Hot Resetting Rear Triangle

Hot Resetting Rear Triangle

Post by Troy A. Courtne » Tue, 31 Aug 1999 04:00:00


Jobst,

You have quote the following as my post, but it was not. The paragraphs you
show as mine were posted by others in response to my post.

The correct poster that these words are clearly attributable to (Richard
Watson) and others, not me. Please see my original response posting rather
than one that has been edited several times.

In my posting I clearly stated that stays should always be done one at a
time with the bottom bracket locked down and support placed at the bridge
junctures to prevent the bridges from being separated from the stays.

If I used the methods other than what I stated and what you espouse, then I
should just sell all my tools and quit repairing frames and quit building
customs frames...because I surely would not be qualified to be doing either.

To all reading...please watch you editing of posts as you can easily effect
the reputation of others.

Regards,
Troy

Quote:

>Troy A. Courtney writes:

>> What kind of spreading tools are used to ensure that the spreading
>> is symmetrical? I'm aware of the simple method using a pair of nuts
>> on a threaded rod which is claimed to do a reasonable job.

>You'll have to explain that one to me.  What makes the two sides of
>the frame spread equilaterally?  The only way I know of without
>fixtures is to bend one side at a time, exactly half of the width
>required.  This is not so much spreading as bending one side at a time
>a desired amount.  After that you use the standard Campagnolo dropout
>aligning gauges that are made to be used on cold steel.

>> Actually, this is not the best method, because it leaves the dropout
>> not parallel, the bending occurs at the bridge (which may or may not
>> be a problem) and it doesn't assure symmetry in any case (yielding is
>> not that predictable).

>That is only desirable.  The farther up the bend occurs the smaller
>the material deformation and the easier it its to bend.  Symmetry does
>not come naturally, there being no two frame sides that are
>identically rigid.  You cannot rely on symmetry of the frame to
>produce a symmetrical spread,

>> The tools I'd use for a job like this is a lever bar with a hook in
>> it. A 2x4 works fine. The hook is the lag-threaded hardware-store
>> variety, with several layers of duct tape to prevent scratching...

>The rest of this procedure sounds like bad news to me.  Don't do that!
>Are you sure that you are speaking from experience?  This all sound so
>theoretical.  How many frames have you done this way?  Ouch!



 
 
 

Hot Resetting Rear Triangle

Post by Jobst Bran » Tue, 31 Aug 1999 04:00:00

Quote:
Troy Courtney writes:
> In my posting I clearly stated that stays should always be done one
> at a time with the bottom bracket locked down and support placed at
> the bridge junctures to prevent the bridges from being separated
> from the stays.
> If I used the methods other than what I stated and what you espouse,
> then I should just sell all my tools and quit repairing frames and
> quit building customs frames...because I surely would not be
> qualified to be doing either.

It's not that complicated and it can be done accurately without a lot
of tools other than a caliper able to reach 130mm and dropout aligning
levers, typically ones like the Campagnolo set the clamps into the
dropouts.

Placing ones foot neat the root of one chainstay, frame laying on its
side, manually bend the upper rear triangle until half the distance is
accurately achieved.  Turn the frame over and repeat so that the full
distance is achieved.  Use the dropout aligners to make the dropouts
parallel.

This assumes the frame was initially on center.  It it was not, then
this can be determined by the head tube to rear dropout string
measurement and sighting over the head and seat tube to see if they
are parallel.  A crocked frame that has several misalignments is ha
headache because one error invades the other so they are not easily
individually corrected.  But then that was not the intent of this
discussion, only hoe to spread the rear end of the frame.



 
 
 

Hot Resetting Rear Triangle

Post by Rick Knowla » Tue, 31 Aug 1999 04:00:00

Quote:

> Troy Courtney writes:

> > In my posting I clearly stated that stays should always be done one
> > at a time with the bottom bracket locked down and support placed at
> > the bridge junctures to prevent the bridges from being separated
> > from the stays.

> > If I used the methods other than what I stated and what you espouse,
> > then I should just sell all my tools and quit repairing frames and
> > quit building customs frames...because I surely would not be
> > qualified to be doing either.

> It's not that complicated and it can be done accurately without a lot
> of tools other than a caliper able to reach 130mm and dropout aligning
> levers, typically ones like the Campagnolo set the clamps into the
> dropouts.

> Placing ones foot neat the root of one chainstay, frame laying on its
> side, manually bend the upper rear triangle until half the distance is
> accurately achieved.  Turn the frame over and repeat so that the full
> distance is achieved.  Use the dropout aligners to make the dropouts
> parallel.

snip

Is it possible that this procedure may result in a small radius bend with
accompanying high stresses?

