Masterclass: Lugs and lugged framebuilding with Llewellyn Custom Bicycles
Welcome to Masterclass, a series where we take you behind the scenes with renowned artisans to share the effort that goes into their craft. In some cases there will be tips and tricks to help you practise at home, other times we’ll simply provide an advanced understanding of how something is created.
In this edition of Masterclass, we look at what’s involved when working with lugs to build a frame with Darrell McCulloch from Llewellyn Custom Bicycles.
There was a time when all road bike frames — indeed, all bicycle frames — were lugged. This method of construction, which can be traced back to the earliest steel frames, is an easy one to grasp: just match each purpose-built socket to the tubes, and the whole frame can be assembled like a child’s construction kit.
Brazing is used to bond each tube in its socket, and provided there is an accurate fit between the two, it produces a very sturdy and durable joint. From the outset, it was a sound strategy, so it persisted for many decades until the industry discovered TIG-welding in the 1970s. TIG-welding was not only quicker than brazing lugs, it gave framebuilders more freedom to vary frame angles.
Nevertheless, some framebuilders persisted in using lugs throughout the ‘80s and ‘90s. This was not a matter of stubborn traditionalism, though. “Technically speaking, a lug provides the gentlest way to join one thin-wall tube to another thin-walled tube,” explained Darrell McCulloch of Llewellyn Custom Bicycles, who has been building lugged frames for the best part of four decades. “It distributes the stress across from one to the other. You can use thinner walls, and smaller diameters, because you have a lug to distribute load from one tube to the other.
“The other thing that’s very nice about lugs is that they allow the builder to impart some of their style and character and put their workmanship on display through elaborations and embellishments to the lugs. It adds a distinct flavour to the frame that’s important for product differentiation. A TIG-welded frame made locally looks like a TIG-welded frame made in America, or Germany, or China. Yes, there can be variations in the quality of the welding, but there’s a lack of flavour there.
“There’s a lot more labour involved with lugs, though. More time is required for the fit-up, and sometimes there are limitations on tubing sizes. I’ve worked ways around that with developing my own lugs for the bigger tubes, sloping top tubes, and so on, but it still takes longer to produce a frame.”
That extra time typically adds to the cost of the frame, which, in today’s market, seems an extravagance, especially when buyers are unfamiliar with lugged frames. “Some people now come to get a frame from me and they have no idea,” said McCulloch. “They are actually surprised that there’s these little embellishments done to the lugs because they’ve come into the cycling world in the last 10 or 15 years and they don’t understand it.”
That’s enough for some to dismiss lugged frames as outdated. “There was a joke a few years ago, [American framebuilder] Richard Sachs was saying, ‘it’s not about civil war reenactments.’ We don’t build nostalgic bikes. That’s like saying you cook nostalgically because you don’t go to McDonalds or you don’t use a microwave. I’m using the best of traditional methods with the best of contemporary design and materials for the construction of my bikes. I’ve used 3D computer-aided CAD programs to design the lugs I use … that’s science fiction that never existed 30 years ago.”
This last point is an important one. Lugged frames may not enjoy the same profile that they once had, but the craft has not come to a standstill. In this regard, McCulloch has arguably done more than most to keep it moving, to ensure that lugs remain relevant to modern framebuilding.
Discovering lugs and framebuilding
McCulloch was 16 years old when he started working as a mechanic at Hoffy Cycles in Sandgate, Queensland, Australia. It was 1979, he was in love with cycling, especially racing, and had an inkling that he wanted to work with his hands, so the job seemed like the perfect fit. There was more to do than simply assemble and service bikes at Hoffy Cycles — the shop was building its own frames. “In the past, they built all the frames with lugs,” recalls McCulloch, “from the little kids bikes, 20 inch bikes, 26 inch, 28 inch, and racing bikes. That little shop built them all, and built them for other bike shops as well.”
It was McCulloch’s first exposure to framebuilding, and in time, he would be playing his part to help the workshop maintain a feverish production schedule. “We used to bang out a frame every two days! We didn’t spend much time on fit-ups and little details like reinforcing the bosses for bottle cages, and we really didn’t do a lot to the lugs other than clean the edges up and use them. It was go, go, go. And the finish work — we weren’t doing much filing and thinning — you just brushed over the lug point and away it went.”
