How to cold-set rear triangle to wider dropout width?

How to cold-set rear triangle to wider dropout width?

Post by Michael R. Vol » Mon, 30 Nov 1992 11:11:35


How do I cold-set the rear triangle of a Reynolds 531 frame from 120mm to
126mm rear dropout width?

I extended my 120mm Shimano rear hub to 126mm with a new axle. I re-dished
the rear wheel for this width. I now have SIS-compatible derailleur, chain,
levers, and freewheel.

I was going to have the local frame builder cold-set the rear triangle for
this hub width. But he's apparently away for a few days. i know lots of
folks used to cold-set rear triangles from 120mm to 126mm. But how is it done?

I tried to improvise a simple jack using a carriage bolt and a nut across
the rear dropouts. It worked admirably to spread the dropouts to 150mm.
But when I took the bolt out, the rear dropout width always sprung back to
its original 120mm (good tubing, eh).

(The frame is a mid-1970's Mercian Olympic of Reynolds 531, lugged and probably
hearth-brazed.)

I sense that one may have to spread the chainstays closer to the bottom
bracket, where they are less springy. But how do I do this? Do I need two
people?

Any help would be appreciated.

--
Michael Volow, Psychiatry, Durham VA Med Center, Durham NC 27712

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by John L.Yoo » Tue, 01 Dec 1992 09:48:24

Quote:

>>How do I cold-set the rear triangle of a Reynolds 531 frame from 120mm to
>>126mm rear dropout width?
>Not for the faint of heart, but I believe it's done with a heavy
>*** mallet and a ruler.  Whack on both sides equally until the
>ruler shows you've succeeded.  I think you're right in that the
>whacking needs to be done closer to the bottom bracket than the
>rear dropouts.  Good luck.
>    =cw=

the only tool that I have seen that is specific to this task is a rather
long wooden bar with a curved notch at one end, handle at the other.  The
notch fits around the seat tube and is effectively a pivot point for a
lever that exerts force on the dropout, pushing it out when you pull on
the handle.  You have to pull past the point that you actually want the
dropout set at.  The amount of work to do this varies from tubeset to
tubeset and it is very easy to mess up a frame when doing this.  It's
best to leave this job to someone who has some experience at it.

I've haven't actually done this for quite a few years and a better
technique might have come around.  Anyone know of any?

--
John Yoon (std. disclaimer)   *           Deslock.. Deslock Deslock!



 
 
 

How to cold-set rear triangle to wider dropout width?

Post by John Re » Sat, 05 Dec 1992 14:44:38


Quote:

>>>How do I cold-set the rear triangle of a Reynolds 531 frame from 120mm to
>>>126mm rear dropout width?
>>Not for the faint of heart, but I believe it's done with a heavy
>>*** mallet and a ruler.  Whack on both sides equally until the
>>ruler shows you've succeeded.  I think you're right in that the
>>whacking needs to be done closer to the bottom bracket than the
>>rear dropouts.  Good luck.
>>        =cw=
>the only tool that I have seen that is specific to this task is a rather
>long wooden bar with a curved notch at one end, handle at the other.  The
>notch fits around the seat tube and is effectively a pivot point for a
>lever that exerts force on the dropout, pushing it out when you pull on
>the handle.  You have to pull past the point that you actually want the
>dropout set at.  The amount of work to do this varies from tubeset to
>tubeset and it is very easy to mess up a frame when doing this.  It's
>best to leave this job to someone who has some experience at it.
>I've haven't actually done this for quite a few years and a better
>technique might have come around.  Anyone know of any?

Given that the tubes in your rear triangle have wall thicknesses of around
0.5mm, and you propose to move each 3mm out of alignment, and there is a
piece of tubing joining these  two stays rigidly together, you should
consider that you are going to introduce permanent creases into the stays
(assuming that they don't actually crack). This will dramatically weaken
the structure, assuming that it doesn't actually fail when you are trying
this. Always remember that if your frame breaks while you are riding it, it
could be your neck that is on the line.

When I lived in Britain, and rode in races all bikes had to be checked
before being allowed to start. The number one no-no was a frame with dented
tubes. Your frame as modified would undoubtedly be rejected.

However, there is a solution to your problem that is safe and not
replacement of your frame in toto. Any competent frame builder can replace
frame tubes. I should talk to one about replacement of your rear triangle.
It should be quick and cheap, as almost no new tubes are needed. It may
also allow you to survive the experience.....

