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Old 10-31-12, 08:39 AM   #1
Maxcalibur
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Welded Tandem Rear Stay: Too Weak for More Touring?

Hi there,

I hope this is the right section, perhaps frame building may have been a better option.

Last week I was touring with my tandem. The back was fairly loaded and halfway through our trip we noticed a crack at the top of the drive side rear stay. The frame is 40 years old, so it could have been something that developed over time before we even owned the bike. We were in the middle of the Irish countryside and no bike workshops around. Fortunately for the trip, a local car enthusiast was around and welded the crack in our frame. He seems to have done a good smooth job and the bike easily lasted the second half of the tour.

My questions are as follows:

1. Is the weld point likely to be a severely weakened point on the frame and should we avoid touring with loaded panniers on it again?

2. If that's the case, is there a way to reinforce the tube now that it's been welded shut. Some kind of outer brace perhaps?

Cheers!
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Old 10-31-12, 08:54 AM   #2
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Depending on the steel tubing (I assume it is a steel frame) used in the bike's construction, the weld could last forever or break in the near future. Thin wall, high-strength steels, typically Cr-mo or Mn-Mo alloys, require proper heat treatment to obtain their strength without brittleness and welding heat will greatly reduce their strength. Lower strength (aka Hi-Ten) steels will have much thicker walls and aren't nearly as sensitive to welding heat since they weren't that strong to begin with and make up for it by using more material.

So, if you know what your frame is made of you can get a better idea of it's probable life after welding.
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Old 10-31-12, 09:03 AM   #3
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Thanks. Sorry, should have mentioned, it's a 531 frame.
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Old 10-31-12, 09:50 AM   #4
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Originally Posted by Maxcalibur View Post
a 531 frame.
Virtually all of these frames were brazed - essentially "glued" together with molten brass, silver, or other metal. So the most likely route to long-term service would be structural reinforcement by brazing- plausible approaches might include things like a doubler, gusset, perpendicular stiffening "fin(s)," or any of many other approaches. Conceptually, this is not out of the range of reasonable consideration.

It's more-or-less impossible to speculate on the practicality, cost, reliability, etc of any of these approaches (or others) without a lot more info- the physical configuration of the joint, the break, and the existing repair, and etc and so on. You could post pic's here, everybody could speculate, probably get a lively debate ... perhaps even heated debate ... underway. That might help you think about it, or maybe not! If you're really thinking about having something done I'd think at some point you want to take it to a framebuilder or 2 and ask them to look, talk, estimate. Ask around nearby- biking friends, bike shops, bike clubs, etc.

Here in the US, I'd guess that not many shops would do anything with it for fear of getting sued at some point in the future. You're in the UK - perhaps liability is slightly less of a concern there.

Of course there are all of the other practical and economic considerations about repair vs replace- how nice your bike is, how much do you have invested in it (economically and emotionally), how well does it meet your present and future biking needs+ wants, etc etc.

Hope that helps, good luck with it.

Last edited by chris ss; 10-31-12 at 09:54 AM.
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Old 10-31-12, 09:57 AM   #5
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If it's a seat stay it will most likely be ok. It is not as strained as the chainstays or other tubes on the bike. The reliability of the repair will depend more on the ability of the weldor.
Most steel used in better bikes is 1040 Chrome-moly and does not require heat treatment after welding. The 531 is Manganese-moly and shouldn't require heat treatment either.
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Old 10-31-12, 10:01 AM   #6
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Quote:
Originally Posted by Maxcalibur View Post
Last week I was touring with my tandem. The back was fairly loaded and halfway through our trip we noticed a crack at the top of the drive side rear stay.
Seat stay or chain stay? Seat stays are not heavily loaded, even on tandems, and your repair could conceivably hold up well. That said, Reynolds 531 tubing was formulated with low temperature brazing in mind, not high temperature welding so it may become an issue at some point.

Chain stays are another matter. Keep a close eye on the repair. If you intend to repaint the frame, use that as an opportunity to replace the damaged stay.
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Old 10-31-12, 11:15 AM   #7
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Most steel used in better bikes is 1040 Chrome-moly and does not require heat treatment after welding. The 531 is Manganese-moly and shouldn't require heat treatment either.
Typo? AISI 1040 is a low carbon mild steel. I presume you meant 4140 which is a Cr-Mo alloy steel.
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Old 10-31-12, 11:36 AM   #8
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Many folks dont know the difference between welding and brazing... most people see a metal repair and call it welding regardless of the actual method...then of course even if it was welded, by what method...

