INEXTERNAL PROCESS - mbk

mariusz said:

hi there,
I am owner of this bike
http://www.allegro.pl/item138978903_mbk_mirage_pro.html
I have question about "INEXTERNAL COLUMBUS TRI CROMOR PROCESS".
What is this all about ?
I don`t trust the way they connected "the pipes" - I prefer much more
traditional style - for example
lugged columbus steel frames.

regards,
Mariusz

Nice bike!

I remember "inexternal" from Pugeot, but Pugeot may be related to MBK.

The "Inexternal" refers to where the brazing takes place, which is a
brass fillet *inside* the tube, rather than outside. I'm guessing it
helped with the automated robot brazing machine, and makes joint clean
up easier (non-existent?). Maybe the brass was even a ring inserted
before brazing, rather than added from a rod by a human during brazing.
All in all, an innovative way to connect steel tubes.

I wouldn't worry about the frame's strength. I don't think I ever saw a
broken Inexternal joint. But it does look a little unusual.

Quoted message said:

mariusz said:

hi there,
I am owner of this bike
http://www.allegro.pl/item138978903_mbk_mirage_pro.html
I have question about "INEXTERNAL COLUMBUS TRI CROMOR PROCESS".
What is this all about ?
I don`t trust the way they connected "the pipes" - I prefer much more
traditional style - for example
lugged columbus steel frames.

regards,
Mariusz

Nice bike!

I remember "inexternal" from Pugeot, but Pugeot may be related to MBK.

Peugeot was French. Motobecane, also French in the past, became MBK.

Quoted message said:

The "Inexternal" refers to where the brazing takes place, which is a
brass fillet *inside* the tube, rather than outside.

IIRC, this refers to internal (plug in) lugs. Motobecane had some bikes
like this in the '80s.

Also, IIRC, Columbus Cromor was a lower end tube set.

Quoted message said:

I'm guessing it
helped with the automated robot brazing machine, and makes joint clean
up easier (non-existent?). Maybe the brass was even a ring inserted
before brazing, rather than added from a rod by a human during brazing.
All in all, an innovative way to connect steel tubes.

I wouldn't worry about the frame's strength. I don't think I ever saw a
broken Inexternal joint. But it does look a little unusual.

mariusz said:

hi there,
I am owner of this bike
http://www.allegro.pl/item138978903_mbk_mirage_pro.html
I have question about "INEXTERNAL COLUMBUS TRI CROMOR PROCESS".
What is this all about ?
I don`t trust the way they connected "the pipes" - I prefer much more
traditional style - for example
lugged columbus steel frames.

regards,
Mariusz

This site shows a Motobecane catalog that talks about "inexternal"
brazing.
http://www.equusbicycle.com/bike/motobecane/motobecane.htm

Especially this page
http://www.equusbicycle.com/bike/motobecane/images/motobecane0003.jpg
shows a diagram of the braze inside as well as outside the tubes.

Quoted message said:

mariusz said:

hi there,
I am owner of this bike
http://www.allegro.pl/item138978903_mbk_mirage_pro.html
I have question about "INEXTERNAL COLUMBUS TRI CROMOR PROCESS".
What is this all about ?
I don`t trust the way they connected "the pipes" - I prefer much more
traditional style - for example
lugged columbus steel frames.

regards,
Mariusz

Nice bike!

I remember "inexternal" from P[e]ugeot, but P[e]ugeot may be related to MBK.

The "Inexternal" refers to where the brazing takes place, which is a
brass fillet *inside* the tube, rather than outside. I'm guessing it
helped with the automated robot brazing machine, and makes joint clean
up easier (non-existent?). Maybe the brass was even a ring inserted
before brazing, rather than added from a rod by a human during brazing.
All in all, an innovative way to connect steel tubes.

I wouldn't worry about the frame's strength. I don't think I ever saw a
broken Inexternal joint. But it does look a little unusual.

Readers of rec.bicycles.tech:

I am of the opinion that the "Inexternal" joints look BETTER than
external lugs [1], especially those with frivolous ornamentation. (Now
I have likely offended a lot of people!)

Of course I may be biased, since my first bike store quality bike was a
Peugeot with internal lugs.

[1] However, I do like the appearance of the Kabuki Submariner
bicycles, with the oversize cast aluminium alloy lugs and unpainted
stainless steel tubing.

--
Tom Sherman - Post Free or Die!