Eisho, still holding up (under a substantial load) on my Dave Tesch. Tesch was a big user of Bikini lugs in the US.
http://www.classicrendezvous.com/
Joe Bender-Zanoni
Great Notch
>
\r?\n> A beautiful artisanal custom bike I saw recently had a fatigue-cracked
\r?\n> head tube, right at the downtube lug edge, and it was not nearly the
\r?\n> first one I've seen.
\r?\n>
\r?\n> The cracked frame had lugs filed down so small that they fell
\r?\n> into the
\r?\n> category of "bikini" lugs. (The name doesn't refer to "two-
\r?\n> piece", as
\r?\n> with the swimsuit, just the tinyness of it. A lug that doesn't
\r?\n> cover up
\r?\n> much of the joint.) That's not a bad thing in itself - I like bikini
\r?\n> lugs.
\r?\n>
\r?\n> In my experience, lugs with a too-small "hand-full" of head tube will
\r?\n> sometimes (depressingly often in fact) cause a crack in the head
\r?\n> tube at
\r?\n> the DT lug, for riders over a certain size/weight and/or miles/power
\r?\n> combo. Cracked head tubes are relatively rare for frames with a
\r?\n> littlemore meat there in the DT lug - including cheap frames.
\r?\n>
\r?\n> An example: Of the two ultimate (to me) '80s-vintage investment cast
\r?\n> bikini lugs, Ohtsuya and Eisho, the Ohtsuya will crack head
\r?\n> tubes at the
\r?\n> DT for big/strong/hi-mileage riders, where the Eisho won't. The
\r?\n> difference is subtle, but enough.
\r?\n>
\r?\n> Eisho is probably best known from Nagasawa:
\r?\n> http://bulgier.net/
\r?\n>
\r?\n> I don't have a great photo of the Ohtsuya DT lug but I think you
\r?\n> can see
\r?\n> the problem area here:
\r?\n> http://bulgier.net/
\r?\n> Look for the red arrow. The lug's grasp of the head tube tapers
\r?\n> down to
\r?\n> nearly zero (under 1 mm) at that point, and that's where the
\r?\n> head tube
\r?\n> crack starts. Eisho has just a silly millimeter or so more meat
\r?\n> there,enough to put fatigue cracks out of the question for all
\r?\n> but the most
\r?\n> abusive riders. Overall though, the Eisho is just as small a lug.
\r?\n>
\r?\n> For years (late-80s - early 90s maybe?), Richard Sachs's ad in
\r?\n> the bike
\r?\n> magazines was a picture of someone's hands holding a file poised
\r?\n> over a
\r?\n> lug. (Presumably the hands are e-Richie's - though he wasn't
\r?\n> known by
\r?\n> that name yet!) The lug in the ad is an Ohtsuya DT, which is pretty
\r?\n> funny in itself, since there is NOTHING to file on those lugs, but
\r?\n> especially funny because the file in the photo is shown poised
\r?\n> to file
\r?\n> RIGHT on that one edge on that lug that is already way too small
\r?\n> - at
\r?\n> the red arrow in my photo. I believe this was an in-joke from
\r?\n> Richie to
\r?\n> the few people who knew how ridiculous it was to file right
\r?\n> there, on
\r?\n> that lug.
\r?\n>
\r?\n> Just so we're clear - this is NOT a slam on Richard Sachs, who has
\r?\n> designed lots of lugs, all of which have plenty of meat at that point
\r?\n> I'm talking about. All the more reason I think the photo in his
\r?\n> old ad
\r?\n> is an in-joke.
\r?\n>
\r?\n> The moral is, lugs can safely be carved down pretty darn small, but
\r?\n> there is a minimum, which varies from one area to another
\r?\n> depending on
\r?\n> the stresses on that area. And the headtube edge of the
\r?\n> downtube lug is
\r?\n> one area where some lugs are carved down too small - fairly frequently
\r?\n> actually, in my experience, at least among high-end or custom
\r?\n> builders.(Cheap frames break too of course, but for different
\r?\n> reasons and mostly
\r?\n> in different places.)
\r?\n>
\r?\n> Mark Bulgier
\r?\n> Seattle WA USA