dunkleosteus

I'm frame builder-curious but haven't built anything myself. I'm wondering, for lugged frame builders who want to design their own geometry, do you make your own lugs, or have them custom-made? I ask because the lugs determine the frame angles, so they almost completely determine the frame geometry (up to DT and ST length I guess). What's the deal?

unterhausen

The nominal angle for a lug is just a suggestion.

Lugged bikes represent a minority of steel bikes made nowadays. Similar numbers are fillet brazed and more are welded. Other people do bilaminate construction, which is similar to "making your own lugs."

Andrew R Stewart 

The angles that lugs are offered in are a result of cost VS sales, nothing more or less. Lug manufactures look at the bell curve of angles (and tube diameters) for each joint and then their projected sales of any one angle (set of diameters). When the projected sales raise above the cost plus needed margin for profits then make that lug. When lugged frames were the norm these numbers of projected sales were enough to allow many angles for any one joint. These days the demand is far less and thus the offerings are found in the meddle of the bell curve, at best.

Thus one either mods the offered lug (by various methods) to change the angles, makes their own lugs (and virtually build the main frame twice) or goes luggless. Having done all three options I can say each has it's limits, time consumption and results.

https://www.bikeforums.net/framebuil...-part-dux.html Is my second thread about my lug making. In the first post is a link to the first attempt. Andy

dunkleosteus

That was a really interesting thread, thanks for the link Andy, and great work!

I did not consider bending, but that makes total sense.

Andrew R Stewart 

Preexisting lugs can be bent and internally ground or cut, changed then patched with braze/weld.

Grinding and/or bending will leave internal gaps that often exceed what silver likes. I have done this to shift angles as much a 4+ degrees then used brass/bronze to braze the joint. Generally more filing is needed on the lug's OD to reduce the bulges that result from significant edge bending. Pressed/stamped lugs are far more easily done then cast ones for reasons of wall thickness and having already empty interior voids. Generally a degree + is about the most before loosing silver filler ability.

Cutting a wedge or slot into the "crotch" of a lug and either compressing or spreading the angle can get a lot more change while doing a better job at maintaining the shore lines and exterior surface "flow" However filling the slot or gap with either weld or brass/bronze adds a big step. Either way a session working the lug's exterior will be needed to make the patch look good. I have not done this before although seen it done by others. I suspect it retains the internal clearances that silver likes better then the first method.

For BB shells bending of preexisting shells is the only way to change angles that I have heard of or done. I have yet to make a shell.

Over on Velocipede Salon"s Smoked Out Steve Garo shows a really fine effort of hand built lugs. Andy