# Lugged Design - Carbon Frames



## bikerneil (Nov 3, 2007)

What are the general advantages or disadvantages, or better yet - what are the major differences in ride quality that one finds with a carbon fiber bike that features a Lugged Tube Design (as opposed to a Carbon Fiber frame that that is layed up completely in a mold)?

Thanks.


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## Retro Grouch (Apr 30, 2002)

Do an internet search and you'll find discussions on the subject like this:

http://forums.roadbikereview.com/bikes-frames-forks/monocoque-carbon-fibre-vs-tubes-lugs-17951.html

Monocoque vs Lugged Carbon Frames?: Triathlon Forum: Slowtwitch Forums

lugged vs monocoque? [Archive] - Bike Forums


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## gamara (May 20, 2002)

Actually there are 3 types of carbon construction: monocoque, tube to tube and lugged.

Ideally if all 3 methods are done correctly there should be no difference in terms of ride quality or weight. I think that the differences in construction have more to do with cost for the manufacturers & range. 

Monocoque construction is one piece structure that requires an individual mold for each frame size. Only large companies can afford to go this route because of the expense involved & it limits the number of sizes that can be offered.

T to T & lugged offer more flexibility by allowing smaller builders to be able to offer more sizes or even custom fit a frame.

So unless you cannot find an oem frame that fits you by any of the above construction methods you can if afford to, find a custom builder to build you a custom carbon frame via T to T or lugged method. That is the only advantage that I can think of.


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## Kontact (Apr 1, 2011)

There are (at least) four methods. Most molded bikes aren't monocoque, they are constructed of sub-units. Trek's OCLVs are probably the most obvious one.

In the end, the ride quality doesn't have a lot to do with the joinery - just like it doesn't have much to do with how a lugged, TIG'd or filleted steel bike rides. The shape and thickness of the tube walls determines ride.


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## stevesbike (Jun 3, 2002)

to the OP's question - the lugged design dominated early carbon production, which was based on steel frame production (e.g., early Look KG frames). Like steel frames, the lug/tube interface was typically the weakest element of the frame (weakening of steel due to heat) and corrosion due to carbon/alloy interface or weakening of glue due to impurities etc. A lugged design - if seen at all today - remains to make custom sizing easy (although Serotta no longer does this on some of their custom frames, for example). 

There is no intrinsic reason for a lugged carbon design. Like others say, the ride quality is determined more by tube shaping, layup, than lugs.


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## flatlander_48 (Nov 16, 2005)

gamara said:


> I think that the differences in construction have more to do with cost for the manufacturers & range.


Monocoque construction made it much easier to tailor the strength and stiffness qualities of a frame. You have control over cross sections of the tubes. Prime examples of this are the enlarged bottom bracket areas, deep chain stays and rectangular or oval shaped down tubes. Ride quality has a lot to do with vertical compliance of the frame. Pedalling efficiency has a lot to do with lateral stiffness. Apart from carbon fiber, usually the only other place that you will see extensive shaping of tubes is in hydroformed aluminum frames. Conversely, when you're dealing with round tubes of constant cross section, it is more difficult to do localized stiffening.


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## Bill2 (Oct 14, 2007)

Check out Viner's non-monocoque, non-lugged method of building custom carbon frames:
Perfect fit: getting a bike made to measure | road.cc | Road cycling news, Bike reviews, Commuting, Leisure riding, Sportives and more


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## Kontact (Apr 1, 2011)

stevesbike said:


> to the OP's question - the lugged design dominated early carbon production, which was based on steel frame production (e.g., early Look KG frames). Like steel frames, the lug/tube interface was typically the weakest element of the frame (weakening of steel due to heat) and corrosion due to carbon/alloy interface or weakening of glue due to impurities etc. A lugged design - if seen at all today - remains to make custom sizing easy (although Serotta no longer does this on some of their custom frames, for example).
> 
> There is no intrinsic reason for a lugged carbon design. Like others say, the ride quality is determined more by tube shaping, layup, than lugs.


There's a lot of fact missing from this. There are still plenty of non-custom lugged bicycles, and real lugs aren't actually very useful for customization because the lug molds set a fixed angle. Check out Colnago C-59 and Calfee Luna.

Your reference to early carbon frames being like steel bikes is strange. Most early carbon frames were internally lugged, a process borrowed from bonded aluminum frames, not steel. You can put the lug inside or out, and inside was more the norm for the first 10 years of carbon production.


