7spd freewheel, axle bending, fork end alignment?



B

- Bob -

Guest
I've seen it sugestted that the reason that rear axles bend/break with
a 7 speed freewheel (aside from the obvious engineering shortcomings
of the long unsupported axle segment) is that the stay fork ends are
not properly aligned. It also seems like the alignment issue being
suggested is that the forks ends are not properly in the plane of the
top tube.

I am having trouble imagining how this could be the issue. I could see
that if the fork ends were not aligned vertically, making one rear
stay higher than the other and then riding the bike in a vertical
plane would put more stress on one side of the axle. Have I
misunderstood the issue? Is it the second problem, not the first?

Thanks,
 
In article <[email protected]>,
- Bob - <[email protected]> wrote:

> I've seen it sugestted that the reason that rear axles bend/break
> with a 7 speed freewheel (aside from the obvious engineering
> shortcomings of the long unsupported axle segment) is that the stay
> fork ends are not properly aligned. It also seems like the alignment
> issue being suggested is that the forks ends are not properly in the
> plane of the top tube.
>
> I am having trouble imagining how this could be the issue. I could
> see that if the fork ends were not aligned vertically, making one
> rear stay higher than the other and then riding the bike in a
> vertical plane would put more stress on one side of the axle. Have I
> misunderstood the issue? Is it the second problem, not the first?


I've never heard the "plane of the top tube" being a factor before. The
issue is usually confined to the faces of the dropout being parallel to
each other.

If the dropout faces aren't parallel, there will be a bending force when
the skewer clamps the axle locknuts to the dropouts. Whichever
component is more flexible- the axle or the frame- is the one that will
bend. I suspect- but don't know- that the axle is more flexible than
the frame. I suppose that both probably flex a bit.

Then you add the bending forces from the rider's weight and from chain
tension, and there's a lot going on down there.
 
pawsibly another trees forest, see?
as aluminum v steel when wheels and tires are the inteface.
line the wheel to the seatpost then enjoy the day
following the component toss
 
On Wed, 21 Mar 2007 08:39:34 -0500, Tim McNamara
<[email protected]> wrote:

>In article <[email protected]>,
> - Bob - <[email protected]> wrote:


>I've never heard the "plane of the top tube" being a factor before. The
>issue is usually confined to the faces of the dropout being parallel to
>each other.


Just using that as a reference for the alignment (for example, as
opposed to the "plane of the BB axle" which is at 90 degrees to the
top tube).

>If the dropout faces aren't parallel, there will be a bending force when
>the skewer clamps the axle locknuts to the dropouts. Whichever
>component is more flexible- the axle or the frame- is the one that will
>bend. I suspect- but don't know- that the axle is more flexible than
>the frame. I suppose that both probably flex a bit.


I see.That makes sense. The fork ends are strong, but might yield a
little at compression since the axle is definitely unlikely to yield
in terms of length. But, we've now set up a force trying to bend the
axle and since it's brittle, and since we put weight/road forces on
it, it breaks (aka bends) in the direction expected.

OK, next questions then:

- how critical is the alignment (as in degrees of accuracy) of the
fork ends in each plane (toe-in and camber).

- how do folks set this without a professional jig? Its seems
difficult to develop a reference point to the proper plane to set the
ends (although I can visualize it :).
 
On Wed, 21 Mar 2007 13:17:37 GMT, - Bob - <[email protected]>
wrote:

>I've seen it sugestted that the reason that rear axles bend/break with
>a 7 speed freewheel (aside from the obvious engineering shortcomings
>of the long unsupported axle segment) is that the stay fork ends are
>not properly aligned. It also seems like the alignment issue being
>suggested is that the forks ends are not properly in the plane of the
>top tube.
>
>I am having trouble imagining how this could be the issue. I could see
>that if the fork ends were not aligned vertically, making one rear
>stay higher than the other and then riding the bike in a vertical
>plane would put more stress on one side of the axle. Have I
>misunderstood the issue? Is it the second problem, not the first?


You're misundertanding the issue. The problem is when the dropouts
aer not aligned with *each other.* Tightening the axle in the frame
results in the axles being bent.
--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
 
- Bob - wrote:
> OK, next questions then:
> - how critical is the alignment (as in degrees of accuracy) of the
> fork ends in each plane (toe-in and camber).
> - how do folks set this without a professional jig? Its seems
> difficult to develop a reference point to the proper plane to set the
> ends (although I can visualize it :).