Just something to think about.
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Old 10-31-12, 11:45 AM   #9
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I have added reinforcing gussets to frame which were cracked and repaired. Not a pretty method but can be very effective. Andy.
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Old 10-31-12, 12:24 PM   #10
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Assuming the frame is lugged, you could always find a bike maker and have the stay replaced..
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Old 10-31-12, 01:48 PM   #11
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I got a maker of stainless steel air distribution Ducts, in Killarney,
to do some bike frame repair welding . [97]


my bike is a mix of TIG and brazed , to build the frame..

As mentioned before : 4140 is different from 4130..

+ 531 is Mn Mo rather than Cr Mo ..
(atomic number 24 vs 25)

As to is it good, now? go visit someone familiar with frame-building

I cant see a damn thing from GMT+8..

Last edited by fietsbob; 10-31-12 at 01:59 PM.
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Old 10-31-12, 02:07 PM   #12
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You'll be fine, tour on.



Of course, you could post a picture so we actually knew what part of the chainstay you were talking about and could see the repair.
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Old 10-31-12, 04:36 PM   #13
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The frame is not lugged. Simply welded at the joints. I'll definitely take it to a frame builder

The repair was done by arc welding I believe. Here's a photo of it, although the bike's a bit dirty and the weld was quickly spray painted to keep the rust away for the rest of the trip.



While we're on the subject of welds. I've just got hold of a new frame this evening and am unsure if there's a weld on one of the chain stays and dropout. Attached are some pictures of the possibly repaired joint (on the right in the picture of both dropouts) and its counterpart (last image):

Attached Images
File Type: jpg IMG_8528.jpg (81.8 KB, 98 views)
File Type: jpg IMG_8524.jpg (49.2 KB, 60 views)
File Type: jpg IMG_8526.jpg (51.9 KB, 66 views)
File Type: jpg IMG_8527.jpg (46.0 KB, 53 views)
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Old 10-31-12, 05:48 PM   #14
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I can't really tell what's going on with the tandem from that picture. But if it's that old chances are it is brazed not welded.

Same thing with the second frame, brazed not welded. If it's repaired it looks fine, maybe a little extra brass showing there.
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Old 10-31-12, 09:26 PM   #15
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I'd trust both those frames from the standpoint of the repairs you show. I think you should consider yourself very lucky to have found such a talented welder for your tandem.

Replacing rear stays is not an insignificant project. I don't think I would do it unless the bike is extremely valuable to you (of a sentimental value).
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Old 11-01-12, 04:28 AM   #16
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The tandem is quite a nice smooth weld by the looks and feel of it. The weld is about 1-2cm below the rear brake arch. If the general consensus is that it's fine then I'm not going to be worried about it!

With regards to the frame I just got, I'm slightly more worried as it's where the drive side chain stay connects to the dropout. I plan on using this bike for touring so I want to be fairly sure it won't break. Apart from that it just looks like a bit of surface rust. The rest of this frame is lugged, but I guess that if brazing was regularly used on frame joints, it will be ok here too even if it was a repair?
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Old 11-01-12, 09:12 AM   #17
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Regarding the "new" frame, there's no reason you shouldn't scrap away the surface rust to see if it has eaten into the joint. Dropout lugs extend into the stays making that particular joint one of the stronger connections on the bike. The repair was probably done because the original brazed joint failed. The repair looks crude (an excess of brazing material indicating poor skill or greater structural damage, it is hard to know) but is probably effective.
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Old 11-02-12, 08:24 AM   #18
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Thanks, I'll scrape away the paint and rust this weekend hopefully to see what's up.

This isn't something that was shown to me when I purchased the frame, though I suppose I should have checked it over myself.
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Old 11-02-12, 09:18 AM   #19
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Thanks, I'll scrape away the paint and rust this weekend hopefully to see what's up.

This isn't something that was shown to me when I purchased the frame, though I suppose I should have checked it over myself.
It should do its job. Did you pay much for it? I'm guessing not.
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Old 11-02-12, 10:22 AM   #20
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No, but I do feel I should have paid less since finding that out!
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Old 11-02-12, 11:47 AM   #21
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Thanks. Sorry, should have mentioned, it's a 531 frame.
To get a good answer, please post some pictures, the brand of the bike/model/builder, a pix of tubing label, and how much total weight you were carrying.

