Dropout spacing and wheel axles.

[* * Chas]

"webhead" <[email protected]> wrote in message
news:cc4666ad-48d2-4f78-8ba8-c63906f78f11@b40g2000prf.googlegroups.com...
>
>
>
> > 1. The derailleur hanger could be misaligned. The derailleur needs to
be
> > parallel to the wheel axis on 2 plains - front to back and top to
bottom.
> > If the derailleur is angled on either plain then it can cause some
> > shifting problems.
> Could be but how do I check this? I've aligned the dropouts by
> screwing something in it resembling that parktool thing for aligning
> them. I sort of used a DIY version of the parktool model.
> I'm somewhat scared of taking the deraileur out again because the
> first mm of thread in somewhat damaged so it's difficult to screw it
> in. I need to get my hands on an M10x1 tap for restoring that but I've
> only got an M10x1.5 lying around, anyhow that's not the cause of the
> misalignment.
> If the derailleur hanger is out of alignment, can this be checked
> somehow ?
>
> > 2. The top jockey wheel in the derailleur could be worn out. The wheel
> > should move freely side to side but have no angular slop.
> It's brand new actually. How much lateral movement are we talking
> about ?

You can eyeball your derailleur from behind and above to see if it's way
out of alignment - see picture in this link:

http://www.parktool.com/repair/readhowto.asp?id=39

A number of companies make tools for aligning the hanger. They screw into
the derailleur hanger. You need to have a well dished and trued wheel in
the frame and have it centered correctly. The tool is rotated around and
you can check the distance a pin in the tool is from the rim.

These tools also act as a lever for bending the hanger. You might want to
have a LBS with one of these tools do the job for you.

Chas.

 

[Michael Press]

In article
<[email protected]
groups.com>,
RicodJour <[email protected]> wrote:

>On Dec 24, 1:22 pm, Michael Press <[email protected]> wrote:
>>RicodJour <[email protected]> wrote:
>>>On Dec 23, 2:01 pm, Ted Bennett <[email protected]> wrote:
>>>>RicodJour <[email protected]> wrote:
>>>>>"* * Chas" <[email protected]> wrote:
>>
>>>>>>Squeezing the dropouts like you are doing can cause them to be misaligned
>>>>>>putting undue pressure on the rear hub axle which can eventually cause it
>>>>>>to bend or break.
>>
>>>>>Why would squeezing the dropouts closer together put any more strain
>>>>>on the hub? Seems to me the only additional strain on the wheel would
>>>>>be on the axle, and it would be entirely an axial strain with no
>>>>>additional bending moments.
>>
>>>>When the stays are bent inwards, the dropout faces don't remain
>>>>parallel. Now when you clamp in (or bolt in) your wheel there is indeed
>>>>a bending moment, which can and does cause the axle to fail in some
>>>>circumstances.
>>
>>>>Yes, the bending moment is small. I will leave the calculations to
>>>>someone else. However the axle is not designed for that loading; best
>>>>to avoid it by adding spacers as necessary, or by cold-setting the frame
>>>>so that the spacing is correct for the hub and the dropout faces are
>>>>parallel.
>>
>>>But the clamping action of the skewer (I said axle in my first post
>>>when I meant skewer) will tend to pull the dropouts against the
>>
>>Assumption: For particular values of tend.
>
>Oh, God, here we go...

You are exasperated? You're the one talking rot about
stress and strain in structures.

>>>essentially immovable, parallel axle lock nuts. I just don't see an
>>
>>Assumption: for some value of essentially immovable.
>>None of this stuff is essentially immovable. It is all elastic.
>>
>>>appreciable difference in. Once it's clamped down, the force is all
>>>axial.
>>
>>No, the bending moment remains non-zero.
>>
>>It is an Euler strut unevenly loaded with a non-zero
>>bending moment, and therefore further toward the edge
>>of its buckling regime than with even loading. That it
>>has not buckled does not prove the condition benign.
>>
>>Look up `imperfection sensitivity' in a text on structures.
>>
>>>Put it this way, there's no more twisting force on the
>>>dropouts, and probably far less, than when the wheel experiences a
>>>sideways load while riding.
>>
>>Assumption: `probably'. And the forces are additive.
>>
>>That failures have not been attributed to out of parallel
>>drop outs does not prove that the condition is benign.
>>Look up `imperfection sensitivity' in a text on structures.
>
>While I'm at it should I look up 'how many angels can dance on the
>head of a pin?' Exactly how sensitive is the imperfection to the
>fookin' 1/3 of 1 degree out of parallel condition?
>
>My comments were in reply to Chas:
>>"webhead" <[email protected]> wrote in message
>>
>>Squeezing the dropouts like you are doing can cause them to be misaligned
>>putting undue pressure on the rear hub axle which can eventually cause it
>>to bend or break.
>
>Squeezing the dropouts is not uncommon. How is it different than
>spreading them to fit a wider hub? That's way more common and I've
>never heard of a broken or bent axle in either situation where the
>difference in hub widths was 4 mm. A 10 mm discrepancy is another
>matter and could cause a problem, but so can crashing the bike or
>running into a curb.
>
>In any event, the OP shimmed the sucker and it's a done deal, but
>thanks for the engineering refresher. I haven't been so lulled by
>droning since Prof. Oral Buyozkuturk way back when. ~

Telling the OP that it is generally ok to force fit
steel triangles is one thing, and is the consensus.
Spouting bilge about the magnitude of the forces and
implying that it is the same as if the rear triangle
were perfectly aligned is another thing. The shop
owners who post here properly separate, center, and
align the dropouts--for good reason.

