[CR]Copper Filler

From: "Norris Lockley" <Norris.Lockley@btopenworld.com>
To: <classicrendezvous@bikelist.org>
Date: Sun, 23 May 2004 23:10:29 +0100
Subject: [CR]Copper Filler

in the early 60s I used to teach engineering in a school not very far from the Carlton factory in Worksop, and on occasion had the infinite pleasure of escorting final year students there on careers visits..

I recall being shown how the company "tacked up" the bottom bracket shells and seat and down tubes on some of their frames - but unfortunately I cannot remeber the models. The brackets were assembled with the tubes, no pinning was used, the assemblies were placed on the hot coke bed of a blacksmiths hearth, heated up and then spot-tacked with a copper rod, with the aid of an oxy-acetylene torch. I think I recall a similar hearth in use at Witcomb's in London in the early 80s.

On the Holdsworth frame mentioned at the outset of this topic it is obvious that the copper rod/or copper alloy was being used instead of using a steel-steel fusion weld to hold the lug and the decorative tang together. I have quite a beaten-up Holdsworth frame of the same model but have never stripped off the paint to check the builder's workmanship or methods, but recalling that frame the main lug is of cast steel. Possibly at that time in the late 40s the quality of the castings might not have been as good as the builder could have wished for, with impurities trapped in the casting. A fusion weld of a mild steel tang onto the cast steel lug could have presented problems - hence possibly the use of copper. In either case copper or fusion weld, the purpode was, as Bob stated, to obtain a join that would not melt when the tubes and lugs were brazed together. There would probably have been a margin of 150 - 200C.

Norris Lockley (wishing he'd paid more attention on those careers visits)