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#21
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Elliptical Chainrings
On 19/07/2013 2:58 PM, Steve Freides wrote:
none (Yannick Tremblay) wrote: In article , Steve Freides wrote: Mower Man wrote: Isn't it the point that elliptical chain rings actually vary the gear ratio? Forget the number of teeth, they're only there 'cos a chain is used. Think of diameter. Variable diameter. Honest. Think drive belt? Big pulley vs small pulley? But big pulley versus small pulley, first of all, means something different for belt drive than for one with teeth. If one pedal revolution gets you 39 teeth spaced evenly apart, what's the difference what the shape is? For a belt driven system, a change in shape could at least mean a change in circumference. For 1 complete revolution, there is no difference. Absolutely correct. However what about 1/4 of a revolution or 1/8 of a revolution? Then the diameter of the "big pulley" does differs. Yan You misread what I wrote. I don't assume that a change in circumference matters, either - you could accomplish the same thing with a larger or smaller, but still round, pulley. The reason tests cannot confirm that this idea works is simple - it doesn't. Neither the rear wheel nor your legs care about the shape of the chainring. When you're pulling one tooth's worth of chain, that's what you're doing, period. -S- I think you've failed to understand my post? Disregard the bloody chain, it's totally irrelevant. Think of the diameter of the chainring. An elliptical ring's diameter varies. It's that simple. If the chainring was the diameter of it's smallest point, gearing would be lower. Conversely, at it's largest point, higher. The chain is just a way (one way) of joining two things in a non slip way. Bet there's an internal combustion engine that uses this stuff to vary camshaft timing. (Research on way?) As for your remarks about "change in circumference", that's exactly what an elliptical ring does. Changes gearing with every revolution. -- Chris 'Fashion is a form of ugliness so intolerable that we have to alter it every six months.' (Oscar Wilde.) |
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#22
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Elliptical Chainrings
On 19/07/2013 7:35 PM, Sir Gregory Hall, Esq· wrote:
"none (Yannick Tremblay)" yatremblay@bel1lin202. wrote in message ... On an ovoid chain rig however, this is not the case. While the ovoid rotate 10 degree, its active diameter also changes. Active diameter doesn't matter. Only the gear ratio matters and that gear ration depends on number of teeth. The change in active diameter of the front can be observed by looking at the derailler moving in an out as the front rig rotates. It is kind of equivalent to the front rig dynamically changing between, say 35 and 37 teeth during a full rotation. (This is possible because only about half of the front rig is touching the chain at any point in time and there is slack in the chain). Wrong! The gear ration doesn't change. Only the slack in the chain changes depending upon the position of the shape of the chainring. The derailleur pulleys are a chain tensioner so of course when the chain becomes slack it takes up the slack. This doesn't mean the gear ratio is changing. One could use a square or rectangular chainring but if it had 53 teeth then the shape of it won't change the gear ratio. It is gear ratio that determines mechanical advantage not gear shape. Oddly shaped gears only result in reduced efficiency compared to circular gears. Wrong. It does. And it's so obvious as to beggar belief. The slack in the chain is utterly irrelevant, too. What is all this 53 tooth numbers stuff about? Old fashioned wrong headed nonsense. The chain just is a convenient non slip way to drive one rotating thing from another. If it was a Vee belt, what would you then think? I assure you that the theory is the same, exactly the same. Did you do "moments" in physics? You should have in the context of this discussion. :-) -- Chris 'Fashion is a form of ugliness so intolerable that we have to alter it every six months.' (Oscar Wilde.) |
#23
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Elliptical Chainrings
On 19/07/2013 7:09 PM, none Yannick Tremblay wrote:
In article , Sir Gregory Hall, Esq· åke wrote: "none (Yannick Tremblay)" yatremblay@bel1lin202. wrote in message ... In article , Steve Freides wrote: Mower Man wrote: Isn't it the point that elliptical chain rings actually vary the gear ratio? Forget the number of teeth, they're only there 'cos a chain is used. Think of diameter. Variable diameter. Honest. Think drive belt? Big pulley vs small pulley? But big pulley versus small pulley, first of all, means something different for belt drive than for one with teeth. If one pedal revolution gets you 39 teeth spaced evenly apart, what's the difference what the shape is? For a belt driven system, a change in shape could at least mean a change in circumference. For 1 complete revolution, there is no difference. Absolutely correct. However what about 1/4 of a revolution or 1/8 of a revolution? Then the diameter of the "big pulley" does differs. True, but *overall* diameter doesn't change as the number of teeth remains the same. So, the gear ratio remains the