All of this is aesthetic. You can make a light, excellent bicycle with any of the methods. But lugs and tubes don't apply well to aero bikes, and that's the current fashion (even when they only look aero). And molded bikes are the least labor intensive, and cheap production with high profit margins is the other current fashion.


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## Jay Strongbow (May 8, 2010)

flatlander_48 said:


> Monocoque construction made it much easier to tailor the strength and stiffness qualities of a frame. You have control over cross sections of the tubes. Prime examples of this are the enlarged bottom bracket areas, deep chain stays and rectangular or oval shaped down tubes. Ride quality has a lot to do with vertical compliance of the frame. Pedalling efficiency has a lot to do with lateral stiffness. Apart from carbon fiber, usually the only other place that you will see extensive shaping of tubes is in hydroformed aluminum frames. Conversely, when you're dealing with round tubes of constant cross section, it is more difficult to do localized stiffening.



I don't disagree with you in theory but would you choose a Parlee Z1 (lugged) over XXXX popped out of a mold with optimal shapes to localized stiffness blah hlah......Which do you think would have the better ride? (If you're not familiar with the Z1, just trust me that most would agree it rates really high in ride quality). By the same token I'd imagine there are some lugged frames with horrible rides compared to other frames made with a different method.


in other words the construction method might matter In theory or in some science lab but for butt on seat testing the method takes a far back seat compared to all the other factors.


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## latman (Apr 24, 2004)

Bill2 said:


> Check out Viner's non-monocoque, non-lugged method of building custom carbon frames:
> Perfect fit: getting a bike made to measure | road.cc | Road cycling news, Bike reviews, Commuting, Leisure riding, Sportives and more


thats simply Tube to Tube construction ? Done in asia looking at that guy pictured with what looks like deda made/sourced seatstays.... hardly unique


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## wim (Feb 28, 2005)

While "lugged" means "visible outside lugs" to most people, Trek engineering (as opposed to marketing) has always refered to their OCLV frames as "lugged," meaning "composite tubes joined by composite connectors." Obviously, this use of the term "lugged" is open to debate. At the link, under "Combining old and ultra-new":
At the top and still climbing : Composites World 

Perhaps getting a little old in the tooth now, but here's a paper that directly addresses the OP's questions:
http://www.calfeedesign.com/tech-papers/technical-white-paper/


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## flatlander_48 (Nov 16, 2005)

Jay Strongbow said:


> I don't disagree with you in theory but would you choose a Parlee Z1 (lugged) over XXXX popped out of a mold with optimal shapes to localized stiffness blah hlah......Which do you think would have the better ride? (If you're not familiar with the Z1, just trust me that most would agree it rates really high in ride quality). By the same token I'd imagine there are some lugged frames with horrible rides compared to other frames made with a different method.
> 
> 
> in other words the construction method might matter In theory or in some science lab but for butt on seat testing the method takes a far back seat compared to all the other factors.


Yes, I am familiar with Parlee ever since Tyler Hamilton used one in the Mt. Washington race after his first suspension. Don't know if it was a Z1 however. Anyway, the point is that you have more things you can change with a monocoque type construction to achieve what you want. That doesn't mean that you can't get to the same place with other methods. It's a matter in how much effort you want to spend. When you have fewer variables to work with, it's a bit more difficult to do.

For lugged construction, you can change tube diameter, tube thickness, mat types, bond length of the lug and tube angles.

For monocoque construction, tube cross section, variable cross section, tube thickness, mat types, transition from tube to tube and tube angles.

From my limited knowledge of carbon fiber bike manufacturing, that's what I see as the things that you can change. So, suppose you make a change to improve the lateral stiffness in the bottom bracket, you have at least one more design parameter that you can change if that increase in stiffness hurts your vertical compliance. I think if there are fewer things that you can change, the possibility of making an undesired compromise increases. I think it is entirely possible to get similar ride qualities by different construction methods, but I would wonder if there wasn't some compromise in some other aspect of the bike.


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## flatlander_48 (Nov 16, 2005)

Bill2 said:


> Check out Viner's non-monocoque, non-lugged method of building custom carbon frames:
> Perfect fit: getting a bike made to measure | road.cc | Road cycling news, Bike reviews, Commuting, Leisure riding, Sportives and more


Too bad the author could not convert .1mm to inches correctly...

