Cracked bottom bracket shell
Sheldon Brown
particularly good fit for me, and I've always lusted after one of these.
My plan is to build it up as a fixed gear. I got it very cheap because
it has a cracked bottom bracket shell, but I'm torn as to what to do
about this.
The crack is about an inch long, and runs down the bottom of the
"valley" between the down tube and the seat tube. I've never seen a
frame fail there before, and it's hard to imagine what might have caused
it. My guess is that the frame was built with a built-in stress trying
to open up the angle between the seat tube and down tube, and that the
crack is fatigue related. The opening up of the crack may have relieved
this stress...so, perhaps, it won't get any worse.
I see two options:
1. Get a framebuilder to run a bead of TIG along the crack.
2. Put it together and ride it the way it is.
Option 1 has the disadvantage of costing money, hassle, and messing up
the paint job (which is original but not in great shape.)
Option 2 has the disadvantage that if the crack were to grow into the
threaded area of the shell it might render the frame irreparable...but
how likely is that?
Has anybody out there had experience with this type of frame damage?
Sheldon "Dilemma" Brown
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Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772, 617-244-1040 FAX 617-244-1041
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Dave Korzekwa
crack tip or just past the tip in the unaffected metal at each end of
the crack. This should reduce the likelyhood of the crack growing
past where the hole is. The hole can be pretty small - 1/16" should
do it. If you are not sure where the crack ends, be conservative and
put the holes farther out.
Dave Korzekwa
Los Alamos National Laboratory
Brian Lafferty
This may not be of any relevance but here goes. My wife's Audi had a tire
that was slow leaking. It turned out to be a cracked Alloy wheel. A local
shop welded the crack and the wheel has been fine ever since. I would try
tig welding it. The worst that is going to happen is that a frame builder
will have to replace the bb shell......I think.
Great find. A buddy in Mobile AL found an early 80s Raleigh Pro at a
garage sale and got it for $50.
Brian Lafferty
Sheldon Brown wrote in message <38E0CDFB...@sheldonbrown.com>...
>I recently bought an early '70s Raleigh Professional frameset. It is a
>particularly good fit for me, and I've always lusted after one of these.
> My plan is to build it up as a fixed gear. I got it very cheap because
>it has a cracked bottom bracket shell, but I'm torn as to what to do
>about this.
>
>The crack is about an inch long, and runs down the bottom of the
>"valley" between the down tube and the seat tube. I've never seen a
>frame fail there before, and it's hard to imagine what might have caused
>it. My guess is that the frame was built with a built-in stress trying
>to open up the angle between the seat tube and down tube, and that the
>crack is fatigue related. The opening up of the crack may have relieved
>this stress...so, perhaps, it won't get any worse.
>
>I see two options:
>
>1. Get a framebuilder to run a bead of TIG along the crack.
>
>2. Put it together and ride it the way it is.
>
>Option 1 has the disadvantage of costing money, hassle, and messing up
>the paint job (which is original but not in great shape.)
>
>Option 2 has the disadvantage that if the crack were to grow into the
>threaded area of the shell it might render the frame irreparable...but
>how likely is that?
>
>Has anybody out there had experience with this type of frame damage?
>
bob...@home.com
Is the frame chromemoly or "mild" steel? If mild steel I would
suggest that a mig would be a more appropriate tool for the job. They
put much less heat into the weld area, limiting paint damage and
distortion. They are also better at "filling" in gaps.
Drilling the ends of the crack and epoxying it is another alternative.
If it were a race car frame (which is waht I'm familiar with) I'd be
inclined to make a patch to be welded on top of the crack, and if
thought the joint was under undue stress (which I'm sure isn't the
case here) make a connecting tube between the seat and downtube.
Goodluck
Bob "just sold my Tig welder or I'd be happy to do it for free"
Quindazzi
Mark MacNab
been badly dented while couriering and the frame builder brazed in the
new tube to minimize the reheating of the 'heat affected zone' from the
initial weld. I'm not conversant in the finer details of
welding/brazing but perhaps brazing presents a third option for your
repair?
