Lug Options

Lugs, lugs everywhere and not a one to drink

Lugs, lugs everywhere and not a one to drink

So, we’re collecting all the parts required to build our first test-of-concept frame:  the Seven Cycles Shop Bike I mentioned last week.  Our intention was to source the four lugs and maybe build one from scratch; making a lug from scratch was to be part of our conceptual test.  Well, it turns out that we can’t find a single lug that will work on this shop bike—not even one.


We’ve looked at too many lug sources—through suppliers and direct from manufacturers, domestic and overseas, road and mountain, high quality and cheap—and cannot find a single lug that will work on any of the four joints that would typically get lugs.  “What the what?” This bike design is completely within Seven’s norms.  In fact, we tried to design the geometry so that we could use some standard lugs.  Still, no dice.

I’m sad to say that this is one of the more enlightening moments of the project for me—and for many others in the Collaborative.  Here we are trying to design a bike—a fairly average bike design, by Seven’s standards—and we can’t find a single lug that will work.

What Are The Four Lugs?

For those that don’t know what I’m talking about, the four common lugs are:

  1. Head tube to down tube
  2. Head tube to top tube
  3. Seat tube to top tube
  4. Bottom bracket to seat tube and down tube

[If I had time I’d include a diagram.  Maybe later.]


Why can’t we find lugs?  The basic reasons include:

  • We want to have this bike employ a “compact” design with 12 degrees of top tube slope.  Yes, this is a bit more than average—Seven’s road bike average being about 8.5 degrees.  But, over the years we’ve built thousands of bikes with 12 degrees or more of slope.  And, apparently, lugged steel bikes must have an average of about 0 degrees of slope.
  • We want to use a 1.25” diameter top tube.  Yes, this is on the unusual side for a road bike.  But, not for a mountain bike—and there are some mountain bike lugs out in the world.  Two reasons we’re going with a 1.25” top tube:  1) This is a shop bike with a big rack on the front—front end torsion can be a challenge, and a stiffer top tube can help.  2) Because we’re butting in house, we can play with diameters, tube walls, and tube butts more so we want to experiment with this tube.
  • We want to use a 1.25” diameter seat tube.  Again, unusual but not crazy.  We have our reasons:  explaining later.
  • Read between the lines.

So, in the end, even when we tried to compromise the design fairly extensively, we still couldn’t find lugs—actually, we found one that would sort of work.  Therefore, we decided to design our ideal since we’d have to make lugs from scratch anyway.  And, maybe a fillet joint or two—that’s a whole other conversation.


5 Responses to “Lug Options”

  1. Quotable #12 « Seven Cycles Collaborative | A group of employees at Seven, working on a long-term project. Says:

    [...] addendum to the “Lug Options” [...]

  2. Dobie Says:

    Since most quality lugs are cast, how do plan on making your own? Oversized tubing can be used to create your own (I’ve seen this done), but that is like a lot of extra labor, materials and clean up for anything looking at production.

  3. Rob Vandermark Says:

    Dobie: Good question. We’ve explored a number of ways to make lugs. I’ll try to post the list tomorrow. :)

    For the Shop bike we’re making the lugs in the fashion you mentioned–using “oversized” tubes to carve into lugs. Good times. They are definitely labor intensive but a lot of lugged frame constructors use this method–or a modified version of this method.

    Thanks for reading. – Rob V.

  4. Peter Says:

    Are you surprised that a frame building method that has its roots in traditional triangle road frame creation cannot accommodate your unique needs? No doubt there are limitations to working with lugs. That’s why you did not use traditional carbon lugs for your carbon bikes.

    While seven sees this project bike as “standard” the lack of adequate supplies to accommodate its creation as a lugged frame surely suggests what you are trying to do
    1. is not a standard project for which one would/should employ lugs
    2. is probably not best achieved with lugs (or else others would have done it and would be supplying the materials to do it again)

    While I applaud the ingenuity and willingness of your team to create your own solution, I can’t help but think you are using the wrong tool for the job, or choosing the wrong job for the tool you have.

  5. Rob Vandermark Says:

    Hey Scott: Yes, I really am surprised, along with the three Seven employees that have a history of building lugged steel frames—some of them having worked with lugs for years. Meaning: they have some credibility even though I don’t.

    In terms of you thinking that the Collaborative is using the “wrong tool for the job,” a very large part of this project is about R&D—research and development. Merriam-Webster’s dictionary partly defines the word research as: “revision of accepted theories”. In other words, taking the existing “tools”—“accepted theories”—and using them in “wrong” ways—“revision”.

    That’s what I call fun, learning, and research; all aspects of the Collaborative. I’ll post more complete thoughts about your comments in the journal itself.