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#11
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 9, 8:51*pm, Frank Krygowski wrote:
On Nov 9, 10:31*pm, DirtRoadie wrote: No. Let get right down to it. Skip the aerodynamics (unless you just want to make that a constant factor). *You as always want *to expound on anything and everything. Please *SHOW me. Here you have taken your hypothesis ans simply restated it as a conclusion. That's sloppy and exactly what you find *so offensive when others do it. Start here. We have two riders CLIMBING at constant speed. EVERTYHING about them is identical except that one is carrying weight in a water bottle that is equal to the amount his rims and tires are lighter than the other rider's (That's to assume we are putting that mass at the wheel perimeter) Now taking into account the fluctuation in force/power in their (identical) pedal strokes, (as exemplified here):http://www.trainright.com/assets/new...ockdiagram.jpg Show me just what happens between these two riders with those fluctuations. *In particular, address the microscopically higher speeds you have noted. And yes there are some minor glitches in this hypothetical -please point those out if you see them. But please also try to stay within the scope of what I have described as much as possible. Look at this as an opportunity to add the "science" you always refer to but rarely provide. Thanks. DR DR: *I _did_ show you, whether or not you understood. *Whether riding on level ground or ascending a hill as you described, the principles are the same. *There are some slight differences in magnitude, but the effects are the same. Sure, you can say the aerodynamics are constant, if you want. *That's an approximation which although not perfectly precise, is certainly close enough to reality, given the tiny fluctuations in velocity. *If we accept that, then the guy on the lighter wheels doesn't actually lose ground. *The two riders would remain exactly side by side. *But the lighter wheels do _not_ provide an advantage. I don't know what part of the explanation you didn't understand, so I can't clear up your confusion for you. Maybe you can dig into one of Carl's favorite calculator sites and plug in the numbers. *Let me know how it comes out. No the principles are different. Not saying the result is different but you make assumptions that are not necessarily justified. First wind drag is lost energy and I am specifically trying to avoid that. (The present discussion has nothing to do with the benefits of aero equipment which are accepted and understood and it just muddies the results of the weight analysis.) Second you use the term "microscopically" (twice) as if it has a value. Small, yes, but not zero and not equal for all values of microscopic . And you use it once to define acceleration/increased speed when the rider is that portion of the pedal stroke where he/she is providing some quantity of forward propulsion which is MORE than the retarding forces (Gravity, friction, air, acceleration) and you use it again when the deceleration is the result of the retarding forces being greater than the mere momentum of the bike and rider. You equate the first "microscopic" with the second yet have not shown how that is the case. It's just a quick "they're equal." It's nothing more than an assumption to say that the power stroke is a nice even sinusoidal curve. Carl's (Tom Compton's) analytical tools are great as far as they go, but they rely upon assumptions which whitewash over what I am focusing on. Give it some thought. Seriously, see if you can come up with something other than "it's too small to matter." That's an engineering perspective, not a scientific one although the latter may lead to the former once quantified. I purposely did not use an "out-and-back time trial" analogy as you did because there is no conservation of energy as is the case (at least hypothetically) with an up-and-back climb. DR |
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#12
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Tue, 9 Nov 2010 19:31:13 -0800 (PST), DirtRoadie
wrote: No. Let get right down to it. Skip the aerodynamics (unless you just want to make that a constant factor). [snip] Dear DR, Why do you think that you can skip the aerodynamics? Cheers, Carl Fogel |
#13
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 9, 10:32*pm, wrote:
On Tue, 9 Nov 2010 19:31:13 -0800 (PST), DirtRoadie wrote: No. Let get right down to it. Skip the aerodynamics (unless you just want to make that a constant factor). [snip] Dear DR, Why do you think that you can skip the aerodynamics? I can do anything I want. But seriously, I wanted to focus on the wheel weight issue as related to power fluctuation in a pedal stroke and use a hypothetical where air resistance was a negligible portion of the retarding forces. DR |
#14
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 9, 10:01*am, Frank Krygowski wrote:
