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Lugs as strong as welds?

Old 07-16-21, 12:09 AM
  #26  
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Originally Posted by Retro Grouch View Post
Well, it's kind of like soldering copper water pipes together. After carefully preping the tubes and pinning them together with the lugs, you heat up the whole assembly with a torch. When the temperature is right, you use molten silver or (more commonly) brass solder to fuse the joint together. I suspect the reason why you don't see more lugged frames being built today is because it's more labor intensive than TIG welding.

I don't know which is actually stronger and I'd argue that it doesn't matter anyway. Both joining methods have been proven to be strong enough.
The irony here is that the main reason lugs were used in the first place was to save labour; simply soldering tubes into lugs saved a lot of skilled work compared to meticulous hand-welding. Of course, this is completely inverted in the era of robotic welding on mass-production lines, and lugs are now an unmistakable sign of a handmade frame.

I personally love the beauty of a quality lugged frame and have huge respect for the craftsmanship a high-grade example requires.







Last edited by hydrocarbon; 07-16-21 at 12:29 AM.
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Old 07-16-21, 07:44 AM
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"and lugs are now an unmistakable sign of a handmade frame" hydrocarbon

There are millions of lugged bikes that were machine brazed. The machine provided heat and filler came before the current popularity of welded joints. Additionally some high volume production frames used tack welds between the lugs and the tubes to hold the structure while the machine brazings were done, much like pins can hold a main triangle before brazing.

Lugs, in them selves, prove nothing about the skills or craftsmanship of the frame. Andy
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Old 07-16-21, 07:55 AM
  #28  
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True; I meant nice lugs on nice frames.
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Old 07-16-21, 08:36 AM
  #29  
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Originally Posted by hydrocarbon View Post
True; I meant nice lugs on nice frames.

By applying the "nice frames" filter you eliminate the vast majority of bikes made, sold and used. Andy
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Old 07-16-21, 09:37 AM
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From the middle '80s and before welded frames were laughed at. Any quality bike was a lugged frame bike. Then came computers and robot welders. Bike mfg quickly found out that they could cheaply produce a frame with a robot and save labor costs. Again it is simply the all mighty dollar speaking.
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Old 07-16-21, 09:57 AM
  #31  
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Since the materials and methods discussed are no longer a mainstay of the current bicycle industry, it won’t be decided here.

But all that is really needed is a search function.

John
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Old 07-16-21, 11:03 AM
  #32  
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Originally Posted by commander_taco View Post
... lugs the steel tubes do not melt, and possibly not as strong as welds ...
Originally Posted by commander_taco View Post
... How come lugs are stronger...
Originally Posted by commander_taco View Post
... I remember reading somewhere that Reynolds 85x (and the like) tubing become stronger after a weld...
I'm not a mechanical engineer, but I'm married to one. I think that you need to define what you mean by "strength". Particularly in this application, for bicycle assembly. Again, this isn't my profession, but I'm pretty certain that this discussion is blurring the meaning by using this word. Maybe a metallurgist or materials engineer can weigh in on this. It would be informative.
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Old 07-16-21, 11:21 AM
  #33  
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Originally Posted by 70sSanO View Post
Since the materials and methods discussed are no longer a mainstay of the current bicycle industry, it wonít be decided here.

But all that is really needed is a search function.

