Llewellyn – OS Compact
The forth Design and Form by Llewellyn the third lug set. Year 2006
The world’s first OS Compact sloping top tube lug set for road bikes.
I needed an OS sloping top tube lug set for use under small to medium sized riders, or to allow the OS frame design to have a high handle bar height. After the success of the XL sloping top tube lug set, I was once again into the design process on the computer towards the end of 2005 for the OS set. These lugs are a reflection of my taste for curvy but simple lug shorelines, which can be left as they are, or allow for elaboration if so desired.
The OS sloping lug set had to have all the usual desired features such as a stainless steel M6 cap-head seat binder bolt, cast M5 gear bosses on the DT lug, and lots of seat tube skirt to allow the builder to trim the skirt to fit their desired seat stay attachment style.
I decided on a 6 degree slope to the top tube. I left lots of stack height on the top head lug that can be trimmed if desired to suit the frame design.
I jokingly call this set my PhD in frame lugs. To further my knowledge of the investment casting process, I visited Taiwan and also opted to try a new casting firm. The change in casting firms had later, rather unfortunate implications, and caused many supply delays L After that trial and error I returned all my production to LongShen J where it remains to this day.
The design of these lugs was also difficult as I wanted the CAD models to have true, unbroken shorelines perpendicular to the tube axis. I consulted many professional CAD draftspersons and they were at a loss to find me an answer. But I persisted, and after much trial and error I developed a method that allows this to be done. I also noted that many existing lug designs have mistakes in the shape of the shorelines, i.e. shorelines that don’t match between the three main frame lugs. I wanted none of that in this set.
The CAD design work was very time consuming, I put a lot of effort in seeking the best design of the lug line aesthetic possible.
The end result was pleasing to me. The OS compact lugs arrived early 2006 but I didn’t bring them into full production not till later in 2007. This lug set has proven extremely popular with builders all around the world.