What about the two minutes' advantage, over 40k, for an aero wheel setup compared to "conventional"? Of all race types, aerodynamic advantage is likely to be most valuable in a time trial. *It's a maximum effort, completely solo, against (usually) nothing but the air resistance. That's been known for probably 100 years. But even that knowledge can turn into a fetish. *I remember a similar discussion here, where one person was honestly claiming that you could count on something like a 0.5 second advantage in a 40k TT based on whether your pinky finger was tucked behind your ring finger or not. Or was it about clipping your fingernails? I didn't say anything about fingernails. Aero advantage of finger position is an example of something that never makes it out of the wind tunnel. *There are other advantages (whether aero, or weight, or inertia) that may possibly show up in a time trial or a match sprint, but get swamped by tactics and random events in any crit or road race. *And only the most extreme advantages (like going to a recumbent, or losing over five pounds) are going to be perceptible in non-competitive riding. We're back to the "swamped in the noise" argument. I maintain that the little advantages never go away. They might be small, very small, but they are still there, all the time. Like losing a pound, even from the 180lb rider + bike package yields whatever-- a second or three in a 40k ITT, is that the amount that's been demonstrated here? It's still real, even if people are foolishly clipping fingernails, etc. etc. Isn't it obvious that _some_ level of theoretical advantage must disappear into the noise? *If not, racers would be shaving their entire bodies. Well, that's another one of your rhetorical devices, to which I can only say, I'm not talking about shaving or clipping fingernails. Pinky in the wind? No, but, as alluded to in that old Jim Martin article, doing a lot of work (some need lots more than others) IRT developing an aero position *with power* will yield positive results, and sometimes (often, usually) big ones. For instance, there was a racer here back in the day, a guy who won "something national on the track" against the names of the day-- attesting to "the motor"; he certainly had one. But something I used to see him do in races, consistently, was to be the only guy in the pack (that I could see at the moment) who was *not* pedaling, and sometimes, the only one not pedaling hard, while we were flying along. That's not "equipment aero" but it sure is aero, and it's real. He was really good at sniffing out a draft, and he did it without causing crashes, too, BTW. That mindset, in addition to the "little details" is what, IMHO, the smart racers do. Tech stuff is often just grounds for neutral (especially, in these modern times, apolitical) conversation. One of the old, gone-away regular posters here used to "go on" about that but for all his smarts, I don't think he got that one. Just a for-instance, but he was only one... There is a component (intentional!) of "geekery" that is IMHO a totally healthy part of a competitive drive. Part of it is plain old snob appeal, showing off the income, "keeping up", etc. etc., but some of it is getting those little advantages that are always there despite "the noise". And what about the racing community-- smart, successful and competitive people who read equipment comparison tests not directly funded by mfg's? I know, and have known, members of the racing community. *As I said, I was on a ride with two of them not long ago. *One was saying "I'm thinking about trying those ceramic bearings for my crank." *Nice guys, but that's not saying much for their technical judgment. The ceramic bearing thing ran its course (semi-intentional!) around here. I'm not in the inner circles of racing but gathering partly from shop scuttlebutt, those bearings were perceived as having a smoother feel in certain BB's (esp., outboard types) than stock parts, these stock BB's being noted for not being very smooth, but the maintenance turned out to be "stupid", to coin a phrase. That's all "reportage", no personal experience here. Sure, *everyone* is susceptible to suggestion; then you go "try it out for yourself", or maybe let someone else try it out for you g. Of course, here I may be writing to a bunch of guys who think ceramic bearings will let them surge into the lead! Maybe a few, but, again, what I see is, most of them are competitors looking for an edge-- like going to a Driveway race where the field is limited to 100 and you can expect a minimum of 50 to show up on a slow night. There's a huge difference between those two mindsets. D-y, it wasn't intended to be abusive - any more, I suppose, than your phrase "which is usual for you." Well, Frank, you do come off as being abusive. What can I say? Saying so doesn't automatically make me abusive. DirtRoadie has frequently gotten hot with me when I express skepticism about the wonderful benefits of the latest marketing gimmick. *Based on that, I take him to be a person who (like my sports-car friend) is