BTW the repaired frame i spoke of has held up quite well to general
riding, racing and touring.
Cheers,
Mark MacNab
Leo C. Castellon
joint. The problem is that the BB shell will have to be heated to the
melting point of the base metal while the brass or silver that was used to
braze the frame originally will melt at a much lower temperature. This
usually results in the brazing metal flowing out of the joint and
contaminating the welding tungsten. I have fixed a few frames with similar
problems by stop drilling the crack and laying a small brass fillet over the
exteranl part of the BB shell where the crack is. This has worked out
extremely well without changing the appearence of the frame too much. I hope
this helps.
Leo
Larry Sokolsky
closely as possible (you could magnaflux if you have this capability)
and drill two crack-stopping holes on either side of the crack, maybe
1/8-3/16 in diameter. I think it would not be a bad idea to then take
it to a welder (midas, local frame-builder, etc) and have them put a
bead on the crack, although you could ride it as is and watch for
further crack growth.
I welded a BB shell crack on a chainstay once. It lasted about 1000
miles, so you never know.
Probably the cheapest reasonable way to do a solid fix would be to take
it to a framebuilder, have him ream out the bb shell, and braze in a new
one lugless. That way you wouldn't have the cook the bb area getting
the old one off.
I doubt you'll do any worse damage riding it as long as the crack
doesn't spread to the lug area of the bb shell and put a crack in the
tube.
Larry
Stephe
>
>I see two options:
>
>1. Get a framebuilder to run a bead of TIG along the crack.
>
I agree that tig/mig wouldn't be the way to go. Too much heat and
the brass from the original weld would get into this area and
cause problems with the weld. I like the drill the ends of the
crack and filet braze the area. You could then even mask off the
shell (and maybe a few other lugs) and paint it some contrasting
color and it wouldn't look bad.
No experience with this type of damage on a bike frame but have
tried to weld NEAR where things have been brazed and had no luck.
Stephe
Mark Hickey
>Option 1 has the disadvantage of costing money, hassle, and messing up
>the paint job (which is original but not in great shape.)
>
>Option 2 has the disadvantage that if the crack were to grow into the
>threaded area of the shell it might render the frame irreparable...but
>how likely is that?
>
>Has anybody out there had experience with this type of frame damage?
Hey, Sheldon... why worry? Let's say you ride 10,000 miles this year.
Split between your 80 or so bikes, that's only a little over a single
century per year on the bike in question.
;-)
Mark Hickey
Habanero Cycles
http://www.cynetfl.com/habanero/
Home of the $695 ti frame
Jim Adney
>I recently bought an early '70s Raleigh Professional frameset. It is a
>particularly good fit for me, and I've always lusted after one of these.
> My plan is to build it up as a fixed gear. I got it very cheap because
>it has a cracked bottom bracket shell, but I'm torn as to what to do
>about this.
The white Raleigh Pros were a brass brazed frame, so I would suggest
that you drill as small a hole at each end of the crack as practical
and then carefully braze the whole crack, flowing brass down into the
full depth of the crack. Retap the BB threads when you're done.
I agree that this is a very wierd place for a frame to crack. Make
sure that there isn't more to this than you've spotted so far. It
often happens that one of the main tubes didn't get brazed well into
the socket in the BB so it fails there and then the crack propagates
outward.
-
-----------------------------------------------
Jim Adney jad...@vwtype3.org
Madison,Wisconsin USA
-----------------------------------------------
Tom Kunich
>
> Sheldon Brown <capt...@sheldonbrown.com> wrote:
>
> >I recently bought an early '70s Raleigh Professional frameset. It is a
> >particularly good fit for me, and I've always lusted after one of these.
> > My plan is to build it up as a fixed gear. I got it very cheap because
> >it has a cracked bottom bracket shell, but I'm torn as to what to do
> >about this.
