Vixen round tube chassis - Braze or weld
Discussion
Yes, I'm pretty sure the original chassis was brazed / bronze welded. The joints are made at a lower temperature than gas welding and effectively 'glue' the joints together, whereas (good) welding melts the base material to fuse them together. Its a bit like soldering end feed copper plumbing joints on a bigger scale
To braze you would need good clean fillet joints and gas welding gear. It heats a much wider area than say mig welding, is harder to get a good joint in my view and is much slower than mig welding, which would be my choice.
To braze you would need good clean fillet joints and gas welding gear. It heats a much wider area than say mig welding, is harder to get a good joint in my view and is much slower than mig welding, which would be my choice.
Yes, brazing / bronze welding is still being used and you can obtain a much better finish on the joints without dressing, but it it will be slower and more expensive. If you want a concourse example true to original specification then that's fine, but unless you are / have someone really competent at brazing / gas welding and fabrication you need to pass it to a specialist as you need good clean tight fitting joints and you 'feel' whether you have a good joint, much like end feed soldering. That why I personally would move away from originality and MIG / TIG it.
Hope that helps
Hope that helps
Interesting. I've been reading the same stuff and it's got me quite enthusiastic about 'bronze welding' or brazing. Not because of 'concours' (definitely not my thing) but more that it would have been the way it was done in period, it's more eco friendly, it's more flexible so less prone to vibration cracks and when done properly it's stronger than the base metal.
Something else to investigate.
Moto
Something else to investigate.
Moto
Moto said:
Interesting. I've been reading the same stuff and it's got me quite enthusiastic about 'bronze welding' or brazing. Not because of 'concours' (definitely not my thing) but more that it would have been the way it was done in period, it's more eco friendly, it's more flexible so less prone to vibration cracks and when done properly it's stronger than the base metal.
Something else to investigate.
Moto
And then there is Tig brazing Something else to investigate.
Moto
N
Moto said:
N,
What do you use for your chassis rebuilds ?
Moto
All Modern chassis are generally migged.What do you use for your chassis rebuilds ?
Moto
All replacement chassis are generally migged.
All of my chassis repairs are sleeved and migged.
Some race chassis where exotic materials are used are Tig Brazed..
Tig brazing represents a knowledge of the parent metals to be joined for a task specific to the application..
Its funny but oxy acetylene brazing was banned for car MOT repairs.. It used to be common place now not to MOT standard.
The method of jointing used depends on the application..
N.
Dollyman1850 said:
Moto said:
N,
What do you use for your chassis rebuilds ?
Moto
All Modern chassis are generally migged.What do you use for your chassis rebuilds ?
Moto
All replacement chassis are generally migged.
All of my chassis repairs are sleeved and migged.
Some race chassis where exotic materials are used are Tig Brazed..
Tig brazing represents a knowledge of the parent metals to be joined for a task specific to the application..
Its funny but oxy acetylene brazing was banned for car MOT repairs.. It used to be common place now not to MOT standard.
The method of jointing used depends on the application..
N.
My first welder, an arc set bought new from an ad in 'Exchange & Mart' (!) in the late 70s came with a spring-loaded scissor-type device holding a pair of carbon rods that you brought together to initiate the arc and kept balanced a few mm apart to maintain it. Made your hand ache! The blazing arc was used as the heat source to braze (the rods never touched the workpiece). Replaced a fair few floor pans etc with that, but it wasn't great for sills
Sheet brazing's OK as long as you have a sizeable overlap. This is probably why it was banned because car bodies aren't designed with large overlap repairs in mind.
Tube brazing, as stated previously, needs careful attention to fit, made far easier for large scale production by using lugs at intersections. All bike and motorbike frames used to be made this way.
I have limited experience of work on Vixen chassis, the two I have done work on, both early seventies cars were CO2 MIG welded not the brazed ones.
I would speculate earlier chassis were brazed, either using gas flame or possibly carbon arc because this was the jointing technology available, prevalent, at the time.
MIG welding , specially MIG welding thin metal, technology was still in its infancy in the early sixties and was probably cost prohibitive.
The advent of cost effective CO2 MIG welding would have superseded brazing because joint preparation is not as critical, less skilled and therefore cheaper.
MIG welding itself is also a fairly low skilled operation.
I think it’s unlikely it was anything to do with engineering or design.
It’s really a matter of choice which method you want to use.
If it’s a brazed chassis why not braze it.
MIGed chassis MIG it.
This may be advantageous if you ever come to sell, being able to say the chassis was refurbished sympathetically to the original specification, it may not!
Good luck with your rebuild.
I would speculate earlier chassis were brazed, either using gas flame or possibly carbon arc because this was the jointing technology available, prevalent, at the time.
MIG welding , specially MIG welding thin metal, technology was still in its infancy in the early sixties and was probably cost prohibitive.
The advent of cost effective CO2 MIG welding would have superseded brazing because joint preparation is not as critical, less skilled and therefore cheaper.
MIG welding itself is also a fairly low skilled operation.
I think it’s unlikely it was anything to do with engineering or design.
It’s really a matter of choice which method you want to use.
If it’s a brazed chassis why not braze it.
MIGed chassis MIG it.
This may be advantageous if you ever come to sell, being able to say the chassis was refurbished sympathetically to the original specification, it may not!
Good luck with your rebuild.
I was reading that some manufacturers such as Caterham still braze their chassis at production. It was and still is also used for many new race car chassis. The reason that MOT stations are no longer allowed to accept brazed repairs is that you can braze onto badly corroded steel and therefore they cannot be sure that repairs are structurally sound. Clearly MOT's are OK for cars with brazed chassis from new.
Moto
Moto
Steve, EVERY (Grantura/Vixen/M/Wedge/S/Griffith/Chimaera) chassis I have every refurbished has been Tig brazed, going back 30 years, (up to M series chassis were gas brazed as OE). With Tig braze, the issue would still be that the welding heat intensity is higher, it flares the original flux out of the old braze, and makes a poor joint (Tig C9 copper/bronze rods are not the same as braze) when grinding the surface clean you can drag braze into the steel. SO, cleaning old braze off is important. A@
Edited by Adrian@ on Friday 5th February 10:02
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