really, really into having the latest and greatest. *Like the guy saying "God, I gotta get a carbon frame" at 1:43 inhttp://www.youtube.com/watch?v=Vn29DvMITu4 Maybe I'm wrong. *But if DR is really so much into high-zoot equipment that he attacks engineering judgment as heretical, he _needs_ to buy high-zoot equipment, and I'm not going to try to convince him otherwise. *That was the meaning of my post. You usually do better the second time around. Am I chiding? Yes, I am. I'm not pretending to be innocent of poke-and-poke-back, either. But, you'll notice, I working on consensus and getting things straight-- or straighter-- here. I hope that's what comes off. I don't think it's stupid to look for those small advantages. Not doing a total body shave might actually translate to "looking for small advantages that are real", if you think about it that way. And I should add, when I talk about these local racerdudes, part of the background is that many (most, nearly all) are dedicated "trainers". Some are a lot better at it than others, and some picked their parents more carefully (check column A for Athleticism), but by and large they, in addition to concern with "parts", also read up on training methods and apply, with rigor. IOW, just to make sure this end of the discussion is covered, so to speak, they're not a bunch of lazy dumbells who expect to eat nachos and drink beer all week and then have their ceramic bearings save them at the races. --D-y |
#15
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 10, 3:31*am, DirtRoadie wrote:
On Nov 9, 7:22*pm, Frank Krygowski wrote: On Nov 9, 5:22*pm, DirtRoadie wrote: On Nov 9, 2:54*pm, Frank Krygowski wrote: ...*I'm trying to realistically talk about bicycle technology. Yes, let's do that as you offered with regard to wheel mass and acceleration within the context of power surges in a pedal stroke. *I am particularly interested in the effect on speed. Now I understand that _energy_ *is conserved, but that does not tell the whole story. Energy is also conserved when doing an up-and-back on a climb, but average speed nonetheless suffers (even assuming no air resistance). So starting there, would you like to do some comparing? OK, if you like. First, let's note that energy is _not_ actually conserved while riding a bicycle. *If it were, you probably wouldn't get tired. *Energy is dissipated as heat, through various mechanisms. *Most of the time (in racing, anyway) the biggest loss by far is through aerodynamic drag. Aero losses are higher when the relative air speed (bike through the air) are higher. *That's why the fastest time trials happen in still air, not on days with winds. *You lose more fighting into a headwind than you gain on the way back. *You also lose more energy to wind resistance when you're speeding down a hill, compared with climbing it, and the faster you go the more you lose. *That's partly why a breakaway is much more difficult on a long downhill. So how does this affect level riding with lighter or heavier wheels? First, we must keep in mind that the differences between light wheels and heavy wheels are, for any competitive bikes, pretty small. *The percentage differences in total system (bike + rider) inertia are even smaller. *A 153 pound rider on a 17 pound (total weight) bike with three pound wheels has barely over 2% of his inertia due to the wheels. Still: *If rider A has lighter, lower inertia wheels than rider B, on the high power portion of each pedal stroke, both riders are going to accelerate very slightly, and rider A is going to accelerate microscopically ahead of rider B. But on the _low_ power portion of each pedal stroke, both riders are going to decelerate very slightly ... and here it is: *Rider A will _decelerate_ microscopically more than rider B. *Rider B gains during that phase. *Why? *Because during the deceleration phase, the wheels with more inertia will act to keep the bike going, to decelerate less. *It's a flywheel effect. Practically speaking, it all averages out during ordinary constant speed level ground pedaling. *Rider A may be going 20 mph plus or minus 0.01 mph (that is, an amplitude of 0.01 mph superimposed on a 20 mph average) while rider B may be going 20 mph plus or minus 0.008 mph, but the practical measurement of each rider's speed is still 20 mph. *There's no advantage to lighter wheels in that context. But there's more. *Does it all average out perfectly? *No - and the tiny differences in speed work to the disadvantage of the guy with lighter wheels! *Here's why: *The guy with lighter wheels would get to microscopically higher peak speeds. *Remember that aerodynamic power losses vary with (actually, the cube of) relative speed. *During the portion of the pedal cycle he's at 20.01 mph, he loses more energy than his side-by-side competitor loses at 20.008 mph. *And like the out-and-back time trialist on a windy day, he doesn't gain it back on the other half of the cycle. *He'll have to be putting out microscopically more power. That's the physics. *In