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Front axle, what thread?



 
 
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  #11  
Old November 13th 17, 10:20 PM posted to rec.bicycles.tech
Joerg[_2_]
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Posts: 4,621
Default Front axle, what thread?

On 2017-11-13 12:38, Frank Krygowski wrote:
On 11/13/2017 2:03 PM, Joerg wrote:
On 2017-11-13 10:29, AMuzi wrote:
On 11/13/2017 12:21 PM, Joerg wrote:

I just noticed that finding a 9mm solid axle from CroMo is
very tough. The ones I found were all non-metric or
sealed-hub BMX. Or no key-way which can make a front wheel
removal in the field hard. I'll probably visit some shops
that sell and service used bikes which is where I bought my
last CroMo rear axle for the old MTB (after which it didn't
bend or break anymore).


You haven't really looked:

https://www.ebay.com/itm/Shimano-Dur...gAAOSwk9dZnPkv



cheaper for a new complete hub:
https://www.ebay.com/itm/SHIMANO-HB-...kAAOSwr6pZ9M1K



Not so fond of a used axle but do you know whether the HB-TX500 has a
CroMo axle or is otherwise sturdy enough for heavy trail use? I'd have
to find some nuts as well but that should be easy.


I'm curious what failure mode you expect in a standard steel solid front
axle.


The failure modes I have experienced several times:

1. Bending.

2. Broken through (not just cracked but split apart).

--
Regards, Joerg

http://www.analogconsultants.com/
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  #12  
Old November 14th 17, 03:01 AM posted to rec.bicycles.tech
[email protected]
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Posts: 6,192
Default Front axle, what thread?

J, how check for bent axles ?

yawl buying cheap metals
  #13  
Old November 14th 17, 03:33 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 5,394
Default Front axle, what thread?

On 11/13/2017 4:20 PM, Joerg wrote:
On 2017-11-13 12:38, Frank Krygowski wrote:
On 11/13/2017 2:03 PM, Joerg wrote:
On 2017-11-13 10:29, AMuzi wrote:
On 11/13/2017 12:21 PM, Joerg wrote:

I just noticed that finding a 9mm solid axle from CroMo is
very tough. The ones I found were all non-metric or
sealed-hub BMX. Or no key-way which can make a front wheel
removal in the field hard. I'll probably visit some shops
that sell and service used bikes which is where I bought my
last CroMo rear axle for the old MTB (after which it didn't
bend or break anymore).


You haven't really looked:

https://www.ebay.com/itm/Shimano-Dur...gAAOSwk9dZnPkv




cheaper for a new complete hub:
https://www.ebay.com/itm/SHIMANO-HB-...kAAOSwr6pZ9M1K




Not so fond of a used axle but do you know whether the HB-TX500 has a
CroMo axle or is otherwise sturdy enough for heavy trail use? I'd have
to find some nuts as well but that should be easy.


I'm curious what failure mode you expect in a standard steel solid front
axle.


The failure modes I have experienced several times:

1. Bending.

2. Broken through (not just cracked but split apart).


On a front axle that's solid steel?

I ask because the distance between the inner races and the supporting
fork ends is very small. That means there's only a very small moment
arm, so the axle is loaded more in shear than in bending. In fact, the
cones and lock nut assembly is smack up against the fork ends, a
situation which provides more reinforcement against bending.

That's in contrast to rear axles on freewheel hubs, which I have broken.
On those, the right side bearing is a considerable distance inboard from
the supporting dropout. That gives a moment arm or lever arm that
imposes bending stresses not seen by the front axle.

What were the details? What did you do that caused this?

--
- Frank Krygowski
  #14  
Old November 14th 17, 09:55 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,621
Default Front axle, what thread?

On 2017-11-13 18:33, Frank Krygowski wrote:
On 11/13/2017 4:20 PM, Joerg wrote:
On 2017-11-13 12:38, Frank Krygowski wrote:
On 11/13/2017 2:03 PM, Joerg wrote:
On 2017-11-13 10:29, AMuzi wrote:
On 11/13/2017 12:21 PM, Joerg wrote:

I just noticed that finding a 9mm solid axle from CroMo is
very tough. The ones I found were all non-metric or
sealed-hub BMX. Or no key-way which can make a front wheel
removal in the field hard. I'll probably visit some shops
that sell and service used bikes which is where I bought my
last CroMo rear axle for the old MTB (after which it didn't
bend or break anymore).


You haven't really looked:

https://www.ebay.com/itm/Shimano-Dur...gAAOSwk9dZnPkv




cheaper for a new complete hub:
https://www.ebay.com/itm/SHIMANO-HB-...kAAOSwr6pZ9M1K




Not so fond of a used axle but do you know whether the HB-TX500 has a
CroMo axle or is otherwise sturdy enough for heavy trail use? I'd have
to find some nuts as well but that should be easy.

I'm curious what failure mode you expect in a standard steel solid front
axle.


The failure modes I have experienced several times:

1. Bending.

2. Broken through (not just cracked but split apart).


On a front axle that's solid steel?


Yup.


I ask because the distance between the inner races and the supporting
fork ends is very small. That means there's only a very small moment
arm, so the axle is loaded more in shear than in bending. In fact, the
cones and lock nut assembly is smack up against the fork ends, a
situation which provides more reinforcement against bending.


Those fork ends are not of the rigidity and size of Mt.Rushmore.


That's in contrast to rear axles on freewheel hubs, which I have broken.
On those, the right side bearing is a considerable distance inboard from
the supporting dropout. That gives a moment arm or lever arm that
imposes bending stresses not seen by the front axle.


Yes, that is a well-know design flaw of freewheels hubs. I bent so many
of those that I don't remember the count. Sometimes within less than a
month of installing a new axle.


What were the details? What did you do that caused this?


I used regular bikes on forest paths and, ahem, sometimes rough
singletrack. Didn't have a choice because we could not buy MTB, at least
not in Europe. IIRC the number of busted front axles was low in
comparison to rear axles, only three or so. None of the bikes had any
suspension.

The symptoms were the usual. When bent the wheel sits in there off
kilter. The axle that broke felt like the bike had become a boat.

What I don't know is whether this could happen with a 9mm non CroMo
front axle on a MTB that has a 4" suspension fork. I only lock that
while on pavement and it muffles the shock forces a lot. Also, I am not
riding as hard as I used to when I was decades younger and "invincible".

--
Regards, Joerg

http://www.analogconsultants.com/
 




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