You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
advantages over arc or gas welding,<br />
since a strengthening plate of, say, 3 or<br />
5 mm thickness can be cut to overlap<br />
the damaged area by a considerable<br />
amount. The filler is flowed in, and the<br />
joint covers a very wide area. Welding<br />
only covers a small area compared to<br />
brazing, and providing brazing rod of a<br />
reasonable tensile strength, 45 kg/mm<br />
(29 t.s.Il, such as Oelikon A101, Afrox<br />
M 15 or similar, is used, the joint will be<br />
stronger and more shock resistant than<br />
the average welded repair. The same<br />
applies to the attaéhing of brackets for<br />
fuel tanks, shock absorbers, etc.<br />
With brazing, cleanliness is of utmost<br />
importance, and it is advisable to clean<br />
using a wire brush, emery cloth or<br />
grinding disc to obtain a metallurgically<br />
clean surface. Flux may be<br />
applied as a liquied or as a powder, and<br />
any residue is usually easiuly removed<br />
by scrubbing<br />
Heat may be applied by any means to<br />
hand. For small jobs a Cadac gas torch<br />
is adequate. The Turbo Gaz blowtorch<br />
will handle medium size jobs - I have<br />
heard of a Land Cruiser chassis being<br />
brazed, the heat being supplied by two<br />
Turbo Gaz torches. For larger jobs<br />
oseypropane, oxy/acetylene or twin<br />
carbon arc serve very well as heat<br />
sources. It is essential that the base<br />
metal is hot enough and well enough<br />
fluxed to promote the flow of filler<br />
metal. The filler can be "chawn" by<br />
application of heat, and correct<br />
capillary action will be observed when<br />
the molten filler disappears into the<br />
joint. This action will be familiar to<br />
those who have been done some<br />
soldering. Absolute cleanliness must<br />
be observed to ensure good capillary<br />
action, and it is essential that parts to<br />
be brazed are clamped together ti give<br />
a joint clearance in the region of<br />
0,2mm. Joints of greater clearance<br />
than this can certainly be brazed, but<br />
the capillary action will not be as<br />
strong or as complete.<br />
Brazing is suitable for joining all carbon<br />
and mild steels, brass, copper and<br />
bronze.<br />
2) NICKEL-BRONZE WELDING.<br />
Brazing gives a tensile strength of<br />
approx. 45 kg/mm (29 t.s.l.) whereas<br />
nickel-bronze welding gives a tensile<br />
strength of about 70 kg/mm (45 t.s.I.).<br />
Types available include Oeillkon. of<br />
Afrox Nickel Bronze, and<br />
Johnson Mathey type DB, 85 kg/mm<br />
(55t.s.I.). The higher strength is very<br />
useful for repairs-to tubular structures,<br />
high strength joints, and general<br />
purpose work.<br />
The technique is very similar to<br />
brazing, except that the joint is<br />
prepared as if for welding, i.e. the<br />
edges are ground as if to accept a filler<br />
metal. Flux is applied, and the joint<br />
heated to red heat (800C approx.l, The<br />
filler rod is melted into the joint where<br />
it acts as a filler, bonding the two<br />
surfaces together. Care must be taken<br />
Your Natal<br />
Jeep<br />
Dealer<br />
~~CJ-6<br />
to avoid overheating, and the filler rod<br />
should be melted more by indirect heat<br />
than by direct contact with the flame,<br />
where possible.<br />
~.-\,:_ •. .l.<br />
iii,<br />
Bronze welded butt joint on 18<br />
SWG x 38 mm square tube. Photos<br />
are of Citroen GS engined car currently<br />
under construction,<br />
intended for Roof of Africa 78.<br />
Brazed joints before cleaning up<br />
and grinding. Brazing used to<br />
achieve maximum flow under<br />
gusset plates.<br />
AU~I<br />
crm<br />
1. Nickel bronze welded joint.<br />
2. Brazing flowed in between subframe<br />
and tubing.<br />
Brazed butt joint with a gusset<br />
plate. Brazing allows plenty of flow<br />
into the joint.<br />
Moto X & Bike NewsSA Vol2 No8 Page51
Change language