practice, it's all probably too small to reliably measure. *That (roughly) 2% of inertia in the wheels is not affected much by the switch to lighter wheels. *I mean, how much lighter? *100 grams total? Then you're playing with maybe a tenth of a percent of the total inertia. *Any effect of that difference will be wiped out if, say, rider A has to wipe sweat out of his eye. *The slightest vagary of breeze, bumps in the road, drafting a bigger rider instead of a smaller rider, etc. will wipe out that difference. "But what if I've trained perfectly, and I've done all I can do and my training has reached a plateau. *Shouldn't I go with the lighter wheels? *(Or maybe the more aero wheels?) Personally, if it were me, I'd spend the money on other things. *A few sessions on tactics with an excellent coach would probably kill any wheel advantage you could buy. *As they say, knowledge is power. No. Let get right down to it. Skip the aerodynamics (unless you just want to make that a constant factor). *You as always want *to expound on anything and everything. Please *SHOW me. Here you have taken your hypothesis ans simply restated it as a conclusion. That's sloppy and exactly what you find *so offensive when others do it. Start here. We have two riders CLIMBING at constant speed. EVERTYHING about them is identical except that one is carrying weight in a water bottle that is equal to the amount his rims and tires are lighter than the other rider's (That's to assume we are putting that mass at the wheel perimeter) Now taking into account the fluctuation in force/power in their (identical) pedal strokes, (as exemplified here):http://www.trainright.com/assets/new...ockdiagram.jpg Show me just what happens between these two riders with those fluctuations. *In particular, address the microscopically higher speeds you have noted. And yes there are some minor glitches in this hypothetical -please point those out if you see them. But please also try to stay within the scope of what I have described as much as possible. Look at this as an opportunity to add the "science" you always refer to but rarely provide. Thanks. DR PS- Love your consistency in ending "Personally, if it were me, ..." The guy with the heavier rims climbs fastest, he drank his water 1/2 hour ago. |
#16
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 10, 6:13*am, DirtRoadie wrote:
On Nov 9, 10:32*pm, wrote: On Tue, 9 Nov 2010 19:31:13 -0800 (PST), DirtRoadie wrote: No. Let get right down to it. Skip the aerodynamics (unless you just want to make that a constant factor). [snip] Dear DR, Why do you think that you can skip the aerodynamics? I can do anything I want. *But seriously, I wanted to focus on the wheel weight issue as related to power fluctuation in a pedal stroke and use a hypothetical where air resistance was a negligible portion of the retarding forces. DR Rear wheel instability and inadequate chain lubrication are typically the largest energy saps when climbing, and the inability to provide a constant torque. Lower gears help.. |
#17
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
thirty-six wrote:
Rear wheel instability and inadequate chain lubrication are typically the largest energy saps when climbing, Your home planet is full of marvels. Chalo |
#18
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 10, 1:13*am, DirtRoadie wrote:
On Nov 9, 10:32*pm, wrote: On Tue, 9 Nov 2010 19:31:13 -0800 (PST), DirtRoadie wrote: No. Let get right down to it. Skip the aerodynamics (unless you just want to make that a constant factor). [snip] Dear DR, Why do you think that you can skip the aerodynamics? I can do anything I want. *But seriously, I wanted to focus on the wheel weight issue as related to power fluctuation in a pedal stroke and use a hypothetical where air resistance was a negligible portion of the retarding forces. So what part of my explanation did you not understand? Is it that you don't get that the inertia of a heavier wheel helps to maintain speed during a deceleration phase? - Frank Krygowski |
#19
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 10, 1:40*pm, Frank Krygowski wrote:
On Nov 10, 1:13*am, DirtRoadie wrote: On Nov 9, 10:32*pm, wrote: On Tue, 9 Nov 2010 19:31:13 -0800 (PST), DirtRoadie wrote: No. Let get right down to it. Skip the aerodynamics (unless you just want to make that a constant factor). [snip] Dear DR, Why do you think that you can skip the aerodynamics? I can do anything I want. *But seriously, I wanted to focus on the wheel weight issue as related to power fluctuation in a pedal stroke and use a hypothetical where air resistance was a negligible portion of the retarding forces. So what part of my explanation did you not understand? Is it that you don't get that the inertia of a heavier wheel helps to maintain speed during a deceleration phase? You might want to address my reply to you rather than my reply to Carl. DR |
#20
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Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.
