Re: [CR] Bikini lugs, cracking the head tube

(Example: History:Norris Lockley)

Date: Fri, 01 Dec 2006 19:18:07 +0000 (GMT)
From: <joebz@optonline.net>
Subject: Re: [CR] Bikini lugs, cracking the head tube
In-reply-to: <e0f3f8fd92dc.45705492@optonline.net>
To: classicrendezvous@bikelist.org
References: <9327C3B25BD3C34A8DBC26145D88A907064281@hippy.home.here>
cc: Mark Bulgier <Mark@bulgier.net>

e-Richie has pointed that's an otsuya lug not an eisho on the Tesch! So this is a test case as I'm heavy and I rather like this bike. I have no idea how it was used before I bought it.

Joe Bender-Zanoni
Great Notch, NJ


----- Original Message -----
From: joebz@optonline.net
Date: Fri, 01 Dec 2006 11:13:00 -0000
Subject: Re: [CR] Bikini lugs, cracking the head tube
To: "Mark Bulgier"
Cc: classicrendezvous@bikelist.org


> Eisho, still holding up (under a substantial load) on my Dave

\r?\n> Tesch. Tesch was a big user of Bikini lugs in the US.

\r?\n>

\r?\n> http://www.classicrendezvous.com/images/USA/Tesch/JBZ/head.JPG

\r?\n>

\r?\n> Joe Bender-Zanoni

\r?\n> Great Notch

\r?\n>

\r?\n> ----- Original Message -----

\r?\n> From: Mark Bulgier

\r?\n> Date: Friday, December 1, 2006 10:57 am

\r?\n> Subject: [CR] Bikini lugs, cracking the head tube

\r?\n> To: classicrendezvous@bikelist.org

\r?\n>

\r?\n> >

\r?\n> > A beautiful artisanal custom bike I saw recently had a fatigue-

\r?\n> cracked> head tube, right at the downtube lug edge, and it was

\r?\n> 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

\r?\n> tube will

\r?\n> > sometimes (depressingly often in fact) cause a crack in the

\r?\n> 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

\r?\n> 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

\r?\n> 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/pics/bike/FrameParts/Eisho_lugs.jpg

\r?\n> >

\r?\n> > I don't have a great photo of the Ohtsuya DT lug but I think

\r?\n> you

\r?\n> > can see

\r?\n> > the problem area here:

\r?\n> > http://bulgier.net/pics/bike/FrameParts/Ohtsuya&Saba.jpg

\r?\n> > Look for the red arrow. The lug's grasp of the head tube

\r?\n> 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

\r?\n> 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

\r?\n> 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

\r?\n> 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

\r?\n> that point

\r?\n> > I'm talking about. All the more reason I think the photo in

\r?\n> 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

\r?\n> 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

\r?\n> frequently> actually, in my experience, at least among high-end

\r?\n> 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