britishtrident
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| posted on 25/12/05 at 09:55 PM |
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MIG brazing anybody using it for chassis ?
A while back there was some post on the subject of MIG Brazing --- out of interest has anybody tried it for chassis joints yet.
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ed_crouch
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| posted on 25/12/05 at 10:21 PM |
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MIG Brazing??
Never heard of it.
If you use the correct type of filler material, brazed joints are stronger than steel (IIRC nickel alloyed wire is the stuff).
I brazed a square steel post to a flat piece of 3mm plate at an engineering course once, and twisted it off with a spanner. The joint held firm and
the steel sheared about 6mm above the joint.
Anyway...
What is MIG Brazing???
Ed.
I-iii-iii-iii-ts ME!
Hurrah.
www.wings-and-wheels.net
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Mark Allanson
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| posted on 25/12/05 at 10:53 PM |
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Its only designed for lap welds, if you use it on a butt weld, it will def break
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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RazMan
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| posted on 25/12/05 at 11:34 PM |
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But why would you braze when a weld would presumeably be stronger?
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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Surrey Dave
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| posted on 25/12/05 at 11:40 PM |
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Caterhams , Kart chassis,and Formula Ford chassis , are Nickel bronze welded which is like brazing.
I can speak for kart chassis, they were very strong, and generally did not break at the joins, there were some kart manufacturers who tried mig type
welding, but it nearly always failed , I believe this may be due to the higher heat needed to weld, making the metal more brittle.
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Chippy
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| posted on 25/12/05 at 11:45 PM |
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IIRC in some instances brazing is actualy to be prefered to welding. I do know that years ago all cycles, both pedal and motor, had brazed together
frames. I'm sure that somebody on here is more into this than me, but as far as I recall it's to do with less heat being better for the
metal molecular structure. Welding is very strong at the joint, if done correctly, but weakens the steel localy to it, more than brazing. If I have
got it wrong, somebody will soon put this right.
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gazza285
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| posted on 26/12/05 at 10:31 AM |
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To be pedantic brazing is, as Mark said, for lapped joints. For butt welds bronze fillet welds are used. The whole idea of using bronze is that it has
a low melting point and as it is softer than steel, it can be used in a stressed situation, as it is more resistant to cracking when slight amounts of
flexing my occur (hence it's popularity for push bike frames).
Although I have brazed many things together, including push bike frames, motorcycle frames, it would be a long job to do a locost chassis, so
I've arc welded mine.
DO NOT PUT ON KNOB OR BOLLOCKS!
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lsdweb
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| posted on 26/12/05 at 11:57 AM |
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Single seater manufacturers and Caterham must know what they are doing 
My Locost was brazed.
Wyn
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cossey
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| posted on 26/12/05 at 12:53 PM |
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according to ppc magazine a few months back it is illegal to braze car chassis together (it was in the top welding tips bit). im not sure if this is
correct but it might be worth checking.
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britishtrident
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| posted on 26/12/05 at 01:13 PM |
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quote:
Originally posted by cossey
according to ppc magazine a few months back it is illegal to braze car chassis together (it was in the top welding tips bit). im not sure if this is
correct but it might be worth checking.
That actually applies to MOT repairs because you can't do a brazed joint where there is any dirt/rust/paint. Caterham (Arch Motors) chassis
has been built with brazed/bronze welded joints since the Lotus days.
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minordelay
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| posted on 26/12/05 at 09:03 PM |
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Mig Brazing is now popular due to the use of high strength steels and boron steel now used in vehicle body shells. Due to the lower heat used, much
less distortion occurs when joining quarter panels on the pillar and produces a far less brittle joint. We had a demo at the college from a welding
supplier recently on a machine which can basically be upgraded by laptop according to the users preference "at a cost" Machine
automatically adjusts the voltage according to the thickness of the metal etc. Apparently most migs put out 18 volts but to get his machine to put out
18 volts the steel thickness needed to be 10.5 mm thick!!!!!
Good bit of kit though
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Peteff
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| posted on 26/12/05 at 11:10 PM |
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Mig brazing is used for galvanised panels as it doesn't evaporate the zinc coating or distort the panels and compromise their rustproof
qualities. A 4kg roll is about £80, why would you buy that when a roll of ordinary wire which will make a good job of it costs under £20.
[Edited on 27/12/05 by Peteff]
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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02GF74
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| posted on 3/1/06 at 04:54 PM |
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quote:
Originally posted by gazza285
(hence it's popularity for push bike frames).
I think it may have a lot to do with tradition and ease/cost of manufacture. Fitting thin walled tube (0.6 mm) into lugs then brazing was the norm
for steel frames as welding thin tube may not be so easy quick or easy.
Nowadays aluminium tubing with thicker walls is used and TIG welded.
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