Hollow vs solid axles-was: Butted vs. straight-gauge spokes



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Dan Baker

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Sheldon Brown <[email protected]> wrote in message ...
> There has been some controversy on this list about the observed greater durability of quick
> release axles vis-a-vis solid axles, and this would seem to support those of us who maintain that
> QR axles are less prone to breakage than solid ones, despite having less material. .....
gee, I hate to get caught between a rock and a hard pace with you two, but its a pretty well-known
fact that tubes are better than solid rods for bending moment stress. which an axle should be if it
is properly tight. Now, if its loose, and in pure shear, then its a different story. the arguement
might be clouded if one considers whether its more likely a person would apply proper tension to a
QR skewer versus a bolt-on nut.

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Jobst Brandt

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Dan Baker writes:

>> There has been some controversy on this list about the observed greater durability of quick
>> release axles vis-a-vis solid axles, and this would seem to support those of us who maintain that
>> QR axles are less prone to breakage than solid ones, despite having less material.

> gee, I hate to get caught between a rock and a hard pace with you two, but its a pretty well-known
> fact that tubes are better than solid rods for bending moment stress. which an axle should be if
> it is properly tight. Now, if its loose, and in pure shear, then its a different story. the
> argument might be clouded if one considers whether its more likely a person would apply proper
> tension to a QR skewer versus a bolt-on nut.

That is not true. The hole in the center does not make the shaft more durable or less fatigue
resistant, although the core of the shaft adds practically nothing to torsional or bending strength.
It is just there. Whether hollow axles are made of better material may be another parameter to
consider but good track axles are at least as durable as QR axles of the same OD.

QR compression increases compressive stress while the magnitude of stress cycles from road shock and
chain tension remain unchanged.

Jobst Brandt [email protected] Palo Alto CA
 
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Ross Ruske

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[email protected] wrote in message news:<[email protected]>...

> Whether hollow axles are made of better material may be another parameter to consider but good
> track axles are at least as durable as QR axles of the same OD.
>
Given the same material and OD, the hardening process affects more of the material in a hollow axle
(from the inside as well as the outside), than it does on a solid axle.
 
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Jobst Brandt

Guest
Ross Ruske writes:

>> Whether hollow axles are made of better material may be another parameter to consider but good
>> track axles are at least as durable as QR axles of the same OD.

> Given the same material and OD, the hardening process affects more of the material in a hollow
> axle (from the inside as well as the outside), than it does on a solid axle.

Could you describe the "hardening" process you believe axles receive and how that is different with
a bore in the axle? What brand of axle do you have in mind?

Jobst Brandt [email protected] Palo Alto CA
 
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Bluto

Guest
[email protected] wrote:

> Ross Ruske writes:
>
> > Given the same material and OD, the hardening process affects more of the material in a hollow
> > axle (from the inside as well as the outside), than it does on a solid axle.
>
> Could you describe the "hardening" process you believe axles receive and how that is different
> with a bore in the axle? What brand of axle do you have in mind?

Carburizing would have the effect Ross describes, as would some variations of heating & quenching. I
know of no axles that are carburized, though.

It's not difficult to imagine that the different cooling rates of solid and hollow axles upon
quenching would produce different minimum hardnesses in their sections. How much difference is
another matter, of course.

I suspect that any disproportionate correlation between solid axles and bending might have something
to do with the fact that solid rears are usually 9.5mm and hollow rears are usually 10mm. It's
indisputable that most horribly cheap axles of unknown and suspect material are solid, too.

Chalo Colina
 
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Ross Ruske

Guest
[email protected] wrote:

> Could you describe the "hardening" process you believe axles receive and how that is different
> with a bore in the axle? What brand of axle do you have in mind?
>
I don't know what "hardening" processes are normally used on axles. I have in mind, campagnolo and
shimano axles that are subject to a "tempering" process that occurs subsequent to the machining
operations.

I'm not familiar with a "hardening" process that would penetrate an entire solid axle. Therefore,
the bore in an axle provides additional surface area for a "hardening" process to affect the
material. Assuming that a "tempering" process penetrates the axle material to a depth of one half
the hollow tube thickness, it would completely "harden" a hollow axle, but only have half the effect
on a solid axle.

Ross
 
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Jobst Brandt

Guest
Ross Ruske writes:

>> Could you describe the "hardening" process you believe axles receive and how that is different
>> with a bore in the axle? What brand of axle do you have in mind?

> I don't know what "hardening" processes are normally used on axles. I have in mind, Campagnolo and
> Shimano axles that are subject to a "tempering" process that occurs subsequent to the machining
> operations.

You mean you can see that the axle went through a "bluing" process because it is dark. That doesn't
mean that the axle is hardened. In fact if you took a file to it, you'd see that it is probably
annealed for stress relieving after machining because the metal is dead soft as far as hardening is
concerned.

> I'm not familiar with a "hardening" process that would penetrate an entire solid axle. Therefore,
> the bore in an axle provides additional surface area for a "hardening" process to affect the
> material. Assuming that a "tempering" process penetrates the axle material to a depth of one half
> the hollow tube thickness, it would completely "harden" a hollow axle, but only have half the
> effect on a solid axle.

Heat treatment isn't a rinse process that would be enhanced by vent such as an axle bore.

Not only are you not "familiar with a "hardening" process that would penetrate an entire solid
axle", but you are unfamiliar with surface heat treatments commonly used on such parts because it
would have no effect on axle strength, the inside wall of the bore being relatively unstressed when
the axle is subjected to bending, the only load an axle carries, the one that causes axle failure. I
detect a case of MAS.

Jobst Brandt [email protected] Palo Alto CA
 
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