Google dropout alignment tool and you will see that there are tools to
do this.
Phil Brown
 
"- Bob -" <[email protected]> wrote in message
news:[email protected]...
>
> - how do folks set this without a professional jig? Its seems
> difficult to develop a reference point to the proper plane to set the
> ends (although I can visualize it :).
>

You can see what the real tool looks like at
http://www.parktool.com/products/detail.asp?cat=48&item=FFG-1. And they
also have a good explanation of the use of the tool at
http://www.parktool.com/repair/readhowto.asp?id=40. I routinely use the
equivalent Campagnolo tool to check frames that pass through my hands, and a
surprising number of new and sometimes quite expensive frames don't have the
dropouts completely parallel.

Nick
 
Nick Payne wrote:
> "- Bob -" <[email protected]> wrote in message
> news:[email protected]...
> >
> > - how do folks set this without a professional jig? Its seems
> > difficult to develop a reference point to the proper plane to set the
> > ends (although I can visualize it :).
> >

> You can see what the real tool looks like at
> http://www.parktool.com/products/detail.asp?cat=48&item=FFG-1. And they
> also have a good explanation of the use of the tool at
> http://www.parktool.com/repair/readhowto.asp?id=40. I routinely use the
> equivalent Campagnolo tool to check frames that pass through my hands, and a
> surprising number of new and sometimes quite expensive frames don't have the
> dropouts completely parallel.
>
> Nick


Sad but true. I have the tools-I'm a builder- use 'em, weigh 215, ride
7 speed 130mm bikes and NEVER bend an axle.
Thus endth the sermon.
Phil Brown
 
- Bob - wrote:
> I've seen it sugestted that the reason that rear axles bend/break with
> a 7 speed freewheel (aside from the obvious engineering shortcomings
> of the long unsupported axle segment) is that the stay fork ends are
> not properly aligned. It also seems like the alignment issue being
> suggested is that the forks ends are not properly in the plane of the
> top tube.


Others have said that the relevant issue is alignment of the fork ends,
or dropouts, with each other, but actually this is involved as well,
since you align the wheel itself to be parallel to the top tube.

On the other hand, the huge unsupported part of the axle, plus the fact
that the fulcrum of that lever is just inside the cone, which is
threaded, make that by far the bigger issue unless the frame has been
crashed, or shipped by USAir.

The solution to the problem is to replace the rear hub with a cassette
hub. The problem will go away.

--

David L. Johnson

"Business!" cried the Ghost. "Mankind was my business. The common
welfare was my business; charity, mercy, forbearance, and
benevolence, were, all, my business. The dealings of my trade were but
a drop of water in the comprehensive ocean of my business!" --Dickens,
 
- Bob - wrote:

> - how critical is the alignment (as in degrees of accuracy) of the
> fork ends in each plane (toe-in and camber).


Toe-in and camber? With respect to what, and in which direction? These
ideas apply to cars, not bicycles. Certainly both should be 0. The
dropouts should be absolutely parallel to each other, centered between
the midline of the frame, and parallel to the top tube and seat tube.
>
> - how do folks set this without a professional jig? Its seems
> difficult to develop a reference point to the proper plane to set the
> ends (although I can visualize it :).


I had an old frame professionally cold-set by a local frame builder. It
made no difference, riding old freewheel hubs with a wide cassette, and
with my wide butt, resulted in several broken axles. 4, I think,
including the solid one I used as a last ditch effort. Once I replaced
the hub with a cassette hub, the problem disappeared. Same frame, no
further adjustments (and, fortunately, no weight gain since).

--

David L. Johnson

"Business!" cried the Ghost. "Mankind was my business. The common
welfare was my business; charity, mercy, forbearance, and
benevolence, were, all, my business. The dealings of my trade were but
a drop of water in the comprehensive ocean of my business!" --Dickens,
 
John Forrest Tomlinson wrote:
> On Wed, 21 Mar 2007 21:58:17 -0400, "David L. Johnson"
> <[email protected]> wrote:
>
>> Others have said that the relevant issue is alignment of the fork ends,
>> or dropouts, with each other, but actually this is involved as well,
>> since you align the wheel itself to be parallel to the top tube.