same. And, as long as the chainring radius is no greater than that of the crank arm there isn't even any leverage difference as if often the (erroneous) claim, due to the fact that it's the length of the crank arms that determines the lever arm. Please, this is pure mathematics and mechanics. The "active" "current" diameter of the front rig changes dynamically during a rotation which means that the current amount of rotation of the pedal that is needs to achieve some specific rotation of the rear wheel with the pedal-crank-rig-chain-cog-wheel assembly changes dynamically. In average over 360 degree it is the same but instantaneously it differs. The problem and complexity occurs when you start introducing a bloody human in the equation and these pesky things are pretty much impossible to model mathematically and are notoriously irregular between individuals. Serously, by all mean disagree that it has any benefits to humans (I am certainly not convinced either) but lets not disagree on mathematics. Yan Congratulations. "Instantaneously". Very nearly the right word. "Progressively" and "variably" would have been even better. I think that there are benefits as we humans a a) good at stamping down b) not too bad at pulling up on the cleats c) not very good at pushing over TDC or BDC. d) ...er, that's it. -- Chris 'Fashion is a form of ugliness so intolerable that we have to alter it every six months.' (Oscar Wilde.) |
#24
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Elliptical Chainrings
Sir Gregory Hall, Esq· wrote:
Froome mostly sits because any energy used moving the body up and down when standing is energy wasted compared to not lifting the body and staying seated. Froome's height is 6 feet, 13 inches. History tells us that smaller racers like to stand more often. Froome, who looks like Lurch, sits - follows past precedent. The little Columbian guy, however, often stands. Whether it's mass or height, I couldn't say, but clearly here, size does matter. -S- |
#25
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Elliptical Chainrings
"Steve Freides" writes:
Sir Gregory Hall, Esq· wrote: Froome mostly sits because any energy used moving the body up and down when standing is energy wasted compared to not lifting the body and staying seated. Froome's height is 6 feet, 13 inches. Maybe he isn't quite that tall. |
#26
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Elliptical Chainrings
"Steve Freides" wrote in message
... Sir Gregory Hall, Esq· wrote: Froome mostly sits because any energy used moving the body up and down when standing is energy wasted compared to not lifting the body and staying seated. Froome's height is 6 feet, 13 inches. History tells us that smaller racers like to stand more often. Froome, who looks like Lurch, sits - follows past precedent. The little Columbian guy, however, often stands. Whether it's mass or height, I couldn't say, but clearly here, size does matter. The little Colombian climber would be better off if he would stay in the saddle and develop his spin technique to put forth max power with fewer calories burned. Probably he looks at the power meter and comes to the conclusion that he creates more power standing. Should this be the case, then he needs to consider calories burned vs. power output. The human body is a machine that runs best when it stays within certain parameters. Standing and pedaling uses more calories even if it should, for a time, create higher wattage. Standing is probably the best thing in a short sprint whereas over the long-haul, climbing included, staying in the saddle will allow greater overall speeds for the long-haul due to energy conserved. It's a fact that the human body is able to burn calories faster than they can be replaced. This is what bonking is all about. So, it would behoove a wise pro cyclist to not ride so close to the ragged edge. Sitting when climbing can develop just as much power as standing if one develops the right technique and with that power comes with a greater efficiency. That's called win-win in a grand classic. -- Sir Gregory |
#27
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Elliptical Chainrings
On 19/07/2013 11:49 PM, Steve Freides wrote:
Sir Gregory Hall, Esq· wrote: Froome mostly sits because any energy used moving the body up and down when standing is energy wasted compared to not lifting the body and staying seated. Froome's height is 6 feet, 13 inches. History tells us that smaller racers like to stand more often. Froome, who looks like Lurch, sits - follows past precedent. The little Columbian guy, however, often stands. Whether it's mass or height, I couldn't say, but clearly here, size does matter. -S- Hold on - how many inches are there in a foot? Answer - a) Over 12 inches b) fewer (note - NOT less) than 12 inches c) 12 OMG. -- Chris 'Fashion is a form of ugliness so intolerable that we have to alter it every six months.' (Oscar Wilde.) |
#28
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Elliptical Chainrings
On 20/07/2013 12:07 AM, Doug Anderson wrote:
