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Thread: Ask the experts

  1. #6776
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    Valid point about spike windup, but thatís something that can happen any time you spin nipples, like just truing the wheel. I donít see that as a reason not to adjust dish.

    As an engineer I can say that spoke windup on a used wheel is the type of thing we donít give two shits about. We design it and itís up to techs/mechanics to deal with this stuff . But trust me, if the issue can be blamed on the the design itself, weíll hear about it. And techs/mechanics are a hell of a lot better than engineers at figuring out how to diagnose and deal with these type of maintenance issues.

    But more to the point (and I hope Iím not misinterpreting what youíre saying, let me know if I am), you consider this adjustment of the dish to be Ďthrowing things off balanceí and it will no longer be Ďsymmetricalí. Well, the rear wheel is never symmetrical, the spokes on one side have higher tension than the other because the rim isnít centered between the hub flanges. GG is building their frames in a way that actually allows them to reduce that Ďasymmetryí. All weíre saying is yes, take advantage of what theyíve designed into their frame.

    I did comment in response to a comment about your analogy, but never saw the analogy itself, so no idea if it was good or bad. Was just trying give a bit of an explanation of how load and spoke tension plays into wheel strength, certainly not a dig at anything you had said about it.

  2. #6777
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    Quote Originally Posted by jm2e View Post
    And yea, when the spokes on top of the circle take a huge load (like the one I left in your mom), the spokes on the bottom of the circle unload.
    I use XXXer's method to deal with windup, but since you self-quoted I'm gonna point out that the spokes at the top never take a huge load (ask your own mom). Spoke tension is basically max at rest and only goes down--unless you go sticking stuff in em. (Have a seat before you ask your mom about that, though, it could take a while.)

  3. #6778
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    Quote Originally Posted by jono View Post
    I use XXXer's method to deal with windup, but since you self-quoted I'm gonna point out that the spokes at the top never take a huge load (ask your own mom). Spoke tension is basically max at rest and only goes down--unless you go sticking stuff in em. (Have a seat before you ask your mom about that, though, it could take a while.)
    FEA visualization of how spokes distribute (a huge) load:


  4. #6779
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    Super cool. Thanks for sharing.


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  5. #6780
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    Quote Originally Posted by J. Barron DeJong View Post
    FEA visualization of how spokes distribute (a huge) load:

    Good visualization. I notice in the comments that the rim deflection goes from 0 to 5 mm. It would be interesting to know what deflection gets you rim damage. I assume not much, since this (linear) model only gets 4 spokes to buckle, but likely different for carbon rims by now anyway?

    Great illustration of the reason more tension is better, too.
    A woman came up to me and said "I'd like to poison your mind
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  6. #6781
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    Quote Originally Posted by jono View Post
    Good visualization. I notice in the comments that the rim deflection goes from 0 to 5 mm. It would be interesting to know what deflection gets you rim damage. I assume not much, since this (linear) model only gets 4 spokes to buckle, but likely different for carbon rims by now anyway?

    Great illustration of the reason more tension is better, too.
    i havenít seen any numbers put to that, but I do recall seeing some impact testing of carbon rims a while ago and it looked like they were able to deflect pretty significantly before cracking. Shallow cross section rims were able to deflect more before cracking (perhaps unsurprisingly). Spokes were definitely losing all tension and then springing back.

    From memory Iíd guess they were deflecting more than 5mm, but Ďfrom memoryí has pretty shitty reliability.

  7. #6782
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    Spoke tension dependant, of course, since an un-tensioned rim should deflect massively at lower stress, so that makes sense and lighter tension would amplify the effect. If your a rim manufacturer, do you publish the low-tension tests? Seems like the marketing people would.

  8. #6783
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    Do you guys keep your old spokes and nipples for future builds/repairs? Or do you wire cutter them out and go straight in the can with 'em?
    I'm a serious packrat, so I've been stock-pile-ing spokes for years. Just sold like 75 short spokes on Ebay from old 26ers.
    Lots of Cream, Lots of Sugar

  9. #6784
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    Quote Originally Posted by jm2e View Post
    Do you guys keep your old spokes and nipples for future builds/repairs? Or do you wire cutter them out and go straight in the can with 'em?
    I'm a serious packrat, so I've been stock-pile-ing spokes for years. Just sold like 75 short spokes on Ebay from old 26ers.
    I keep mine, and occasionally build a wheel with them. But mostly because old spokes are super useful.

    - grind a point onto them to use as a pokey thing.
    - bend them into a "u" to hold a chain slack while installing master links
    - use them as a disposable pokey thing to jam glue / epoxy into small holes (like when installing ski bindings)
    - use them to hang small parts to dry after painting

  10. #6785
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    Could be imagining this: Is there a separate thread with photos of badass organized pro mechanic type tool boxes or was that buried somewhere in this thread?

    Thanks.

  11. #6786
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    Quote Originally Posted by jm2e View Post
    Do you guys keep your old spokes and nipples for future builds/repairs? Or do you wire cutter them out and go straight in the can with 'em?
    I'm a serious packrat, so I've been stock-pile-ing spokes for years. Just sold like 75 short spokes on Ebay from old 26ers.
    I just threw away a ton and cleaned out my shit in general. Trying to reform. Iíll just buy more if I need 1 or 2.

    Quote Originally Posted by Whiteroom_Guardian View Post
    Could be imagining this: Is there a separate thread with photos of badass organized pro mechanic type tool boxes or was that buried somewhere in this thread?

    Thanks.
    That was Dee. I donít think it was this thread.

