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what do you mean it's not tension at the top? did you misspeak? bicycle spokes are solely under tensile forces. they can't support compressive forces at all. i

what do you mean it's not tension at the top? did you misspeak? bicycle spokes are solely under tensile forces. they can't support compressive forces at all. i'm a hobbyist wheel builder and a once upon a time professional bicycle mechanic during hs & college. if you want to test this take nearly all the pretension out of your spokes and sit on your bike. feel which ones are taught and which ones are completely loose. or just go to walmart. those bikes hardly have any pretension in their wheels.

bradyd 3y ago
They even make spokes that are rope https://berdspokes.com/pages/technology https://berdspokes.com/pages/technology
- hinkley 3y ago
  I wonder if those have less or more breakin issues compared to spokes. With a spoke you have to reset the angle of the bend to the shortest distance between the hub and the rim. But with cables they have to settle in along their entire length. Doesn’t change the answer. They’re still compressing. They’re just pretensioned.
  - denimnerd42 3y ago
    you sound highly confused, what is compressing? the rim? the spoke?
    - hinkley 3y ago
      You need to reread Brandt. There are two situations when you can push on a string. One is when it’s frozen, and the other when it’s tensioned. How do you unload a bow string? You push it off the notches.
      - denimnerd42 3y ago
        bro. you're wrong. just build a bicycle wheel some time. it becomes very obvious how they work as you take it through the various stages of tensioning.
        hinkley 3y ago
        Why do you think someone would talk about Brandt’s work if they hadn’t used it? I’ve built more than half a dozen bicycle wheels. My set, my spare that my brother road (into the ground - my first set and practically the only problematic ones, but he road over bumps without getting out of the saddle), a set my dad commissioned from me, and a pair that he had me build for a friend. All by age 17. I then worked as a mechanic for two summers of college. I was never the fastest, but if we had a customer we could not afford to disappoint, I or the senior mechanic got the job because my repairs did not come back. I saved three or four wheels that would have been scrap by unwinding the spokes halfway and building it back up again like a wheel build. Only added an extra ten or fifteen minutes but it works a charm. When a good customer comes in on Wednesday before an out of town bike ride you can’t afford to fuck it up. I think I only built a couple professionally, and usually singles. That’s a lot of labor and few will pay.
  - wiredfool 3y ago
    There's a lot more creep early on, which is compensated for by a staged tensioning over the course of a few days. They may require the spoke holes in the hub to be radiused, which can be a warranty issue between you and the hub manufacturer. Windup is controlled by a flat on the small bit of spoke used for threads. They're ok (i.e., made it through Tour Divide with no issues), done well they're certainly better than badly done steel spokes, but it's not clear if the best builds are better than the best steel builds.
hinkley 3y ago
That book I linked has another name, “the wheel building bible”. Jobst Brandt earned an obituary in Bicycling magazine including quotes from his friend Tom Ritchey (one of the original mountain bike makers). Jobst was a bike fanatic and a mechanical engineer. Bike spokes are not loose, they’re under substantial tension. Bolts, I just learned a couple weeks ago, work in the opposite way. A tightened bolt compresses the two pieces of metal together, and when you tug on them, the bolt doesn’t stretch more. The tension instead first cancels out some of the compressive force on the two pieces of metal, before the bolt ever feels more load. Conversely, all the spokes on the wheel are under tension. When you put the wheel on a surface and push down, the compression cancels out some of the tension on the bottom of the wheel. Cancel out all of the tension, and the wheel turns into a potato chip if you don’t reload it exactly, perfectly on axis. IIRC, none of the prior models or theories for how a spoked wheel works could adequately explain how potato chipping happens. His does. I used his book to build half a dozen wheels or so and the information it contained to fix many more.
- denimnerd42 3y ago
  i own the book.. and also The Art of Wheelbuilding - Gerd Schraner of course in a properly built wheel usually all the spoke are under tension... i was just demonstrating the fact that the spokes on the upper half of the wheel are supporting the hub and are under greater tension than the bottom ones, the spokes on the bottom half of the wheel should remain in tension, but only through the fact that they are already under tension applied during the building of the wheel. the fact that the wheel works by tension of the spokes becomes obviously apparent when you start to remove the pretension and then the spokes will feel loose on the bottom half. of course you'd never want to ride a wheel like that because it will quickly become out of true.. just like a walmart wheel.
  - hinkley 3y ago
    I think one of us needs to reread that book, because he emphatically denies that tension at the top of the wheel increases. It’s tension at the bottom that decreases. > of course in a properly built wheel usually all the spoke are under tension... No, a properly built wheel all of the spokes are always under enough tension you can bounce a penny off them. Always.
wiredfool 3y ago
This dialogue is reminiscent of rec.bycycles.tech arguments with Jobst, ca 1993. A bike wheel is a linear elastic system, that can be thought of as a superposition of a uniformly set of tensioned spokes as one state, and a set of spokes in compression in the loaded zone (bottom of the wheel) as the other state. So long as the superposition of the two states obeys the limiting conditions (i.e. spokes in tension) they can be analysed separately. The size of the loaded zone is related to the relative stiffness of the spokes (axial) and the rim (bending), and can be calculated using beam on elastic foundation methods. For typical rim/spoke combinations, this is approximately 4 spokes. Outside of the loaded zone, spoke tensions essentially don’t change.
- hinkley 3y ago
  And thread. Thereby proving my point: Almost nobody knows how bicycle wheels actually work.
  - denimnerd42 3y ago
    Well. I wish we could sit in front of a bicycle wheel and discuss it. Because I have a feeling we are shooting arrows at different targets. As a mountain biker I'm more interested in what happens when an extreme amount of load is applied to the wheel, not the model with assumptions applied. Definitely a difficult concept to discuss with only text. Anyways.. glad to have a good discussion with you about bicycle wheels. Don't find many people like you. :)
    - hinkley 3y ago
      I think I would have been a mechanical engineer if I were born 20 years earlier or 20 years later. Software was just new and shiny enough and it let me build things with my mind, at a time when I believed I was clumsy (I actually have always had excellent fine motor skills, it's macro motor control I lagged behind in). One of my better friends in college was an ME. Learned all sorts of things about metal fatigue and oddly enough picosecond lasers from him. I don't know if I found Lego or Lego found me, but I definitely think in terms of shapes. I was past my midlife crisis before I realized that I don't have a large working memory (smaller than average in fact) it's just that I've been doing mind palaces without pictures since I was very small. When I'm thinking of large computer systems I'm essentially thinking of them as physics problems. I really should figure out space to have a bike again. I never rode when I lived in Seattle (Seattle drivers are nuts) but I don't live there anymore and I need to catch up on 20 years of tech.

