New Carbon DuraAce cranks

[Dietmar]

It's a tool of rhetoric called 'reductio ad absurdum'

You may want to refresh your knowledge of rhetorics too, in addition to your basic mechanics. A reductio ad absurdum is quite different from the poor attempt at an argument you had made. Hint: The reductio is also known as a proof by contradiction, and is not typically listed as one of the classic devices of rhetoric.

I was using it to draw attention to the fact that it is quite ridiculous to ignore the main point of the argument and focus on an entirely insignificant, semantic side issue.

So you are saying that the semantics, in other words the meaning, of your argument is irrelevant? That certainly explains a lot...

Anyway, what prompted my response was your trying to ridicule the notion of different frames having noticeably different ride quality, among other things because of differences in vertical compliance, by putting forward the ludicrous notion of a bicycle frame as a "rigid truss structure". You responded with an even sillier comparison of the effect of vertical compliance in a bicycle frame to effects that are many, many orders of magnitude smaller than what we are talking about. By the way, "hyperbole" was the rhetoric device you were looking for.

I believe that manufacturers have added stiffness to that list as an easily understood differentiator and not because there are any performance benefits.

That may or may not be the case. You may have noticed, however, that even for high-end sports equipment performance is not the only relevant factor.

 

[ScienceIsCool]

You're totally right. I had to look it up. Although reductio ad absurdum is widely held as a tactic in rhetoric, it is not formally recognized as such.

My use of it was subtle, but correct though. I demonstrated a correct case, but used its ridiculousness to posit a counter-example. This is not what you would do in a formal logic argument such as proving a math theorem, but linguistically it was quite good. I thought it was clever.

And yes, I think it is disingenuous to discard an argument because of an unrelated point of semantics.

John Swanson
www.bikephysics.com

 

[JTE83]

If they made this in a triple and if I make good money on my next job I'd gladly put this on my 2007 Trek Pilot 2.1 spa.

Well, nevermind... It might be an $800 upgrade for the crank, BB, and labor... so it's not worth it putting it on a heavy 27.4 lb commuter bike. Unless I won the lotto...

 

[Dietmar]

And yes, I think it is disingenuous to discard an argument because of an unrelated point of semantics.

Agreed. To cut through the ****, I think we both agree that some of the argument surrounding stiffnes of various components, or frames, is specious. The decision between parts of different stiffness is probably more properly phrased in terms of personal preference. Some people here seem to highly dislike it when parts or frames feel "flexible", others don't care much. That may also be a function of how much torque certain riders are capable of producing...
In any case, I am fairly certain one could win the TdF either way, given the right engine...

To get back on topic, I think the D-A cranks look alright, but Campies look better, and any other differences between them are irrelevant

Personally I wish they (both Shimano and Campagnolo) would offer reasonably-priced integrated torque/power measurement devices, wireless ANT-Sport compatible, with their cranksets.

 

[alienator]

Perceptions, though, are usually a lot more accurate than you give them credit for.

Wrong. Human perception is wildly inaccurate. Full stop. You've yet to give any evidence whatsoever that Record UT cranks are "noodles." In fact, I seriously doubt that you would understand any data presented to you.

I don't have a job? Really? Your idiocy grows greater each day. You should be more careful.....especially if you're venturing far from your nursing home.

 

[CAMPYBOB]

Ah...the oxygen thief returns.

Wrong. Human perception is wildly inaccurate.

You're so damn moronic the only thing that's kept you alive is that it's against the law to kill stupid people. I am surprised your "human perception" enables you to tell a red light from a green one. Of course, you're one of the genius 'scientists' that would insist the Vitus was a "stiff" frame. I can also tell you my FSA Energy bars are way more flexible than my old Cinelli's. Care to bat that one down next, Mr. Moron? Jeezus H. tapdancing Christ on a pogo stick, are you brain dead or just a mouthy dork trying his best to impress the kiddies.

I get the distinct feeling you have no ability to discern up from down or left from right without instrumentation...but, it's equally likely you're just an argumentative idiot.

Full stop.

Speak English, dweeb boy. This isn't Western Union, although your posts do resemble Candygrams.

You've yet to give any evidence whatsoever that Record UT cranks are "noodles."

Uh...yes I did. If you were only bright enough to read you wouldn't make such dumbass remarks. No...no, you would STILL make dumbass remarks. Common sense isn't your long suit, that's for certain.

In fact, I seriously doubt that you would understand any data presented to you.

Well, all pertinent 'data' points to you being an idiot.

I don't have a job? Really?

We don't count Mcdonald's french fry cook. Go back to minimizing the miniscus of mercury mirrors. Oh wait...like the ER nurses, they're still laughing at your dumb ass, too.

Your idiocy grows greater each day. You should be more careful.....especially if you're venturing far from your nursing home.