John Reid
--

CP Software Export Pty Ltd,                 Phone  : +61 3 823 0222
19 Cato Street, Hawthorn 3123 Australia     Fax    : +61 3 824 8068
ACN 006 640 133

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Wayne I » Sun, 06 Dec 1992 05:04:46

Quote:



>>>>How do I cold-set the rear triangle of a Reynolds 531 frame from 120mm to
>>>>126mm rear dropout width?
>[John Reid says don't cold set it but ...]
>However, there is a solution to your problem that is safe and not
>replacement of your frame in toto. Any competent frame builder can replace
>frame tubes. I should talk to one about replacement of your rear triangle.
>It should be quick and cheap, as almost no new tubes are needed. It may
>also allow you to survive the experience.....

This is rather drastic -- replacing the entire rear triangle.  At the
*most* you would have to replace the brake bridge and the chainstay
bridge with *slightly* longer ones.

However, I question John's claim that coldsetting would introduce
wrinkles or significantly weaken the tubes.  By my back-of-the-envelope
estimations, if you assume the deformation is located at a point source
(an unreasonable assumption I might add) then the walls of the tube
must stretch (and fold to accomodate) approximately 0.0005 inches or
about a hundreth of a mm.  I doubt that this would weaken the tubes,
let alone be visible to the eye.  In actuality, the deformation would
be distributed over some distance, thereby reducing the impact of the
coldset even further.


ps: re-brazing your tubes would probably weaken the material more than
a judicious coldset.

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Bruce Krueg » Tue, 08 Dec 1992 06:09:34

Quote:

>Given that the tubes in your rear triangle have wall thicknesses of around
>0.5mm, and you propose to move each 3mm out of alignment, and there is a
>piece of tubing joining these  two stays rigidly together, you should
>consider that you are going to introduce permanent creases into the stays
>(assuming that they don't actually crack). This will dramatically weaken
>the structure, assuming that it doesn't actually fail when you are trying

   *******
   ...oh, bunk.  john, are your eyes brown, or what?   have you *ever* done
   the above, or heard of anyone having a problem with "creasing" a chain-
   stay (they're more on the order of 0.6-1.2mm wall thickness, btw), or
   are you coming up with this as a thought exercise??  while you're at it,
   you might figure out the angular bend that will result in
   a deflection of 3mm in a tube 300+mm long.   I'll give you a hint: it
   approaches nil.  clearly, you don't know what you're talking about, and
   despite the fact that net "wisdom" is often worth exactly what you pay
   for it, it annoys me when folks with a little knowledge purport to being
   experts in the field, and their word is Fact, and Woe to He Who Disregards
   those Words.  like I said, bunk.

Quote:
>this. Always remember that if your frame breaks while you are riding it, it
>could be your neck that is on the line.

  *ahem*  like I said...

Quote:
>When I lived in Britain, and rode in races all bikes had to be checked
>before being allowed to start. The number one no-no was a frame with dented
>tubes. Your frame as modified would undoubtedly be rejected.

   *******
   if it was properly re-set, they wouldn't even be able to detect it, much
   less reject it.  "dents??"  again, have you ever done this?  I have, and
   unless you're talking about a heat-treated aluminum frame or some kind
   of composite, you're not going to induce dents anywhere, even if you're
   re-aligning a frame that's bent an order of magnitude more than
   what you're proposing.  

Quote:
>However, there is a solution to your problem that is safe and not
>replacement of your frame in toto. Any competent frame builder can replace
>frame tubes. I should talk to one about replacement of your rear triangle.
>It should be quick and cheap, as almost no new tubes are needed. It may

            ***^!!!!!!!!!!!!^***  ..yeah, right. do you have any idea what
            kind of project you're proposing??  I suppose the paint job that's
            going to be necessitated is going to be 'quick and cheap,' too.

            I'm not saying that your average schmoe-off-the-street can do
            this correctly (don't try this at home, folks) (though, on the
            balance, neither do you have to be a brain surgeon..), but with
            some practice, it's really pretty easy.  it's just a matter of
            getting a 'feel' for how much force to exert, just as straight-
            ening potatoe-chipped wheels is possible (not to mention fun,
            and profitable) if you know what you're doing.  I do.

            bruce "frames stretched while you wait" krueger

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Richard Engelbrecht-Wigga » Tue, 08 Dec 1992 12:35:35


Quote:

>   unless you're talking about a heat-treated aluminum frame or some kind
>   of composite, you're not going to induce dents anywhere, even if you're
>   re-aligning a frame that's bent an order of magnitude more than
>   what you're proposing.

