Lightweight Frame Tubing and "Planing"

[geordanh]

Originally Posted by marciero

You are conflating the two issues I mentioned.

...and speaking of carbon-it is too bad no one seems interested in testing different layups. If planing is a real phenomenon and people are not just imagining it or making it up, and if it is attributable to frame flex in certain places I would think it could be dialed in and isolated better with carbon.

Ok. So the test should then be power kept constant over some repeatable period of time, and heart rate should be lower for a given effort on the flexy frames. Right?


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[Doug Fattic]

I always feel that whenever a discussion starts about Bicycle Quarterly and “planing” they unfortunately almost always go off the rails. I am a frame builder that has actually built frames out of .7/.4/.7 (for myself and others) and like the ride of them better than frames built out of heavier or bigger diameter tubing. As I mentioned before it is easy for negative opinions on the theory of “planing” to erode into negative attitudes onto frames built with thin wall standard size tubes (with 1” top tubes). The 2 should be kept separate.

When I ride a frame built out of heavier wall standard or oversize tubing they feel clunky by comparison. I suppose it is like going from a double butted frame to one built with straight gauge “hi ten” (which stands for hi tensile steel). They have a dead feel. Production steel frames were built so that the biggest heaviest strongest person would not break them and as a result sue the company. They also made/make frames out of heavier tubing because it is easier manufacturer. So tubing choice was not chosen by companies that made bicycles in volume for what would be the ideal ride quality of an average person.

Jan Heine studies of classic European builders has been an enormous benefit to American frame builders. He has had more influence than any other single source. As riders have aged and no longer want a racing bicycle and younger riders are wanting practical bikes to ride for transportation, we don’t have to reinvent the wheel again but look at Jan’s research to see what worked well in the past. His curiosity on why he liked his Rene Herse bicycle (made in Paris by one of the best custom builders in the world) better than his Bob Jackson (a custom builder in England) led to his discovery of the advantages of thin wall tubing over heavier stuff. I learned how to build frames in England in the middle of the 70’s and the type of custom bicycles there and in France were different.

My personal bicycle built with standard size tubing with .7/.4/.7 wall tubing is not “flexy”. I don’t feel it bending at all when I pedal. Actually my frame built with .6/.3/.6 didn’t feel flexible to me either. They just don’t have that clunky heavy feel. Only when I got out of the saddle in a sprint could I notice any flex on the 6/3 (and I rarely ever do that). I don’t ever feel flex in my 7/4 frame. I would be interested in the observations of others that have actually ridden this kind of frame. I am not interested in critical opinions of those that haven’t.

Because I greatly prefer my 7/4 frame to heaver ones and have genuinely appreciated Jan’s body of work, I hold my thoughts on “planing”. I don’t think as of yet there is complete understanding of the different ride characteristics of frames made from a variety of tubing diameters and wall thickness and heat treatments. I don’t know why my light skinny tubes frames have a superior ride. I have heard various theories from other builders but I’m not sure anyone really knows yet.

[bicipunk]

Originally Posted by adampaiva

To the OP. Don't do it. You'll be slow and won't like your bike and your friends will make fun.

Haha I'm 23... All my riding friends (who are always older than I) don't make fun of me because I hold my own in the paceline on brevets and they get a wonderful draft because of it

[marciero]

Originally Posted by geordanh

Ok. So the test should then be power kept constant over some repeatable period of time, and heart rate should be lower for a given effort on the flexy frames. Right?


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Something like that, yes.

[rain dogs]

Originally Posted by marciero

No BQ claims ever violated the second law of thermodynamics, which is what you suggested. "Jan will lead you to believe that you put 200W in, and X is lost into frame flex/heat (because thermodynamics exist) and then X+Y is coming back? where Y>0.




A rider will produce more power if they are less fatigued, or more efficient. But you've raised, and perhaps conflated, two separate questions-whether there is energy that is stored in the frame and returned to the rear wheel with a flexy frame, and whether the rider is able to produce more power with the same effort and level of fatigue. To test the latter, and in particular whether it depends on frame/rider dynamics, you would need a test of average power over some duration- it makes no sense to have the the rider produce the SAME power, unless you wanted to ask them afterward if they were more or less fatigued, which would be okay, though more subjective.

The second law of thermodynamics is the entropy law. And I never suggested that his claims violate thermodynamics, just common sense.

You do know the test he lists was a sprint, correct? 300m if I recall. This isn't a test over a brevet.

All I'm wondering is where this extra 15% output is coming from? Is it coming from the rider? (If so, that capability should exist with all bikes. If you're doing a 300m sprint you can't just suddenly "find" 150 never found before Watts. If it's the bike, how does the bike produce power? Magic? Electric?

The energy put into a spring doesn't come back with MORE energy. A spring doesn't create energy. Can we at least agree on that?

[marciero]

Originally Posted by rain dogs

The second law of thermodynamics is the entropy law. And I never suggested that his claims violate thermodynamics, just common sense.

You do know the test he lists was a sprint, correct? 300m if I recall. This isn't a test over a brevet.

All I'm wondering is where this extra 15% output is coming from? Is it coming from the rider? (If so, that capability should exist with all bikes. If you're doing a 300m sprint you can't just suddenly "find" 150 never found before Watts. If it's the bike, how does the bike produce power? Magic? Electric?

The energy put into a spring doesn't come back with MORE energy. A spring doesn't create energy. Can we at least agree on that?

