john
Cracks develop due a stress concentration and stress cycles. The stress
down in the crack, will exceed the "endurance limit" (~half ultimate
tensile strength), and the crack grows a tad with each cycle of stress.
This is in one particular location on a tube or on a dropout. It doesn't
mean the rest of the tube or dropout is bad, just that particular spot was
made poorly to begin, or something happened along the way that made a stress
concentration. . Repair that spot and things are basically as good as
new. (for tubes, excluding rust damage..) and also IMHO in most cases *it
is higher quality repair then replacing tubes and re- cooking lugs*, etc.
most frames i have fixed were a rear dropout crack. These are particular
easy to fix, new dropouts are not needed, just a good cleaning of the crack
and some high strength brass into crack is usually enough. I did this in a
motel room once and still riding the frame 15 years later. (as most know
with rear dropouts it is important to keep them aligned and the wheel's axle
spacing (overlocknut dist) correct, or bending stress will be added to
whatever other stresses are there, if overall is over fatigue limit, a crack
will probably start). Other frames i added a little silver lap over the
brass filled crack for added strength..
One frame i fixed the initial build was poor, the brass wasn't flowed all
the way into the joint. Probably took 10-15 years? to finally fail and work
the crack through lug. The repair was a good cleaning and brass flowed into
the crack. Another the tube cracked circumferentially clean through... it
was rust damage, and from a tig weld spot.. chances of cracking again at
another rust crevice were high, but since the repair was so easy i repaired
anyway. I simply split a tube of same diameter and splint it over the crack
and silvered it in. The lap doesn't have to be long.. only 3 or 4 mm
either side of crack. The frame is still going as far as i know. Really it
is no different than brazing a tube into a lug or into a s&s coupling..
Cracks around the head tube and on curved parts of lugs are much harder,
and yes i can't recommend that. I have done them on my own junker bike and
watched the crack just keep going... almost threw it, but then I was lazy
and didn't feel taking the components off, so i would drill a hole at the
crack base, but a little patch over and keep riding, didn't even take the
fork out.. did this three times, before it appeared as it was holding up.
The bike got stolen so i hope the cracks kept growing, but of
course unfortunately wont fail spectacularly.
I rather enjoy doing these repairs because it economical and responsible (ie
use things to their useful end.). Its safe, other then the fork tube
catastrophically breaking there is really nothing else on a bike frame that
if it breaks one cant' safely get the bicycle stopped in time (i even had a
fork dropout break... the other side held up ).
Although i enjoy it, i would rather framebuilders do these repairs. One i
don't do it for living, but mainly because for me cleaning is bitch. I
don't have a proper sandblaster. and cleanliness is the key to doing a
proper repair. I am hoping this email convinces some that yes patching can
be a proper and more than adequate method to fix a cracked frame (bent is
another matter), and is incredibly quick and easy! the only way to know for
sure and to convince yourselves is to start doing it, and get a history of
it working. I also don't get as much practice feathering a flame for
flowing silver on thin tube... It should also be a great marketing tool for
framebuilders, that heh frame breaks, we can get you up and running again
economically and overnite...as long as you don't mind the temporary rattle
can paint over the repair..
If what you after is a work of art, and there is absolutely nothing wrong
with this, hang the steel bike up in the living room and commutte on that
aluminum, ti, or carbon fiber frame !! Okay low blow, but seriously
consideration and different levels should be available, not just the
standard, 400 dollars(guessing) to replace a tube, or dropouts. there should
be $40 repair option, otherwise, why buy steel ?
On Sun, Jan 24, 2010 at 9:31 AM, Tony Pereira wrote:
> That's one way to do it, but if I'm going to repair a frame I usually
> replace the cracked tube. Replacing tubes is neither quick or easy. Depends
> on what you're after.
>
> My $.02,
>
>
> -Tony
>
> Pereira Cycles
> Portland, Oregon, USA
> www.pereiracycles.com
> 503.333.5043
> twitter: @pereiracycles
>
> john wrote:
>
>> Actually a crack in a steel frame is usually a simple and fast repair.
>> Anymore it is about the only advantage a steel frame has over cf or al.
>> Although many tout the repairability of steel, it seems that rarely do
>> framebuilders take advantage of it. why take steel's main advantage and
>> through it out the window ! Steel frames are great! Clean around the
>> crack, make a little lap joint, and flow some silver in, done. get riding
>> again. 15 minutes, maybe 30 minutes if including chit chat. I would hope
>> 30 minutes of work would still be cost effective. It is environmentally
>> friendly also.
>> On Fri, Jan 22, 2010 at 12:12 PM, Tony Pereira > elists@pereiracycles.com>> wrote:
>>
>> Have him contact me. It is not cost-effective to repair most frames,
>> but I'm happy to discuss it with him.
>>
>> -Tony
>>
>> Pereira Cycles
>> Portland, Oregon, USA
>> www.pereiracycles.com
>>
>> 503.333.5043
>> twitter: @pereiracycles
>>
>> Kevin Mansker wrote:
>>
>> Hello all,
>> Anyone know someone local that can repair a cracked steel frame?
>> My fathers co-worker just cracked his frame was was looking for
>> someone.
>>
>> I have no idea how bad the frame is or if it is even worth
>> repairing, just hoping for some names and numbers :)
>>
>> Thanks,
>> Kevin
>>
>>