Thu, 17 Jul 2008 14:13:43 -0600, Bret Wade wrote: wrote: The original question was whether a rider can _feel_ such tiny changes--that same old laughable "noticeably robust forward thrust." I wouldn't put it in those words but I have felt that sensation when switching from a 4 lb Ti frame to a 2.5 lb Al frame. It felt faster from the first pedal stroke. It was a team bike that I was somewhat skeptical of riding, so it wasn't just wishful thinking. Others on the team had similar experiences. I understand physics well enough to know that the sensation was misleading. Bret Dear Bret, Forgive a long-winded answer, but you're so refreshingly reasonable that I want to avoid any offense. What interests me is the idea that a 1.5 lb lighter frame "felt faster from the first pedal stroke"--possibly a generalization or even hyperbole, but it's what we have to work with. I don't know the actual weights, but it was a whole team, so a 150 pound rider and a 16.5 pound bike would probably be in the ballpark. That theoretical 166.5 pound bike and rider would drop to 165 pounds, about 0.9%. The bike itself would have dropped from 16.5 to 15.0 pounds, about 10%. The bike might twitch from side to side or heave forward 10% easier. But I gather that we agree that the speed and acceleration improvements are going to be so small that a calculator is necessary to see them. In fact, they don't show up on my first effort: http://bikecalculator.com/veloUS.html I tried 400 watts, a 150 pound rider, 15 and 16.5 pound bikes, tubulars, and drops. Because the calculator has only 2-decimal precision, both bikes went the same speed--27.85 mph. (A quick look at the time for 20 miles reassured me that the calculator is still grinding out infinitesimal details--43.08 minutes versus 43.09 minutes, a 0.01 minute lead, 0.6 seconds.) Let's send the bikes up the Alp d'Huez, which I have handy at 8.1% and 13.8 km (8.56 miles): http://en.wikipedia.org/wiki/Alpe_d'Huez The steep grade teases out a speed difference, but it's still nothing that a rider could detect. I get 41.03 minutes versus 41.33, a 0.3 minute or 18 second lead after almost 2500 seconds. That's ~1% faster. The speeds are 12.52 mph versus 12.43 mph. Raise the power to 500 watts, and the time and difference shrink to 34.04 versus 34.27, a little under 14 seconds, at 15.09 versus 14.99 mph. In other words, it takes the Alp d'Huez and a light, world-class rider to produce a tenth of a mile per hour and 14-second difference with a 1.5 pound lighter bike. So I'm glad that you understand the physics well enough to know that the impression was probably misleading. In unblinded testing, it's hard to tell which way our misperceptions will go. Just paying attention (because we're testing) distorts what we think we feel. Evil psychologists love to demonstrate how students will mis-measure the same lumber with the same measuring tapes, according to whether they've been told that it's important for the boards not to be too long, for them not to be too short, or that the measurement accuracy does (or doesn't) really matter. Cheers, Carl Fogel Dear Carl, No need to apologize, I understand that bad habits can be hard to break. The hardest thing I've done in my life is break a pack a day Marlboro habit. Anyway, I'll just point out that your very detailed analysis involves steady state aerobic climbing whereas most "Wow, this bike is fast!" moments will come during anaerobic accelerations. Not that I think the result would be much different. A small change in total mass won't affect either situation much. The bike weighed 16 lbs, rider was 165 lbs and max power was 1350 watts. Cheers, Bret Dear Bret, It doesn't much matter whether we talk about a momentary acceleration or steady-state cruising. Heck, it doesn't much matter whether we're talking about a grandmother setting off to the grocery store or a pro suddenly giving everything he's got up the Alp d'Huez. The mistaken belief that Newton's world changes dramatically for really powerful riders or really steep hills keeps coming up in this thread, so forgive me for ploughing through the same old stuff again. *** 160 + 16.0 = 176.0 lbs = 72.727 kg + 7.273 kg = 80.000 kg 160 + 17.5 = 177.5 lbs = 72.727 kg + 7.955 kg = 80.682 kg 177.5/176.0 = ~1.008, so acceleration should increase 1% in the real world. Sprint acceleration calculator: http://www.analyticcycling.com/DiffE...n500_Page.html First, let's see how much faster the 1.5-lb-lighter bike accelerates from a standing start at 1350 watts up a convenient 8.1% stretch of the Alp d'Huez. Use max power 1350, avg power 1349.9, slope 0.081, and do it for a distance of 10 meters (the very last field). Then do it again for a max power of 100 watts and an average of 99.9. 