Re: [CR]More about Silver vs Brass

(Example: Framebuilders:Norman Taylor)

Date: Tue, 27 Sep 2005 19:34:01 -0500
From: "John Thompson" <>
Organization: The Crimson Permanent Assurance
Subject: Re: [CR]More about Silver vs Brass
References: <>
In-Reply-To: <> wrote:
> Now back to those silver joints coming apart. I didn't make this up. It
> just didn't happen during this test. We get a lot of crashed bikes in for
> repairs, and Bill says he has seen many frames brazed with silver pull apart
> during a crash. Not just ours, but from other very well known builders too. I
> should point out that we have used Silver to braze also for many years on very
> light tubing. I have seen a number of these too, and somehow remembered them
> as being in the test. Some particular lugs are more prone to this than
> others. The Otsuya lugs that we used back the early 80s had very small surface
> area behind the head tube, and these were more prone to coming apart, as you
> might expect. I crashed my Davidson with these lugs in a high speed front
> ender in 1988, and while it did wrinkle the frame pretty good, it didn't come
> apart.

We had some trouble with a "church-key effect" using investment cast head lugs with 753 tubing. Sometimes on a strong front impact the points of the lugs tear tubing like using a church-key type can opener. When we switched to formed head lugs (The #1810 & 1830 lugs depicted here:

On the early 753 frames we used an old Ishiwata cast fork crown (actually left-overs from a long-discontinued model from the mid-70s). Although they were investment cast, they were quite malleable, especially after we got done machining them down. I still have a partially finished one here:

We started calling them the "frame-saver forks" because the frames that shipped with these forks never had church-key failures; instead, the crown always bent in the milled out section between the blade sockets and the steer tube.

John (
Appleton WI USA