--
Michael Press

 

[* * Chas]

"Michael Press" <[email protected]> wrote in message
news:[email protected]...
> In article
> <[email protected]
> groups.com>,
> RicodJour <[email protected]> wrote:
>
> >On Dec 24, 1:22 pm, Michael Press <[email protected]> wrote:
> >>RicodJour <[email protected]> wrote:
> >>>On Dec 23, 2:01 pm, Ted Bennett <[email protected]> wrote:
> >>>>RicodJour <[email protected]> wrote:
> >>>>>"* * Chas" <[email protected]> wrote:
> >>
> >>>>>>Squeezing the dropouts like you are doing can cause them to be
misaligned
> >>>>>>putting undue pressure on the rear hub axle which can eventually
cause it
> >>>>>>to bend or break.
> >>
> >>>>>Why would squeezing the dropouts closer together put any more
strain
> >>>>>on the hub? Seems to me the only additional strain on the wheel
would
> >>>>>be on the axle, and it would be entirely an axial strain with no
> >>>>>additional bending moments.
> >>
> >>>>When the stays are bent inwards, the dropout faces don't remain
> >>>>parallel. Now when you clamp in (or bolt in) your wheel there is
indeed
> >>>>a bending moment, which can and does cause the axle to fail in some
> >>>>circumstances.
> >>
> >>>>Yes, the bending moment is small. I will leave the calculations to
> >>>>someone else. However the axle is not designed for that loading;
best
> >>>>to avoid it by adding spacers as necessary, or by cold-setting the
frame
> >>>>so that the spacing is correct for the hub and the dropout faces are
> >>>>parallel.
> >>
> >>>But the clamping action of the skewer (I said axle in my first post
> >>>when I meant skewer) will tend to pull the dropouts against the
> >>
> >>Assumption: For particular values of tend.
> >
> >Oh, God, here we go...
>
> You are exasperated? You're the one talking rot about
> stress and strain in structures.
>
> >>>essentially immovable, parallel axle lock nuts. I just don't see an
> >>
> >>Assumption: for some value of essentially immovable.
> >>None of this stuff is essentially immovable. It is all elastic.
> >>
> >>>appreciable difference in. Once it's clamped down, the force is all
> >>>axial.
> >>
> >>No, the bending moment remains non-zero.
> >>
> >>It is an Euler strut unevenly loaded with a non-zero
> >>bending moment, and therefore further toward the edge
> >>of its buckling regime than with even loading. That it
> >>has not buckled does not prove the condition benign.
> >>
> >>Look up `imperfection sensitivity' in a text on structures.
> >>
> >>>Put it this way, there's no more twisting force on the
> >>>dropouts, and probably far less, than when the wheel experiences a
> >>>sideways load while riding.
> >>
> >>Assumption: `probably'. And the forces are additive.
> >>
> >>That failures have not been attributed to out of parallel
> >>drop outs does not prove that the condition is benign.
> >>Look up `imperfection sensitivity' in a text on structures.
> >
> >While I'm at it should I look up 'how many angels can dance on the
> >head of a pin?' Exactly how sensitive is the imperfection to the
> >fookin' 1/3 of 1 degree out of parallel condition?
> >
> >My comments were in reply to Chas:
> >>"webhead" <[email protected]> wrote in message
> >>
> >>Squeezing the dropouts like you are doing can cause them to be
misaligned
> >>putting undue pressure on the rear hub axle which can eventually cause
it
> >>to bend or break.
> >
> >Squeezing the dropouts is not uncommon. How is it different than
> >spreading them to fit a wider hub? That's way more common and I've
> >never heard of a broken or bent axle in either situation where the
> >difference in hub widths was 4 mm. A 10 mm discrepancy is another
> >matter and could cause a problem, but so can crashing the bike or
> >running into a curb.
> >
> >In any event, the OP shimmed the sucker and it's a done deal, but
> >thanks for the engineering refresher. I haven't been so lulled by
> >droning since Prof. Oral Buyozkuturk way back when. ~
>
> Telling the OP that it is generally ok to force fit
> steel triangles is one thing, and is the consensus.
> Spouting bilge about the magnitude of the forces and
> implying that it is the same as if the rear triangle
> were perfectly aligned is another thing. The shop
> owners who post here properly separate, center, and
> align the dropouts--for good reason.
>
> --
> Michael Press

Most 130mm wide freewheel hubs and some with cassettes have around 35mm of
unsupported hollow 10mm diameter axle hanging out beyond the right side
hub bearing. Shimano partially solved the problem by moving the right side
bearing further outboard when they brought out their first freehubs.

I've checked the alignment on a lot of steel frames and I've seen very few
with properly aligned rear triangles even on new ones from the factory or
builder. I'm talking about dropouts up to 1/2" (12mm) out of whack.

Most steel dropouts have 11+mm wide axle slots which allows quite a bit of
vertical "adjustment" so that the rim can be centered between the rear
brake blocks. A wheel that is several degrees misaligned at the dropouts
can have the rim seriously out of alignment from the axis of the frame.

Bikes with misaligned frames tend to handle squirrelly especially when
trying to ride hands off.

There is always the possibility that spreading the rear triangle 4mm could
bring the dropouts into better alignment but it could also exacerbate the
problem too. That's why I suggested to the OP that he check the alignment
of his dropouts.

I've never checked it but I think that a hollow 10mm diameter rear axle is
going to accommodate misaligned dropouts a lot more than vice versa.
Logically I would guess that most of the stresses in the axle would be
unevenly distributed between the right side bearing and the end of the
axle, a space of ~35mm. However most of the broken rear axles that I've
seen failed on the inside of the hub towards the middle. These were in
120mm and 126mm freewheel style hubs.

Chas.