Bicycle Frame Lug Types

Evaluating a few lug methods

Evaluating a few lug methods

Early in the Seven Cycles Collaborative we discussed the ways in which we could go about sourcing or making lugs.  Here are a few of the ways to make bicycle frame lugs:

  • Investment casting:  This is the most common method of making high quality lugs.  This is the oldest form of metal forming on the planet.  It’s a pretty amazing way of making a formed part.
  • Stamped from sheet:  This is the lease expensive way to make lugs in large quantities.
  • Bulge forming:  This has only been used a few times, relatively speaking, compared to other methods.  Basically, a steel tube is put into a lugged shaped mold and hydrostatic pressure is used to expand and shape the tube into a lugged form.
  • Welding or brazing tubes together:  This is the method that Seven Cycles is using for the Collaborative Shop Bike.  Photos to follow.  This is also the method that Seven uses on our titanium and carbon mix frames.
  • Machined:  This is not something I’m aware of for steel frames but some other lugged construction frames start with a molded part and then final machine the angles and details.  I include this on the list because it’s one of the ways that we are evaluating making lugs for the Collaborative.  However, it would be more appropriate for a production setting, not so much for the Colab project.
  • Combination:  This is very common, particularly among artisan frame builder.  Combo lugs take an investment casting and the add material, or more commonly, remove material to end up with a different look and characteristic than a raw casting.

We discussed a few other ways to make lugs but we’re keeping those ideas under wraps for the moment.

Lots of options; all with challenges.  More later.

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