1350 watts 100 watts 176.0 177.5 176.0 177.5 meters time time time time 1.0 0.3 0.3 1.1 1.1 2.5 0.6 0.6 2.4 2.4 5 1.2 1.2 4.2 4.2 10 2.1 2.1 7.6 7.6 15 2.8 2.8 10.9 11.0 20 3.3 3.3 14.3-14.4 25 3.9 3.9 17.6-17.8 50 6.4 6.4 34.4 34.7 100 10.6 10.7* 68.0 68.6 150 14.6 14.6 101.7 102.5 200 18.4 18.4 135.4 136.5 250 22.0-22.1 169.2 170.6 300 25.7-25.8 203.1 204.8 * shows how rounding can affect things In other words, a 1.5-lb acceleration difference takes a long time up an 8.1% grade to show up on a calculator that reads in tenths of a second. It takes 250 meters for a ~0.5% time difference to show up reliably on a 0.1 second stopwatch for the powerful rider. Neither rider is going to notice an off-the-line ~1% acceleration increase with the seat of his pants. If he's extrapolating from the change in how he can heave the 10% lighter bike around, then he must have an impressive calculator inside his head. *** For steady-state cruising up the same hill, the speed differences are even less than the acceleration differences. Use 1350 watts, 8.1% grade, rider 160, bikes 16 and 17.6 lbs, tubulars, hoods he http://bikecalculator.com/veloUS.html I get 27.99 mph versus 27.90 mph, 99.678% as fast. Once you accelerate to cruising speed, the high speed wind drag effect reduces the ~1% idealized mass difference to ~0.3%. Now try grandma at 100 watts up the same 8.1% grade. She goes 3.15 versus 3.17 mph. *** As has been suggested, something besides the 1.5 lb frame difference might account for the faster-from-the-first-pedal impression. All of the technical possibilities (stiffer frame, different tires, better aero, and so on) are dwarfed by the stubborn psychological effect of trying a new bike. Even the same thing with a different paint scheme will feel "different" if we're told "go ahead and try this new [fill in the blank]." Trying something with an eye toward comparing it puts us in an entirely different position than just using something familiar. Cheers, Carl Fogel You can stop now Carl. You take away peoples illusions and beliefs with your straightforward calculation. What illusions? I specifically said that a small change in mass doesn't have much affect. I someway this ****es them off. I'm not mad. You are arguing now with people who don't want to belief. We're not arguing. No point in that. No. '...... anaerobic accelerations.....' Geezes what crap is that? That crap is the **** that will kill them in uphill sprint finishes. Bret |
#528
|
|||
|
|||
Steel frames and le Tour
On Fri, 18 Jul 2008 14:40:56 -0700 (PDT), "
wrote: On Jul 17, 4:10 pm, "Tom Kunich" cyclintom@yahoo. com wrote: "Tuschinski" wrote in message ... And indeed when you look at the actual numbers of failures you find that a correctly built steel frame, even superlight ones, very seldom fail and when they do it is pretty plainly a workmanship or material error. Oh come on Tom, that's blatantly false. Back in the days, when we all raced Reynolds/Columbus we broke frames. Some of it by crashing, some by bad handling, some by bad manufacturers. And yes, we also broke Alu frames. And now we break CF frames *shrug*. Such is life ^^ I don't follow you here. Well built steel frames seldom fail. Well built AL frames (the super light ones) fail whether you take good care of them or not. I have personally observed quite a few carbon fiber failures and these bikes are EXPENSIVE. And the total savings a My Time VX costs almost 4 times more than my Basso Loto and they ride almost identically and weigh within a lb of each other. I used to have a Basso Ascot. It was my favorite bike ever. It died in a collision with a car and I didn't do too well either. It was a great frame, though. I think that it was the geometry that made the bike feel really nice. I don't know if your Lotto has the same geometry as my Ascot, but if it does, I know why you like it. I am sure that I will also be able to get a great ride with frames of different materials that have the same geometry as