Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 10-14-09, 05:45 PM   #1
GitanePro83
Junior Member
Thread Starter
 
Join Date: Oct 2009
Bikes:
Posts: 9
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Broken Frame

Hey guys, this is my first post in these forums. Hopefully someone can help me.

My bike frame (an older racing bike, from the early 80's) recently broke. It occurred along the bottom of the rear part of the frame (the part of the rear triangle which is parallel to the ground), right where it meets the dropout.

Is this irreparable? Could I weld it?
GitanePro83 is offline   Reply With Quote
Old 10-14-09, 05:55 PM   #2
facial
Junkmaster
 
Join Date: Aug 2007
Location: Arcadia, California
Bikes: Lemond "Alpe d'Huez," several X-marts, and two Trek hybrids
Posts: 134
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
What's the material? Some pics would help.

If it's metal, then most likely it is repairable.
facial is offline   Reply With Quote
Old 10-14-09, 05:57 PM   #3
davidad
Senior Member
 
Join Date: Feb 2009
Bikes:
Posts: 4,854
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
It's the chainstay. You could cut out the old one and weld or braize in a new one. Do you have the training to GTAW or gas weld in the new part?
davidad is offline   Reply With Quote
Old 10-14-09, 06:07 PM   #4
GitanePro83
Junior Member
Thread Starter
 
Join Date: Oct 2009
Bikes:
Posts: 9
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by davidad View Post
Do you have the training to GTAW or gas weld in the new part?
No

And to answer the earlier question, it's made of steel alloy
GitanePro83 is offline   Reply With Quote
Old 10-14-09, 06:44 PM   #5
sch
Senior Member
 
Join Date: May 2003
Location: Mountain Brook. AL
Bikes:
Posts: 3,005
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Somewhat chancey to weld bike tubing absent a VERY experienced welder. Replacement chainstay
tube is ~$10 or so eg: http://www.cycle-frames.com/bicycle-...20mm-LONG.html
New tube could be fitted to the bike in a fairly straight forward fashion, brazing/silver soldering at the
dropout and mitering and welding at the BB. Some risk of heat distorting the BB exists. Results likely
to be better than welding the cracked tube itself.
sch is offline   Reply With Quote
Old 10-14-09, 07:25 PM   #6
Scooper
Decrepit Member
 
Scooper's Avatar
 
Join Date: Aug 2005
Location: San Francisco California
Bikes: Waterford 953 RS-22
Posts: 10,137
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Whether or not it can be easily repaired really depends on where the break is. This fracture occurred very near the chainstay-to-dropout brazed joint and was repaired for $50 by framebuilder Paul Sadoff of Rock Lobster Cycles in Santa Cruz. He machined a "V" notch on both the inside and outside of the fracture, then welded (not brazed) a bead on both sides and ground/filed it flush. It has held up well. The frame is a 1987 Schwinn Paramount with SL/SP tubing and Shimano forged dropouts.





Can you post a close-up of the break?
__________________
- Stan
I'm with her.
Scooper is online now   Reply With Quote
Old 10-14-09, 08:56 PM   #7
GitanePro83
Junior Member
Thread Starter
 
Join Date: Oct 2009
Bikes:
Posts: 9
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Uploading the pictures...

The image of the green bike... it's almost in the exact same spot, but it is a complete separation.
GitanePro83 is offline   Reply With Quote
Old 10-15-09, 01:36 AM   #8
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
That's a fairly easy repair. You should also get the dropouts aligned afterwards to make sure they're parallel. Out-of-alignment dropouts are a major contributor to those kinds of breaks, and broken axles as well.
DannoXYZ is offline   Reply With Quote
Old 10-15-09, 03:01 PM   #9
GitanePro83
Junior Member
Thread Starter
 
Join Date: Oct 2009
Bikes:
Posts: 9
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Here are some pictures of the break... finally



GitanePro83 is offline   Reply With Quote
Old 10-15-09, 03:53 PM   #10
Homebrew01
Super Moderator
 
Homebrew01's Avatar
 
Join Date: Jul 2004
Location: Ffld Cnty Connecticut
Bikes: Old Steelies I made, Old Cannondales
Posts: 19,700
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 105 Post(s)
The frame should be repairable, but those other cracks make me think it might be better to replace the dropout instead of welding it. You can also post in the framebuilder forum.
__________________
Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike
Homebrew01 is offline   Reply With Quote
Old 10-15-09, 04:14 PM   #11
Scooper
Decrepit Member
 
Scooper's Avatar
 
Join Date: Aug 2005
Location: San Francisco California
Bikes: Waterford 953 RS-22
Posts: 10,137
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
That's definitely repairable, but like DannoXYZ says, the dropouts need to be made parallel.

Whomever does the repair should attempt to get the dropouts as close to parallel as possible and held in that position with a fixture while performing the repair so that any post repair cold setting to get the dropouts precisely parallel doesn't put undue stress on the repair.

Parallelism can be checked before and after using the Park Tool FFG-2.
__________________
- Stan
I'm with her.
Scooper is online now   Reply With Quote
Old 10-15-09, 05:20 PM   #12
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If that frame is chrome-plated, that contributed to the crack. The acid-treatments and resultant hydrogen-embrittlement that occurs from chrome-plating tend to collect and concentrate at the tight angles, nooks & cavities of the joints.
DannoXYZ is offline   Reply With Quote
Old 10-15-09, 06:37 PM   #13
davidad
Senior Member
 
Join Date: Feb 2009
Bikes:
Posts: 4,854
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
From the looks of the weld I'd say it's been repaired once.
davidad is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 07:26 AM.