  12. #6787
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    Quote Originally Posted by jono View Post
    Spoke tension dependant, of course, since an un-tensioned rim should deflect massively at lower stress, so that makes sense and lighter tension would amplify the effect. If your a rim manufacturer, do you publish the low-tension tests? Seems like the marketing people would.
    No, not in the industry at all. Used to work at a shop back in high school and college, now just an engineer who still likes bikes but doesnít get work with them professionally.

    The testing I saw was something a manufacturer had posted, but canít seem to locate it anymore.

  13. #6788
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    Quote Originally Posted by jm2e View Post
    Do you guys keep your old spokes and nipples for future builds/repairs? Or do you wire cutter them out and go straight in the can with 'em?
    I'm a serious packrat, so I've been stock-pile-ing spokes for years. Just sold like 75 short spokes on Ebay from old 26ers.
    I keep a few old spokes around, but like toast I donít actually use them for their intended purpose.

    Spokes are pretty cheap, so Iíd rather just put a new one on and be confident. Building a complete wheel with used spokes can be a hassle - or so the mechanics always told me - so Iíve always used a full set of new spokes to build (Iím also not hard on rims, so itís not like Iím replacing rims yearly or monthly. New spoke costs could add up in that situation).

  14. #6789
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    if you are just replacing the rim with the exact same rim you can just tape the rims together and transfer spokes but other wise what are the chances of the spokes actualy being the right length ?

    I know an LBS owner who would let the local kids do this ^^ in his shop along with giving them credit, the kids were always cool and they always pay or they didnt get to play
    Lee Lau - xxx-er is the laziest Asian canuck I know

  15. #6790
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    Quote Originally Posted by J. Barron DeJong View Post
    No, not in the industry at all. Used to work at a shop back in high school and college, now just an engineer who still likes bikes but doesnít get work with them professionally.

    The testing I saw was something a manufacturer had posted, but canít seem to locate it anymore.
    Sorry, I meant that to say "imagine you were a rim manufacturer: would you publish the videos of tests with slack spokes?" I'm thinking yes, because those would be more dramatic to look at than the ones that make the rims look brittle without illustrating the load applied. Even though the higher tension wheels take more load, they'd be less exciting to look at.

  16. #6791
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    Quote Originally Posted by jono View Post
    Sorry, I meant that to say "imagine you were a rim manufacturer: would you publish the videos of tests with slack spokes?" I'm thinking yes, because those would be more dramatic to look at than the ones that make the rims look brittle without illustrating the load applied. Even though the higher tension wheels take more load, they'd be less exciting to look at.
    that’s obvious now that I re-read it. I need to get in the habit of finishing my morning coffee before posting…

  17. #6792
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    Stories from Snowshoe WC of French teams experimenting with loose spoke tension. Then thereís Daprelaís exploding wheel Ö..


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  18. #6793
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    Quote Originally Posted by J. Barron DeJong View Post
    that’s obvious now that I re-read it. I need to get in the habit of finishing my morning coffee before posting…
    I'm seeing roughly 520 lb/mm for that model (maybe more). Been a while since I've used Ansys outside of the standard small deflection assumption, so I'm not sure how confident I'd be of a linear model for this. But if that holds it would mean over a ton of force is shown by the end. Does that seem right?

    Would you mind checking my estimates? I'm looking at almost 3 seconds (call it 40% on the slider, so roughly 2 mm, maybe 2.5 mm) and I see the tension in the bottom 6 spokes changing by about 4500 N (1000 x 4 + 250 x 2) while the top 6 change by about 1500 N and the rest are not quite symmetric about the horizontal plane through the hub, but close. So I'm calling that 1350 lb net and saying those 12 spokes are within about 15 degrees of vertical gives a conservative estimate of 1300 lb at 2.5 mm.

    I think this is the same video I've seen criticized for using a defined deflection instead of a force, but I don't see why that would necessarily matter. Unless the beads crack at 1000 lb, which would make the majority of the illustration a little bit moot (kinda--I'd certainly prefer the tire blows out before total structural failure, but then again this model doesn't seem capable of predicting a taco anyway).
    A woman came up to me and said "I'd like to poison your mind
    with wrong ideas that appeal to you, though I am not unkind."

  19. #6794
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    Got new wheels for the GG and the GG wheels went to the hardtail. I may never have noticed the offset if not for this thread. Iím inclined to try and forget it cause I also am lazy.
    Remind me. We'll send him a red cap and a Speedo.

  20. #6795
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    Quote Originally Posted by bagtagley View Post
    Got new wheels for the GG and the GG wheels went to the hardtail. I may never have noticed the offset if not for this thread. I’m inclined to try and forget it cause I also am lazy.
    you don't need to do anything if the wheels don't rub thru the frame while riding
    Lee Lau - xxx-er is the laziest Asian canuck I know

  21. #6796
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    Been over a month. Pretty slim chance Iíll address it at this point.
    Remind me. We'll send him a red cap and a Speedo.

  22. #6797
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    You lazy GG guys ever notice the rim being off 3 mm when riding no hands?

  23. #6798
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    shimano xt 3x10 drivetrain on my old hardtail is shot, thinking replacing with shimano xt 1x11, which should fit old freehub and non-boost frame. Remove front Derailleur and 2 chainrings and everything should fit/work, right? Not wanting to spend a lot of money, but do plan to use the bike for a few more years.

    https://www.jensonusa.com/Shimano-XT...Speed-Cassette

    Am I missing something:
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  24. #6799
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    Crank, chainring, and possibly BB?

  25. #6800
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    ^^^I was thinking I'm good to use the front crank and middle or small chain ring? But does the 11 speed chain not work on old chainring?

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