Julich's elliptical chainrings

[bcm119]

Whats up with these (http://www.cyclingnews.com/photos/2005/tech/probikes/?id=julich_csc_cervelo/dsc00678) things? 5 seconds per km advantage? Whats climbing like with them? Anyone ever ridden these? Sorry if this has been discussed already. They look super duper funky.

[BumbleBeeDave]

Sounds like Bio-Pace rings to me. Maybe he got a good deal on some NOS on eBay . . . :rolleyes:

BBDave

[Dr. Doofus]

if you look at how they are elliptical, you see that the gear ratio increases as bobby goes through the top and the 12-4 phase of the pedal stroke...which makes sense for a typical euro pro 2-3cm back behind the spindle position, which gives you more power over and through but less at full extension and back...

what's cool about these is that, unlike biopace where the gear ratio got smaller, the gear ratio gets bigger through the phase where you have more muscle moving, and also, you could adjust when the gear gets bigger based on saddle setback...a TT rider could bolt the rings on so that the ratio increased from 2 to 6 (where the power would be in a forward TT position)....

[pale scotsman]

The cranks are pretty scuffed up so I wonder if they are prone to overshifting...

[dave thompson]

It looks like the outer cage plate on the front dérailleur has been cut and shaped accommodate the elliptical ring. Depending how how hard a shift to the big ring was banged, it could overshift the chain when the lowest portion of the ring was on top.

[oracle]

julich was already riding those things in europe last winter; i'm not sure why it has taken the press over a year to report this 'story'.

[Brian Smith]

I used to rotate biopace chainrings one position to achieve very nearly the same thing.
Then I discovered Mavic oval inner rings with multiple (4 or 5) possible mounting positions.
It took a good amount of "mechanicing" to get any of those old ovalish rings to shift well, particularly if mixed with round rings, but I think it was worth it.

Isn't it great how old ideas come back around?

[csb]

oracle, been saving turtles?

[lnomalley]

http://www.osymetric.com


reminds me of that old last-chance smartassdrunken pick-up line, "you're ugly, but i'm interested".

[oracle]

hi csb,

no turtles, but i did rescue a bird, a beautiful morning dove that had perhaps been attacked by a cat and was bleeding from its wing and unable to fly. i rode about 3 miles with it in my hand until we got home and then i drove it to a place that specializes in such cases. two weeks later they emailed me and told me that he was fine and they released him exactly where i told them he had been found.

oracle

[Sandy]

That was very tweet tweet of you, I mean sweet of you. There is a lot of truth to the statement that how a person treats an animal tells a lot about the person. Great deed on your part.

If it had been a baby Kevan, would you have carried it in your hand or would you just have stomped on the little creature?? :) :)


Stomping Sandy

[Sandy]

I read once that your foot traces an elliptical path and not a circular one. Could that have anything to do with it?

Square Sandy

[oracle]

If it had been a baby Kevan, would you have carried it in your hand or would you just have stomped on the little creature??

i guess that depends on how badly off the little critter was... :-)

p.s. my brain moves in an eliptical path......

p.p.s btw, sandy as per #2 on your list of goals on the other thread, have you ever ridden rollers? a great and wise man once told me when i was but a wee lad that rollers are the magic cure for smoothing out one's pedaling inefficiencies, and he was indeed correct.

[Dr. Doofus]

the elliptical path the foot in a normal walking/running gait is the foundation behind most elliptical ring things...they've been done and done...and they usually don't work because duh...you're pedaling, not running.

anyway, the idea behind the OSyms is that you have more power and greater muscle activation though about 4-5 "numbers" of the pedal stroke (if you see it as a clock...someone with better math skills could talk about degrees...jerk?)...all bets are off if the rider has a greater than 90 degree angle when you "connect the dots" from the pedal axle to the hip to the shoulder and a curved back (i.e., its not going to make a big difference for a very upright position on a touring/comfort bike)...if the rider is positioned with a 80-90 degree pedal-to-hip-to shoulder angle (what...that would be like 30? degrees if you just measured the hip angle in relation to a horizontal line from the joint...hel me out here jerk...doof knows it when he sees it but is getting lost in the lingo), then there is enough glute and upper quad getting involved so that the rider cab push more meat through the power phase...so the OS rings make the gear bigger through that part, then decrease it back to the "normal" (assuming a 53 ring) gear as the rider moves past full extension and unloads the pedal....

