|
|
|
|
#16
10-02-2017, 12:31 PM
|
|||
|
|||
|
Theory and hypothesis aside about how a rider might generate more power with a flexible frame ...
If a flexible frame that "planed" could allow a rider to generate 15% more power (as claimed in the second article), than why wouldn't professional racing teams use such frames? A 15% difference in power would vault a middle-of-the-pack racer into being an untouchable winner. Heck, that's probably a bigger advantage than blood doping can provide. That kind of improvement could not be ignored, even if you wanted to for business/financial reasons. I call BS. 
|
|
#17
10-02-2017, 01:08 PM
|
|||
|
|||
|
Quote:
|
|
#18
10-02-2017, 01:18 PM
|
|||
|
|||
|
Quote:
Greg
|
|
#19
10-02-2017, 01:46 PM
|
|||
|
|||
|
15% increase in power output?..what a load....However, I have to testify that a bike built with light gauge tubing in standard diameter can feel fantastic. I have a Peugeot (Pro 10) built in very early 1982 that is made with Reynolds 531 with 0.5 mm tubing save for the top tube which is *believed* to be 0.3 (you can squeeze it). The bike has the greatest ride characteristics, and I can fully understand why somebody would coin a term such as "planning" to describe it. Of course, there are no free lunches and you wouldn't want to have the bike fall over into the corner of a brick wall....It's also not the best bike that I have ever ridden for stomping up a short steep hill in the big ring, but you can still do it especially if you make enough grunting and heavy breathing sounds to drown out the sound of a little front derailleur rubbing...I think that light gauge tubing might a fair portion of the "magic" that is often attributed to many of the bikes built by constructeurs such as Rene Herse and Alex Singer. They really tended to go light except for the full campeur models or the ones built for tall or heavy riders.
Last edited by El Chaba; 10-03-2017 at 11:36 AM.
|
|
#20
10-02-2017, 01:58 PM
|
|||
|
|||
|
Quote:
|
|
#21
10-02-2017, 05:53 PM
|
|||
|
|||
|
As others have stated...if there was this level of untapped free power laying around all these decades it wouldn't be such a secret.
Regarding tubing thickness - I have a slightly different approach: if I am paying for the services of a highly skilled professional frame builder who's job it is to take in all the factors necessary to build a great end product for me, I have no business trying to tell them what specifications of the materials should be used. If they need me to tell, I should find a different builder. If they let me dictate what the material specs should be, I would be very cautious.
|
|
#23
10-02-2017, 10:27 PM
|
||||
|
||||
|
He claims 15%! I don't remember reading that before.
That is laughable, I like bq but opinions are not facts, it is fine to do basic unscientific/semi scientific tests but in the end the result is still mostly, "I like this one more". As far as frame flex = mechanical reservoir thing. It seems to me more likely that in the dead spots that stored energy in the frame is expended slowing your feet down (partially, as long as you are applying some load some will go to drivetrain?)not speeding the bike up, that is a much easier path for it to travel. (I am no engineer). If this does work why not make cranks out of leaf springs and store more energy in those to be used later? Besides , less frame flex would just apply that power directly, sounds just as good to me. If we could make a robot pedal a test rig we could compare frames to see if more power is getting to the wheels on the flexy ones. I guess storing power to be released in the dead spots could reduce small pulses in acceleration which sounds like it could be more efficient. If that is what it is doing and if the losses in the "storage" are smaller than the "gains". Seems unlikely but possible I guess. Not sure if an average speed of 18 achieved by always going 18 is more efficient then micro pulsing above and below 18. I am crap at equations and physics and biomechanics and aerodynamics, etc. As far as frame flex is suspension goes. On rock hard thin tires go for it, but why bother on a bike with nice big tires? Let the frame do its job and the tires can suspend it. Obviously it is always some of both, just more about the design priorities of each component. Shimmy- flexy frames have more shimmy, shimmy sucks. Obviously people like all kinds of bikes and use them and like them so who cares really I guess. It would just suck to wait two years to get a frame built to specs that you don't really like because an opinionated eccentric expert ( I fit this description as well) likes those specs. On the other hand, I really like big smooth tires for road use now and that was largely inspired by weirdos (grant, jan)
__________________
please don't take anything I say personally, I am an idiot. Last edited by bicycletricycle; 10-04-2017 at 02:43 PM.
|
|
#24
10-03-2017, 07:03 AM
|
|||
|
|||
|
The first article cites a value of 12% for one test. To make a blanket claim this would need to be replicated by lots of tests. But nobody does this. I appreciate that BQ even does these tests. The weight to give them is up to the reader, but I consider them as evidence-beyond anecdote and opinion. Who even does double-blind tests with real riders on otherwise identical bikes? No, the tests are not perfect but keep in mind that many, perhaps most, peer-reviewed health-related studies are far from perfect in that there are often many confounding variables, they do not or cannot use randomized subjects, etc.