On Nov 11, 3:26*am, " wrote:
On Nov 9, 10:01*am, Frank Krygowski wrote: Aero advantage of finger position is an example of something that never makes it out of the wind tunnel. *There are other advantages (whether aero, or weight, or inertia) that may possibly show up in a time trial or a match sprint, but get swamped by tactics and random events in any crit or road race. *And only the most extreme advantages (like going to a recumbent, or losing over five pounds) are going to be perceptible in non-competitive riding. We're back to the "swamped in the noise" argument. I maintain that the little advantages never go away. They might be small, very small, but they are still there, all the time. Like losing a pound, even from the 180lb rider + bike package yields whatever-- a second or three in a 40k ITT, is that the amount that's been demonstrated here? It's still real, even if people are foolishly clipping fingernails, etc. etc. I agree with this. If a tenth of a second can win a 40 km ITT, then 1h = 60min = 3600sec = 36000 tenths of a second, and (1/36000) * 100 = 0.0027% Not a big change necessary if it came down to it. For instance, there was a racer here back in the day, a guy who won "something national on the track" against the names of the day-- attesting to "the motor"; he certainly had one. But something I used to see him do in races, consistently, was to be the only guy in the pack (that I could see at the moment) who was *not* pedaling, and sometimes, the only one not pedaling hard, while we were flying along. That's not "equipment aero" but it sure is aero, and it's real. He was really good at sniffing out a draft, and he did it without causing crashes, too, BTW. That mindset, in addition to the "little details" is what, IMHO, the smart racers do. We've got one of those. I saw him actually hit the front of the bunch a few weeks back and said "What's this? Can you feel the wind in your face?" He smiled and replied, "Not for long." The ceramic bearing thing ran its course (semi-intentional!) around here. I'm not in the inner circles of racing but gathering partly from shop scuttlebutt, those bearings were perceived as having a smoother feel in certain BB's (esp., outboard types) than stock parts, these stock BB's being noted for not being very smooth, but the maintenance turned out to be "stupid", to coin a phrase. That's all "reportage", no personal experience here. I also draw a line between acceptable and unacceptable expense required to make a measurable or perceived improvement in either performance or reliability. I could afford to spend a whole lot more on equipment, but I don't see the returns as they diminish quickly. Sure, *everyone* is susceptible to suggestion; then you go "try it out for yourself", or maybe let someone else try it out for you g. Like outboard BB bearings. I reckon they're the bees knees. I used to replace cartridges every year, now it's been about 4 years on the same BB! I just regrease the bearings occasionally. As well, there was a marked improvement in perceived BB stiffness. It felt like I was riding a totally different frame. Whether or not it helped me go faster, was probably lost in the noise though ;-) Well, Frank, you do come off as being abusive. I think Frank talks down to so many students, he talks to everyone else the same. It's annoying. He knows not to whom he speaks. James. |
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