the short and clear way of saying it is that if you're positioned like a flexible racer, these will help. If not, yerrwastinyercash.

again, the clever thing here is that these rings make the gear bigger, where biopace took the opposite tack, making it smaller...which was just stupid unless you're sheldon brown...who is cool...but anyway....

[Chief]

What goes around comes around! :rolleyes:

[Roy E. Munson]

They're part of a churning mechanism, used to make sure all the dope he's on gets evenly distributed in his bloodstream.

[oracle]

pezcyclingnews.com

PEZ: That’s cool – do have any parting words for PEZ-Readers from from sunny France?

Bobby: yeah… I do have 1 word… well actually two words …

“O-Symmetric chainrings”

PEZ: … really!


Bobby: Have you noticed the chainrings I’ve been using for the last year and half?


PEZ: Okay we’re gonna have to get these onto the test bench…

[Too Tall]

DocDoof, THAT made sense. Thanks, I "get it" in theory anyway. My g-d can you imagine how it would feel to go back to regular cranks after adapting to these? Ouch.

[Brian Smith]

the elliptical path the foot in a normal walking/running gait is the foundation behind most elliptical ring things...they've been done and done...and they usually don't work because duh...you're pedaling, not running.

Actually, the crank length does not change when installing oval or elliptical chainrings in place of round chainrings. I've heard that kind of dismissal of non-round chainrings before, and this is not to say that I don't think they should be dismissed, but the path of the pedal spindle does not change when using them. I wonder where that elliptical foot path idea originated.


anyway, the idea behind the OSyms is that you have more power and greater muscle activation though about 4-5 "numbers" of the pedal stroke (if you see it as a clock...someone with better math skills could talk about degrees...jerk?)...[big snip].... the short and clear way of saying it is that if you're positioned like a flexible racer, these will help. If not, yerrwastinyercash.

The timing of the chainring must relate to the position "around the clock" of the rider's "power stroke," if you can simplify it for the sake of "argument." The only atypical crank/chainring system that I've seen permitting an adjustment for timing is the Rotor system, which is very different from these simple non-round chainrings meant to bolt onto your existing cranks and are probably "calibrated" for an "average-proportioned" rider on an "average" rider-ositioned bike, however they decide that! Again, not to say that non-round chainrings shouldn't be dismissed, but the need for them to be properly timed for the rider does not dismiss their viability for any particular rider or type of rider. Maybe the cost would have to increase substantially in order for the company to offer them in different timings and to help you determine the timing required for the application, but people are already spending more loot for other cranks and chainrings than would be required.



again, the clever thing here is that these rings make the gear bigger, where biopace took the opposite tack, making it smaller...which was just stupid unless you're sheldon brown...who is cool...but anyway....

I agree on both points there, doc!

The shape of these rings looks pretty severe.
Not as severe as the Bullsye rings, does anyone remember those? I can't find an image right now, but yow, those put the O in Oval!

[Dr. Doofus]

brian --

doncha think you'd really need an 80-90 hip angle (the way dan empfield measures it) to take advantage of those? not being able to engage a lot of glute would put a lot of pressure on the knees with those things...that's why yerrdoof thinks you'd need a flat back and low bars to move those things without problems....

thoughts?

[BumpyintheBurgh]

That's not a chainring, it's the ChopMaster Table Saw Blade with a crankarm attached. I swear that I saw one of those at Home Depot. I hear there is a patent infringement case pending against OSymetric.

