Can broken seatstay be brazed by a autobody worker?



S

Sir Ridesalot

Guest
Hi there.

I was prepping this Norco touring frame for a friend prior to painting
it.

When I cleaned the gunk off the seatstay I discovered the left one is
broken very close to where it joins the seat tube.

There aren't any bicycle frame builders or bicycle shops in our area
that do this kind of repair.

Therefore we wonder if experts here think a competent auto body
repairman could braze/weld such a break in a manner that would last.

Here is a link to an image of the break.

http://www.flickr.com/photos/73832500[email protected]/209509671/

My friend and I thank you in advance for your expert advice.

Peter
 
L

Leo Lichtman

Guest
"Sir Ridesalot" wrote: (clip) Therefore we wonder if experts here think a
competent auto body repairman could braze/weld such a break in a manner that
would last. (clip)
^^^^^^^^^^^^^^^
Well, it's either fix it or throw away the frame. Do I see this correctly?
The crack runs right through the letter "N." The problem is that the part
that is still stuck to the seat tube is what is going to carry the load, and
you have to get a connection from the other piece through the thin fractured
end. So here is how I would do it:

File off the entire surface where the name "Norco" is embossed, so it is
smooth, flat and clean. Make an oval patch the same size and shape as the
oval, and silver solder it on. Maybe make the patch a little oversize, and
hammer it down to slightly wrap over the broken tube, and make sure
everything is really clean and well fluxed, so you get good flow of the
filler into every crevice.

If you really want to play it safe, you should leave it unpainted, and watch
it for a while, to make sure no new cracks start. Maybe spray it with some
clear finish to protect against rust until you are satisfied that it is safe
to paint it.
 
J

jim beam

Guest
Sir Ridesalot wrote:
> Hi there.
>
> I was prepping this Norco touring frame for a friend prior to painting
> it.
>
> When I cleaned the gunk off the seatstay I discovered the left one is
> broken very close to where it joins the seat tube.
>
> There aren't any bicycle frame builders or bicycle shops in our area
> that do this kind of repair.
>
> Therefore we wonder if experts here think a competent auto body
> repairman could braze/weld such a break in a manner that would last.
>
> Here is a link to an image of the break.
>
> http://www.flickr.com/photos/[email protected]/209509671/
>
> My friend and I thank you in advance for your expert advice.
>
> Peter
>

anyone that can braze can "repair" that frame. but the real question
is, why bother? it's not that great a frame, and if you're paying
someone to fix it, as opposed to having a friend fix it for free, you'd
be much better off putting the money towards a frame that'll give longer
service, be lighter, won't rust, and more shimmy resistant, something
like one of those cheapo aluminum frames from nashbar.
 
W

Werehatrack

Guest
On 7 Aug 2006 16:05:44 -0700, "Sir Ridesalot"
<[email protected]> wrote:

>Hi there.
>
>I was prepping this Norco touring frame for a friend prior to painting
>it.
>
>When I cleaned the gunk off the seatstay I discovered the left one is
>broken very close to where it joins the seat tube.
>
>There aren't any bicycle frame builders or bicycle shops in our area
>that do this kind of repair.
>
>Therefore we wonder if experts here think a competent auto body
>repairman could braze/weld such a break in a manner that would last.
>
>Here is a link to an image of the break.
>
>http://www.flickr.com/photos/[email protected]/209509671/


First, determine if that shaped end on the tube (with "NORCO" stamped
in it) is a formed part of the tube or an insert that was pushed in
prior to brazing the frame together.

If it's part of the tube, then I'd expect that the best repair would
involve a bit more than simply brazing over the crack. Mostly that's
because unless the crack is opened up so that all the corrosion can be
removed, the brazing will not migrate into and bond to the faces; all
you'll accomplish is an overlay of brass across the crack, and it'll
break through again in short order. Also, that crack probably doesn't
stop at the edge of the flat part.

If the NORCO badging is via an insert that's separate from the tube,
it's still going to get interesting. In that case, it's likely that
the insert was supposed to have been brazed or silver soldered in
place around the entire margin of the part, but the joint wasn't
properly made; if that was the case, then the reason for the crack
also becomes apparent. I'd hesitate to try to predict the best repair
route in that instance; ideally, removing the plug, cleaning all of
the corrosion off, and reinstalling it with the joint correctly
sweated might be enough...but I'd be a lot happeir if it could be left
stronger than it started, and this would not necessarily be
accomplished by what I just described.

All things considered, the original question of whether an auto body
artist could properly repair this can only be answered with full
knowledge of the person's skills. I've known body men that I'd trust
with this...and I've also known some whose ability to make things look
good was unsurpassed, but whose attention to the necessity to preserve
structural integrity left a great deal to be desired.

I think I'd be tempted to set this frame aside and work on something
else until the right person could be found to do the repair.
--
Typoes are a feature, not a bug.
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C

Chalo

Guest
Sir Ridesalot wrote:
>
> Therefore we wonder if experts here think a competent auto body
> repairman could braze/weld such a break in a manner that would last.


Yes. It's neither a highly stressed joint nor a difficult repair. The
challenge lies primarily in fixing it without reflowing the surrounding
braze joint.

My guess is that the existing joint is brass brazed (though it's not a
certainty) and that a healthy dose of 45% silver brazing material over
the whole area will fix the problem. Be sure to clean the cracked
portion down to bare metal with a hacksaw, file, or Dremel tool.
Opening a gap in the process is OK, as the gap will be filled with
fresh brazing filler.

Use only as much heat as necessary to flow the new silver, so that the
old joint will not be disrupted.

Chalo Colina
 

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