http://www.velonews.com/tech/report/articles/6807.0.html
Apparently he’s been riding these all year, but I hadn’t seen them yet.
They look like a front derailleur nightmare, not to mention kind of choppy on the rear derailleur as well.
Can you say, “Biopace” ?
Didnt like them Francois?
Phil White from Cervelo told me (just before the Alpe d’Huez TT stage) that Julich used the dual oval rings for TT’s and kept the oval inner ring even for road stages during the TdF. Can’t argue with his results.
Francois dude, you got all the gear (rotorcranks, powercranks and these oval things) !
Dev
There is something to be said about ‘train with what you are planning to race with’. This is why I don’t totally buy Frank’s exclusive use of powercranks theory. Unless you plan to race on Powercranks, I think you have to mix it up with riding real cranks once you have adapted :-). Same goes for Rotors or these funky Julich cranks. Perhaps you will race to your expectation once you chose your tool (be it conventional, rotor, oval chainring or PC’s) and then commit to that approach ?
Dev
Are they for shimano crank arms? If so I will take them.
My brain doesn’t get the advantage. There are still 53 or so teeth and they all need to go around once per revolution. So why would my legs care what shape that 53 teeth are? Wouldn’t the oblongness just move the rear derailuer in and out as the chain length changes? Anyone follow my logic? The chain in anygiven spot is on both the elongated and non elongated sides simultaneously, given a few links or so. In my mind this seems to accomplish nothing and was not faster than tylers round chainrings. If it were only on the “big” side when pedaling down, and then on the “small” side to speed up the dead spot, I’d get it. But in my mind it can’t do that as the chain is on at least 3 sides all the time.
My brain doesn’t get the advantage. There are still 53 or so teeth and they all need to go around once per revolution. So why would my legs care what shape that 53 teeth are?
It’s a leverage issue, I think. The oblong rings are sorta like a bigger chainring at the point where you have the most leverage, and a smaller ring where you have the least leverage.
was not faster than tylers round chainrings.
That’s true, but it’s the wrong question. The question is, are they faster than *Julich’s *round chainrings?
Actually its an instantaneous torque issue. The distance from the axle centre to the chain changes through the ellipse changes. We also know that the Torque (Force x distance) applied by your legs to the crank arm varies at different parts of the pedal stroke. The idea is to bring you through the dead spot a bit more easily by taking the irregular torque that your legs apply to the cranks and then smoothing it out as that same energy is transferred via the chainring to the chain. Perhaps the likes of Oracle can provide the research that either substantiates or refutes the utility of such cranks.
Francois,
Where did you get your chainrings?
I emailed the company a while back, but I never got a response.
Haim
The power curve of the human body is not constant through the revolution of the crank, so theoretically this is trying to match the power output of the body with the most efficient use of that power on the bike.
That said, I’m still not sure I buy it because if your legs are most powerful at 3/9 o’ clock, just because you increase the crank radius at that point doesn’t mean that you’re putting power through the wheels any more efficiently - it just increases the effective gearing. Given that power is power, I’m not sure it’s any more efficient; i.e., you may go faster through that part of the curve, but you’re probably pushing harder as well.
you’re forgetting that you’ve also got a decrease in effective gearing on the chain ring as well.
I think that’s what I was getting at. Now if your crank arms could extend out at 3, and go back in, I would buy more leverage. And, unless, your pedals speed up on the smaller part of the ring (which I can’t see hapening) it’s doing nothing. Anyone with the old biopace, could you feel it as it went around? If it does then I’m on board, unless it was just perceived.
Yup, Biopace with a new marketing name.
I’ve got some Biopace chainrings that are VERY oval, nearly square. Shimano had more than one version of their go at oval rings.
These have a minor axis/ major axis difference of almost 10%
-SD
Many years ago I had a mountain bike with biopace chainrings. I disliked them, and replaced them with round rings. This was totally a subjective judgement on my part, I never attempted any kind of quantitative test.
The biopace chainrings that I saw in the late 80s were all moderately oval, nowhere near as pronounced as Julich’s. The ovalization was, as someone else has pointed out, a bit ‘squared’ off. More importantly, if my memory serves me well (and it doesn’t always) the axis of the oval was the reverse of Julich’s; in other words, the chainrings were effectively larger at the dead spot, and smaller at the point where you deliver the most power. My understanding is that this counterintuitive setup was based on extensive testing by Shimano… of untrained cyclists with very low cadences! I don’t know any experienced cyclist that ever liked them.
I’m not familiar with exactly how the variable leverage/leg speed setup of RotorCranks works, are Julich’s chainrings essentially doing the same thing in a much simpler way, or is there something else that the cam in RotorCranks accomplishes?
“I’m not familiar with exactly how the variable leverage/leg speed setup of RotorCranks works, are Julich’s chainrings essentially doing the same thing in a much simpler way…”
I was thinking the same thing. It definitely seems like the answer is “yes”. Although I could also believe that the effect may be more pronounced with the Rotors over these chainrings. I would imagine the asymmetic chainring approach to be much cheaper, lighter, and reliable since there’s no new complex mechanism introduced. But I also think the Rotors would shift better and they’ve got the all important asthetic advantage, they just look cooler.
Francois, you’ve ridden both, what are your thoughts as to the differences??
*"“I’m not familiar with exactly how the variable leverage/leg speed setup of RotorCranks works, are Julich’s chainrings essentially doing the same thing in a much simpler way…” *
These chainrings, although a neat idea, do nothing to eliminate the dead point. There is still a power void, a rider’s pedals are still at 6 and 12 o’clock (dead point).
With Rotor Cranks, a rider does not have the void in power output, because the cranks are offset (cams) and correspond at 6 and 1 o clock, powering through the void.
This allows Rotor Cranks riders to be able to apply constant power at all times, eliminating the “power pause”, and this happens 10,000 time an hour. Doing the math, the small benefit that Rotor provides each revolution equals about 2 seconds of additional ground covered in a minute of riding for a rider who can ride 25 MPH, and possibly even more benefit for riders who average 20-24 MPH.
2 seconds per minute seems small, and it is if you are riding a mile. However over a 40k TT this is 2 minutes, and about 10 minutes for an Ironman.
I was thinking the same thing. It definitely seems like the answer is “yes”. Although I could also believe that the effect may be more pronounced with the Rotors over these chainrings. I would imagine the asymmetic chainring approach to be much cheaper, lighter, and reliable since there’s no new complex mechanism introduced. But I also think the Rotors would shift better and they’ve got the all important asthetic advantage, they just look cooler. "
I am not sure how the chainrings shift, but I imagine is is not too smooth. I have not used them. The way I see them working is by imagining myself shifting to a easier gear when my pedals are at 3 and 9 and a harder gear when my pedals are at 6 and 12. Not sure how well this would help me to reduce the dead point.
You were doing great until you mentioned the time improvements. And the 10mins for IM is ridiculous.
Why is that? 2 seconds per minute advantage over a 5 hour ride = 10 mins.
You don’t think a rider with Rotor Cranks could ride 4:50 vs. 5:00 with standard cranks?
Eneko Llanos did it in 2003 as the world champion.
So had lance used them in the tour, he would have won by an additional 2 and a half minutes huh?
On the flip side, everyones favorite german would have won the tour last year had he only been riding rotorcranks.
A new world record would be had in just about every single event with these things if track riders started using them.
so about how far behind did everyone’s favorite german finish in the olympic TT? about 2 minutes? So he was just a pair of rotorcranks away from gold, huh?
Will you be coming out with a model that gives blow jobs too?