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Thread: Solid axle flex

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    laterally compliant keevohn's Avatar
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    Solid axle flex

    It was mentioned in a recent thread about the Suzue Jr. hub that the cones should be adjusted with just a little play, which would go away once the wheel was bolted back onto the bike. This is commonly done with QR axles because when the QR is properly tightened, the hollow axle flexes enough affect the cone tightness.

    But. Would a solid axle flex? I'd think there would be too much material in a solid axle for it to compress once bolted down. However, it would suck to find out that I've been inadvertantly over-tightening my cones and increasing wear on my hubs. Opinions?

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    Track Rat gotambushed's Avatar
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    well, depends on the material the axle is made of, using normal steel axles,
    i did the standard statics of materials drill, the elasticity of a 3/8" diameter 5" long effective compression, with 3600 in-Lbs of torque on the axle nuts, the axle will compress 0.00543 inches.
    5 thousandths is a small number,
    but, it is not zero, the trick is to expirement and see if you can leave the hub as loose as possible, right about were it'll start getting play in the axle if its any looser, then install it, and check for play,
    you'll find out how much to preload that way, and you won't have to worry about hub damage.
    Almost is only for horseshoes and hand grenades.

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    Eschew Obfuscation! enduro's Avatar
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    A bolt-on axle is not under compression like a QR axle is. Think about it...the QR pushes towards the middle of the axle, from both sides. The bolts only exert force against the nut on the other side of the dropout, not all throughout. Therefore compression in the axle does not exist. It's only tension in the few millimeters of axle that pass through the dropouts.

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    Team Beer Cynikal's Avatar
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    I had the opposite thing with my suzue. I would crank it down so tight that the cones would loosen. I relplaced the axel and the bearings and havn't had a problem since.
    I'm not one for fawning over bicycles, but I do believe that our bikes communicate with us, and what this bike is saying is, "You're an idiot." BikeSnobNYC

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    Direct Hit Not Required BlastRadius's Avatar
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    Quote Originally Posted by enduro
    A bolt-on axle is not under compression like a QR axle is. Think about it...the QR pushes towards the middle of the axle, from both sides. The bolts only exert force against the nut on the other side of the dropout, not all throughout. Therefore compression in the axle does not exist. It's only tension in the few millimeters of axle that pass through the dropouts.
    Actually a QR skewer does not push on the axle. The axle is shorter than the thickness of the dropouts therefore the skewer ends clamp the dropout against the cone locknut. Think about it, if the skewer ends push on the axle, the wheel would fall out of the dropout.

    For the original poster, try adjusting the cones as loose as possible leaving a tiny bit of play then install the wheel and tighten the axle nuts. Check for play. It's the only way to see for sure. This was advice given to me by a wrench a American Cyclery and it works for me, however YMMV.

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    laterally compliant keevohn's Avatar
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    Quote Originally Posted by Cynikal
    I had the opposite thing with my suzue. I would crank it down so tight that the cones would loosen. I relplaced the axel and the bearings and havn't had a problem since.
    How does cranking down on the track nuts cause the cones to loosen? I've had loose cone issues on my Suzue hub as well, but never thought it was due to me being hamfisted with my nuts (MAN that sounded bad...)

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    Retrogrouch in Training bostontrevor's Avatar
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    I used to have this problem. I'm not sure if my axle threads were stipped or what, but I couldn't tighten both sides too hard or the damn thing would bind up. I would tighten up the drive side spper tight and then the NDS plenty tight. Never took out the axle to investigate.

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    Team Beer Cynikal's Avatar
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    I envisioned the axel stretching toward the dropout as I tighten down. It eventually stripped so I bought a better one. No longer an issue.
    I'm not one for fawning over bicycles, but I do believe that our bikes communicate with us, and what this bike is saying is, "You're an idiot." BikeSnobNYC

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    Senior Member trespasser's Avatar
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    Quote Originally Posted by BlastRadius
    Actually a QR skewer does not push on the axle. The axle is shorter than the thickness of the dropouts therefore the skewer ends clamp the dropout against the cone locknut. Think about it, if the skewer ends push on the axle, the wheel would fall out of the dropout.
    no, enduro is right on this case, he/she didn't mention actual QR skewer pushing the axle, but the faces of dropouts pushing Locknuts from both side, causing axle compression. this does not happen on bolt on solild axles because of what enduro explained.

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    Track Rat gotambushed's Avatar
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    a QR axle does not directly push on the axle, rather on the dropout and inturn the cones and locknuts. since theyre threaded to the axle, they will compress the axle from the outside points on the axle where the lock nuts are towards the center.

    on a solid axle, the axle nuts squeeze the dropout against the locknuts,
    if you sum the forces on the axle, what you end up with is the axle nuts pulling the axle in elongation from the lockout nut towards the end of the axle, while the equal and opposite pressure of the locknut pushes towards the center of the axle,
    so, in theoretical physics, the axle would have no compression and no elongation due to them cancleing out, in practice however, i think your looking at that .005 compression and an almost equal elongation from the locknut out towards the ends.
    i don't have the equipment to test this, so this is mostly theory and hypothesis from physics and statics of materials, not so much from hard evidence.
    i should take a hub to the lab and measure the stretch/elongations or lack there of.
    .... just a thought
    Almost is only for horseshoes and hand grenades.

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    cxmagazine dot com pitboss's Avatar
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    I bent the axles on both Sovos hubs I used commuting downtown. And I beat on them, 150+ miles a week. But they are a cheaper, Bic-esque hub option. Only reason I ever used them was the price. And I got what I paid for.
    Deathlap - cyclocross, training, beer,...escape hatch

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    Direct Hit Not Required BlastRadius's Avatar
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    Quote Originally Posted by trespasser
    no, enduro is right on this case, he/she didn't mention actual QR skewer pushing the axle, but the faces of dropouts pushing Locknuts from both side, causing axle compression. this does not happen on bolt on solild axles because of what enduro explained.
    Quote Originally Posted by gotambushed
    a QR axle does not directly push on the axle, rather on the dropout and inturn the cones and locknuts. since theyre threaded to the axle, they will compress the axle from the outside points on the axle where the lock nuts are towards the center.

    on a solid axle, the axle nuts squeeze the dropout against the locknuts,
    if you sum the forces on the axle, what you end up with is the axle nuts pulling the axle in elongation from the lockout nut towards the end of the axle, while the equal and opposite pressure of the locknut pushes towards the center of the axle,
    so, in theoretical physics, the axle would have no compression and no elongation due to them cancleing out, in practice however, i think your looking at that .005 compression and an almost equal elongation from the locknut out towards the ends.
    i don't have the equipment to test this, so this is mostly theory and hypothesis from physics and statics of materials, not so much from hard evidence.
    i should take a hub to the lab and measure the stretch/elongations or lack there of.
    .... just a thought
    OK, that makes sense.

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    laterally compliant keevohn's Avatar
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    Summing up:

    Yes, the solid axle flexes (compresses), but very minimally.

    This is probably cancelled out by the axle tension between the cone locknuts and track nuts.

    But with regards to cone tightness, just test it out and see what happens.


    And [165] bent his axles.

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