That experience provided McCulloch with something of an apprenticeship in the craft, but it was a pragmatic one at best. “For blokes like Eric [Hendren, the owner of Hoffy Cycles], it was a job. He didn’t know anything else. He was different from me. He wasn’t driven to use a lathe, or even a drill press. I wanted to be a craftsperson making frames. I’d see these pictures of lugs and think ‘I’d love to have my own lugs one day.’”
McCulloch didn’t feel the need for any formal tuition, though. As an autodidact, he was happy to explore the craft on his own terms. “I used to take home a set of lugs and I’d cut a set of playing card suits — hearts, diamonds, clubs and spades — in the lugs, and a big ‘H’ in the bottom bracket for Hoffy. I used to do that in my bedroom with just a few jeweller’s files and a pistol drill.”
Shaped to reduce stress
There is more to the function of a lug than simply anchoring one tube to another. As mentioned above, a lug also helps spread the forces that are applied to the frame over a larger area so as to improve the durability of the joint. “When you have a sharp transition of stress, like a joint where two tubes meet, the way you reduce that stress is you use more material, or, bigger diameters,” McCulloch explained. “A lug is like a sleeve that goes over the joint, and that spreads the load over a larger area and away from the actual sharp transition of the two tubes meeting.
“When they first brought out TIG-welded frames in the ’80s, they were failing left, right and centre. They had tubes tearing out, bottom brackets tearing away at the seat tube, because they suddenly went from lugged construction to using the same tubing for TIG-welded construction. The loading of the stress of the joint was lousy, and it failed. So they increased the tube diameters, which made for a longer weld-line, or stress-joint line, to reduce stress on the joint.”
As beneficial as a lug can be, it can also create problems. “You can have a bad lug design with points in the wrong spot that actually creates what’s called a stress-riser, which is a concentration of stress and loading in a very small area,” McCulloch said. “Hence why you see on the underside of the down tube at the head tube, that point is always rounded. It’s a very stressed area and framebuilders learnt long ago to get rid of the point or you will fracture the down tube.
“You might notice that 99% of my bikes, the bottom brackets do not have points. They’re rounded off because I’ve seen them fail there. You could build 100 frames and only have one fail after five years of hard use because of a point, so I’d rather not take the risk. I do the same for the front derailleur braze-on — I round that radius off to get rid of the stress riser.”
Some framebuilders argue that thinning the points of a lug will achieve the same goal, but McCulloch disagrees. “When you have a point, that is a stress riser whether it’s thin or thick. When the tube is in torsion, that thin point is just as much a stress riser as one at twice the thickness. If there is a bending moment against it, there might be a slight reduction in stress, but if you really want to reduce the stress, you should round the point off, put a radius on the end of it.”
The other major stress that McCulloch worries about is heat and distortion. “The other nice thing about lugs is that they allow low temperature brazing. Brazing can be done with a brass-based filler to bond the tubes to the lug, however most craftsmen builders use a silver-based filler. It’s more expensive because it has a silver content of 55% or more, but it requires less heat than a brass filler.
“The idea is to melt the filler so it can run between the close gap between the tube and the lug by capillary action. The skill of the builder is using the torch to heat the joint to allow that flow of silver to go from one end of the lug to the other and fill the whole joint. You get nowhere near the temperatures used for welding, which actually melts the steel, and that can degrade its grain structure. Modern steel is much better at handling welding, granted, but silver-brazing is still the most gentle way because you avoid those really high temperatures.”
The evolution of lug shapes
The earliest frame lugs were derived from pipefittings, and so, for many years, the sockets were simply squared-off and lacked any kind of decoration. In time, small flourishes started to appear as framebuilders endeavoured to distinguish themselves and prove their skill.
“Lug cutting is an old process that the English excelled at,” McCulloch explained. “If you go back to the Second World War, everyone was using the same frame parts and tubing, so they started elaborating the lugs to show their workmanship and impress their customers. A lot of builders had their own little style and that’s how they differentiated themselves from each other.”
While some framebuilders, like Hetchins, created highly ornate lugs, most were content with small flourishes, such as letters and emblems. The stamped and sand cast lugs that predominated at the time required hours of preparation before they could be used to build a frame, so there was always a limit on the amount of time, and motivation, that was available for decorating lugs.