>
> I've never looked at the top tube of my bike in aligning the wheels
> and find it remarkable that you seem to do that. Why?


Shouldn't the wheel be aligned with the centerline of the bike? Isn't
that the top tube? Granted, usually we just align the center of the
tire with the downtube, and one would hope that that gives the same
alignment.

--

David L. Johnson

"Business!" cried the Ghost. "Mankind was my business. The common
welfare was my business; charity, mercy, forbearance, and
benevolence, were, all, my business. The dealings of my trade were but
a drop of water in the comprehensive ocean of my business!" --Dickens,
 
On Mar 21, 8:04 pm, "David L. Johnson" <[email protected]>
wrote:
> - Bob - wrote:
> > - how critical is the alignment (as in degrees of accuracy) of the
> > fork ends in each plane (toe-in and camber).

>
> Toe-in and camber? With respect to what, and in which direction? These
> ideas apply to cars, not bicycles. Certainly both should be 0. The
> dropouts should be absolutely parallel to each other, centered between
> the midline of the frame, and parallel to the top tube and seat tube.
>
>
>
> > - how do folks set this without a professional jig? Its seems
> > difficult to develop a reference point to the proper plane to set the
> > ends (although I can visualize it :).

>
> I had an old frame professionally cold-set by a local frame builder. It
> made no difference, riding old freewheel hubs with a wide cassette, and
> with my wide butt, resulted in several broken axles. 4, I think,
> including the solid one I used as a last ditch effort. Once I replaced
> the hub with a cassette hub, the problem disappeared. Same frame, no
> further adjustments (and, fortunately, no weight gain since).
>


By "wide cassette", do you mean an 8SP *freewheel*? Were these 8SP
freewheel set-ups using a conventional axle and 130mm OLD?
 
On Wed, 21 Mar 2007 21:58:17 -0400, "David L. Johnson"
<[email protected]> wrote:

>Others have said that the relevant issue is alignment of the fork ends,
>or dropouts, with each other, but actually this is involved as well,
>since you align the wheel itself to be parallel to the top tube.


I've never looked at the top tube of my bike in aligning the wheels
and find it remarkable that you seem to do that. Why?


--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
 
if the major tubes do not lay in the same plain then we may state a
frame problem exists. the down tube is in the same plaine as the top
tube. DJ knows that and my leg is fractured. try and search for the
string alingment method: i'll try to rememebrer.
tie a string to the down tube or two strings and bring the strings
back, touch the seat tube then tie the strings off to a chair or
whatever then eyeball the dropouts measure!
now my frame is assymetrical but the rim location should be somewhat
centered.
Cheops used strings.
the concept of mangled made easy:
in practicing mechanics, measurement eyesight becomes more and mroe
accurate. what was once negligible is now an overnight hike.
so I, who is duffer, clearly see (and i'm half blind) 1/10 of a
millimetert and on a good day 1/2 of 1/10 mm. that is not a mangled
dropout observation parameter. in fact measuremnts of 1-2mm off in any
direction may not be correctable with THE TOOL as the metal may spring
back unless hit while tooled. anyway, at that level of used dropout
only the original factory jig may tell you that dropouts are out.
mangled is when you pull a clod of the street and poitn out the
dropouts and ask him if its bent. if he sez "yeah dude. thats bent"
then its bent, no problem.
 
- Bob - wrote:
> I've seen it sugestted that the reason that rear axles bend/break with
> a 7 speed freewheel (aside from the obvious engineering shortcomings
> of the long unsupported axle segment) is that the stay fork ends are
> not properly aligned. It also seems like the alignment issue being
> suggested is that the forks ends are not properly in the plane of the
> top tube.
>
> I am having trouble imagining how this could be the issue. I could see
> that if the fork ends were not aligned vertically, making one rear
> stay higher than the other and then riding the bike in a vertical
> plane would put more stress on one side of the axle. Have I
> misunderstood the issue? Is it the second problem, not the first?


With four and five speed freewheels there's a slight overhang and broken
axles are nearly always at the right side cone. With 6, 7, 8 that is a
severe and chronic problem as the extended axle beyond the right cone is
longer. Add wheel tension issues ( aka 'dish') and you have a series of
interrelated problems with all these formats.