bradyd 3y ago

They even make spokes that are rope https://berdspokes.com/pages/technology https://berdspokes.com/pages/technology

hinkley 3y ago
I wonder if those have less or more breakin issues compared to spokes. With a spoke you have to reset the angle of the bend to the shortest distance between the hub and the rim. But with cables they have to settle in along their entire length. Doesn’t change the answer. They’re still compressing. They’re just pretensioned.
- denimnerd42 3y ago
  you sound highly confused, what is compressing? the rim? the spoke?
  - hinkley 3y ago
    You need to reread Brandt. There are two situations when you can push on a string. One is when it’s frozen, and the other when it’s tensioned. How do you unload a bow string? You push it off the notches.
    - denimnerd42 3y ago
      bro. you're wrong. just build a bicycle wheel some time. it becomes very obvious how they work as you take it through the various stages of tensioning.
      - hinkley 3y ago
        Why do you think someone would talk about Brandt’s work if they hadn’t used it? I’ve built more than half a dozen bicycle wheels. My set, my spare that my brother road (into the ground - my first set and practically the only problematic ones, but he road over bumps without getting out of the saddle), a set my dad commissioned from me, and a pair that he had me build for a friend. All by age 17. I then worked as a mechanic for two summers of college. I was never the fastest, but if we had a customer we could not afford to disappoint, I or the senior mechanic got the job because my repairs did not come back. I saved three or four wheels that would have been scrap by unwinding the spokes halfway and building it back up again like a wheel build. Only added an extra ten or fifteen minutes but it works a charm. When a good customer comes in on Wednesday before an out of town bike ride you can’t afford to fuck it up. I think I only built a couple professionally, and usually singles. That’s a lot of labor and few will pay.
- wiredfool 3y ago
  There's a lot more creep early on, which is compensated for by a staged tensioning over the course of a few days. They may require the spoke holes in the hub to be radiused, which can be a warranty issue between you and the hub manufacturer. Windup is controlled by a flat on the small bit of spoke used for threads. They're ok (i.e., made it through Tour Divide with no issues), done well they're certainly better than badly done steel spokes, but it's not clear if the best builds are better than the best steel builds.

