Welding

[xerxes]

(10-25-2010, 10:10 PM)KC-Steve Wrote:  I would tend to disagree with welding being cheaper unless you are referring to materials ONLY. We have gone full circle now, back to my post#4.

I was actually referring to the initial manufacture. I imagine a brazed steel frame is easier to repair than a welded one as you could de-braze/solder a tube, clean it up and braze in a new one. Whereas I'm guessing that with a welded steel frame you'd have to cut out a tube, then grind off remnants of the tube and the original weld before welding in a new one.

With regard to repair, I agree, unless the frame was something pretty expensive to start with or perhaps had a special sentimental value, repair probably isn't going to be economical, regardless of what it's made of or how it's constructed.

[LHMadman]

Noob here, and sorry if it's poor etiquette to revive/threadjack an old thread. Be gentle if I've crossed the line....


I just discovered a crack in the aluminum mounting bracket for my front derailleur. It has probably been there for a while, because I've been having intermittent problems with shifting, but had never inspected the mounting - I just made other adjustments to the derailleur.

Here's what the crack looks like. As you can see, it's a through-and-through crack of the upper part of the bracket.



If possible, I'd like to salvage this frame. I don't have a lot of money for a new frame, and would have to pay more money to have someone take the components off my current frame and rebuild it, since I'm physically incapable of doing it by myself.

Is this something that can be safely welded, or am I just asking for trouble down the line? The frame is otherwise intact.

If this is feasible, then if anyone has welder recommendations in the San Jose, CA area, I would appreciate it.

[Bill]

Now this is most definitely, in my own opinion, a different story! I want to say yes it can be as this is like an add-on part to the frame! BUT I am also in the same turn say what do ya think guys?

[DaveM]

I don't know if it's repairable. But if not, one option is to very carefully grind off the mount and then get a derailleur that that clamps directly to the frame. I think you can also get brackets that clamp around the frame and give you the same mounting point that is currently welded on there.

[Bill]

(04-25-2011, 01:03 PM)DaveM Wrote:  I don't know if it's repairable. But if not, one option is to very carefully grind off the mount and then get a derailleur that that clamps directly to the frame. I think you can also get brackets that clamp around the frame and give you the same mounting point that is currently welded on there.

Dave,
I was going to suggest something like that too but wasn't too sure. As new people here there are quite a few new thing I am learning as well .

[JohnV]

Well, here is my 2¢ worth about the original post. We have two people on this forum, one an engineer (Nigel) the other a welder (Steve) that both say "don't do it." Why argue?

As for the broken derailleur mount, I agree that there are clamp on mounts that can be used as a replacement to the one that is cracked. These are not very expensive and go on relatively simple, once the old mount is flattened with a grinder or cut off at the bend.

[Darrenjs92ni]

check the diameter of the tube to make sure you can get a derailleur that fits. i have never seen a derailleur mount on a bracket like that! what age is your bike about?

[Tim M]

(04-25-2011, 04:19 AM)LHMadman Wrote:  Noob here, and sorry if it's poor etiquette to revive/threadjack an old thread. Be gentle if I've crossed the line....


I just discovered a crack in the aluminum mounting bracket for my front derailleur. It has probably been there for a while, because I've been having intermittent problems with shifting, but had never inspected the mounting - I just made other adjustments to the derailleur.

Here's what the crack looks like. As you can see, it's a through-and-through crack of the upper part of the bracket.



If possible, I'd like to salvage this frame. I don't have a lot of money for a new frame, and would have to pay more money to have someone take the components off my current frame and rebuild it, since I'm physically incapable of doing it by myself.

Is this something that can be safely welded, or am I just asking for trouble down the line? The frame is otherwise intact.

If this is feasible, then if anyone has welder recommendations in the San Jose, CA area, I would appreciate it.

There are reasons why braze-on der mounts fell out of favor. From the photo I would guess that repairs (re-weld, replacing with clamp-on der) are cost-prohibitive for that bike. I would move on from the bike or, if really $ strapped, remove the front der and shifter and make the bike a 1 by x (where x is whatever you're running in back -- 5, 6, 7). Of course, you can always just leave things as they are and not shift the front.

[GeorgeET]

You are referring to old posts re fixing a frame crack Mr. JV. Thats different.

The braze on holder could most likely be fixed and with wet rags on the frame paint can be protected. Why don't you ask around for MIG and TIG welding shops in your area and ask the welder. He would need to V grove both sides of crack and lay a bead in. Not to much load on that part. Some cast aluminum can be very difficult to weld because of impurities.

The clamp on replacement is a good option.

[JohnV]

George,

Yes, I was referring to the original question on the cracked frame.

As for the derailleur hanger, there are several possible fixes for that including some good ole' fashioned ingenuity. If you can't find a hanger for that at a bike shop, once the angled part of the old hanger is ground down or cut off and filed flat, you can make a new hanger for it with an angle bracket, a drill and two drill bits (different sizes), a file and two hose clamps, all of which can be found at any hardware store.

[KC-Steve]

(04-25-2011, 11:00 PM)GeorgeET Wrote:  You are referring to old posts re fixing a frame crack Mr. JV. Thats different.

The braze on holder could most likely be fixed and with wet rags on the frame paint can be protected. Why don't you ask around for MIG and TIG welding shops in your area and ask the welder. He would need to V grove both sides of crack and lay a bead in. Not to much load on that part. Some cast aluminum can be very difficult to weld because of impurities.

The clamp on replacement is a good option.

Yeah, I would agree with George on THIS ONE. It isn't a load bearing support of the frame, so as long as you don't allow heat to transfer to the frame then I think it can be safely fixed, but use a qualified weldor that knows how. You don't want the frame to become brittle from heating and cooling. TIG would be safer than MIG (better heat control). A clamp-on replacement would be safer yet, and much cheaper too!

Steve

[KC-Steve]

This subject seems to draw a lot of attention. As of this post, this thread has gotten 2400 views. That's much higher than most threads.

Steve

[LHMadman]

Thanks, everyone, for your thoughtful responses and suggestions. A local shop also suggested eliminating the front derailleur altogether, which I'm considering. I hadn't thought about replacing it with a clamp-on - that's a great thought. I wonder how easy it would be to grind off the existing mount.

Anyways, I found the name of a local aluminum welder who gets good comments on a motorcycle forum, and I called him yesterday to describe the repair. Don't know whether he'd be willing to take on such a small job, but he said I could bring it by sometime.

Lots for me to think about. Thanks again!

[LHMadman]

An update: I was able to find a local TIG welder who was able to repair the hanger. It's not pretty - some of the paint had to be removed in order to do the weld - but it's solid.

I looked into clamp-on options, but since the seat tube isn't round, I thought it might be difficult to find something that would work. Also, it seemed like it was going to be more trouble to grind off the broken hanger than to try and fix it.

[Bill]

(Sigh) All I can say is good luck with it and be VERY careful!

[LHMadman]

(05-09-2011, 01:57 AM)Bill Wrote:  (Sigh) All I can say is good luck with it and be VERY careful!

Yes, absolutely! Thanks! This is a great forum.

[framekenstein]

(08-21-2010, 12:16 PM)KC-Steve Wrote:  Yes, brazing STEEL TUBING is a good option using a MAPP torch for frame building. I plan to try it someday since I have many years of soldering skills. However, it is expensive. You can find many tubing sources around the Internet.

http://www.cycle-frames.com/bicycle-frame-tubing/

Steve

Thanks for that info. I am just beginning the odyssey of making a pedal-powered four-wheel bike-ish jeepy something or other, and need to cast my research net wide. The link you gave out is going to be very useful!