[CR]Bikini Lugs Cracking at the Head Tube

(Example: Racing:Wayne Stetina)

From: "Norris Lockley" <norris.lockley@talktalk.net>
To: <classicrendezvous@bikelist.org>
Date: Sun, 3 Dec 2006 17:06:38 -0000
Subject: [CR]Bikini Lugs Cracking at the Head Tube

During the List's debate on this issue Kurt Sperry recalled a contribution made some months ago on a simliar topic:-

"Wasn't the List told a year or so ago that lugs perform no real significant structural function once a frame has been built up and they were essentially used only to facilitate building up?"

I remember this earlier thread well and think that I am correct in saying that it was Brian Bayliss who made this statement.. The thread had been running for some time and had raised a few hackles, so I decided not to throw in my ten-penny-worth just in case it raised a few more.

However now that Kurt has raised the point again I would wish to question the accuracy of the point being made.

I think Brian (apologies if it wasn't Brian) was making the point that a correctly and accurately mitred frame, the tubes are joined firmly by the brazing material at those junctures, thereby holding the tubes together..ie its not the lugs that hold the joints in place any more.

However I think that any framebuilder who has also carried out repairs, including replacing tubes, will know well that not all frames have perfect mitres..not by a long way.

Unless I am way out in my logic, the "no need for lugs" argument falls down when the jointing of the frame at the bottom bracket is considered. At that point the tubes are not held in place by any accurate mitres but simply by the pipes of the bracket shell. It is these short tubular extensions that hold the frame together..unless you build a frame like a Thanet with the D/T and the SD/T mitred together and the bottom bracket shell cradled in the apex above.

I think that many many frames are held together by their lugs rather than the mitred joints. However I would support a claim that a bronze-welded frame ie without lugs, and using a fully cylindrical bracket shell ie without pipes or holes, is held together by accurately mitred and brazed joints, Peugeot made hundreds of thousands of such frames...including tandems.

Or is advancing senility clouding my logic? Perhaps the real essence of Brian's argument is in the word "significant".

Norris Lockley...Settle UK