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DIY way to stiffen rear triangle?

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DIY way to stiffen rear triangle?

Old 10-29-18, 09:29 PM
  #51  
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I've heard the foam thing third hand (maybe in the track forum?) that Keirin racers in Japan did/do spray it into their frames to increase stiffness. I couldn't imagine it actually does anything.
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Old 10-29-18, 09:39 PM
  #52  
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Originally Posted by Kapusta View Post
The flaw in that argument as I see it is that even if the frame does act as a perfect spring, and returns all the energy stored in it when flexed, it does not necessarily mean it returns the energy in the most useful way. For example, since the frame is releasing the energy at the same time as you are easing up on the force on the pedals, it may go into slowing your pedal stroke down more than making the bike go faster. In other words, the energy may get transferred from a very efficient spring (the frame) to a terribly inefficient spring (your legs and body).
Yeah, I never felt like planing was very plausible; the energy stored in the frame will be released at the moment when the very least of it will be transferred into forward motion. For that not to be the case, propelling bike and rider forward would have to be easier than other things it could do.
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Old 10-29-18, 09:48 PM
  #53  
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Another thread whereby the OP has not responded to anyone.

Yet the pointless conversation continues, and nobody asks the obvious questions like:

What kind of frame, or bike do you have?

Any pictures?

How does this compare to other frames or bikes?

Why is frame flex so important?

Surely its easy enough to get a stiffer (or more flexible) bike?
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Old 10-29-18, 11:25 PM
  #54  
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Yes, now the losses are crystal clear (in the imagination), just not detectable or measurable. Very convincing at ~100 Hz!
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Old 10-30-18, 06:25 AM
  #55  
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Originally Posted by SHBR View Post
Another thread whereby the OP has not responded to anyone.

Yet the pointless conversation continues,
Hey, speak for yourself. I actaully made a suggestion that directly addressed the OPs question.
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Old 10-30-18, 07:12 AM
  #56  
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Originally Posted by woodcraft View Post
When you guys get this worked out,

you can look into the amount of heat generated when a hair is split.
That's how myths like this stay alive.
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Old 10-30-18, 07:16 AM
  #57  
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Originally Posted by Kapusta View Post

Hey, speak for yourself. I actaully made a suggestion that directly addressed the OPs question.
So did I, several of his questions in fact. Where it went wrong was people citing the myth to say "wrong question" and "doesn't matter".
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Old 10-31-18, 08:41 AM
  #58  
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Easiest way to reduce rear triangle flex without drilling, hacks, welds, etc...

...is to increase the surface area contact between the frames rear dropouts and the hubs locknuts or end caps.

There's a reason why old school track hubs would have oversize locknuts versus the regular road model of the same model line hub.

But then again...if you're someone spending your whole time watching your BB swing both ways...

...you're riding the wrong addiction.

(No dirty minds please...)

=8-)
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Old 10-31-18, 03:24 PM
  #59  
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Originally Posted by Kimmo View Post
Yeah, I never felt like planing was very plausible; the energy stored in the frame will be released at the moment when the very least of it will be transferred into forward motion. For that not to be the case, propelling bike and rider forward would have to be easier than other things it could do.
The concept of planing is difficult to test. Heine's contention is that a rider can actually put out *more power* on a frame that planes for them. They went so far as to have visually identical frames with weight equalized in a true double-blind testing environment. Two of the three testers were notably faster on the more-flexible (thinner-walled steel) frame, consistently over number of trials. But assuming the test results are real and true (as opposed to being just a result of randomness) the issue that different people are affected differently still makes this a tough spot to make personal decisions. Unless we're as lucky as Mr. Heine and have lots of test bikes and time to ride them over significant distance and get used to the frame.
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Old 11-02-18, 03:41 PM
  #60  
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I did the foam in the frame tube thing way back when my job was spraying foam. What it does is completely eliminate the possibility of condensation forming inside the tubes. A steel frame will not rust from inside out after being foamed. Foam doesn't have any kind of structural strength that would be noticed inside a steel tube. Also weighs nothing. And at least seemed to make the bike a bit quieter.
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Old 11-03-18, 11:19 PM
  #61  
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Originally Posted by TallRider View Post
..

The concept of planing is difficult to test. Heine's contention is that a rider can actually put out *more power* on a frame that planes for them. They went so far as to have visually identical frames with weight equalized in a true double-blind testing environment. Two of the three testers were notably faster on the more-flexible (thinner-walled steel) frame, consistently over number of trials. B...

.
I have no problem imagining a frame might work like a vaulting pole... but, it's a lot harder to believe.
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Old 11-04-18, 12:59 PM
  #62  
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Originally Posted by McBTC View Post
I have no problem imagining a frame might work like a vaulting pole... but, it's a lot harder to believe.
That's why blind testing is brilliant. Nets placebo out of the equation.
The difficulty is, different riders (weight, power, pedaling style) interact with frames differently.

One thing that makes this easier to think through is to go back to the days when steel bikes were normal, and tubing sizes were all the same dimensions. Cheaper steel had thicker walls, and hence stiffer tubing. And stiffer frames were slower (and not just because of the weight).
Of course, that doesn't prove anything for certain (because conventional wisdom has often been wrong).
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Old 11-06-18, 08:19 PM
  #63  
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OK, this thread really took off! I had to take a break for halloween.

To answer the question, I am riding a 59cm Peugeot PSN-10. The tubing is Super Vitus 980, my cranks are Ultegra 6800 and my rear wheel is a HED Belgium C2 with a Dura Ace 9000 hub.

I do some spinning and some mashing... if I could find a way to wrap the stays in carbon and ensure there was some way to get it back off again if I didn't like it, I'd totally do it!!

I used to weigh around 130 and now I weigh 150lbs. I have noticed that some of the springiness went away. Going over bumps can be more of a "squish" feeling than a bounce. This would imply to me that its not all that uncommon for a frame to be too flexy.

Last edited by Stormy Archer; 11-06-18 at 08:23 PM.
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Old 11-07-18, 10:29 AM
  #64  
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Time to either get a new bike, frame of oversize tubing since you are tall so tubes are longer..

or just live with it as a feature, not a flaw.
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Old 11-07-18, 07:20 PM
  #65  
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Originally Posted by Andrew R Stewart View Post
I'm not sure how much stiffness a missing bridged frame would gain if a bridge was added, at the usual location. Years ago Bicycling magazine had a series of articles involving what was then considered leading edge engineering, a finite stress analysis computer modeling, of bike frames. They used a few different arrangements of frames including with and without chainstay bridges. Their findings were that the CS bridge didn't change the results. My seat of my pants experience bears this out.

I attribute the focus on stiffness as a selling quality began about the same time. Cannondale had just begun to go to the bank on Klein's patented use of oversized tubes to increase frame stiffness. Those of us who rode small sizes already knew the truth, overly stiff frames increased rider fatigue and this led to a slower end of ride. Andy.
I have always regarded "stiffness" as applied to bicycle frames to be rather silly. A super stiff bicycle(in that I include all other components that add to "stiffness") can be simply very unpleasant to ride. If you only want to ride a bike in the last kilometer of a race sprint, you want to ride a super stiff bike. Otherwise, you have to figure out how your bike will keep you comfortable enough to get you to be there for that final sprint
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