Twelve years ago, I bought a used Exxon Graftek (composite) frame.  It
was spaced for five speeds (Yes, that dates me, doesn't it:-))  I wanted
six, so I just pulled the dropouts apart slightly just long enough to
pop in a wheel with a six speed freewheel.  About 5000 miles later, I
did have a problem...the rear brake bridge came unglued on one side;
apparently spreading the dropouts without bending the seat stays had
resulted in tension across the bridge.  I replaced the bridge by a
home machined piece of aluminum bolted in place.  I still use the bike.
(BTW, I went the composite route initially because my sweat makes
anything steel rust in a hurry.  Unfortunately, the lugs on the Graftek
rust :-(.)

..Richard E+17

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Michael R. Vol » Tue, 08 Dec 1992 22:58:57

Quote:



>>   unless you're talking about a heat-treated aluminum frame or some kind
>>   of composite, you're not going to induce dents anywhere, even if you're
>>   re-aligning a frame that's bent an order of magnitude more than
>>   what you're proposing.

>Twelve years ago, I bought a used Exxon Graftek (composite) frame.  It
>was spaced for five speeds (Yes, that dates me, doesn't it:-))  I wanted
>six, so I just pulled the dropouts apart slightly just long enough to
>pop in a wheel with a six speed freewheel.  About 5000 miles later, I
>did have a problem...the rear brake bridge came unglued on one side;
>apparently spreading the dropouts without bending the seat stays had
>resulted in tension across the bridge.  I replaced the bridge by a
>home machined piece of aluminum bolted in place.  I still use the bike.
>(BTW, I went the composite route initially because my sweat makes
>anything steel rust in a hurry.  Unfortunately, the lugs on the Graftek
>rust :-(.)

>..Richard E+17

Hell, the Graftek had problems with its adhesive even without trying
to change dropout widths. In the late 1970's a friend had problems with
a couple of Graftek frames.
--
Michael Volow, Psychiatry, Durham VA Med Center, Durham NC 27712

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Richard Fou » Tue, 08 Dec 1992 23:11:21

Quote:
>Given that the tubes in your rear triangle have wall thicknesses of around
>0.5mm, and you propose to move each 3mm out of alignment, and there is a
>piece of tubing joining these  two stays rigidly together, you should
>consider that you are going to introduce permanent creases into the stays
>(assuming that they don't actually crack). This will dramatically weaken
>the structure, assuming that it doesn't actually fail when you are trying
>this. Always remember that if your frame breaks while you are riding it, it
>could be your neck that is on the line.

Free advice is sometimes worth less than you pay for it.

People who know little or nothing about a subject probably shouldn't
give advice about it.  I called several local bike shops and all
said they could perform this type of bending with no problem.  Accuracy
is the harder part, not simply bending without damage.

Quote:
>When I lived in Britain, and rode in races all bikes had to be checked
>before being allowed to start. The number one no-no was a frame with dented
>tubes. Your frame as modified would undoubtedly be rejected.

This is absurd.  Unless he uses a sledge hammer to do the bending, no one
will likely be able to tell.  What dents?  This is a minor amount of
bending we're talking about.  You can actually fit a wheel in there
just by spreading the stays with your hands, (the bending is to relieve
the stress).

Quote:
>However, there is a solution to your problem that is safe and not
>replacement of your frame in toto. Any competent frame builder can replace
>frame tubes. I should talk to one about replacement of your rear triangle.
>It should be quick and cheap, as almost no new tubes are needed. It may
>also allow you to survive the experience.....

This is easily more problematic than the simple bending being discussed,
and much more expensive.

--

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Art LaVal » Wed, 09 Dec 1992 07:23:14

Quote:

> Given that the tubes in your rear triangle have wall thicknesses of around
> 0.5mm, and you propose to move each 3mm out of alignment, and there is a
> piece of tubing joining these  two stays rigidly together, you should
> consider that you are going to introduce permanent creases into the stays
> (assuming that they don't actually crack). This will dramatically weaken
> the structure, assuming that it doesn't actually fail when you are trying
> this. Always remember that if your frame breaks while you are riding it, it
> could be your neck that is on the line.

> When I lived in Britain, and rode in races all bikes had to be checked
> before being allowed to start. The number one no-no was a frame with dented
> tubes. Your frame as modified would undoubtedly be rejected.

Hmmm! This is the first time I've heard this. Although a "worst case scenario"
might cause this type of failure, I believe this is the exception and not the
rule.

