3 ms·

Do you have a calculation that would quantify the amount of work lost due the torsional elasticity of the wheel? Because my experience is that if someone is ta

Do you have a calculation that would quantify the amount of work lost due the torsional elasticity of the wheel? Because my experience is that if someone is talking about bicycles and stiffness, most of the time they haven't done the math. If stiffness were really the problem, no one would be using low spoke count wheels, or radial/2x rears, or any of the funky asymmetric ones.

jacquesm 10y ago
Low spoke count is a trade-off between aerodynamics and stiffness.
- deleted 10y ago
  [deleted]
- wiredfool 10y ago
  And funky lacing patterns are a tradeoff between engineering and marketing.
rawland 10y ago
There are little papers, which have "done the math", as it is an interaction of many components and people tend to measure or, let's use a more "unscientific" word you used, "experience" the overall system answer, as in: Gavin, H. (1996). "Bicycle-Wheel Spoke Patterns and Spoke Fatigue.", J. Eng. Mech., 10.1061/(ASCE)0733-9399(1996)122:8(736), 736-742. and/or by riding many different wheels and speaking to other cyclists, who happen to be engineers. Which happens more often than one thinks after reaching higher levels in the sport [1]. There is little money for that kind of research. TU Delft is the only university I know investing here. I'd be happy about anybody pointing me towards groups doing that, as I'll finish my Dr.-Ing. (as an engineering PhD is called here) in Germany this year. Furthermore, jacquesm's comment nailed it: It's an aero compromise, as many (jackmott, thedufer, slashdotdash, etc...) already more or less said: Multiobjective Optimization at its best. --- [1]: http://teamgiantalpecin.com/team-giant-alpecin-to-accelerate-innovation-projects-with-delft-university-of-technology-partnership/ http://teamgiantalpecin.com/team-giant-alpecin-to-accelerate...
- wiredfool 10y ago
  Ah good, that paper mentions Jim Papadopoulos. I did a small experiment with him back in '95 on perception of weight on the frame. Looking at that paper, I've got a couple of comments: 1) I'm not clear where they're getting lateral forces when a bicycle is cornering, unless the rider is hanging off the side of the bike motorcycle style. (which is generally unnecessary as bikes have enough clearance to corner at ~45 degree lean angles). 2) It's unfortunate that they didn't instrument a trailing spoke as well, so that they could disentangle the torsional strains from the radial strains. 3) While the tangential/torsional strains are high, it's not clear what the loaded zone is there, nor how much energy is being stored in the wheel due to power pulses. I suppose I could pull out my old FEA model and port it to see.

jacquesm 10y ago

Low spoke count is a trade-off between aerodynamics and stiffness.

deleted 10y ago
[deleted]
wiredfool 10y ago
And funky lacing patterns are a tradeoff between engineering and marketing.

rawland 10y ago

There are little papers, which have "done the math", as it is an interaction of many components and people tend to measure or, let's use a more "unscientific" word you used, "experience" the overall system answer, as in: Gavin, H. (1996). "Bicycle-Wheel Spoke Patterns and Spoke Fatigue.", J. Eng. Mech., 10.1061/(ASCE)0733-9399(1996)122:8(736), 736-742. and/or by riding many different wheels and speaking to other cyclists, who happen to be engineers. Which happens more often than one thinks after reaching higher levels in the sport [1]. There is little money for that kind of research. TU Delft is the only university I know investing here. I'd be happy about anybody pointing me towards groups doing that, as I'll finish my Dr.-Ing. (as an engineering PhD is called here) in Germany this year. Furthermore, jacquesm's comment nailed it: It's an aero compromise, as many (jackmott, thedufer, slashdotdash, etc...) already more or less said: Multiobjective Optimization at its best. --- [1]: http://teamgiantalpecin.com/team-giant-alpecin-to-accelerate-innovation-projects-with-delft-university-of-technology-partnership/ http://teamgiantalpecin.com/team-giant-alpecin-to-accelerate...

wiredfool 10y ago
Ah good, that paper mentions Jim Papadopoulos. I did a small experiment with him back in '95 on perception of weight on the frame. Looking at that paper, I've got a couple of comments: 1) I'm not clear where they're getting lateral forces when a bicycle is cornering, unless the rider is hanging off the side of the bike motorcycle style. (which is generally unnecessary as bikes have enough clearance to corner at ~45 degree lean angles). 2) It's unfortunate that they didn't instrument a trailing spoke as well, so that they could disentangle the torsional strains from the radial strains. 3) While the tangential/torsional strains are high, it's not clear what the loaded zone is there, nor how much energy is being stored in the wheel due to power pulses. I suppose I could pull out my old FEA model and port it to see.