My LBS is willing to try cold setting my frame but has cautioned that
frames sometimes fail during this process (a risk I'm willing to take
provided the LBS exercises due dilligence), and several have developed
cracks that rendered them useless within a few months.  I don't know
whether this is evidence of shortcomings in their skill, in the whole
enterprise of cold resetting, or in their willingness to help me avoid
buying a new frame.

I have watched people bend steel tubing in fabricating shops, and they
usually use dies that prevent the tubes from crimping and spread the bend
over a longer radius.  Has anyone tried this?  Am I being overly cautious?

 
 
 

Hot Resetting Rear Triangle

Post by Jobst Bran » Tue, 31 Aug 1999 04:00:00

Quote:
Rick Knowlan writes:
>> It's not that complicated and it can be done accurately without a lot
>> of tools other than a caliper able to reach 130mm and dropout aligning
>> levers, typically ones like the Campagnolo set the clamps into the
>> dropouts.
>> Placing ones foot neat the root of one chainstay, frame laying on its
>> side, manually bend the upper rear triangle until half the distance is
>> accurately achieved.  Turn the frame over and repeat so that the full
>> distance is achieved.  Use the dropout aligners to make the dropouts
>> parallel.
> Is it possible that this procedure may result in a small radius bend with
> accompanying high stresses?

No more so that other methods one might use.  The angles involved here
are so small that you can only see the deviation if you sight along
the tube.  The way you describe it, it sounds like a huge bend.

Quote:
> My LBS is willing to try cold setting my frame but has cautioned
> that frames sometimes fail during this process (a risk I'm willing
> to take provided the LBS exercises due diligence), and several have
> developed cracks that rendered them useless within a few months.  I
> don't know whether this is evidence of shortcomings in their skill,
> in the whole enterprise of cold resetting, or in their willingness
> to help me avoid buying a new frame.

They're partially right about that.  Some frames have cold joints with
no brass in them, on the verge of breaking.  I think you'll be better
off knowing about this than continuing to ride around with a crack
that's happening.  Some of these have only an external meniscus of
brass and nothing in the joint, something a nice paint job will cover.

Quote:
> I have watched people bend steel tubing in fabricating shops, and
> they usually use dies that prevent the tubes from crimping and
> spread the bend over a longer radius.  Has anyone tried this?  Am I
> being overly cautious?

That's true, but they aren't bending the tube 1/2 degree or less as is
required for this adjustment.  Again, this is a subject that is blown
out of proportion by two orders of magnitude (100x), just like the
rotating mass BS that assumes enormously exaggerated accelerations.
These effects exist but do not apply here.


 
 
 

Hot Resetting Rear Triangle

Post by Rick Knowla » Wed, 01 Sep 1999 04:00:00

snip

Quote:
> >> Placing ones foot neat the root of one chainstay, frame laying on its
> >> side, manually bend the upper rear triangle until half the distance is
> >> accurately achieved.  Turn the frame over and repeat so that the full
> >> distance is achieved.  Use the dropout aligners to make the dropouts
> >> parallel.

> > Is it possible that this procedure may result in a small radius bend with
> > accompanying high stresses?

> No more so that other methods one might use.  The angles involved here
> are so small that you can only see the deviation if you sight along
> the tube.  The way you describe it, it sounds like a huge bend.

> > My LBS is willing to try cold setting my frame but has cautioned
> > that frames sometimes fail during this process (a risk I'm willing
> > to take provided the LBS exercises due diligence), and several have
> > developed cracks that rendered them useless within a few months.  I
> > don't know whether this is evidence of shortcomings in their skill,
> > in the whole enterprise of cold resetting, or in their willingness
> > to help me avoid buying a new frame.

> They're partially right about that.  Some frames have cold joints with
> no brass in them, on the verge of breaking.  I think you'll be better
> off knowing about this than continuing to ride around with a crack
> that's happening.  Some of these have only an external meniscus of
> brass and nothing in the joint, something a nice paint job will cover.

> > I have watched people bend steel tubing in fabricating shops, and
> > they usually use dies that prevent the tubes from crimping and
> > spread the bend over a longer radius.  Has anyone tried this?  Am I
> > being overly cautious?

> That's true, but they aren't bending the tube 1/2 degree or less as is
> required for this adjustment.  Again, this is a subject that is blown
> out of proportion by two orders of magnitude (100x), just like the
> rotating mass BS that assumes enormously exaggerated accelerations.
> These effects exist but do not apply here.

Thanks to Jobst and other contributors on this thread.  I have learned a lot
from the discussion.

I am going to proceed with a cold reset at the LBS, and if the frame comes
through intact, have it media blasted and repainted.  I'll check very closely
for cracks after the media blasting, maybe even try a little dye penetrant to
make them more visible.