“When you look at frames from the ’70s and ‘80s, and earlier, a lot of them were simply race bikes,” said McCulloch. “Contrary to what some people think, they weren’t beautiful works of art. They were rough. The finish work, the sharpness of the shorelines … file marks … that didn’t really matter back then. They had to be sort of churned out to make a living.”
The introduction of investment cast lugs during the ’80s did a lot to encourage this mindset. These lugs generally required less manipulation and preparation before they were ready for brazing, so while they were more expensive, they offered an immediate increase in productivity. At the same time, those lugs didn’t provide a lot of canvas for decoration, but some framebuilders, especially those in the USA, were finding new ways to embellish lugs.
“It was only really in the ’80s that I started following what they were doing in the USA,” McCulloch said. “It was the U.S. that was really pushing it, more than the Italians. The Italians were drumming their framebuilding down to the cheapest common denominator … they were in a situation where they wanted to reduce the labour and make more profit. Nothing wrong with that. The Americans were differentiating themselves by thinning things out.”
Adding to this struggle was the rise of alternative framebuilding materials during the ‘90s, starting with titanium, then aluminium, and ultimately, carbon fibre. Where once lugged frames were ubiquitous, they were becoming outdated and devotees like McCulloch had to adapt to a changing market by lifting their level of craftsmanship to a new, higher, level.
“We used to sort of manipulate the shorelines a little bit, but 20 years ago, we just had to get them out the door. Then Kirk Pacenti brought out his stainless steel artisan lugs, which had a lot more canvas shape to them … you could use them how they were, but they were quite big, so there was some room for elaboration. I’d been using stainless steel dropouts since the early ‘90s, so I slowly morphed into using stainless steel fittings. By polishing the lugs, I was able to do an upmarket version of what used to be done traditionally with chrome-plating.”
At the same time, McCulloch started experimenting with new motifs to decorate his lugs. “I did some designs that had a snake tongue sort of thing at one point. There were flowers in there, too, and a vine growing around the heavens and the earth and lightning bolts and all sorts of things, inspired by John and Richard Murphy, the creators of Columbine frames.
“In the end, I drifted away from that and discovered the open heart. As I did my own lug designs and castings I sort of elaborated on that design. It has a slight asymmetrical shape to it, which is interesting to my mind rather than just being pure symmetrical. I think some of that came from something I saw of Peter Weigle’s 15 years ago, 20 years ago maybe; something I saw that I liked and I just elaborated on it.”
Designing his own lugs
McCulloch created the first Llewellyn lugs in 2004, starting with a set of stem lugs, followed by a set of frame lugs (dubbed Crescendo) to suit XL tubing and a sloping top tube. For a craft that was obviously in decline, it seemed like a foolhardy endeavour, however he was frustrated with the shortcomings of what the market had to offer.
“My first set of lugs allowed me to use the tubing diameters and angles that I needed, including a sloping top tube. A lot of the lugs back then had been designed before integrated brake/gear levers, so the bottom head lug didn’t have bosses for the cable adjusters. Some of them only suited the old standard tubing diameters, too, whereas I only use OS and XL, which was developed 13 years ago.”
Since then, McCulloch has added more sets of lugs to his catalogue, always with a view to serving his needs, first and foremost. “I was using another brand of lugs from a colleague of mine from America, but I couldn’t fit the seat stay on with a semi-wrap very easily. It was an old style of lug made for those plugs that you put on the top of the seat stay, and I detest them. I had to modify the lug by adding more material, and I thought, this has got to stop, so that was part of the inspiration for my Custodian lugs in 2006.”
Designing lugs also allowed McCulloch to attend to the fine details to ensure that each one is easy to work with, both before and after the frame is built. “Good appearance out of the box is important, and the lugs have got to fit reasonably well, because you always need to tweak the lug angles and fit. My seat lugs use an M6 cap head bolt rather than the old style Campagnolo seat pin bolt, because an M6 bolt has twice the strength and you can buy it at any local shop, virtually.