.1mm = .0039"


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## stevesbike (Jun 3, 2002)

Kontact said:


> There's a lot of fact missing from this. There are still plenty of non-custom lugged bicycles, and real lugs aren't actually very useful for customization because the lug molds set a fixed angle. Check out Colnago C-59 and Calfee Luna.
> 
> Your reference to early carbon frames being like steel bikes is strange. Most early carbon frames were internally lugged, a process borrowed from bonded aluminum frames, not steel. You can put the lug inside or out, and inside was more the norm for the first 10 years of carbon production.
> 
> ...


I realize you have a need to one-up every post, but this simply isn't true. Early carbon frames like the TVT, Look KG86, Trek 2500 etc all featured tubeset and external lug designs. Some of the lug and tube diameters may have been the same - some weren't like the headtube/lug, but it was the same design philosophy as steel based frames. A tubeset, lugs, and some bonding method. Look's own bikes like the KG96 (I still have one hanging on my wall) were the prototype for lugged design that Time, Colnago, and others still use.

Lugs are completely useful for custom frames - Serotta even custom machines lugs for each frame. It is much more economical to make new lug sets than molds. Even the C59 of your example can be custom made- Voeckler's features a custom tube set... 




Example: This page, Calfee technical white paper, Serotta page...

Lugged construction using RTM or fillament-winding carbon tubes
This was the original method of carbon frame manufacture and is a direct descendant of the lugged frame construction used for steel frames. Frames made using the lugged process can offer high performance, but the main reasons for the use of this method to make contemporary frames are: ease of custom geometry changes and lower labour and equipment costs. (Carbon fiber technology for bicycle frame manufacture)


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## Winters (Dec 4, 2011)

Nope, the author has it right. ... That's .1 mm / .1 degrees ... not .1mm / .1 ".
.
re: " Digitally controlled, it ensures that everything is made to within 0.1mm/0.1° of the design spec. It’s a high-tech business. "
.


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## flatlander_48 (Nov 16, 2005)

Winters said:


> Nope, the author has it right. ... That's .1 mm / .1 degrees ... not .1mm / .1 ".
> .
> re: " Digitally controlled, it ensures that everything is made to within 0.1mm/0.1° of the design spec. It’s a high-tech business. "
> .


Smallest degree symbol I've ever seen...


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## Bill2 (Oct 14, 2007)

latman said:


> thats simply Tube to Tube construction ? Done in asia looking at that guy pictured with what looks like deda made/sourced seatstays.... hardly unique


No, Marco Bertoletti's shop is near Bergamo here in Italy: Italian, not Asian. Here's some more pics of their carbon, titanium and steel bike fabrication (under the Legend brand)
Bici da corsa | bdc-forum.it - Visualizza messaggio singolo - Visita a Legend. Handmade by Bertoletti

Good pics of the factory and staff also here:
Legend factory


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## danl1 (Jul 23, 2005)

Kontact said:


> There's a lot of fact missing from this. There are still plenty of non-custom lugged bicycles, and real lugs aren't actually very useful for customization because the lug molds set a fixed angle.


There's an exception to this, from one of the companies you mention. Calfee Dragonflies are made in the same essential manner as the Luna is, but they custom-make the lug molds as required.

The technique is interesting. Take a block of material, bore out the 'lug' shapes, and cut the block in half. Lay in the tubes, wrap them in carbon, squeeze the blocks together to form the lugs. OK, so that's a vast oversimplification, but it's the core of it.


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## danl1 (Jul 23, 2005)

flatlander_48 said:


> For lugged construction, you can change tube diameter, tube thickness, mat types, bond length of the lug and tube angles.
> 
> For monocoque construction, tube cross section, variable cross section, tube thickness, mat types, transition from tube to tube and tube angles.
> 
> From my limited knowledge of carbon fiber bike manufacturing, that's what I see as the things that you can change. So, suppose you make a change to improve the lateral stiffness in the bottom bracket, you have at least one more design parameter that you can change if that increase in stiffness hurts your vertical compliance. I think if there are fewer things that you can change, the possibility of making an undesired compromise increases. I think it is entirely possible to get similar ride qualities by different construction methods, but I would wonder if there wasn't some compromise in some other aspect of the bike.


