http://www.cyclingnews.com/road.php?id=road/2005/mar05/critint05/critint053
Criterium International race results
Mon, 03/28/2005 - 6:28am
Mon, 03/28/2005 - 11:42am
#1
After winning Paris-Nice, another awesome performance!
Julich used these odd elliptical chainrings in the time trial. He claims they save him five seconds per kilometre.
http://www.cyclingnews.com/photos/2005/tech/probikes/?id=julich_csc_cerv...
How do some of you gearheads explain its effectiveness?
Mon, 03/28/2005 - 11:57am
#2
Psychosomatism.
Mon, 03/28/2005 - 12:43pm
#3
That's part of it but I was hoping for a mechanical rather than a psychological explanation.
Mon, 03/28/2005 - 1:26pm
#4
"Julich uses French O.Symetric Harmonic elliptical chainrings,
To get the obvious question out of the way, this isn't a resurrection of Shimano's Biopace rings of the 1980s. An elliptical chainring changes the effective gear ratio as you pedal. Biopace reduced the gear ratio as crank passed through the horizontal; the O.Symetric Harmonic increases it. The idea is that the sector of the pedal stroke where the crank is horizontal or nearly so is where you can push hardest, so it makes sense to increase the gear at that point, then drop it to get your foot through top and bottom dead center quickly. It's the same idea as British component maker Chris Bell's Eggrings and, well, just about every other inventor who has come up with elliptical chainrings since shortly after chain drives were invented.""
"
Mon, 03/28/2005 - 1:30pm
#5
Elliptical chainrings
"Look at the Biopace article on Sheldon Brown's site. Biopace chainrings are not elliptical, by the way.
"
Mon, 03/28/2005 - 1:41pm
#6
"I think what you really want is a physiologial explanation, but I don't think one is forthcoming. The ""mechanical"" explanation is that the longer axis of the ellipse creates an effectively higher gear when the pedals are horizontal to the ground and the shorter axis of the ellipse creates an effectively lower gear when the pedals are at TDC and BDC.
But my point was, the first recorded use of elliptical chainrings that I am aware of was in 1892. There may have been earlier incarnations as well. (AFAIK, there were no elliptical-wheel ordinaries...) Thus, if elliptical chainrings really were far superior, and offered a significant advantage, and didn't hurt your knees, it's unlikely that this fact would have been discovered in this century. Or the one prior.
I'm happy that Bobby likes his chainrings, but I don't think you'll find a credible physiological explanation.
Mordecai, any evidence of elliptical wheel ordinaries you've seen?
- Christian
"
Mon, 03/28/2005 - 2:20pm
#7
Elliptical wheels
"Elliptical wheels will work. Square wheels will work too. That is, provided that the road is properly built. A square wheel will work excellently on a road composed of inverted catenaries: http://www.sciencenews.org/articles/20040403/mathtrek.asp."
Mon, 03/28/2005 - 2:31pm
#8
:-)
I was more wondering whether these claims pre-dated chainrings entirely.
I hope the catenary bike is a fixed-gear or hub-brake model, because it'll be hell to design a caliper brake that will work for it...
Mon, 03/28/2005 - 2:36pm
#9
e-mail to firstname.lastname
Say firstname, I hate to skew off here, but I sent an e-mail to the address on ur web site. Would that be a valid account, and/or one that you check regularly?
tnx
Mon, 03/28/2005 - 2:46pm
#10
Yes. It was about spokes et al, yes? I can't access personal mail from work, though.
But the short answer is no. I've used BikeWorks on the LES, Harris Cyclery in Newton, and Bicycle Workshop in Tenafly. I've never found it to be much cheaper than having wheels built.
It's only cheaper if I want specific components (IRO hubs, Sun CR-18 rims, DT Competition spokes) AND don't want to pay the $40-75 for the build.
- Christian
Mon, 03/28/2005 - 8:05pm
#11
These would be good for the Williamsburg Bridge...
Mon, 03/28/2005 - 2:18pm
#12
Biomechanics
"Abstract of ""Physiological and biomechanical factors associated with elite endurance cycling performance.""
Coyle EF, Feltner ME, Kautz SA, Hamilton MT, Montain SJ, Baylor AM, Abraham LD, Petrek GW.
Department of Kinesiology and Health Education, University of Texas, Austin 78712.
In this study we evaluated the physiological and biomechanical responses of ""elite-national class"" (i.e., group 1; N = 9) and ""good-state class"" (i.e., group 2; N = 6) cyclists while they simulated a 40 km time-trial in the laboratory by cycling on an ergometer for 1 h at their highest power output. Actual road racing 40 km time-trial performance was highly correlated with average absolute power during the 1 h laboratory performance test (r = -0.88; P less than 0.001). In turn, 1 h power output was related to each cyclists' VO2 at the blood lactate threshold (r = 0.93; P less than 0.001). Group 1 was not different from group 2 regarding VO2max (approximately 70 ml.kg-1.min-1 and 5.01 l.min-1) or lean body weight. However, group 1 bicycled 40 km on the road 10% faster than group 2 (P less than 0.05; 54 vs 60 min). Additionally, group 1 was able to generate 11% more power during the 1 h performance test than group 2 (P less than 0.05), and they averaged 90 +/- 1% VO2max compared with 86 +/- 2% VO2max in group 2 (P = 0.06). The higher performance power output of group 1 was produced primarily by generating higher peak torques about the center of the crank by applying larger vertical forces to the crank arm during the cycling downstroke. Compared with group 2, group 1 also produced higher peak torques and vertical forces during the downstroke even when cycling at the same absolute work rate as group 2. Factors possibly contributing to the ability of group 1 to produce higher ""downstroke power"" are a greater percentage of Type I muscle fibers (P less than 0.05) and a 23% greater (P less than 0.05) muscle capillary density compared with group 2. We have also observed a strong relationship between years of endurance training and percent Type I muscle fibers (r = 0.75; P less than 0.001). It appears that ""elite-national class"" cyclists have the ability to generate higher ""downstroke power"", possibly as a result of muscular adaptations stimulated by more years of endurance training.
Sorry guys, its all about smart hard work and genetics (abundance of Type I muscle fibers).
"
Mon, 03/28/2005 - 2:27pm
#13
Posting race results
"It's easy to get excited about a result and want to shout it to the world, unwittingly ruining the surprise for those who wanted to find out for themselves. Fortunately, the web guy caught it this morning and changed the thread title, maybe there wasn't too much damage done.
But with major races just around the corner (Paris-Roubaix, for example), I would like to ask PLEASE DON'T POST RACE RESULTS IN A THREAD TITLE!!! Tell us something like - ""Criterium International - Amazing Results!"" but save the details for those who open the thread. Thanks."