my Ascot. A lot of the times, a cyclist may like a bike more because the geometry makes it feel faster. I believe , like Carl, that the feeling is just that and your speed does not necessarily increase or decrease that much. However, it is great to ride on a bike that has "that" feeling. Andres Dear Andres, The day after I removed the 7 pounds of weights from my bike, I went for my usual afternoon ride. I didn't notice any surge in speed or acceleration when I lost the 7 pounds. In fact, I didn't even have a twinge of boy-I'd-like-a-lighter-bike! I suspect that a whole new bike might have felt (and looked) different enough in various ways (tires, wheels, geometry, saddle, brakes, and so on) to make me easy prey for a salesman. But just strapping the extra weight onto the same old bike without changing anything else left me with nothing more than the very suspect feeling that the bike felt "heavier". Much of that "heavier" feeling was probably just the vibration damping of the extra rubber-encased 7 pounds on the top tube. (After all, it amounted to only a 3.2% weight increase.) The rest of the "heavier" feeling was probably due to all the extra attention that I paid (does it feel heavier? lighter? how does it normally feel?), plus the unavoidable knowledge that there were _seven_ whole pounds sitting right there in plain sight whenever I looked down at the speedometer. Some posters might want to try the experiment of just adding a few extra pounds to their familiar bike and comparing whatever difference they "feel" to whatever happens to their actual times around a familiar route. Cheers, Carl Fogel |
#529
|
|||
|
|||
Steel frames and le Tour
"Bret Wade" wrote in message
m... Lou Holtman wrote: You can stop now Carl. You take away peoples illusions and beliefs with your straightforward calculation. What illusions? I specifically said that a small change in mass doesn't have much affect. I someway this ****es them off. I'm not mad. You are arguing now with people who don't want to belief. We're not arguing. No point in that. No. '...... anaerobic accelerations.....' Geezes what crap is that? That crap is the **** that will kill them in uphill sprint finishes. Seems to be sort of weird that the people claiming the math explains everything are those who don't seem able to understand the entire point of the conversation. |
#530
|
|||
|
|||
Steel frames and le Tour
On Sat, 19 Jul 2008 00:57:07 +0200, Lou Holtman
wrote: wrote: On Thu, 17 Jul 2008 23:08:40 -0600, Bret Wade wrote: wrote: On Thu, 17 Jul 2008 14:13:43 -0600, Bret Wade wrote: wrote: The original question was whether a rider can _feel_ such tiny changes--that same old laughable "noticeably robust forward thrust." I wouldn't put it in those words but I have felt that sensation when switching from a 4 lb Ti frame to a 2.5 lb Al frame. It felt faster from the first pedal stroke. It was a team bike that I was somewhat skeptical of riding, so it wasn't just wishful thinking. Others on the team had similar experiences. I understand physics well enough to know that the sensation was misleading. Bret Dear Bret, Forgive a long-winded answer, but you're so refreshingly reasonable that I want to avoid any offense. What interests me is the idea that a 1.5 lb lighter frame "felt faster from the first pedal stroke"--possibly a generalization or even hyperbole, but it's what we have to work with. I don't know the actual weights, but it was a whole team, so a 150 pound rider and a 16.5 pound bike would probably be in the ballpark. That theoretical 166.5 pound bike and rider would drop to 165 pounds, about 0.9%. The bike itself would have dropped from 16.5 to 15.0 pounds, about 10%. The bike might twitch from side to side or heave forward 10% easier. But I gather that we agree that the speed and acceleration improvements are going to be so small that a calculator is necessary to see them. In fact, they don't show up on my first effort: http://bikecalculator.com/veloUS.html I tried 400 watts, a 150 pound rider, 15 and 16.5 pound bikes, tubulars, and drops. Because the calculator has only 2-decimal precision, both bikes went the same speed--27.85 mph. (A quick look at the time for 20 miles reassured me that the calculator is still grinding out infinitesimal details--43.08 minutes versus 43.09 minutes, a 0.01 minute lead, 0.6 seconds.) Let's send the bikes