Spreading a 120 bike to 125, 126, 128, 130 without checking the ends
_or_ replacing a broken axle without checking alignment can leave the
frame with ends not parallel. In that situation, clamping the skewer
closed bends the axle making axle problems worse. This is above any
obvious build errors which you refer to.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
>> - Bob - <[email protected]> wrote:
>> I've never heard the "plane of the top tube" being a factor before. The
>> issue is usually confined to the faces of the dropout being parallel to
>> each other.


>> - Bob - <[email protected]> wrote:

> Just using that as a reference for the alignment (for example, as
> opposed to the "plane of the BB axle" which is at 90 degrees to the
> top tube).


> Tim McNamara <[email protected]> wrote:
>> If the dropout faces aren't parallel, there will be a bending force when
>> the skewer clamps the axle locknuts to the dropouts. Whichever
>> component is more flexible- the axle or the frame- is the one that will
>> bend. I suspect- but don't know- that the axle is more flexible than
>> the frame. I suppose that both probably flex a bit.


>> - Bob - <[email protected]> wrote:

> I see.That makes sense. The fork ends are strong, but might yield a
> little at compression since the axle is definitely unlikely to yield
> in terms of length. But, we've now set up a force trying to bend the
> axle and since it's brittle, and since we put weight/road forces on
> it, it breaks (aka bends) in the direction expected.
> OK, next questions then:
> - how critical is the alignment (as in degrees of accuracy) of the
> fork ends in each plane (toe-in and camber).
> - how do folks set this without a professional jig? Its seems
> difficult to develop a reference point to the proper plane to set the
> ends (although I can visualize it :).


Bottom photo here:
http://www.yellowjersey.org/twist.html

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
On Wed, 21 Mar 2007 22:27:38 -0400, "David L. Johnson"
<[email protected]> wrote:

>Shouldn't the wheel be aligned with the centerline of the bike? Isn't
>that the top tube?


Sure, but that's just happens to work. No one looks at the top tube
to align wheels - or at least I've never heard fo such a thing. Do
you?

And if something else is outof whack on the bike -- say, the rear
triangle is a little off, or dish is off, aligning by the top tube
sems like it would make the axle more likely to bend.

>Granted, usually we just align the center of the
>tire with the downtube,


Do you really do this? I've never looked at the downtube when
installing a wheel. If anything, I look at distance the tires are
from the chainstays.

>and one would hope that that gives the same
>alignment.


Hope, sure. But do you actually look at the tubes you mention?

--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
 
I used to break axles all the time, with 5sp freewheel, in the 70s, just
inside one of the cones (don't remember which, left or right). It turns
out you can ride a bike with a broken rear axle almost indefinitely,
once the entire width of New Jersey to get home. One good trick
is to keep the tire wet where it rubs the frame; otherwise you get
an instability where if you pedal too hard the tire hits the frame,
and that raises the drag so you have to pedal harder yet, and thus
there's a hard limit to how hard you can pedal when the occasion
demands. With a wet tire, it's more of a soft limit.

I haven't broken an axle since going to Huffy MTB's, even with heavy
loads. I think it's more that the wide tires soften the axle-flexing
shocks than that axles have improved. So that's since 1988 or so.
--
Ron Hardin
[email protected]

On the internet, nobody knows you're a jerk.
 
On Thu, 22 Mar 2007 12:47:21 GMT, Ron Hardin <[email protected]>
wrote:
> It turns
> out you can ride a bike with a broken rear
> axle almost indefinitely,


I rode a bike with a broken axle (Campagnolo freewheel hubs, 125mm
spacing) for possibly weeks and didn't even know it was broken -- the
quick release was on tight and it was only when I removed the wheel
that I noticed anything. The wheel didn't wobble much at all before I
took it off.

--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
 
right. with the string method, tubes are wrap shimed out with same
thickness material, rubber sheet used for tire repair or cardboard so
a square, i use castoff plexiglass or carbonate but cardboard is an
accurate 90 degree factory corner, is placeable along the stringline,
placed into the dropout area, atop wood or book blocks for stabile
eyeballing of the dropouts alignment(s)