Failing Fork?

I have a 80's vintage Raleigh. Reynolds 531c, built in England,
standard (not Raleigh special) threading. Reddish orange paint with
black rear triangle and black fork.

It has a sloping fork crown that inserts into the fork tubes (rather
than integral lugs that are on the outside of the tubes). Very graceful
fork arrangement.

However, today I noticed on one fork tube, the paint was cracked in a
perfect line across the inside of the top of the tube (where it meets
the crown). Normally one cannot tell where the tube ends and the crown
begins. It is definitely not fatigue of the tube... too straight and
too high.

Should I be concerned that the braze joint, or the crown itself, is failing?

David

today i noticed a crack in my fork, along the brazing line, of my
integral sloping-crown fork.

I think this can happen even if the fork is fine. the fork will flex
and the brazing may not have covered the joint evenly all the way to
the surface in that area. In that case, both surfaces of metal could
move in different directions during flexion and disturb the paint.

in addition, something as small as different coefficients of
expansion, over a period of years, could also disturb the paint.

- Don Gillies
San Diego, CA

David N. Makinson wrote:
I have a 80's vintage Raleigh. Reynolds 531c, built in England,
standard (not Raleigh special) threading. Reddish orange paint with
black rear triangle and black fork.

It has a sloping fork crown that inserts into the fork tubes (rather
than integral lugs that are on the outside of the tubes). Very graceful
fork arrangement.

However, today I noticed on one fork tube, the paint was cracked in a
perfect line across the inside of the top of the tube (where it meets
the crown). Normally one cannot tell where the tube ends and the crown
begins. It is definitely not fatigue of the tube... too straight and
too high.

Should I be concerned that the braze joint, or the crown itself, is
failing?

David

yes. take it to a frame repairer for a check-up, just to be sure.

by the sound of it, it's a failing braze joint.

Donald Gillies wrote:
snip
in addition, something as small as different coefficients of
expansion, over a period of years, could also disturb the paint.

if it were coated in some esoteric kind of glass, that may theoreticaly
be possible, but a paint, even enamel, is /way/ more flexible than the
truly miniscule difference in expansion coefficient of these materials.

jim beam wrote:
Donald Gillies wrote:
snip
in addition, something as small as different coefficients of
expansion, over a period of years, could also disturb the paint.

if it were coated in some esoteric kind of glass, that may theoreticaly
be possible, but a paint, even enamel, is /way/ more flexible than the
truly miniscule difference in expansion coefficient of these materials.

Sorry, paint cracking is pretty common. But I'd scrape the paint away
and see if the joint is cracked anyway. A fork failure is pretty
painful.
Phil Bbrown

jim beam wrote:

yes. take it to a frame repairer for a check-up, just to be sure.

by the sound of it, it's a failing braze joint.

Or a cracked fork blade, as there is a severe stress riser at this
point. Jobst's views on internally lugged fork crowns are well known.

(Donald Gillies) writes:

today i noticed a crack in my fork, along the brazing line, of my
integral sloping-crown fork.

I should have said that you should have a local frame builder check
the fork for cracks (or mail it off, only costs $8 each way to ship it
- far cheaper than a hospital visit.)

In the past 3 days I found that some cracks in a seatstay cap, that
had decided to make a 90 degree turn and start traveling through a
frame tube, on another bike of mine. Even if the framebuilder ok's
it, you may want to check it periodically to make sure it isn't
growing.

- Don Gillies
San Diego, CA

Dear David, & list

I know this fork and crown setup. Very graceful! I would be concerned
about a braze joint failing. It could have been a cold joint, easy to
do in a factory setting, hard for an inspector to spot. But paint
cracks like that are usually bad news.

I would send the fork off to a really good framebuilder, someone like
Richard Sachs who builds his own forks. If it were I, I would have the
fork repaired. The fashioon today is flat crown, retro-lookling forks.
I like those streamlined, full-sloping crown forks!

good luck

jn

"Thursday"

On Tue, 27 Sep 2005 18:44:28 +0100, Zog The Undeniable
wrote:
jim beam wrote:

yes. take it to a frame repairer for a check-up, just to be sure.

by the sound of it, it's a failing braze joint.

Or a cracked fork blade, as there is a severe stress riser at this
point. Jobst's views on internally lugged fork crowns are well known.

Wasn't the crack described by OP at the top of the fork blade, and isn't
that stress riser at the end of the internal crown a little bit further
down the blade?

Jasper

Jasper Janssen wrote:
On Tue, 27 Sep 2005 18:44:28 +0100, Zog The Undeniable
wrote:

jim beam wrote:


yes. take it to a frame repairer for a check-up, just to be sure.

by the sound of it, it's a failing braze joint.


Or a cracked fork blade, as there is a severe stress riser at this
point. Jobst's views on internally lugged fork crowns are well known.


Wasn't the crack described by OP at the top of the fork blade, and isn't
that stress riser at the end of the internal crown a little bit further
down the blade?

Jasper

I talked with a local frame builder. She is figuring the crown may be
broken within the tube. She recommends a replacemnent fork, which is OK
by me and that is what I am going to do.

David