"Steve Freides" writes: Sir Gregory Hall, Esq· wrote: Froome mostly sits because any energy used moving the body up and down when standing is energy wasted compared to not lifting the body and staying seated. Froome's height is 6 feet, 13 inches. Maybe he isn't quite that tall. Another LOB. How - given that there are 12 inches to a foot (FFS why do you lot not use the metric system? Sooooo much simpler) is 6 feet 13 inches really 7 feet one inch? LOB = Met Police slang, "Load of ********". -- Chris 'Fashion is a form of ugliness so intolerable that we have to alter it every six months.' (Oscar Wilde.) |
#29
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Elliptical Chainrings
Yannick Tremblay yatremblay@bel1lin202.(none) wrote:
In article , Friso wrote: Yannick Tremblay yatremblay@bel1lin202.(none) wrote: In article , Steve Freides wrote: Mower Man wrote: Isn't it the point that elliptical chain rings actually vary the gear ratio? Forget the number of teeth, they're only there 'cos a chain is used. Think of diameter. Variable diameter. Honest. Think drive belt? Big pulley vs small pulley? But big pulley versus small pulley, first of all, means something different for belt drive than for one with teeth. If one pedal revolution gets you 39 teeth spaced evenly apart, what's the difference what the shape is? For a belt driven system, a change in shape could at least mean a change in circumference. For 1 complete revolution, there is no difference. Absolutely correct. However what about 1/4 of a revolution or 1/8 of a revolution? Then the diameter of the "big pulley" does differs. I think that's the point of Biopace and this new system (has it got a name yet?). The strength needed to rotate 1 cycle is equal, but with an elliptical chainring this strength is supposed to be more equally distributed. The key is that the human ability to deliver power and generate torque varies depending on the position of the pedals. If you had a human with perfect spinning pedalling movement able to generate the same amount of torque at every points over 360 degs then these system would be useless. But they are an attempt to compensate for the imperfect human engine (and pedals). Given the way everything is shaking and non-smooth there must be an effect. I would think this effect is negative, also given the silent passing of Biopace, but given the performance of Froome that doesn't make sense. Why would you think that they have a negative effect? First, thanks for your posts, they give a really good insight in why this might (or might not) work. The reason why I think it has a negative effect is non-scientific. It doesn't look smooth, the chain is jumping, body is shaking. Part of it is just Froome's style. Maybe the 'juming of the chain' is just the effect of the low gears Froome is using. I mainly think that not-smooth is not-100% effective. Shimano, Rotors, and the like have made scientific studies on the subject. We could dismiss some of it as marketing gimmick, other as flawed science but I would not dismiss the Sky team and David Brailsford. The UK cycling team has achieved so much success in the Olympics and WC in large part by preparing and training better, harder and more scientifically than anyone else. Team Sky is most probably the most scientifically trained and tested team. I would be incredibly surprised if Chris Froome has not spent hundreds of hours on a training bikes in the lab trying different setup including circular chain rig and ovoid chain rig. The difference may have been only 0.5% or even less but Brailsford believes in summing all these small minor advantages and making it a winning difference. I wouldn't even be surprised that the exact angle of the ovoid for Froome differs between his mountain climbing bike and his time trial bike and that they all differ from Wiggins ones all of that based on labs measurement for the specific athlete under specific conditions. Brailsford and his team are that anal with regards to details. In act, the above probably highlight one of the problem with Biopace in that it was one setup that may have been good for a certain type of rider with a certain pedalling style but not for a different rider with a different pedalling style. That might very well be true. I would like to add another point to the equation, which is the placebo effect. All this training and figuring out the right ovoid might give Froome the idea that he is very ahead of the rest, while strictly looking at the scientific facts he isn't. But a it gives more 'morale' and therefore has a positive effect on his perormance in the Tour. I wonder: is it still possible to stand up on your pedals when you're going uphill, or is this why Froome is almost always sitting? Hmm, not sure. In theory "dancing on a bike" is not very good and a waste of effort in the long term although climbers like to do it for short efforts. I don't seem to recall someone like Indurain standing up too often either. I'd put it down to riding style. Yani |
#30
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Elliptical Chainrings
Sir Gregory Hall, Esq· wrote:
The little Colombian climber would be better off if he would stay in the saddle and develop his spin technique to put forth max power with fewer calories burned. You are arguing with facts. I don't know _why_ little climbers like to stand, but it's indisputable that they do. Speaking for myself, even though I'm not that little, I do find standing sometimes just feels right when climbing. (I weigh 68 kg or about 150 lbs.) -S- |
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