“My lugs also tend to have a fair wrap around the head tube — I call them the cheeks — that spread the load from one tube to the other better, but it also reduces distortion of the head tube when you’re brazing. You get less ovalisation, which makes it better for the reamer. It is one of those little things I do that adds up.”
From the outset, every lug was designed using CAD, in part because it was more powerful than pencil on paper, but also because McCulloch wanted to limit the risk that any of the important details might be lost in translation. “I like drawing, and I liked technical drawing back in the days at school, so I started teaching myself basic CAD, then Kirk Pacenti suggested I try Solidworks. It’s a different style of drafting … parametric modelling, they call it, where you draw, for example, a square and then you dimension it to push it into shape.
“One of the beauties was you could send it to a person who could 3D-print it in plastic. I first did that in 2006. That allows you to hold it in your hand, and it helps you aesthetically. You can scribble on it, and occasionally, you can see problems … then, you email the file and a new plastic piece comes back a couple of days later. Then you email the file across the other side of the world and the samples come back, cast.”
Designing each lug was time-consuming, and once it came to final production, it was also very costly. McCulloch had to pay for all of the tooling up front, which amounted to tens of thousands of dollars. Framebuilders around the world may have embraced Llewellyn lugs, but the size of the market remains very small.
“That’s the folly of it all, that’s why not many people do it. You’ve got to spend a lot of time and money, and it’s not like I’m selling them by the thousands. If I was selling thousands a year, well it would be worthwhile. It’s a trickle, so it takes three to five years to repay the cost on the tooling, let alone the time spent.”
There is a certain amount of romance surrounding lugs, due in part, perhaps, to all of the history and tradition associated with them. Much of that disappears in the workshop because it’s unglamorous work that leaves the hands filthy and raw.
At the very least, every lug must be carefully cleaned, inside and out, before it can be brazed, and the tubes must fit each socket properly. “You make sure the lug is clean, you make sure that the dust is off, and you make sure the shorelines are right,” McCulloch said. “You can’t proceed if the tube is a tight fit — that’s going to give you a problem when brazing because the flow won’t happen properly. There are points where you don’t make compromises, but you know, perfection is impossible. You have tolerances that you work to, and that’s as good as your tooling, your materials, and what you’re prepared to invest in.”
McCulloch relies on a mixture of tools for this work, some powered, and some unpowered. “You have got to hold the lug first, so you have a thing called the lug vice which is like an expanding-type tube. You’ve got to have a vice with various diameters to hold different lugs, then you can hold that device in some wooden blocks in a vice so you can then shift the lug around to work on it at different angles.
“Some people use jeweller’s saws for lugs. I don’t — just a hacksaw with a 32-tooth blade — not worth the hassle, especially on stainless steel. I have lots and lots and lots of files, all different types, jeweller’s files of different types, too. I don’t buy the cheap run of the mill stuff. Vallorbe and Pferd, they’re generally the ones I use.
“I use a hand drill and also a pedestal drill. I have a mini die grinder with these little wheels. I use them a lot because they will cut through high-speed steel, but they can be very delicate. And then you have your other die grinders with abrasive drums of different sizes and grit. I try to use the die-grinder and cut-off wheels as much as I can, but I go back and forwards all the time.
“Whether it’s a stainless steel lug or normal steel, I mechanically clean the lugs, then de-burr the inside edges a little bit. It’s all quite labor-intensive. In the factories they just dunk them in sulphuric or hydrochloric acid, rinse them, flux them, and then bang them on, but you can’t do that with stainless lugs. I mechanically clean all my lugs with new abrasive drums and a die grinder. If you get a burr on the edge, you can knock that back with a needle file or a bit of emery to break the edge. That just makes for a cleaner edge, which helps the brazing.”
Working with stainless steel lugs only adds to the amount of effort required in the workshop. “Straight from the box they are harder. To start with, the stainless lug usually has a lot more distortion in it. It’s not as accurate a lug in terms of how well it fits the tube. So I have to heat them up and tap them down into shape, just to get a neater fit of the lug. They are also more problematic at the brazing process. The stainless, even though it looks clean, it actually has an oxide on it, and you have to get rid of it and braze within a few hours.