It's all fun and games until the Viagra kicks in!

Nice try, Robin. Now, go trade in your flexible flyer Moots on a Look. You'll gain the bling your attention-seeking ego so desparately seeks in addition to an increase in stiffness even a pencil neck geek like you desires...wait!...better get out the accelerometers out, fixture that frame and post 'data' on da innernet to prove your scientic hypothesis.

 

[CAMPYBOB]

The measured flex difference with only 124 pounds of pedal pressure applied ranges 30+% between four models. Now, how much force can your legs apply powering up a 17% wall?

Maybe you're not up to the standards of a nation track pursuiter, but i'll guarandamntee you'll far exceed 124 pounds of applied force.

"The first person we tested was a National-caliber track rider (he actually has a national championship in pursuit) we were all floored when he could easily hit 800 lbs. When he actually tried he could hit 1000 lbs."

You care to measure that deflection at 600 pounds? In the side plane of the arm? Pfft! You can't even tell what's flexi and what's stiff without a labratory behind your sorry ass.

It doesn't take dial indicators, pneumatic cyclinders, a bench fixture or strain gages to 'see' how much an UltraTorque Campy crank arm moves. Just go grab one and push/twist. Nor does this gage measure deflection in the opposite plane which is often the failure plane.

 

[ScienceIsCool]

That graph is a bit out of whack. It shows a 1.5 mm deflection for a 0.25 kg load... Or about a foot and a half of deflection for 140 pounds. Where did you get it from? It's better if you attribute data that's not your anyways.

John Swanson
www.bikephysics.com

 

[CAMPYBOB]

John,

The source is easily found by right-clicking the picture.

http://www.bikesportmichigan.com

The 'load' you're reading is component weight.

The actual test load applied was 124 pounds.

Cranks flex. Some more than others. Some less. Does it matter a hill of beans? Probably not, but it is easily detected by "human perception".

The same goes for my wet spaghetti FSA Energy bars. Of course, Alieninstrumentator will tell us there's no way in hell something as "wildly inaccurate" as a human being with 35 years of cycling expirience could possibly figure out they are more flexible than old Cinelli 65's.

 

[ScienceIsCool]

I've been burned so many times from looking at early experimental data and thinking that X is clearly brighter, or Y is so much slower just by looking at it. Then completing the analysis to find out I was totally wrong. Human perceptions are muzzy at best and absolutely useless at picking out signal from noise. For example, I can pick out a 10 micron ridge on a flat, smooth surface using just my fingernail, but I have a tough time figuring out surface roughness without using a meter. We also tend to percieve patterns in noise which just aren't there.

A great primer on all this is Mind Hacks, which is an incredible book. Right now, I'm trying to use whacked out human perceptions and info from the book to hide relatively large signals by using low levels of noise. Destroying perceptions by breaking up the patterns. Geeky cool.

So I would have to agree with Alienator that I don't believe a person can reliably pick out +/- 0.5 mm of flex in a system (frame, crank, tires, wheels, etc) that is moving 10 mm or more.

John Swanson
www.bikephysics.com

 

[bobbyOCR]

damn, no popcorn emoticon.

 

[CAMPYBOB]

So I would have to agree with Alienator that I don't believe a person can reliably pick out +/- 0.5 mm of flex in a system (frame, crank, tires, wheels, etc) that is moving 10 mm or more.

A crank arm can be flexed underfoot far more than a millimeter.

Again, go grab a Campy UltraTorque arm by the pedal and push on it and twist it. It flexes. More than a millimeter. With only your hand as input force.

 

[ScienceIsCool]

The data you posted says the crank only moves 1.5 mm for 124 pounds of load. If, by hand, you're getting that much flex you must be feeling the frame, wheels, fork, and tires move. Which illustrates my point nicely. Perceptions can be confused and are often unable to pick out a weak signal (crank flex) from the noise (total flex).

John Swanson
www.bikephysics.com

 

[alienator]

The data you posted says the crank only moves 1.5 mm for 124 pounds of load. If, by hand, you're getting that much flex you must be feeling the frame, wheels, fork, and tires move. Which illustrates my point nicely. Perceptions can be confused and are often unable to pick out a weak signal (crank flex) from the noise (total flex).

John Swanson
www.bikephysics.com

To reinforce this, without having the cranks in a fixture whose stiffness is characterized, you really can't say that is the crank flexing. In fact, it's more likely to be the bike flexing near the BB shell when people say they've seen flex in the cranks.

Just qualitatively looking at loads and load paths, the crankarms see the vast majority of their load in their plane parallel to the frame's plane. Any component normal to that plane is comparitively small to very small.

