Reynolds 531 Magic Tubing

danson67

Retrobike Rider
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Yes, you are right, 531 is the approximate ratio. The important thing is that it's Manganese-Molybdenum not Cr-Mo and cannot be welded easily.
It was a super-high tech product when launched in the 1930s. Aircraft wing spars were made of it, notably the Hawker Hurricane. It was also used in racing car chassis in the 1950s.
It is actually pretty easy to weld, much the same as Cr-Mo...The big problem with welding Mn-Mo alloys is the risk of the manganese particulates or vapour being released. Nasty stuff: https://en.wikipedia.org/wiki/Manganism

Good welding practice nowadays is to avoid Mn (along with chromate, cadmium, zinc and thoriated tungstens) without full breathing filtration and skin protection PPE.

All the best,
 

Prodigal Son

Senior Retro Guru
Hey, no laughing here it is a case of saving them any way we can... Looks like a cool ride. So the frame is 531 Magnum tubing which was an oversized (larger diameter) tubing. 631os
It´s the play betwen the diameters of top, down,seat tubing plus stays that makes the magic happen. Not the tubing brand. Never get fixated on tubing brand, model, number or even aluminum x steel. It´s how the builders work w/ the material.
 

Tsundere

Fat Chance Fan
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I have a soft spot for these old Peugeot's, they were never really fashionable bikes, but the company has such a rich and laurelled history in cycling and that pedigree shines through, especially with their top end bikes. The internal brazing on some frames is wonderful and leaves such a clean finish, the colour schemes are iconic in their unique way and they always produce a nice ride.
 

danson67

Retrobike Rider
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What is used in place of thorium for tungstens now?
There have always been alternatives depending on material, AC or DC, welder type (inverter ot transformer), start method (HF or scratch), wave form etc.

Thoriated electrodes always kept a really good point with solid low amp HF starts, and are still widely available...but it is mildly radioactive, with hazardous dust and vapour produced while sharpening and welding if not done very carefully...and spent electrodes should not be disposed of as normal waste.

So options include pure tungsten, and alloys with cerium oxide, lanthanum oxide, multi-blends etc, but most welders these days use either 1.5 or 2% zirconium oxide electrodes pretty much all work, since it's a good all-rounder.

Personally, I have an HF start inverter, so use 2% Zirc for DC on steel, but prefer 1.5% Ceriated on AC for aluminium since it gives a more stable arc.

All the best,
 

KermitGKona88

Gold Trader
Overbury's Fan
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There have always been alternatives depending on material, AC or DC, welder type (inverter ot transformer), start method (HF or scratch), wave form etc.

Thoriated electrodes always kept a really good point with solid low amp HF starts, and are still widely available...but it is mildly radioactive, with hazardous dust and vapour produced while sharpening and welding if not done very carefully...and spent electrodes should not be disposed of as normal waste.

So options include pure tungsten, and alloys with cerium oxide, lanthanum oxide, multi-blends etc, but most welders these days use either 1.5 or 2% zirconium oxide electrodes pretty much all work, since it's a good all-rounder.

Personally, I have an HF start inverter, so use 2% Zirc for DC on steel, but prefer 1.5% Ceriated on AC for aluminium since it gives a more stable arc.

All the best,
Wow I very nearly understood some of that... 🤣
 

faber26

Retro Guru
Wow this is turning in a very sharp discussion! 😅

So in light of all this, it doesn't seem so impossible to replicate the Eden Rock frame "behavior". By this I mainly mean, vertical compliance, energy transfer and bottom bracket movement. The geometry of a new frame could be slightly adapted from the Eden's for 27,5" disc wheels, the main thing would be finding an equivalent material to replicate the frame mechanical properties.

What is available today to match the 531 Magnum tubes characteristics? Or can those tubes still be found "NOS"-like?
 

faber26

Retro Guru
I've just measured the diameters of the diagonal tube (35mm) and the seat and horizontal tubes (32mm), indeed quite unusually big.
 
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