Panasonic brazing

In article <[email hidden]>,

toddio said:

Just received a Panasonic Professional Frame (model designation PR
6000 here in Europe, from ca. 1992), made of Tange Prestige Tubing,
investment cast Lugs, BB shell etc. After dismantling it, i had a
good look inside the BB shell. On the chainstays there were just
blobs of brass, no brass flowing between shell and tube.

That sounds like the tubes were not properly cleaned before brazing or
that enough flux was not used. Flux protects the heated metal and
facilitates the molten filler wetting the surface of the tubes and
fittings.

Quoted message said:

The chainstay tubes do not enter the shell fully, the same with the
seat tube and the down tube.

Some bike manufacturers insert the tube fully but leave the ends squared
off, sticking into the BB shell chamber. Ugly.

Quoted message said:

Is this good workmanship?

It depends. Are the ends of the tubes mitered to match the interior
curve of the bottom bracket shell? This isn't a very good photo of what
I mean and no doubt someone else can find a better picture online:

http://www.frostybobs.org/photos/bbshell.jpg

If the ends of the tubes are mitered to match the inside of the BB
shell, that is usually a sign of good workmanship. If the tubes
protrude into the BB shell and are cut square, that's not such a good
sign. If the tubes are cut off square and not fully inserted so that at
least part of the tube end is flush with the inside of the shell, that's
also not a particularly good sign.

Quoted message said:

Panasonic frame have a high reputation, wrightly or wrong? Are there
any known failures of panasonic frames?

I am sure there are some known failures of Panasonic frames- they've
built millions of them. Panasonic not only sells bikes under their own
label but also makes bikes under contract for other labels as well. I
have never heard complaints about broken Panasonic-built frames.

Tim McNamara said:

I am sure there are some known failures of Panasonic frames- they've
built millions of them. Panasonic not only sells bikes under their own
label but also makes bikes under contract for other labels as well. I
have never heard complaints about broken Panasonic-built frames.

IIRC, they make the Quickbeam fixie frame for Rivendell.

toddio said:

Just received a Panasonic Professional Frame (model designation PR
6000 here in Europe, from ca. 1992), made of Tange Prestige Tubing,
investment cast Lugs, BB shell etc. After dismantling it, i had a good
look inside the BB shell. On the chainstays there were just blobs of
brass, no brass flowing between shell and tube. The chainstay tubes do
not enter the shell fully, the same with the seat tube and the down
tube. Is this good workmanship? Panasonic frame have a high
reputation, wrightly or wrong? Are there any known failures of
panasonic frames?

Small builder handmade frames often show meticulous if not obsessive
mitering of the tubes and stays inside the shell. Frequently a pretty
meniscus of bronze and threads cut into the chainstay ends.

That being said, straight-cut chainstays and less than beautiful braze
finish of production frames have been shown over millions of iterations
to be quite suitable and dependable. I owned this 1985:
http://www.yellowjersey.org/panateam.html

which is still being ridden by its fourth owner despite visibly
less-than-perfect finish work as shown. Call Richard Sachs for a nice
looking perfectly finished BB. But don't worry about yours.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

In article <[email hidden]>,

Hank Wirtz said:

Tim McNamara said:

I am sure there are some known failures of Panasonic frames-
they've built millions of them. Panasonic not only sells bikes
under their own label but also makes bikes under contract for other
labels as well. I have never heard complaints about broken
Panasonic-built frames.

IIRC, they make the Quickbeam fixie frame for Rivendell.

I think that is correct.

Tim McNamara said:

If the ends of the tubes are mitered to match the inside of the BB
shell, that is usually a sign of good workmanship. If the tubes
protrude into the BB shell and are cut square, that's not such a good
sign.

Nonsense.

In this case function does not follow form, and it is an error to use form
as an indicator of construction quality. Your statement is equvalent to
saying that box-lining is a sign of a durable paint job.

In article <[email hidden]>,

_ said:

Tim McNamara said:

If the ends of the tubes are mitered to match the inside of the BB
shell, that is usually a sign of good workmanship. If the tubes
protrude into the BB shell and are cut square, that's not such a
good sign.

Nonsense.

In this case function does not follow form, and it is an error to use
form as an indicator of construction quality. Your statement is
equvalent to saying that box-lining is a sign of a durable paint job.

Cutting off the tubing square and sticking it into the BB shell is a
corner that's just been cut. If they're cutting visible corners, what
invisible corners are they cutting? Are they mitering the rest of the
tubes or cutting those off square too? That makes a difference to the
strength and durability of the joint. You may scoff but there are
plenty of reports by reputable frame builders of finding exactly this
situation when repairing frames by well-known bike companies.

Also, with reference to mitering to fit the inner chamber of the BB
shell, it's much easier with properly mitered tubes to make sure that
the filler material, whether brass or silver, has had good penetration
into the joint. With the square end of the tube obstructing the
brazer's view, it's harder to tell. This is not merely an aesthetic
concern.

Quoted message said:

Tim McNamara said:

If the ends of the tubes are mitered to match the inside of the BB
shell, that is usually a sign of good workmanship. If the tubes
protrude into the BB shell and are cut square, that's not such a good
sign.

_ said:

Nonsense.
In this case function does not follow form, and it is an error to use form
as an indicator of construction quality. Your statement is equvalent to
saying that box-lining is a sign of a durable paint job.

Clearly 100% joint penetration is probably good, adequate contact is
probably adequate. I base that opinion on a few hundred million
iterations of straight cut chainstays which have proved adequate.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Tim McNamara said:

Cutting off the tubing square and sticking it into the BB shell is a
corner that's just been cut. If they're cutting visible corners, what

Quoted message said:

into the joint. With the square end of the tube obstructing the
brazer's view, it's harder to tell. This is not merely an aesthetic
concern.

In a mass production environment you don't always have the luxury of
lavishing painstaking craftsmanship on everything. It's much easier to
chop the stays off square and a little short, then let everything get
held in the correct place by the assembly jig.

In article <[email hidden]>,

amakyonin said:

Tim McNamara said:

Cutting off the tubing square and sticking it into the BB shell is
a corner that's just been cut. If they're cutting visible corners,
what

Quoted message said:

into the joint. With the square end of the tube obstructing the
brazer's view, it's harder to tell. This is not merely an
aesthetic concern.

In a mass production environment you don't always have the luxury of
lavishing painstaking craftsmanship on everything. It's much easier
to chop the stays off square and a little short, then let everything
get held in the correct place by the assembly jig.

Which creates other problems. There ain't no free lunch. Light, cheap,
durable: pick two.

amakyonin said:

In a mass production environment you don't always have the luxury of
lavishing painstaking craftsmanship on everything. It's much easier to
chop the stays off square and a little short, then let everything get
held in the correct place by the assembly jig.

Or long. I've seen more than a few production frames where the ends of
the chainstays and frame tunes appear to have been shortened by the taps
that ran through the BB shell after brazing.

Attention to detail in areas that aren't always visible -- like the
inside of the BB shell -- is something you can expect of a higher
quality frame, but as Andy Muzi points out, you can make a perfectly
functional frame without this level of detail.

--

John ([email hidden])