lugless 531 frame

[QUIST]

Are such frames noticeably weaker than lugged frames?

[NATURAL ANKLING]

Hi,
Will always be, but it might be good enough.
Will be good enough if done right.

[ANTONISH]

The late Phil Brook seemed to specialise in lugless frames. I believe they were much sought after.

[jimlews]

Are lugless 531 frames noticeably weaker than lugged? NO!

Edit: That is, fillet brazed 531 frames are no weaker; if the builder takes sensible precautions to minimise ovality of the head tube and the seat tube.
531 doesn't like to be tig welded-due to the very high temperatures consequent on melting the tubes together.

[Valbrona]

A fillet brazed/lugless frame will, I think, always be weaker than lugged, but the consideration is almost irrelevant in as much as both ways of joining 531 make strong frames that will pretty much last a lifetime. But take a lugged and a fillet brazed frame into a lab for destructive testing and I reckon the lugged one will last longer.

A tig welded 525 frame is something better altogether. Welding represents an actual fusion of material - something you do not get with 531 because it is not a material that you should tig weld - and no lugs needed, so lighter.

[9494arnold]

Very much dependant on the skill of the framebuilder.
I have had 2 fillet brazed Higgins Trikes ,both dating from the 1950's one of which suffered headset distortion issues but I fear it had been used with a worn out headset rather than overheated, and I have seen many that do not have issues . Just bringing second one back into running order. Longstaff is a more recent Trike builder and a lot of his trike frames are fillett brazed (lugless) and I haven't seen a broken one, including Tandem Trikes.
Friend of mine is a very skilled welder. He has built his own frame, and I have been party to a discussion between him and a professional frame builder , they both discussed the " heat affected area" associated with a lugless frame , this is an area where the tubing can be weakened if too much heat is applied to run the braze into the joint. Lugs act almost like a wooden joint does,(don't forget tubes need to be mitred In either lugged or lugless frame . )

[cycleruk]

Reynolds produced a special tube "531 Millenium" that could be welded. It had shorter thicker butts to withstand the heat.

Bought 2001 and I sold it through the forum in 2017.

[fastpedaller]

A tig welded 525 frame is something better altogether. Welding represents an actual fusion of material - something you do not get with 531 because it is not a material that you should tig weld - and no lugs needed, so lighter.

Open to debate - I'm sure there will be some coming
I tend to think welding or brazing both have their merits, and a poor (or good) frame can result with both. I'll be bold and say that modern mass-produced frames (probably welding in the main by robot machine?) along with good quality control are better than mass-produced frames from decades ago with (maybe) minimal brass flowed in the joint - I'll wait correction from others.
In absolute terms (ie best processes for brazing and welding) I'd suggest both are good but 'different'

[PT1029]

An argument for lugless is stronger. Sudden changes in wall thickness can act as a stress raiser, so weakening the tube and/or reducing its fatigue life.
Lugs are a sudden change in wall thickness, so could be said to be weaker than fillet brazed lugless which has a smooth change in thickness.
The biggest factor is probably correct heating and workman ship of the fillet brazing - I have seen some where the joint was under cut (thinner) due to excess filing.

[NATURAL ANKLING]

Hi,
Braze / hardsolder the latter being at a lower temp means that the tube material will suffer less with heat degrading of the properties of the tube.
Better Braze Welding than simple fillet brazing, a braze welded frame probably as good as you need to get, but requires better tooling and more skilled labour.
Its of course quite likely that a modern machine mig or tig welded frame can be made to last a lifetime.

I've cut up a fillet brazed frame , will post pics of the internals latter.

There are problems with fillet brazing, getting reliable fillets on the ends of thin tube...........

[AndyA]

The seat tube on a butted 531 frame is 0.6mm thick at the top IIRC. This is usually reinforced with a seat-lug and it's very common to see a fillet frame fail on the seat tube/seatstay/top tube junction. The super thin tube just isn't up to the stresses. If the frame was built with a plain guage seat tube you've got a much lesser chance of it breaking cos the wall thickness is more like 1mm, and you can tell if this is the case because the seatpost size will be correspondingly smaller (ie 26.4mm).

Ritchey (and many other notable fillet builders especially MTB) put a sleeve around the seat-tube here to reinforce this area. Modern tubesets negate this by externally butting the seat-tube so you can have a substantial 0.9-1.2mm wall thickness and still use a 27.2mm seatpost.

You've got a similar problem at the head-tube as well, it'd certainly be a good idea for a fillet frame to either use a thicker head tube, or braze on some other reinforcements at the bottom top of the head tube.

Both problems are exacerbated by poor technique - if the brazer does a poor job and the seat tube/head tube are ovalized, reaming to fit will remove even more of the already marginal thickness.

[AndyA]

Here's a pic of a Ritchey seat tube reinforcement, rather nicely done!

[jimlews]

Reynolds produced a special tube "531 Millenium" that could be welded. It had shorter thicker butts to withstand the heat.
Donohue.jpg
Bought 2001 and I sold it through the forum in 2017.

Ah ! That's just like mine !

Edit: Not sure that it is actually 531. I suspect that '531 millenium' may be a case of 'salesman speak' and it's probably CroMoly. Doesn't seem to feel like 531 when ridden. Still a nice ride, though.

[Brucey]

if you turn the issue on its head and look at broken frames and why they broke, you will find that there are very many things that can go wrong (with any technique and material) and this usually dominates over the selection of a particular joining method per se.

The metallurgy of what is going on is very complicated indeed and in many cases it isn't amenable to broad brush ideas about more /less heat being good/bad etc. For example very many frames are, unseen, subject to very high levels (higher than the service loads) of residual stress that will break them.

TIG welding is popular because it is flexible and cheap. It is not particularly good, necessarily, because it can result in some extremely undesirable microstructures, high levels of residual stress, and/or high stress concentrations. If a TIG weld looks bad it probably is bad, but even ones that look good can be bad and you wouldn't know until something breaks.

A similar comment could be made about most methods used for frame joints, in fact. The strength of the frame usually lies in the design, the materials used, and the quality of the joining method as it is applied. The latter isn't obviously/reliably good or bad by appearance alone.

cheers

[cycleruk]

Reynolds produced a special tube "531 Millenium" that could be welded. It had shorter thicker butts to withstand the heat.
Donohue.jpg
Bought 2001 and I sold it through the forum in 2017.

Ah ! That's just like mine !

I wonder why.
Is it up and running ?