No, springs wont create energy. His claim is that the capability does not exist, or is not the same with all bikes. In the first article that was cited are the test results-yes, for short sprints. In the second article he conjectures as to why the output is not the same, essentially that on a non-flexible frame less of the rider effort is converted to work, and why this might be so. (I think the all-out effort is an attempt to ensure that the effort is close to the same, or follows a predictable downward trend.) I just think the test itself, even setting aside questions like statistical significance (small sample size...), along with all the anecdotal experience, at least raises questions for further investigation or testing. He mentions some other tests but I've not seen or cant recall them.

[Mark McM]

Originally Posted by marciero

No, springs wont create energy. His claim is that the capability does not exist, or is not the same with all bikes. In the first article that was cited are the test results-yes, for short sprints. In the second article he conjectures as to why the output is not the same, essentially that on a non-flexible frame less of the rider effort is converted to work, and why this might be so. (I think the all-out effort is an attempt to ensure that the effort is close to the same, or follows a predictable downward trend.) I just think the test itself, even setting aside questions like statistical significance (small sample size...), along with all the anecdotal experience, at least raises questions for further investigation or testing. He mentions some other tests but I've not seen or cant recall them.

I think there are only 3 possible explanations for the "more power" claim:

1) A "planing" bike returns more of the energy that is transferred into it.

2) A "planing" bike makes the rider produce power more efficiently.

3) A "planing" bike allows the rider to generate more power.


I think we can put number 1 to bed, based on evidence we already have. A rider applies power to the bike through the cranks/pedals, and the power is applied to the road through the rear wheel. Any energy that is absorbed or returned through flexing of the bike must therefore occur somewhere between the cranks and the rear wheel. There are plenty of reports of bikes with both a crank or pedal power meter and a wheel power meter that shows that the wheel power meter will report a few percent less power than the crank power meter. However, other tests have shown that typical chain drive is about 95-98% efficient, so the power difference between crank/pedal power meters and wheel power meters can be completely accounted for through drivetrain friction. There is no evidence of any significant power/energy lost in the frame.

I don't know of any specific evidence about number 2, although I think it can be obtained. Bicycle metabolic power testing is now available to the general public (through companies like https://www.intelligentfitnessvermont.com/ or http://www.hopecam.org/race-for-hope...abolic-testing). Testing riders on "planing" and non-"planing" bikes should be able to determine if the riders have any metabolic differences between the frames.

There might be a little bit of truth behind number 3 - but in the opposite way as claimed for "planing" frames. If a bike is so flexy that it becomes difficult to control when applying large drive forces, than that could certainly produce a limit to how much power a rider can produce and still be able to control the bike. But I think a bike would have to be very flexy before this becomes significant. And this would only come into play during maximum power sprint efforts - lower power endurance efforts would probably not be affected.

(Anecdotally, I do own a very flexy bicycle frame - 2002 Litespeed Ghisallo, then the lightest production bike frame in the world, and often regarded as one of the flexiest bikes in the world as well. My Medium/Large model frame weighs 865 grams, which is very light for a titanium frame, and comparable to the lighter carbon fiber frames today. The frame visibly flexes under hard out of saddle efforts, and you can even feel the frame flex under rapid steering maneuvers. I'm pretty sure I can't sprint as fast on this frame as I can on my stiffer bikes, due to my inability to apply maximum muscle force because of frame flex. On the other hand, I can do longer sustained steep climbs faster on this bike. In addition to the light frame, this bike also has ultra-light wheels and components, resulting in a total bike weight of about 4 -5 lb. less than my other bikes, or a total bike/rider mass decrease of about 3% - which corresponds to about how much faster I can do sustained steep climbs on this bike.)

[Wayne77]

This is about efficiency. The language and terminology in the BQ testing is misleading...Barring the addition of other energy inputs/torque generating devices like electric motors, "more" power simply cannot be generated by any static component or frame construction in the complex chain of events between power to the pedal and power between tires and road. EVERYTHING after the power to the pedal is a loss. A 100% efficient'system (the frame being only one variable) would transfer 100% of the energy to the road. It is IMPOSSIBLE for a spring to generate more energy. A spring simply takes some energy input, stores it, and delays the output. But there is still some incremental loss (i.e. cost) in doing so. The question is whether the delay, from a timing perspective, is helping or hurting the efficiency of the overall system. To suggest that it can help universally, without accounting for so many other variables that hurt or improve efficiency is not even close to being scientifically valid. Some frame flex may help one person and hurt another...or work well for one type of bike or mode of use but not another (climbing, sprinting, continuous power, burst power) or may hurt or help one persons perception a given frame "feels good" purely from an intangible enjoyment perspective. I imagine a frame that "feels good" could contribute to someone being faster...regardless of whatever factors we think contribute to those good vibes actually improve efficiency of power delivery.

It's quite possible that there is no direct correlation between "I love the way this frame feels!" and "this frame is a faster climber/sprinter/descended/etc"

I get the hobby driven enthusiasm and "joy of scientific discovery" the article is coming from, but suggesting the findings are scientifically valid, and especially concluding that the results based on an EXTREMELY small sample size are reliables is a stretch. Let's just call it what it is and appreciate it that way...nothing wrong with enthusiastasts expressing that certain frame qualities seem to help them feel faster or SEEMINGLY made them faster in a few cases.

[Pastashop]

:^)

I only jest... I appreciate a lively bike as much as anyone. To each his / her own!

But this whole thing reminds me a bit about a Radio Lab episode that covered ultra-endurance athletes, and how they can trick their brains / bodies into going longer / farther, on the belief that more energy will be available (e.g. tasting something sweet, even though it’s artificially sweetened). Wonder if it’s about tricking the body into perceiving that it’s able to produce more power than necessary that it even flexes the bike...

(unless of course the whole effect is attributable to the bike weighing less when built with thinner and slimmer tubing, all other things being equal, as Mark may have implied.)