Not sure where the 15% blanket value in the second article was arrived at, but keep in mind that this is about "optimized" flex characteristics; that is, flex optimized to the rider, and, probably, the style of riding. Just as a weekend golfer using a flexy carbon-shafted driver can hit a ball much farther (I would guess 15%, easy) than he could with a XXX-shafted club that a pro might use, I find it conceivable that a featherweight climber might be much better off with a flexy bike than he would with a stiff bike that a sprinter might perform better with. Am pretty sure the big companies that sponsor pro riders dont do custom carbon lay-ups for each rider. At one time some of the stars did get this. Is a shame since the flex characteristics of carbon are so tune-able.
|
|
#25
10-03-2017, 09:08 AM
|
|||
|
|||
|
There are very few frames in existence anywhere that were made with 1" top tubes with a wall thickness of .7./4/.7mm in the top and down tubes. Production frame companies avoid such tubing because it is more likely to fail (they could be ridden by someone bigger and heavier than the frame is intended to support) and thin wall heat treated tubing requires more care when building. Neither of these issues help their bottom line. I kind of remember there were some Japanese frames made in the 80’s I think that were made with thin walled tubing (maybe Shogun?) and Raleigh owned by the same company as Reynolds made some frames out of 753 tubing in the 70’s. There was a pro team that rode them. Bill Davidson had a bigger frame making operation in the 80’s and 90’s that turned out hundreds of units a year that used Tange Prestige tubing some of which was probably 7/4/7.
There are a number of custom frame builders who also avoid this tubing because of philosophy or their preference for the looks of a frame with bigger diameter tubes or they buy heavier tubing in bulk because it is cheaper and therefore more profitable. Jan began researching why his old French Herse and Singer bicycles seemed to him to have superior ride qualities. He was told that their top and down tubes were "3 tenths" - which I have understood to mean that the middle of the tubes were .3mm (3/10th) thick. This is a bit of a mystery to me because any tubing I am familiar with that has a center of .3mm, would have ends that would only be .6mm. This is very thin and would not tend to hold up under normal use like the classic old frames he loves to ride. But I digress. Long before I ever heard of Jan Heine or when the Bicycle Quarterly was first published I have personally built frames with 1” heat treated thin wall top tubes. I vastly prefer the ride. It is what I would describe as more “lively”. It is easy for me to tell the difference between 7/4/7 and 9/6/9 when I am riding them. I can also tell the difference between thin walled 1” and 1 1/8th inch top tubes. Back in 1978 or so I built a 56 cm frame with Ishiwata 015 tubing that had top and down tube with wall thicknesses of .6/.3./.6. The whole bicycle weighted about 15 1/2 pounds and has been in the Three Oaks bicycle museum for the last 25 years or so. The ride was not too flexible for me. In fact going by memory it didn’t seem that flexible at all. However some of my bigger racing buddies thought it was. This is an illustration that what tubing wall thickness and diameter is best is based on a number of a personal preferences. The problem with 6/3/6 tubing is that it is easily damaged. I am sorry that the hypothesis called “planing” became associated with light tubing. The problem as I see it is that it can become easy to reject the use of 7/4/7 tubing because of skepticism of the theory. I am not saying planning is wrong or right, I just know I personally very much prefer the ride of a frame made out of standard size (1” top tubes) and light tubing (.7/.4/.7mm top and down tubes). Your mileage may vary.
|
|
#26
10-03-2017, 09:22 AM
|
||||
|
||||
|
Hey Doug,
I was always under the impression that tubing diameter (and shape) contributed more to stiffness than wall thickness. But in your 3rd paragraph seems to slightly contradict that -- maybe I'm misreading? To your idea of a "lively" bike, that seems to be a bit different than what Jan is talking about. Your description makes me think of a bell or tuning fork. If a bell is made well it will sound beautiful, if it's not done right it's horrible and shrill. Seems to be a similar when building a bike ... it's gotta be tuned and a 1-size fits all doesn't work for some folks. To your note about production thin wall bikes. You're spot on. I've worked with a few factories that refuse to do anything under 1mm straight gauge tubing (they really prefer 1.2mm) b/c they cannot guarantee that a frame will leave the factory w/out dents.
__________________
IG: elysianbikeco Last edited by false_Aest; 10-03-2017 at 09:37 AM.
|
|
#27
10-03-2017, 10:30 AM
|
|||
|
|||
|
I didn't realize how hotly debated this topic was. I'm wondering if those who are pro thin walled tubes see any downsides to riding those bikes with loads. I would imagine they would be more noodley? Standard diameter 8/5/8 might be a good place for me to start to try lighter weight tubes considering the lightest I've ridden is old reynolds 531 with 9/6/9...
|
|
#28
10-03-2017, 10:40 AM
|
|||
|
|||
|
Quote:
|
|
#30
10-03-2017, 10:42 AM
|
||||
|
||||
|
Quote:
Really, if you have a lot of time you could build a bunch of iterations TT 969, 858, 747 DT 969, 858, 747 (I think that's Columbus Life range) Then on to chain stays. Round, Round-oval-round, 30x16, 26x16, single bend, s-bend. Seat Stays: 16-12.5 taper, 14-10.5 taper, single bend, s-bend There's 16 combos right there! Then you could start combining the combos. Then other brands of tubing! Then joining methods: lug, fillet braze, tig, bi-lam, TIG braze, MIG, arc, etc. By the time you're done you'll have enough practice to go into business! ---- If you're not going to do this yourself don't tell the builder what to build with. Tell the builder what you're hoping for and have faith. Telling a builder what to do is like having a seamstress tell a luthier what wood to choose for her uncle's cousin's friend's sister's guitar.
__________________
IG: elysianbikeco
|
 |
| Tags |
| 650b, free energy, lightweight tubing, low-trail, planing, pseudoscience, randonneur |
|
|
Linear Mode