John
Surely after 17 years we can find some way to continue to beat this horse.....
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Old 07-16-21, 01:29 PM
  #34  
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Originally Posted by Andrew R Stewart View Post
By applying the "nice frames" filter you eliminate the vast majority of bikes made, sold and used. Andy
Fine, but current-production cheap lugged frames are a rarity. Low-cost bikes have gone over almost entirely to welded construction.
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Old 07-16-21, 01:38 PM
  #35  
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Originally Posted by shelbyfv View Post
Surely after 17 years we can find some way to continue to beat this horse.....
You mean beat this horse better than it's already being beaten?
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Old 07-16-21, 09:34 PM
  #36  
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Originally Posted by Retro Grouch View Post
Heating steel enough to weld it weakens the metal...
There is an exception, air-hardening steels, an example is Reynolds 853, primarily a carbon, manganese, chrome, molybdenum, silicon, copper alloy which with welding and air cooling forms a fine grain structure giving it improved yield strength and a resistance to shock.
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Old 07-17-21, 06:17 PM
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Originally Posted by easyupbug View Post
There is an exception, air-hardening steels, an example is Reynolds 853, primarily a carbon, manganese, chrome, molybdenum, silicon, copper alloy which with welding and air cooling forms a fine grain structure giving it improved yield strength and a resistance to shock.
And there is a critical temp that these air hardening steels have to be heated to for this to happen. IIRC the low brazing temps of silver isn't high enough. But this has nothing to do with the strength of the joining. Andy
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Old 07-17-21, 06:21 PM
  #38  
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Originally Posted by hydrocarbon View Post
Fine, but current-production cheap lugged frames are a rarity. Low-cost bikes have gone over almost entirely to welded construction.
At the risk of seeming self centered... I'll quote myself from post #23 "In real life of making frames (from steel) these joining methods chosen are much more about cost, builder's skills, marketing aesthetics then theories."

This is why the industry has gone to welding for frame construction as much as it has. Welding is strong enough when done properly and can be done so at a lower cost. Andy
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Old 07-17-21, 06:26 PM
  #39  
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Originally Posted by rydabent View Post
From the middle '80s and before welded frames were laughed at. Any quality bike was a lugged frame bike. Then came computers and robot welders. Bike mfg quickly found out that they could cheaply produce a frame with a robot and save labor costs. Again it is simply the all mighty dollar speaking.
Unfortunately facts donít support your anti business narrative. It was the development of affordable tig welders and the advancements in metallurgy which the tubing manufacturers took advantage of and created tubesets specifically for welding. A tig welded frame is as hand made and has the implied quality as any lugged frame.

I love this, a 17 year old thread is resurrected like a old one hit wonder coming back to life.
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Old 07-18-21, 09:03 AM
  #40  
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Originally Posted by Atlas Shrugged View Post
Unfortunately facts don’t support your anti business narrative. It was the development of affordable tig welders and the advancements in metallurgy which the tubing manufacturers took advantage of and created tubesets specifically for welding. A tig welded frame is as hand made and has the implied quality as any lugged frame.

I love this, a 17 year old thread is resurrected like a old one hit wonder coming back to life.
Are you trying to convince us that the Asian mfg that make the lions share of all frames dont love welding robots? Even in China, mfg have to pay workers to braze lug frames. Welding robots and work 24 hours a day if need be, with no breaks.

One more thing------------------if the frame is welded, it is hard to define a really cheap big box store frame from a $10,000 frame.

Naw------------its the money.

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Old 07-18-21, 02:47 PM
  #41  
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Originally Posted by Atlas Shrugged View Post
Unfortunately facts don’t support your anti business narrative. It was the development of affordable tig welders and the advancements in metallurgy which the tubing manufacturers took advantage of and created tubesets specifically for welding. A tig welded frame is as hand made and has the implied quality as any lugged frame.
Dude, what the hell are you talking about? Yeah, welded frames can be high-quality, but the reason they became dominant is that they became cheaper to produce than lugged joints due to automation and moving production to where labour is cheap.

Last edited by hydrocarbon; 07-19-21 at 12:45 AM.
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Old 07-18-21, 03:13 PM
  #42  
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Welded frames are cheaper to build than lugged, but that doesn't mean lugged is "better."

Advantages to (TIG) welded include: lighter, cheaper, faster to build, no constraints on angles.

Personally, I like lugged, but the above are real advantages. Not to mention, lugged is limited to steel. TIG is used on steel, aluminum, and titanium.

BTW, very few welded frames are welded via robotics. Most are TIG welded by hand, even in high volume shops.
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Old 07-18-21, 04:54 PM
  #43  
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^
Good post. I can appreciate both, and itís nice to have options to suit different styles of bikes.
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Old 07-18-21, 05:15 PM
  #44  
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Originally Posted by shelbyfv View Post
Surely after 17 years we can find some way to continue to beat this horse.....
It must be lugged, to be able to handle this much flogging!
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Old 07-18-21, 05:35 PM
  #45  
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Originally Posted by commander_taco View Post
I...

