Cycling UK Forum

LollyKat wrote:

David9694 wrote:When you say welded, do you mean fillet brazed?

Not being an engineer I'm not too sure of the difference . I meant lugless.

Put simply brazing is used as a glue that runs in to a tiny gap between adjacent surfaces. Welding is a join that melts the adjacent faces together.

531 could be built with lugs or lugless brazed. If the latter it was important that the tubes were cut and finished to produce a perfect mating surface and a strong joint. This can involve a lot of time filing by hand.
631 can be welded so the builder can save time and expense on the tube interfaces by just cutting to shape and letting the weld bridge the imperfections.

Thanks. With either of those methods can a tube be replaced if necessary?

David9694 wrote:When you say welded, do you mean fillet brazed?

I don’t know who you’re asking, when I say welded that’s what I mean.

David9694 wrote:When you say welded, do you mean fillet brazed?

https://www.kaempfandharris.com/industry-news/difference-between-brazing-and-welding

As the article says welding means melting the metal so the bits become one piece

i would think that a frame that has tubes where you can see some join metal then its brazed - seems like my 1-Down is brazed not welded and dont have lugs.

Back in the mists of time, say 1960s/70s, fillet brazing was also known as bronze welding.

I have several frames from 1956 to 2012 which are filet brazed, and several lugged frames. No welded frames.

Brazing is joining two steel parts (eg tubes) using another metal with a lower melting point, possibly in conjunction with lugs. Welding involves melting the steel itself and is a much higher temperature procedure.

LollyKat wrote:Thanks. With either of those methods can a tube be replaced if necessary?

Yes, in theory. Replacing a brazed tube is a case of reheating the joints and sliding the tube out whilst it’s hot. When properly done the new joint and the tube strength is not compromised and should be straight and as strong as the original joint.
With a welded joint the situation is a bit more complex as the heat applied is far more intense and the material strength, tube proportions and frame geometry can be adversely affected.

wasn't there also an oversized tubset in 631?

Dawes one-down



appears to be tig welded in the main triangle, with brazed joints to the dropouts, BO fittings and to secure the seat collar.

'Bronze-welding' (AKA fillet brazing) is most like high temperature brazing, and (unlike filler for brazing of lugs) the bronze welding filler stays mushier for longer but (under a microscope) there is noticeable dissolution of the steel tubes into the filler material. Brompton frames are Bronze-welded.

cheers

peetee wrote:

LollyKat wrote:

David9694 wrote:When you say welded, do you mean fillet brazed?

Not being an engineer I'm not too sure of the difference . I meant lugless.

Put simply brazing is used as a glue that runs in to a tiny gap between adjacent surfaces. Welding is a join that melts the adjacent faces together.

531 could be built with lugs or lugless brazed. If the latter it was important that the tubes were cut and finished to produce a perfect mating surface and a strong joint. This can involve a lot of time filing by hand.
631 can be welded so the builder can save time and expense on the tube interfaces by just cutting to shape and letting the weld bridge the imperfections.

I’m not an engineer either, but my understanding is that you braze (bronze, silver) at a much lower temperature than you would weld - I don’t think you would want to weld any Reynolds tubing.

David9694 wrote: I don’t think you would want to weld any Reynolds tubing.

Some, if not all, modern Reynolds tubes are specifically intended to be suitable for welding. As already said my 631, 725 and 853 frames are welded.

PH wrote:

David9694 wrote: I don’t think you would want to weld any Reynolds tubing.

Some, if not all, modern Reynolds tubes are specifically intended to be suitable for welding. As already said my 631, 725 and 853 frames are welded.

Very true. Putting two and two together I would surmise that Reynolds had no choice but to market steel tubing that allowed this. The market for costly hand built frames was diminishing and the only option was to offer a steel that would cater for the volume builder with a eye on the cost book.