Re: [CR]Lugless bikes/frames under appreiated?

(Example: Framebuilders:Bernard Carré)

From: <Hughethornton@aol.com>
Date: Fri, 28 Jan 2005 10:28:47 EST
Subject: Re: [CR]Lugless bikes/frames under appreiated?
To: classicrendezvous@bikelist.org


In a message dated 28/01/05 03:37:13 GMT Standard Time, Huemax writes:


> In 1960's I was told that the lugless frame could be stronger than some
> luggd frame per weight.
>
> Can this be true? Some lugged frame can be weaker due to the fact the
> stress
> point where the edge of lug (strong double thickness) can concentrate all
> force
> to the tube wall to cuase damage athough the shape of lug trying to spread
> the
> force?

In the early days, lugs had square cut ends which acted as a "stress-raiser" on the tube where it enters the lug and fractures were more prone to start at these points. The effect of shaped lugs is to avoid these high stress areas by giving a more gradual transition from tube to lug. It seems that when frame builders realised this, they started playing around with the shape of the lugs to provide aesthetic as well as structural advantages. And then some builders got really carried away and produced wonderful or monstrous designs, depending on your point of view (people either tend to love or hate excesses like the Hetchins Magnum Opus, few are indifferent).

In terms of weight and structural integrity, the simple pointed lug is probably about the best. I wouldn't like to generalize about whether lugged frames are stronger/stiffer/lighter than lugless. There is a body of opinion that says lugless frames are less stiff, which some builders counteracted by fitting oversize top tubes, as on my Gillotts.

Hugh Thornton
Cheshire England