up the Alp d'Huez, which I have handy at 8.1% and 13.8 km (8.56 miles): http://en.wikipedia.org/wiki/Alpe_d'Huez The steep grade teases out a speed difference, but it's still nothing that a rider could detect. I get 41.03 minutes versus 41.33, a 0.3 minute or 18 second lead after almost 2500 seconds. That's ~1% faster. The speeds are 12.52 mph versus 12.43 mph. Raise the power to 500 watts, and the time and difference shrink to 34.04 versus 34.27, a little under 14 seconds, at 15.09 versus 14.99 mph. In other words, it takes the Alp d'Huez and a light, world-class rider to produce a tenth of a mile per hour and 14-second difference with a 1.5 pound lighter bike. So I'm glad that you understand the physics well enough to know that the impression was probably misleading. In unblinded testing, it's hard to tell which way our misperceptions will go. Just paying attention (because we're testing) distorts what we think we feel. Evil psychologists love to demonstrate how students will mis-measure the same lumber with the same measuring tapes, according to whether they've been told that it's important for the boards not to be too long, for them not to be too short, or that the measurement accuracy does (or doesn't) really matter. Cheers, Carl Fogel Dear Carl, No need to apologize, I understand that bad habits can be hard to break. The hardest thing I've done in my life is break a pack a day Marlboro habit. Anyway, I'll just point out that your very detailed analysis involves steady state aerobic climbing whereas most "Wow, this bike is fast!" moments will come during anaerobic accelerations. Not that I think the result would be much different. A small change in total mass won't affect either situation much. The bike weighed 16 lbs, rider was 165 lbs and max power was 1350 watts. Cheers, Bret Dear Bret, It doesn't much matter whether we talk about a momentary acceleration or steady-state cruising. Heck, it doesn't much matter whether we're talking about a grandmother setting off to the grocery store or a pro suddenly giving everything he's got up the Alp d'Huez. The mistaken belief that Newton's world changes dramatically for really powerful riders or really steep hills keeps coming up in this thread, so forgive me for ploughing through the same old stuff again. *** 160 + 16.0 = 176.0 lbs = 72.727 kg + 7.273 kg = 80.000 kg 160 + 17.5 = 177.5 lbs = 72.727 kg + 7.955 kg = 80.682 kg 177.5/176.0 = ~1.008, so acceleration should increase 1% in the real world. Sprint acceleration calculator: http://www.analyticcycling.com/DiffE...n500_Page.html First, let's see how much faster the 1.5-lb-lighter bike accelerates from a standing start at 1350 watts up a convenient 8.1% stretch of the Alp d'Huez. Use max power 1350, avg power 1349.9, slope 0.081, and do it for a distance of 10 meters (the very last field). Then do it again for a max power of 100 watts and an average of 99.9. 1350 watts 100 watts 176.0 177.5 176.0 177.5 meters time time time time 1.0 0.3 0.3 1.1 1.1 2.5 0.6 0.6 2.4 2.4 5 1.2 1.2 4.2 4.2 10 2.1 2.1 7.6 7.6 15 2.8 2.8 10.9 11.0 20 3.3 3.3 14.3-14.4 25 3.9 3.9 17.6-17.8 50 6.4 6.4 34.4 34.7 100 10.6 10.7* 68.0 68.6 150 14.6 14.6 101.7 102.5 200 18.4 18.4 135.4 136.5 250 22.0-22.1 169.2 170.6 300 25.7-25.8 203.1 204.8 * shows how rounding can affect things In other words, a 1.5-lb acceleration difference takes a long time up an 8.1% grade to show up on a calculator that reads in tenths of a second. It takes 250 meters for a ~0.5% time difference to show up reliably on a 0.1 second stopwatch for the powerful rider. Neither rider is going to notice an off-the-line ~1% acceleration increase with the seat of his pants. If he's extrapolating from the change in how he can heave the 10% lighter bike around, then he must have an impressive calculator inside his head. *** For steady-state cruising up the same hill, the speed differences are even less than the acceleration differences. Use 1350 watts, 8.1% grade, rider 160, bikes 16 and 17.6 lbs, tubulars, hoods he http://bikecalculator.com/veloUS.html I get 27.99 mph versus 27.90 mph, 99.678% as fast. Once you accelerate to cruising speed, the high speed wind drag effect reduces the ~1% idealized mass difference to ~0.3%. Now try grandma at 100 watts up the same 8.1% grade. She goes 3.15 versus 3.17 mph. *** As has been suggested, something besides the 