Cold setting or springing the rear triangle as described in this thread has been
commonplace for many years. In fact a number of "competent" frame builders and
"racing mechanics" use this method - and they seem comfortable with it.

If you don't believe me then pick up a copy of "Bicycle Mechanics in Workshop
and Competition", Steve Snowling and Ken Evans, Leisure Press - 1986. In this
book the authors describe how to spring a frame (Chapter 7 - pg 82) in order
to increase rear end width.

Quote:
> However, there is a solution to your problem that is safe and not
> replacement of your frame in toto. Any competent frame builder can replace
> frame tubes. I should talk to one about replacement of your rear triangle.
> It should be quick and cheap, as almost no new tubes are needed. It may
> also allow you to survive the experience.....

> John Reid

"Quick and Cheap" ? If it's a lugged frame, just sweating out the old tubes,
reinstalling them (brazed or soldered), finishing them off (joint filing etc.),
prepping the frame, repainting it, new decals, clearcoating it, etc. etc. -
will cost an amount probably greater than the original purchase price of a
custom frame of a few years ago...Unless you've got a frame in the $1000 (US)
price range, you're going to come pretty close to surpassing the original cost
of the frame with this kind of work.
 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Bob Bun » Wed, 09 Dec 1992 04:42:31

It's worth noting that frame builders bend the frames to get them
in alignment in the first place.  They often have to bend them far
more than 3mm.  If this is a problem, then most of us are riding
defective bicycles.  When a frame is brought up to brazing temperature,
the steel is actually quite soft and the frame can distort in various
unpredictable ways as it is cooling.  The way the frame builder takes
care of this is to put the whole thing in a jig (alignment table)
and bend away until things are lined up.  It works for them and
it can work for you.

Bob Bundy

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by John Thomps » Sat, 12 Dec 1992 03:04:47

Re: coldsetting rear triangle

The best way I've found to do this is to clamp the bottom bracket\
shell in a vice (_sans_ cups, of course) and simply pull the stays out to where
they need to be.  The trick is doing it symmetrically; this is best developed
with practice, but few of us have enough frames to practice on :-).
Do the best you can, then check spacing and centering.  Once you get the
spacing right, you can sometimes move both stays to center by putting
an axle or hub in the driopouts and pulling like h***.  Good luck!

--



 
 
 

How to cold-set rear triangle to wider dropout width?

Post by david.d.therri » Sat, 12 Dec 1992 04:28:45

Quote:

>Re: coldsetting rear triangle

>The best way I've found to do this is to clamp the bottom bracket\
>shell in a vice (_sans_ cups, of course) and simply pull the stays out to where
>they need to be.  The trick is doing it symmetrically; this is best developed
>with practice, but few of us have enough frames to practice on :-).
>Do the best you can, then check spacing and centering.  Once you get the
>spacing right, you can sometimes move both stays to center by putting
>an axle or hub in the driopouts and pulling like h***.  Good luck!

>--




I've never tried this before, but I am considering upgrading my road bike
to 6 or 7 speeds.  The idea of bolting in an axle and then cold setting is
interesting.  I am thinking about bolting on an appropiately spaced axle
and then clamping the BB in a vice as suggested.  I would then move both
stays to one side (cold set them off center) and then cold set them
back to being centered.  This should result in a new spacing somewhat
equal to the axle that is bolted in since I am forcing the material
into the plastic flow region.  The advantage is that I get the spacing
right the first time.  

Comments?

Dave

 
 
 

How to cold-set rear triangle to wider dropout width?

Post by Michael Batcheld » Sat, 12 Dec 1992 08:04:57

|> It's worth noting that frame builders bend the frames to get them
|> in alignment in the first place.  They often have to bend them far
|> more than 3mm.  If this is a problem, then most of us are riding
|> defective bicycles.  When a frame is brought up to brazing temperature,
|> the steel is actually quite soft and the frame can distort in various
|> unpredictable ways as it is cooling.  The way the frame builder takes
|> care of this is to put the whole thing in a jig (alignment table)
|> and bend away until things are lined up.  It works for them and
|> it can work for you.
|>
|> Bob Bundy

Not just frames get bent into the desired shapes.  Frame builders
(cro-mo ones, anyway) bend the forks to get the desired rakes.  This
sounds awful, but the bending actually hardens the metal in the area
where the metal must expand.  You can test this phenomenon: get a small
piece of wire and bend it around something several times.  Each time
(up to a point) it should be more difficult to bend the wire.  This
phenomenon does have its limits, but under "reasonable" loads it works.

Michael Batchelder