>
> The white Raleigh Pros were a brass brazed frame, so I would suggest
> that you drill as small a hole at each end of the crack as practical
> and then carefully braze the whole crack, flowing brass down into the
> full depth of the crack. Retap the BB threads when you're done.
Wow, I'm sure that Sheldon would know better than to even try that. If
the bottom bracket split from the stress of sprinting or whatever and it
is steel, what makes you think for even a second that it would hold with
nothing but bronze?
Now I suppose as old and slow as Sheldon is that he might get away with
inert gas welding the bracket and cold setting and retapping the damage,
but the only real fix is to have a frame builder replace the bottom
bracket.
Unfortunately that would probably cost a good deal. But I'd bet that
Sheldon has friends in the business.
Stephe
Tom Kunich wrote in message <38E2E88F...@home.com>...
Yea and we see how all those filet brazed bikes just fall
apart...
I've seen 150 MPH 80HP go kart racing frames with nothing but
bronze filets between the frame tubes and they hold up just fine.
How is this ANY different?
Have you ever tried inert gas welding near a brazed joint?
Obviously not.
Stephe
Tom Kunich
news:38E0CDFB...@sheldonbrown.com...
> I recently bought an early '70s Raleigh Professional frameset. It is a
> particularly good fit for me, and I've always lusted after one of these.
> My plan is to build it up as a fixed gear. I got it very cheap because
> it has a cracked bottom bracket shell, but I'm torn as to what to do
> about this.
>
> "valley" between the down tube and the seat tube. I've never seen a
> frame fail there before, and it's hard to imagine what might have caused
> it. My guess is that the frame was built with a built-in stress trying
> to open up the angle between the seat tube and down tube, and that the
> crack is fatigue related. The opening up of the crack may have relieved
> this stress...so, perhaps, it won't get any worse.
Now that I have the original posting I see that the case appears to be that
you have some damage caused by overheating the BB or perhaps an inclusion in
the original fitting.
> I see two options:
>
> 1. Get a framebuilder to run a bead of TIG along the crack.
>
> 2. Put it together and ride it the way it is.
I believe you've analyzed it correctly and that 1. is the answer. I would
also drill the ends of the crack before I proceeded with the welding
operation. Paint be danged though I don't remember any decals in that area
and you might very well be able to carefully repaint and blend it into the
original paint. Women are much better at color matching than men because
they detect about 20% more colors than men. Go to a paint store that has a
woman or take someone that has the 'knack'.
> Has anybody out there had experience with this type of frame damage?
I've never even heard of that particular damage and suggest that it is in a
nasty location since that area is flexed by someone as big and strong as you
are.
I have heard of bottom brackets being replaced in old frames but MAN what a
drag that would be.
Stephe
Tom Kunich wrote in message
>Women are much better at color matching than men because
>they detect about 20% more colors than men.
Where in the world did you read that?
Stephe
David L. Johnson
The truth is that women _believe_ more about the importance of color
matching. They will fuss about whether "alpine white" is better than "ivory"
for the living room walls. Men know better. They know that a can of "alpine
white" is just white paint with a squirt of color, and so is "ivory".
Depending on who does the squirting, they could be identical.
--
David L. Johnson david....@lehigh.edu
Department of Mathematics http://www.lehigh.edu/~dlj0/dlj0.html
Lehigh University
14 E. Packer Avenue (610) 758-3759
Bethlehem, PA 18015-3174
"What am I on? I'm on my bike, six hours a day, busting my ass. What are you
on?"
--Lance Armstrong
Ted Bennett or Lisa Kaskan
Tom Kunich wrote:
>
> Women are much better at color matching than men because
> they detect about 20% more colors than men. Go to a paint store that has a
> woman or take someone that has the 'knack'.
Sorry Tom but you are wrong here. Assuming no color vision defect, and lots of
men suffer from that, there is no difference in color discrimination between
men and women.
The amazing thing is that in some parts of the visible spectrum, humans can
discriminate by color between monochromatic lights separated by only one
Angstrom unit (a millimicron).
Ted Bennett