1.5 lb frame difference might account for the faster-from-the-first-pedal impression. All of the technical possibilities (stiffer frame, different tires, better aero, and so on) are dwarfed by the stubborn psychological effect of trying a new bike. Even the same thing with a different paint scheme will feel "different" if we're told "go ahead and try this new [fill in the blank]." Trying something with an eye toward comparing it puts us in an entirely different position than just using something familiar. Cheers, Carl Fogel You can stop now Carl. You take away peoples illusions and beliefs with your straightforward calculation. I someway this ****es them off. You are arguing now with people who don't want to belief. No point in that. '...... anaerobic accelerations.....' Geezes what crap is that? Lou Dear Lou, Well, it's the kind of thing that I'd have come up with myself before I looked into things. Bret seems quite reasonable to me. He felt _something_ different, and so did his whole team, so if it doesn't make sense with 350 watt examples, maybe it was because of the 1350 watt sprint? Until you work through some of these things, it's normal to think that a lot of power or a really steep hill or a standing start or _something_ will explain all the big jumps and falling-off-the-back and other things that seem so obvious. Remember, it took an awfully long time before people decided that hefty objects dropped from a tower fall at about the same rate. And we still have to explain on RBT that heavier riders coast downhill faster because the power from gravity pulling on their extra mass rises faster than their wind drag does. That's why I keep working through the examples suggested by other posters. (I keep wondering why they don't try playing with the calculators themselves--it's not that hard.) What if the Alp d'Huez really did produce a dramatically different result for 7 extra pounds? What if a 1200-foot climb in 2.9 miles somehow exaggerated the effect of extra weight? Does a 1350 watt burst by a sprinter change the outcome that a 350 watt rider will see? It turns out that F = M * A is dreadfully stubborn. Armstrong could have carried a 7-lb handicap up the Alp d'Huez before he slowed down to Ullrich's speed. People really do see jumps, but they're due to either massively mismatched power or one rider jumping a fraction of a second ahead of the other, not 1, 2.2, or even 7-lb weight differences. The greater the power, the _less_ the actual difference because wind drag isn't linear. Riders do fall off the back. But if you can't keep up while drafting on the flats, you certainly haven't got the power to pull ahead. They usually fall off when the pack hits a climb. The guys in back have been hanging on because they could keep up while putting out 10% to 20% less power. That advantage dwindles rapidly as the pack slows down on the hill. That's when the guys who were in front show the real power difference and pull away. That's why it's called being "dropped"--they don't just creep away at 180 meters per hour (0.18 km/h), they pull away at ten times that speed (a whopping 1.8 km/h, which should remind us how tiny the differences are in bicycling). When that happens, it's human to blame it on the extra weight. After all, every bicycle magazine and article weighs every part to the nearest gram. I expect that many posters believe in good faith that they're feeling speed or acceleration when they're just feeling how much easier a lighter bike is to heave back and forth and tip side to side. That feeling is an order of magnitude greater than the acceleration or speed change, so it's hard reason yourself out of it. An analogy would be how fast does 75 mph feel on the highway? In a bouncy short wheelbase jeep with deep-tread tires, 75 mph feels much "faster" than the same 75 mph in a limousine (or 500 mph in a jetliner). Cheers, Carl Fogel |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Steel Frames: Surly, Gunnar, Soma | [email protected] | General | 7 | February 25th 08 01:18 AM |
Italian/steel frames need more prep? | Phil, Squid-in-Training | Techniques | 84 | April 13th 06 03:56 PM |
BB on steel frames | PJay | Techniques | 8 | November 1st 05 04:16 AM |
Steel Road frames | firewolf65 | General | 8 | April 12th 05 03:59 PM |
Good Steel Frames | danimal | Off Road | 2 | May 29th 04 05:46 AM |