A 124lb force in the plane of the flexure isn't realistic at all. If you assumed that that 124lbs was 1/3 of the total force delivered to the pedal--which it's not--that would mean the cyclist in question was delivering 672lbs of force to the pedal. That ain't happenin'. The largest load the pedal will see is about the rider's weight.

 

[CAMPYBOB]

I just got back from riding, as opposed to debating, but before I left I did a little expiriment.

I'm sure it doesn't meet the considered minds of the scientific community, but it meets my standards.

I simply went back into the bike room and started tugging, pushing, pulling and twisting on a few bikes...the left side pedal at various crank rotations to be exact.

Using my non-NIST calibrated left hand/arm I tweaked a C-Record 172.5, two Super Record 172.5, two Records 170 and 172.5, a Dura-Ace track 170 (please...don't tell anyone I own that!) an old Gran Sport 3-arm (just for ***** and giggles) and a 2006 Chorus 172.5. All of the above are alloy arms.

Be aware I have no particular affinity for alloy arms as the only arm I ever broke was alloy (a Record left side that cracked tangent to a stress riser in the lightening groove. that one threw me into oncoming traffic!).

I then walked out to the garage before loading the bike equipped with 2007 Chorus carbon UltraTorque and tugged a little on it.

The result?

The carbon arm was easier to flex and moved more distance. Simple as that.

I've been an aerospace design engineer for 28 years...mainly jigs, fixtures, gages, injection mold dies, production machinery, etc. for the turbine engine industry. It's my opinion the Chorus carbon arm is NOT as stiff.

As usual...YMMV.

Of course, you 'experts' can also debate the great Fabian Cancellara.

He rides a cheap ol' $139 Gossamer crankset.

Why?

He thinks its stiffer. I'll bet I would agree after a simple pull & push test.

Fabian's mechanic's quote:

"According to Team CSC mechanic Alejandro Torralbo, Cancellara began using the Gossamer cranks during the Spring classics, but grew more comfortable on them than carbon ones because he feels that they're stiffer."

 

[mikesbytes]

The measured flex difference with only 124 pounds of pedal pressure applied ranges 30+% between four models. Now, how much force can your legs apply powering up a 17% wall?

Maybe you're not up to the standards of a nation track pursuiter, but i'll guarandamntee you'll far exceed 124 pounds of applied force.

"The first person we tested was a National-caliber track rider (he actually has a national championship in pursuit) we were all floored when he could easily hit 800 lbs. When he actually tried he could hit 1000 lbs."

You care to measure that deflection at 600 pounds? In the side plane of the arm? Pfft! You can't even tell what's flexi and what's stiff without a labratory behind your sorry ass.

It doesn't take dial indicators, pneumatic cyclinders, a bench fixture or strain gages to 'see' how much an UltraTorque Campy crank arm moves. Just go grab one and push/twist. Nor does this gage measure deflection in the opposite plane which is often the failure plane.

Blonde question, whats the difference between the red bars and the yellow bars?

 

[CAMPYBOB]

Red bars = displacement dimension under load in inches...'stiffness'.

Yellow bars = weight of the component in grams.

 

[dhk2]

Red bars = displacement dimension under load in inches...'stiffness'.

Yellow bars = weight of the component in grams.

The link works, but I can't find the article on the webpage. Can you point me to it?

Would like to know what deflection they are talking about, and how it was measured. At first glance, the results appear in the "insignificant" range, but maybe there is more than what I'm reading into it.

 

[ScienceIsCool]

I just got back from riding, as opposed to debating, but before I left I did a little expiriment.

So.... You figured that since you knew which cranks are most flexible, you'd give them a squeeze and verify, eh? And big surprise, your perceptions matched your expectations! To channel Alienator: I hope your years as an aeronautical engineer were spent designing kites. Nah. I bet you were a fine engineer, but I heard Alientor's voice in my head and thought that was funny.

But seriously, you've got to agree that your perceptions are going to verify your expectations about 100% of the time whether they're real or not. C'mon. That was an incredibly silly test! I'll give you the benefit of the doubt on this one.

John Swanson
www.bikephysics.com

 

[sideshow_bob]

The link works, but I can't find the article on the webpage. Can you point me to it?

Would like to know what deflection they are talking about, and how it was measured. At first glance, the results appear in the "insignificant" range, but maybe there is more than what I'm reading into it.

it's not only insignificant, it's also a single data point that is measured perpendicular to the crank axis on a jig.

a) the flex may or may not be linear as a function of force (or more accurately is probably linear over a range though the resulting slope will be different for different materials) applied, a single data point tells you exactly nothing.

b) the force is applied in a direction that generally doesn't see any significant force applied in a pedalling action, unless maybe you are sprinting and thowing the bike around between + and - 45 degrees from the perpendicular plane.

it's a marketing experiment nothing more and nothing less.

--brett