Induction welding bicycles

[jimlews]

Peugeot cycles of the less pretentious sort used to be welded by mitering then assembling the tubes in a jig where a powerful electric charge was passed through the assembly, thus welding the whole together in an apparently seamless way.
I think this was called induction welding.
To my eye, the result seemed particularly neat, with none of the ropey weld bead that results from the TIG or MIG welding that predominates today in cycle manufacture.

So, the question is, why has this construction method fallen out of favour?
Would it be applicable to Al & Ti frames?
What are its advantages and disadvantages?
What were they like to ride?
I never heard tell of one of these Peugeots coming apart in use.


https://www.gumtree.com/p/bicycles/vint ... 1382825188

A random picture - I've no connection with the vendor.

[hamster]

It's Projection welding. The problem is that the current flows unevenly through the joint and the weld is irregular. That's fine with a thick frame tubeset, but insufficient for lightweight tubing.

If you look at super-cheap £59 steel bikes they often have such frames - the welds look a total mess.

[Jdsk]

Electric resistance welding
https://en.wikipedia.org/wiki/Electric_resistance_welding

Projection welding
https://en.wikipedia.org/wiki/Spot_welding#Modifications

Induction welding
https://en.wikipedia.org/wiki/Induction_welding

Jonathan

[Norman H]

Peugeot also introduced what they called internal brazing. As I understand it the mitred tubes had a preformed ring of brazing material on their internal surfaces the frame was assembled in a jig and automated ring torches completed the process. The resultant joint was very neat with only a narrow fillet visible on the outside.

[Jdsk]

"Direct Brazing System", "PBS".



Jonathan

[Brucey]

Peugeot certainly didn't use projection welding for the main joint, (but they might have done to assemble the parts prior to brazing).. IIRC they called the process they used to connect the main frame tubes 'internally lugged brazing' or somesuch, in which a pre-placed ring of braze metal was included within the joint along with an internal lug of some kind before it was heated. The internal lug may have been assembled using welding (eg projection welding) in such a way that the joint was further consolidated subsequently by flow of the braze metal.

They may have used induction heating for the brazing (IIRC it was electrical heating of some kind) but lurking in the back of my mind is a notion that in order for induction heating to work well on a tube to tube joint, the induction coils should surround the joint, which is 'topologically inconvenient' if you are assembling a bike frame.

Anyway I would say that the resultant joints were pretty good.... for a cheaply-made mass-produced frame. The advantages for manufacture were that the joint was self-fixturing and provided the braze metal had flowed and showed a continuous ring at the tube to tube mitre, probably it was stuck together reasonably well. The internal lug itself could be a cheap pressing, it didn't have to look pretty. However it didn't have to be lightweight either; such frames were (between the internal lugs and the gas pipe (er, 'carbolite' which sounds more like diet food than steel tube these days) in the frames they were not especially lightweight. In fact between real issues and perceived issues, even Peugeot didn't push it with this process; their posher frames were lugged and brazed in the usual way for most of the time the 'internal brazing' was used on the more pedestrian models.

The heating method used by Peugeot might have been fancier but the basic idea was as old as the hills; for example the traditional Raleigh 'tube' fork crown is actually a similar construction; the crown is pressed from sheet metal and is self-fixturing into the fork blades. Two tangs fit inside the fork blades and a pre-placed ring of braze metal is melted and runs through the joint. In latter years Raleigh used a molten salt bath for much of their brazing. In 1978 it was said that Raleigh could produce an entire steel frame for about £2, but (apparently) that still wasn't cheap enough....

The PBS thing may be different again or just another twist.

cheers

[Brucey]

this is how the (later?) internal brazing process was depicted in the catalogue; no internal lug. Is this what they called PBS?





This is motobecane's version



cheers

[greyingbeard]

My elderly Pug mountain bike is internally brazed 531. Hasnt shown any signs of breaking. They made some decent bikes this way.

in 1978 £2 bought a lot more than a bag of chips. A packet of polos was 3 1/2 p

[sukuinage]

Interesting. I think my touring bike is probably constructed like this. I've no idea what the tubeset is, just says "Peugeot Cromoly". I bought it secondhand a couple of years ago and renovated it, think it dates from the mid nineties. It can't have been a cheap bike originally as it had, I think, all XT components fitted.

[Brucey]

report of an internally lugged Peugeot here

http://www.thevelocollective.com/peugeot-pro-team-hle/

including reference to two frame breakages

This 'how its made' video is from a Canadian factory that took a licence out from Peugeot for internal brazing (without internal lugs)

https://www.youtube.com/watch?v=7ZPS_iwoeJg

Gas flame heating is used.

cheers

[NATURAL ANKLING]

Hi,
Peugeot.

[NATURAL ANKLING]

Hi,

[NATURAL ANKLING]

Hi,
What's this type of welding then

[tim-b]

Hi
Inertia friction weld?
Regards
tim-b

[NATURAL ANKLING]

Hi,
Got to admit I know the process, thats know of from way back when, but the actual name I wouldn't of guessed
[youtube]o4HcBf7tg7g[/youtube]