The bending stress is maximum at the end point of a cantilever. If a tube fails due to cyclic stress, then chances are it fails at the point where it is attached to other tube. A welded joint also has more metal (due to welding bead and butting) just like a lug. Unless the welder left stress raisers (sharp notches) it would be intuitive to reason that a lug will separate earlier in this application since the lug joint is not as strong as a welded one inch per inch. If anything a welded joint cannot be weaker!...
But, for a weld you have a total area of the tubing diameter times the weld width (what? 1/4"?). For a lug you have the tubing diameter times an inchof lug or perhaps more. On top of that, you have on a quality build, contact between the mitered tubes and both the tube thickness and the lug thickness (which can be a lot more than the tube thickness). So far more material where it matters. No thinning of steel at the lug or braze border because it never go hot enough to flow, unlike the weld that takes the steel to very hot

Proof? Look at all the very old bikes out there that are lugged and doing just fine. A lot are older than the process of TIG welding steel.
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Old 07-19-21, 08:44 PM
  #46  
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Steel lugged or welded frames are too retro. Carbon is so...Millennial. Aluminum creaks more than grandpa's knees. The future of bikes is bamboo I tell you. Yep, bamboo butted with carbon lugs, welded steel fenders, boron seat post and a hemp La-Z-Boy saddle.
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Old 07-19-21, 09:05 PM
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Originally Posted by 79pmooney View Post
But, for a weld you have a total area of the tubing diameter times the weld width (what? 1/4"?). For a lug you have the tubing diameter times an inchof lug or perhaps more. On top of that, you have on a quality build, contact between the mitered tubes and both the tube thickness and the lug thickness (which can be a lot more than the tube thickness). So far more material where it matters. No thinning of steel at the lug or braze border because it never go hot enough to flow, unlike the weld that takes the steel to very hot

Proof? Look at all the very old bikes out there that are lugged and doing just fine. A lot are older than the process of TIG welding steel.
Lugged frames were the best method at the time given the materials and technology availability. That doesn’t mean it’s the best currently because it is not, for steel, aluminum or titanium that would be tig welded. The affection for older or retro lugged frame fills a nostalgic need for some people. The sad truth is the classic frames we look back on such as Colnago, Cinnelli, Masi etc. were as mass produced as today’s carbon S-Works, there were tens of thousands produced and distributed around the world.
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Old 07-19-21, 10:39 PM
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Dunno if this has been mentioned, but the geometry of a lugged frame is controlled by the angles of the lugs.
To build a frame that doesn't correspond to the angles (and tube diameters) of available pre-made lugs, you have to make your own.
And of course some builders do just that, for aesthetic reasons as well.







Last edited by Rolla; 07-19-21 at 10:45 PM.
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Old 07-20-21, 12:29 AM
  #49  
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Originally Posted by Atlas Shrugged View Post
Lugged frames were the best method at the time given the materials and technology availability. That doesn’t mean it’s the best currently because it is not, for steel, aluminum or titanium that would be tig welded. The affection for older or retro lugged frame fills a nostalgic need for some people. The sad truth is the classic frames we look back on such as Colnago, Cinnelli, Masi etc. were as mass produced as today’s carbon S-Works, there were tens of thousands produced and distributed around the world.
Why is that sad?

I think it's great that there are a lot of these high-quality steel frames out there. They were skillfully made and finished using durable, repairable materials instead of being made of fancy plastic shat out of a high-pressure mould.

Composite frames can be extremely profitable, which is why the bike companies push them so hard. I'm personally not that interested in having a trendy disposable bike, though.

Plus the old-school Italian steel frames actually look good.

Last edited by hydrocarbon; 07-20-21 at 02:32 AM.
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Old 07-20-21, 02:16 AM
  #50  
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Originally Posted by Rolla View Post
Dunno if this has been mentioned, but the geometry of a lugged frame is controlled by the angles of the lugs.
To build a frame that doesn't correspond to the angles (and tube diameters) of available pre-made lugs, you have to make your own.
And of course some builders do just that, for aesthetic reasons as well.
Oh, absolutely. High-grade lug-making is an art in its own right.

And to be fair, there are even a few decent-looking carbon frames out there, too.


Last edited by hydrocarbon; 07-20-21 at 02:36 AM.
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