While this is true, it's also surprisingly irrelevant. While you objectively have the ability to 'customize' all of these parameters, because of the cost and effort involved in doing the engineering and designing and building the molds, you end up 'customizing' a bike for an 'average' rider. So, if you are that 'average' rider that the designer built around, all is well. Otherwise, one of the theoretically lesser construction methods will usually be able to deliver fewer compromises for the rider in question.


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## -Boat- (Feb 29, 2012)

Would an old lugged design be a worthwhile build up? I'm looking for a lightweight carbon fiber frame for a build project and a quick search on eBay found this. What do you guys think a frame like this is worth?


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## flatlander_48 (Nov 16, 2005)

danl1 said:


> While this is true, it's also surprisingly irrelevant. While you objectively have the ability to 'customize' all of these parameters, because of the cost and effort involved in doing the engineering and designing and building the molds, you end up 'customizing' a bike for an 'average' rider. So, if you are that 'average' rider that the designer built around, all is well. Otherwise, one of the theoretically lesser construction methods will usually be able to deliver fewer compromises for the rider in question.


The original message asked a question in general terms and was not aimed at custom frames built for one person.


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## flatlander_48 (Nov 16, 2005)

-Boat- said:


> Would an old lugged design be a worthwhile build up? I'm looking for a lightweight carbon fiber frame for a build project and a quick search on eBay found this. What do you guys think a frame like this is worth?
> 
> I can't post the link (post count) but here's the item number...
> 
> 300673154140


Note what the entry said:

_"I'm sure it will make someone a very nice *vintage road bike project*."_


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## Kontact (Apr 1, 2011)

stevesbike said:


> I realize you have a need to one-up every post, but this simply isn't true. Early carbon frames like the TVT, Look KG86, Trek 2500 etc all featured tubeset and external lug designs. Some of the lug and tube diameters may have been the same - some weren't like the headtube/lug, but it was the same design philosophy as steel based frames. A tubeset, lugs, and some bonding method. Look's own bikes like the KG96 (I still have one hanging on my wall) were the prototype for lugged design that Time, Colnago, and others still use.
> 
> Lugs are completely useful for custom frames - Serotta even custom machines lugs for each frame. It is much more economical to make new lug sets than molds. Even the C59 of your example can be custom made- Voeckler's features a custom tube set...
> 
> Example: This page, Calfee technical white paper, Serotta page...


One of the earliest successful (didn't constantly break like the Graftek) carbon bikes were the 1982 Vitus Carbone, which are built the same way as the 2500 - a wedge shaped lug is inserted _into_ a beveled carbon tube. TVT and Look (same thing at the time) had two lugs that put the tube inside the lug - head tube and seat tube - but the rest were built the same way; internally. Here's the later KG96. The tiny lugs have neither the length nor diameter to contain a carbon tube - that's because the tube stops where you see it and the lug runs several inches inside.








And a very clear view of this type of construction:









Craig Calfee's initial design wasn't lugged, either. The first generation of bikes and the current Tetra are externally wrapped lugs, formed using dies. Later Luna and Dragonfly designs use the same die technology to form lugs around dummy tubes. I don't know who first inserted a carbon tube into a lug, but I suspect that the 1990 Allez might have been it.

Colnago can make you a custom C-59, as long as what you want can be built from their range of stock lugs - which will usually do the job. But it wouldn't be difficult to ask for something, like a level top tube - that they wouldn't be able to do.

Serotta's method is kind of the exception that proves the rule. They take oversized molded lugs and machine them to take the tubes at a desired angle. You couldn't build a bike with their lugs without a CNC machine.


And I have no interest in showing you up. I just though your post distorted both the history and engineering of carbon build methods. Externally lugged carbon is actually the newest technique employed for building bikes.


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## elviento2 (Mar 1, 2012)

Frankly, it's the same thing as the difference between a traditional stem handlbar combo or the integrated stem/bar (Ram, Alenara, Plasma).


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## Bill2 (Oct 14, 2007)

Here in Italy instead of lugs some builders hand-layer dozens of individually-shaped pieces of pre-impregnated carbon fabric to build a junction between tubes. These are called fascette.


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## zigmeister (Jan 26, 2012)

Some companies feel using a sectional approach is easier to manage during the molding/post molding process when using bags to inflate inside the tubes during the process. Having one big section, or complex sections with multipe turns makes it more difficult to remove the internal bags and the corners/rounded areas are cleaner and better designed with multiple pieces to a frame.

Felt is using this method and has changed things around some this year with their molding techniques.


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