“You’ve got to go around all the shorelines — every single millimetre — with some 320 grit emery and clean it all because, if you haven’t done it that morning, there’ll be an oxide on there. The braze might not wet against it, or it might look like it, but it hasn’t actually. Brazing is a complicated process — it actually absorbs some of the parent material into the surface of the braze and that’s why it gives you a molecular bond — but if it’s got an oxide on there, that doesn’t occur properly.
“Any work on the lug requires sharp tools because stainless steel work hardens. If you’ve got a blunt tool or a blunt drill, it rubs, and then it gets harder and you get more heat. You’ve got to push harder to get the cut to occur. It’s the same with using sandpaper on it — you always use a fresh drum. You’ve got to have this nice brand new sharp stuff. I’ll always pull out fresh new jeweller’s files for a stainless job, then they get put away, or used on other stuff before I’ll get rid of them.”
A considerable investment of time
The amount of time that is required to prepare and decorate a lug can stretch to hours, especially when McCulloch is working with stainless steel lugs. “It depends upon the elaboration, but for a stainless steel down tube lug, four hours. That starts with heating it up and pushing around the mandrel to get rid of the distortions. Then, I’ve got to sand and polish it to get a really nice, smooth finish, rather than the casting finish, so I can see the edge of the lug shoreline. That can take a little while, then I’m ready to start cutting and shaping.”
McCulloch uses a permanent marker to sketch out the cuts that he needs to make. Most of this work is done freehand, though he takes care to mark a centreline. “If you’re doing something that’s sort of symmetrical and you cut too far on one side, then you go back to the other side and make them match. It’s a bit like solo rock-climbing, you’re not tethered to anything.
“I make mistakes all the time. When you’re getting down to very thin points, you’ve got to be delicate because you can bend them. It’s high risk workmanship, because if you ruin it, then that day’s work can go down the drain. I keep a lug that I wrecked on my bench as a reminder. I would have spent a whole morning working on it … four hours of work down the drain.
“Occasionally, there might be little imperfection in the lug, which doesn’t do anything to ruin the lug, until suddenly, the point falls off. It was a little flaw in the casting, and as you cut away the material that was supporting it, your nice little point just falls off. That’s relatively rare; I wouldn’t have that happen every year.”
For those stainless steel lugs that will be polished to a mirror finish — for a “tuxedo” build — McCulloch can spend dozens of hours to complete the final set of lugs. “A pair of lugs for a handlebar stem, for example: to cut them, the best part of five to six hours; the polishing, between eight and 12 hours. The polish doesn’t take long; it’s the preparation — all the filing and the sanding — prior to polishing that takes a long time.
“You’ve got to file the whole lug to get a nice smooth even finish and you can’t cut corners. That can take a wee while because it’s stainless, so it’s hard, and then you bring that down with finer files. You start off with a coarse file and get the thickness even, then you thin it out to get a smoother finish.
“Then, you go into the grits. You’ve got to be very careful that you don’t over-cut, because you don’t want to round off the edge. The shoreline edge has got to stay sharp because that’s where your paint line is going to end up. The neater and sharper you have that, the better the finish. You’ll see some framebuilders have pretty lousy shorelines, so the paint doesn’t look very sharp and neat.
“I usually start with about 120 grit, sometimes 240 or 320 grit. You can’t just run sandpaper in the same direction, because it creates little grooves, and the grits will just follow the grooves. It might look a bit smoother and smoother, but when you go to polish it, you’ve still got scratches. You’ve got to work the opposite way all the time, and that’s what’s time consuming.
“If you look at the reflections of the lug, that tells you a lot by how straight and smooth the reflections are. I’m proud of what I do there because I’ve seen some lousy ones over the years. Some people say you can do it by mechanised means, but no, you can’t. If you use buffing wheels, you round off the edge of the lug so you don’t have a sharp shoreline and you get a wavy finish to the surface. That looks dreadful.
“I wrap the emery around old files that are smooth or balsa wood sticks, and work it and work it and work it and work it until I get down to 1000 grit wet and dry, and then down to 1500 grit, which is what I finish with. I probably spend more time with the 1000 and 1500 grit, but then when you go to polish it, it pretty well goes within minutes. It might take four hours of filing and sanding, but the final polish can then be done in ten minutes.”
