frame welding

I'am having a frame built w/true temper s-3 tubing, the instructions that came w/tubing recommended
tig welding; my builder is well known and respected, however he filet brazed the frame and I'am
concerned about the strength. He made a good point that tig welding create's more heat stress than
brazing. Any frame builders W/opinions welcome. Thanks

 

Joe wrote:

> I'am having a frame built w/true temper s-3 tubing, the instructions that came w/tubing
> recommended tig welding; my builder is well known and respected, however he filet brazed the frame
> and I'am concerned about the strength. He made a good point that tig welding create's more heat
> stress than brazing. Any frame builders W/opinions welcome. Thanks

Your builder is right about the heat, but True Temper S-3 is designed to be welded, with thicker,
shorter butts to prevent unacceptable weakening of the area of the joints.

Welding is very common these days because it takes less time than brazing, either with lugs or with
fillets. Because welding can be regarded as uncontrolled casting, either the tubing must be extra
thick at the joints, or preferably also heat treated afterwards, as pretty much every aluminum frame
(and lots of steel) is done. Many purists want only brazed, probably because they like the looks of
nicely done lugwork.

Bottom line is the skill of fabrication, in any method of joinery. There is no downside to what your
builder has done, and I'll wager that the frame comes out a little prettier.

--
Ted Bennett Portland OR

 

In article <[email protected]>, Joe <[email protected]> wrote:
>I'am having a frame built w/true temper s-3 tubing, the instructions that came w/tubing
>recommended tig welding; my builder is well known and respected, however he filet brazed the frame
>and I'am concerned about the strength. He made a good point that tig welding create's more heat
>stress than brazing.

It's a steel tube. It's OK to fillet braze it. A tigged joint would probably be stronger but brazing
is "strong enough" - they don't have a problem coming apart at the joints unless the welder makes a
mistake. And TIG welding mistakes can be pretty awful too. If the builder is competent and careful
then the bike is safe.

People fillet-braze Reynolds 853 as well.

--Paul

 

By "fillet brazed" you mean lugless brazing, right?

If that's the case, then yes, it's not being joined according to manufacturer spec. Your builder's
point about TIG creating "more heat stress" is simplistic. Does brazing create less "stress" due to
temperature? - Yes. That used to be a concern with non-air hardening tubesets as their strength
degraded at high temperatures. But your S3 tubeset is *air-hardening*. It /needs/ sufficient
temperature elevation in the weld zone to start the hardening process.

*Low temperature* lugless brazing looks pretty but almost certainly does not comply with True
Temper's spec and so your tubes will not reach their full design strength in the high stress zones
of the joints. I'd check the tube spec, which I believe will give a minimum braze temperature for
air hardening to occur, and check with your builder to see if his brazing method met those criteria.

Jim

Joe wrote:
> I'am having a frame built w/true temper s-3 tubing, the instructions that came w/tubing
> recommended tig welding; my builder is well known and respected, however he filet brazed the frame
> and I'am concerned about the strength. He made a good point that tig welding create's more heat
> stress than brazing. Any frame builders W/opinions welcome. Thanks

 

>I'am having a frame built w/true temper s-3 tubing, the instructions that came w/tubing recommended
>tig welding; my builder is well known and respected, however he filet brazed the frame and I'am
>concerned about the strength.

Curious who the builder is?

jon isaacs