Ok, unless it is a Jack Taylor 531 tandem, it is more than likely one of the tandems built out of 531 single bike tubing. A brand such as a Bob Jackson was like this, but there were many others. They were ridable and available, but I would NOT recommend pushing one of those too hard or with a large load as you could break something... sort of like what happened.

To the question of repairing it; If it was been stick welded with gas, then the repair is unlikely to hold up very long. A good TIG weld of the crack itself is good roadside temp fix to get you home, but not a permanent solution.

At this stage, I would find a frame builder. If the crack is a bit away from the bottom bracket, he could fetch a cut off stub of another chainstay frm his scrap bin, split it to make a clamshell patch. After cleaning everything up, he would flux it up, clamp the patch over the repaired area and fix it on with brass or silver. He will likely want to shape the patch to best disperse the forces along the length of the stay. Professionally done, you would put it back to almost the original strength. A more invasive and more expensive repair would be to have the entire stay replaced. With that there is risk of weakening the other joints and tubes in the area. Ask questions and listen to what the framebuilder recommends. Keep cost in mind... you can pick up a good used modern era tandem under $1,000 easy enough and keep or sell the old one as a wall hanger "Vintage Collectable"
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Old 11-03-12, 05:15 PM   #22
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To the question of repairing it; If it was been stick welded with gas, then the repair is unlikely to hold up very long. A good TIG weld of the crack itself is good roadside temp fix to get you home, but not a permanent solution.
The only permanent solution is the continuous replacement of frames. Let's face it, no matter how good the repair, the fact that it failed in an indication that the frame is ending its service life. (It's 40 years old!)

I wouldn't spend money getting it professionally repaired, chances are there will be a new crack opening up in a month's time after.
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Old 11-05-12, 02:30 PM   #23
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The only permanent solution is the continuous replacement of frames. Let's face it, no matter how good the repair, the fact that it failed in an indication that the frame is ending its service life. (It's 40 years old!) I wouldn't spend money getting it professionally repaired, chances are there will be a new crack opening up in a month's time after.
As originally described, it would seem that the break was the result of a not so great frame being pushed too hard. So not disagreeing with your position on this at all...getting a new frame and one that is correctly suited to the described useage is indeed the best solution. Given that most folks are not really initially going to do that or perhaps they can't justify the expense, then for an attempt to make a repair, the discussion I provided is imho credible enough. Point is to get some good metal spanning the crack and get it properly brazed. Would it break again? Yes, likely so if the load or stress is not reduced. After repair I would recommend a rider total of 275 pounds and a bag limit of about 30 pounds plus a good talk with the owner about not hammering it hard unless they want to walk home or have a real accident.

If I were to ponder a repair estimate, I would say about $250 for the work I suggested less paint and reassembly labor. This based on about 3 hours labor, plus or minus. If any more work than that is necessary, then looking for a decent used bike is much better answer (but it is the owners decision) and it would likely be a more modern unit (Burley, Trek, Santana, others are readily available used) which would make the original issue go away and leave the riders with a bike that can carry a touring load without hesitation. Hope this corrects the apparent misunderstanding from my original input.
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Old 11-05-12, 02:37 PM   #24
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No problem. I recently replaced the seat tube on my steel-frame racing bike (mid-eighties vintage) and for $40, a fellow that has a metal fabrication business at our local shipyards silver-brazed the tube. I'm thinking that the op'er could probably get something similarly fashioned if he wasn't particular about the finished look.

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Old 11-07-12, 08:25 AM   #25
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No problem. I recently replaced the seat tube on my steel-frame racing bike (mid-eighties vintage) and for $40, a fellow that has a metal fabrication business at our local shipyards silver-brazed the tube. I'm thinking that the op'er could probably get something similarly fashioned if he wasn't particular about the finished look.
Very nice repair. At $40...the tube alone would be close to half that (plus shipping), depending on the metal pedigree......well, you have good friends. I would charge about $200-$250 to replace a seat tube and probably would only take the job on if the friend couldn't afford a replacement or the bike was of significant vintage. You done good! Appreciate if you could post some pictures after the paint is re-done.
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