>
> All these lugs suffered from the internal radius problems
> ie voids or empty
> pockets in the joint that did not exist in cast lugs. The
> way I was taught
> to overcome the problem was quite ingenious, but it made
> more work., but
> it was a technique that was easy to employ, in a sense,
> because we buil
> t the frames without the aid of jigs.
>
> We started the brazing process by brazing the top head-lug
> to the top-tube,
> and by brazing the bottom head lug to the down tube. Note
> that the head tu
> be is not mentioned. We would braze these joints by
> applying the filler rod
> from inside the lug and drawing it through the joint and
> along the tube. T
> he void would then be over-filled. When cool the surplus
> braze material on
> the inside of the lug would be carefully filed to ensure
> that the void no
> longer existed and that the joint had a perfect mitred
> profile so that to
> all intents and purposes the inside of the lug was as
> accurate as a cast on
> e. Later on we bought an expanding reamer that gave more
> precise profiles a
> nd diameters. When we had filled these joints we carried
> out the same proce
> ss by attaching the seat lug to the other end of the top
> tube, backfilling
> the joint with braze material and then filing away the
> surplus
> Once the top-tube head-tube and down-tube were assembled
> and ready for braz
> ing we would carry out the process with silver solder that
> melted about 230
> degrees lower, thereby ensuring that the braze material in
> the voids wou
> ld not be melted and the integrity of the joint not
> compromised. The s
> ame process was applied to the seat tube joint.
> As for the bottom bracket joints and chainstays, the
> brazing rod was applie
> d from the inside of the shell and sucked up the tubes.
> Back-filling any ra
> dii in the bracket was quite easy.
Thanks for the benefit of your experience Norris. I've heard of a similar technique: fill in the lug radii with brass (sans tubes), shape with the file so the internal radii have sharp corners, silver braze. Haven't tried that - still thinking I can defeat physics with practice and cleverness. I could always punt and use IC lugs but the pressed variety I get from Ceeway are dainty and light, and I figure my brazing will be the better for the attempts.
>
> In later years and following training with the British
> Oxygen Company I bec
> ame much more proficient in controlling the movement of
> brazing spelter
> with the torch flame within a lugged joint and also
> outside on lugless f
> rames. I abandoned my early void-filling technique and
> became very ski
> lled at filling the voids by using an externally applied
> rod of thicker
> than normal diameter, say about 1/8", and a smaller
> than normal nozzle, usu
> ally a No1. With the much smaller flame I could almost
> stroke and coax th
> e slightly pastier filler rod into the voids, by
> controlling the heat and t
> he rate of flow of the braze material at the same time. As
> my tutor at the
> BOC always said...Always use the smallest nozzle possible.
> It may take a li
> ttle longer..but a craftsman with a lighted torch in his
> hand should neve
> r be in a hurry.
>
> Hope this helps, John. Neither way gives rise to any real
> difficulties..it'
> s all a question of time..and practice...and control.
All at a premium, in short supply. Thanks for the ideas.
John Clay
Tallahassee, Florida
USA
>
> Norris Lockley....Settle UK