Needless to say, this kind of work is tiring, and McCulloch admits that it borders on futile. “The stainless work is really just … it’s unnecessary. It’s not needed to make a good bike, and once the owner washes the bike a few times, it doesn’t matter. But it is certainly a showcase of the craftmanship, and I can prove to myself what can be done.”
The final fit-up
Every lug, polished or not, and decorated or not, ends up in the same place, namely a framebuilders jig for brazing. This is where the lugs are manipulated to suit the tubes and the final frame angles. However, before the lugs can be fitted, the tubes must be mitred so that they sit cleanly against one another.
“All the tubes go into the jig without the lugs as they are mitred,” McCulloch said. “I send my customers photographs of that to show that mitres are close … we’re not talking two-tenths of a millimetre or anything like that, but they are close. The really critical ones are at the head tube. It not only improves the strength of the joint but it keeps the frame in alignment during the braze. That requires good fixtures and attention to setting up the fixture before cutting the mitre.
“There’s a slight variation in mitring angles because your tubes aren’t dead straight. They have a slight bow: you roll the tube and orientate the bow so it’s not going from side to side, it’s orientated in the plane of the frame. And so you get a like a tenth of a degree or two variation in angle due to that. You work with the material that you have. So a little touch up with the file is sometimes required for the mitres, just a very fine file until the each tube nestles into its spot, nice and tight.
“Once you’ve got that done, then you get the lug and fit it to that joint. In the factory, they don’t do that. They actually lean on it, bend it, and tap it down because it’s a faster process. It is a lot more time-consuming to form the whole frame up and then fit each lug to each joint. Sometimes you’ve got to take it apart a few times, undo the jig, pull the head tube out. It can take an hour to fit a good lug properly.
“It’s important the frame goes together in the fixture with the tubes all being held at the right places with no stress in the lugs. You’re not actually forcing the tube, and the jig isn’t constraining or pushing the tube into place. It should all just fall into place. Nestle. There can’t be a tight fit with the lug, because the braze won’t flow. Capillary action has to take it through there.
“In the perfect world, you would have about a tenth to two-tenths of a millimetre clearance all the way around between the tube and the lug. If there is a little bit tightness, then you give the lug — not the tube — a light rub, very carefully, until it eases the fit. If you get it right, then when you go to braze it — if you’re brazing correctly and everything is tacked right — you keep very good alignment, and that’s important to me.
“My tolerance is 0.3mm over 400mm of head tube alignment to the seat tube. I can get there at least 90% of the time without any cold setting of the main triangle because I do it joint by joint. It’s all about preserving that alignment, because cold-setting a frame … modern materials with large diameters and thin walls do not like that. If you do all these steps — the mitring, the lug work, good brazing, and removing any inbuilt stresses in the frame that you get from cold-setting — then the bike rides better.
“There is no such thing as perfect. I know it’s a cliche, but there isn’t. Chainstays always move because they get squashed and shaped, so they’ve got inbuilt stresses and you’ve got to cold-set to correct them. There is never a perfect shoreline braze, either. There’s always something that you have to file off … there are some I’ve been extremely satisfied with, but they’ve never been perfect.”
After almost four decades building frames, McCulloch has earned a place as a senior figure in the world of framebuilding, but his perspective on his craft hasn’t really changed. He still focusses on the small details that are important to the next frame in his jig, and he remains devoted to upholding the high standards he has created for himself.
“None of my frames have a lug as it comes out of the box,” he said. “I always change the shorelines a little bit, or change the radius of a curve — little odds and ends like that — because it’s just me and part of my flavour. I could drum my frames down to half the labor content that I have now, but I like doing it, and for what it’s worth, some people appreciate it.
“I’ve still got lots of ideas, like the lugged Colossus. I’d like to tool up and do some new tubes and castings for that, but my production is never going to warrant the investment. I’d love to do my own bracket shell, too, because I can see improvements there — just for ease of use — and I’d like to do my own fork crowns.”
Clearly, there is still room for progress, but McCulloch isn’t worried about the future of the craft. Rather, he is heartened to see that there are still people intent on mastering the craft of building lugged frames. “I’ve tried keep the scene alive by encouraging genuine people. There are a few who are trying, so I don’t think it’ll disappear. I don’t worry about it because there will always be something to keep it alive, despite the fact that it is not the industry it once was.”