hinkley 3y ago

That book I linked has another name, “the wheel building bible”. Jobst Brandt earned an obituary in Bicycling magazine including quotes from his friend Tom Ritchey (one of the original mountain bike makers). Jobst was a bike fanatic and a mechanical engineer. Bike spokes are not loose, they’re under substantial tension. Bolts, I just learned a couple weeks ago, work in the opposite way. A tightened bolt compresses the two pieces of metal together, and when you tug on them, the bolt doesn’t stretch more. The tension instead first cancels out some of the compressive force on the two pieces of metal, before the bolt ever feels more load. Conversely, all the spokes on the wheel are under tension. When you put the wheel on a surface and push down, the compression cancels out some of the tension on the bottom of the wheel. Cancel out all of the tension, and the wheel turns into a potato chip if you don’t reload it exactly, perfectly on axis. IIRC, none of the prior models or theories for how a spoked wheel works could adequately explain how potato chipping happens. His does. I used his book to build half a dozen wheels or so and the information it contained to fix many more.

denimnerd42 3y ago
i own the book.. and also The Art of Wheelbuilding - Gerd Schraner of course in a properly built wheel usually all the spoke are under tension... i was just demonstrating the fact that the spokes on the upper half of the wheel are supporting the hub and are under greater tension than the bottom ones, the spokes on the bottom half of the wheel should remain in tension, but only through the fact that they are already under tension applied during the building of the wheel. the fact that the wheel works by tension of the spokes becomes obviously apparent when you start to remove the pretension and then the spokes will feel loose on the bottom half. of course you'd never want to ride a wheel like that because it will quickly become out of true.. just like a walmart wheel.
- hinkley 3y ago
  I think one of us needs to reread that book, because he emphatically denies that tension at the top of the wheel increases. It’s tension at the bottom that decreases. > of course in a properly built wheel usually all the spoke are under tension... No, a properly built wheel all of the spokes are always under enough tension you can bounce a penny off them. Always.

wiredfool 3y ago

This dialogue is reminiscent of rec.bycycles.tech arguments with Jobst, ca 1993. A bike wheel is a linear elastic system, that can be thought of as a superposition of a uniformly set of tensioned spokes as one state, and a set of spokes in compression in the loaded zone (bottom of the wheel) as the other state. So long as the superposition of the two states obeys the limiting conditions (i.e. spokes in tension) they can be analysed separately. The size of the loaded zone is related to the relative stiffness of the spokes (axial) and the rim (bending), and can be calculated using beam on elastic foundation methods. For typical rim/spoke combinations, this is approximately 4 spokes. Outside of the loaded zone, spoke tensions essentially don’t change.

hinkley 3y ago
And thread. Thereby proving my point: Almost nobody knows how bicycle wheels actually work.
- denimnerd42 3y ago
  Well. I wish we could sit in front of a bicycle wheel and discuss it. Because I have a feeling we are shooting arrows at different targets. As a mountain biker I'm more interested in what happens when an extreme amount of load is applied to the wheel, not the model with assumptions applied. Definitely a difficult concept to discuss with only text. Anyways.. glad to have a good discussion with you about bicycle wheels. Don't find many people like you. :)
  - hinkley 3y ago
    I think I would have been a mechanical engineer if I were born 20 years earlier or 20 years later. Software was just new and shiny enough and it let me build things with my mind, at a time when I believed I was clumsy (I actually have always had excellent fine motor skills, it's macro motor control I lagged behind in). One of my better friends in college was an ME. Learned all sorts of things about metal fatigue and oddly enough picosecond lasers from him. I don't know if I found Lego or Lego found me, but I definitely think in terms of shapes. I was past my midlife crisis before I realized that I don't have a large working memory (smaller than average in fact) it's just that I've been doing mind palaces without pictures since I was very small. When I'm thinking of large computer systems I'm essentially thinking of them as physics problems. I really should figure out space to have a bike again. I never rode when I lived in Seattle (Seattle drivers are nuts) but I don't live there anymore and I need to catch up on 20 years of tech.