Why the curved (as opposed to sloping) top tubes?
09-10-12, 02:45 PM
#26
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Sloping and curved TT road bikes are so Freds can ride a 56cm with the headtube of a 62cm.
09-10-12, 07:37 PM
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Thin, straight and horizontal top tubes for me. Curved top tubes have that beach cruiser look.
09-10-12, 08:23 PM
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Dammit, I want more lugs. And level top tubes. At chrome. Give me my chromed sleeves and stays.
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09-10-12, 08:24 PM
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09-10-12, 08:49 PM
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this thread is a major dissapointment. we were curving toward breasts, and the you guys derailed it.
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09-10-12, 11:43 PM
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Last edited by gsteinb; 09-12-12 at 05:34 AM.
09-11-12, 01:10 AM
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i love carbon, not a big fan of plastic.
i guess the plastic goes well with the knock off Scattante...flame on, but you cant deny it (deep inside)
Last edited by gsteinb; 09-12-12 at 05:34 AM.
09-11-12, 04:08 AM
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i love clean lines. i'm sorry, but that's just the way I am. I'm getting all emotional now. excuse me.
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09-11-12, 04:13 AM
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Isn't that why they call them "plastic bikes"?
Who looking @ her face?!?
09-11-12, 05:23 AM
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09-11-12, 06:27 AM
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To be honest, as much as the curved top tubes, I hate the super beefy straight forks. I'm sure they're more aero, but forks are where curves are sexy. Well, and Ms. Hendricks, et al. obviously.
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Last edited by himespau; 09-11-12 at 06:33 AM.
09-11-12, 06:45 AM
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Curved TT's are 'supposed' to reduce road buzz through the frame. The shape is 'supposed' to have a small degree of flex to dampen things.
09-11-12, 07:00 AM
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Lay-ups are evolving. Those who remember the early carbon bikes will remember round tubes bonded into alloy logs just like the alloy versions of the same frames. It was a starting point but didn't push any boundaries for the material.
A few decades later and engineers are experimenting more with shapes and lay-up to tune the ride characteristics of their frames. You can argue whether or not they are succeeding or not and whose line of thinking you feel is the best but what we are seeing is the exploration of the materials.
There is also an aesthetic component to these frame designs and the same considerations apply.
09-11-12, 08:52 AM
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Bending properties of arched structures is different than flat beams in the case of a bicycle top tube is the short answer OP. This changes the ratio of vertical compliance to torsional stiffness. A curved top tube offer greater torsional rigidity per the same level of beam bending providing vertical compliance. Also, look no further than arched structures such as bridges or at the curvature of a human's back in nature.
The overall vertical compliancy of the frame...aka Roubaix...as tensile forces act on this arch which can elongate due to the weight of rider over road disturbances offers more elongation per equivalent section straight tubes which are effectively columns that don't elongate much...are very strong in ratio of tensile force to bending...whereas arched sections can elongate at lower tensile force for same level of bending stiffness.
So the kinematics of an arched beam as in the case of the top tube is different than a straight beam with equivalent cross-section. Bike designer aka engineers have determined this design works which comports with my experience as well as an owner of bike with a curved top tube.
For math/engineering types interested in some of the nomenclature and calculus:
https://www.roymech.co.uk/Useful_Tabl...ved_beams.html
The overall vertical compliancy of the frame...aka Roubaix...as tensile forces act on this arch which can elongate due to the weight of rider over road disturbances offers more elongation per equivalent section straight tubes which are effectively columns that don't elongate much...are very strong in ratio of tensile force to bending...whereas arched sections can elongate at lower tensile force for same level of bending stiffness.
So the kinematics of an arched beam as in the case of the top tube is different than a straight beam with equivalent cross-section. Bike designer aka engineers have determined this design works which comports with my experience as well as an owner of bike with a curved top tube.
For math/engineering types interested in some of the nomenclature and calculus:
https://www.roymech.co.uk/Useful_Tabl...ved_beams.html
Last edited by gsteinb; 09-12-12 at 05:18 AM.
09-11-12, 12:03 PM
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I like straight top tubes just fine but went for a very curved Specialized Secteur because it rode so well and fit me like a glove. I can't attest to the physics and math of arch construction but have used arched structures and trims in my construction business for years and intuitively I get it. By the way I love how my Secteur looks!
09-11-12, 02:44 PM
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From where I'm standing, look like the peak of the TT is right in front of the seat.
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FB4K - Every October we wrench on donated bikes. Every December, a few thousand kids get bikes for Christmas. For many, it is their first bike, ever. Every bike, new and used, was donated, built, cleaned and repaired. Check us out on FaceBook: FB4K.
Disclaimer: 99% of what I know about cycling I learned on BF. That would make, ummm, 1% experience. And a lot of posts.