[Brian Smith]

brian --

doncha think you'd really need an 80-90 hip angle (the way dan empfield measures it) to take advantage of those? not being able to engage a lot of glute would put a lot of pressure on the knees with those things...that's why yerrdoof thinks you'd need a flat back and low bars to move those things without problems....

thoughts?

Doc -
I'm totally in agreement that the makers of those rings have chosen a particular segment of the pedal stroke to place the "higher" effective gear and another segment to place the "lower" effective gear. I agree, if I correctly understand the gist of what you're saying, that if your most powerful segment of your pedal stroke does not coincide with what the makers had in mind, then the system will be less than optimized, and therefore even less worth pursuing than normal. This suboptimization would be not due to the fact that the chainrings are not round, but instead that their timing was incorrect for the application to the particular rider in question.
It would be possible to make elliptical chainrings tailored for a rider's particular pedal stroke, whatever it might be.


Whether your hip angle (Empfield style) is 80-90 or if it is 110, there is a segment of the pedal stroke wherein the bulk of the torque is applied and wherein the peak torque is contained. Elliptical chainrings are a device to try to speed you through and past the parts of the pedal stroke outside of this area often called the "power stroke," so that more time per average unit chain travel is spent within the "power stroke" than would ordinarily be the case for round chainring use. Some people might argue that an effectively "higher gear" created during the power stroke causes extra stress upon the knees. So is using too high of a gear through a click of the right hand (for example.) Too little mechanical advantage is too little mechanical advantage, whether it's because your chainring is round and says 55 on it and your cog says 12, or whether your elliptical chainring has only 50 teeth and your cog still says 12. Solving the mechanical advantage problem is a gearshift away.

Having said all that, there are reasons for not wanting to use elliptical chainrings. Someone has already mentioned the possibility that the front derailer might have to be modified. Setting the height of the front derailer becomes a big exercise in compromise. The shift performance on the OSyms seems suspect for sure. Note that even the pros who've endorsed their use for a time trial don't seem to use them for general road use. The concept has merit, especially for a special application wherein front shifting was irrelevent, but I'd suspect that for most of us elliptical chainrings are just a neat idea to think about rather than actually try and derive benefits from.

Rubber side down...

[Too Tall]

http://www.hscycle.com/

You guys munch on this (link above) and tell me what you think. Tom has a very interesting solution that I've seen work for leg length discrepencies. Why wouldn't you use it to tune the peak power output of a TT rider? You want tunable? This will do it. But I still think that the oval rings are an engineers dilema. The supposed solution is disconnected from how riders develop power and effective technique through a huge investment in neruromuscular adaptation and (force) specific exercise. Genetic freaks such as ummmm let's just say all cat 1's and pros are genetic freaks and will whip your and my butt using a 50 lbs. Huffy, let's face it. So, you give them some device like this and they will figure out how to make it go.

What makes one he!! of alot more sense to me is to tune the rider. Forget about all the bike / rider fit stuff we've been bantering about and say the issue is moot for the following argument's sake. Let's talk about specific muscular and bike position tuning in real time. Just suppose, I had a device with sensors attached to the major upper and lower leg muscles. The sensors would monitor: duration, intensity and timing. Now, I have this displayed on a bar graph and we have the rider sitting on their bike using a computrainer. Got the picture? Now I tell them things like "drop your heels" or "knees a little further from the top tube" or "move back in the saddle some" and we watch the watts and HR to find their most effective combinations? Take it up a notch...let the rider watch the graphs while they sit on the trainer and try various things to find what works best...hmmmm.

That would make some practical sense for any athlete with the $$s to burn for goochie chain rings. But I'm just supposin' ain't I ;)

[bostondrunk]

They're part of a churning mechanism, used to make sure all the dope he's on gets evenly distributed in his bloodstream.

Yer such a ****. How could you say such a thing???
Even with forums like below, I just refuse to believe there are any drugs in proffesional or amature ranks......... :p

http://www.cuttingedgemuscle.com/Forum/forumdisplay.php?s=&forumid=9