On Mon, 17 Dec 2007 18:54:14 -0600, Chris
wrote:

need someone to fabricate a custom aluminum curved radiator, with
integral oil cooler . Going to make 10 units

How big, and what's it for? Does it really need to be parallel-pass
small tube like on a car? Does the oil cooler really have to be
integral, or can you use an external one? And consider that a "It
has to look like this, cost be damned" is really going to get pricy,
but it certainly can be done. Guessing $2,000 each, quantity 10 -
$5,000 for one.

For cooling a large automobile or truck engine, you are much better
off using a tried and true design. Go the simple and effective route:
design a decorative curved grille and "radiator shell" for your
project that hides the functional flat factory-built radiator. And
when it comes time to replace that radiator (and you will), you just
call up and order "a Modine Number XXXX radiator for a Camaro" and get
one cheap fast and easy.

If you really have to go custom? For starters, forget about
Aluminum as a practical material for making a one-off (or 10 off) -
between the lousy bending qualities of AL (without multiple anneal
steps and bending mandrels it will crack if you look at it funny), you
then have to TIG weld or Spoolgun weld it together. The stuff
oxidizes so easily that soldering methods are extremely tricky and
full of Fail.

Note that on commercially made AL radiators the tubes are all welded
to custom stamped AL headers, and assembled using crimped and gasketed
joints to custom injection molded plastic header tanks. And they have
a nasty habit of never sealing quite right if you try opening and
cleaning them - for all intents and purposes they are disposable.
When they start leaking or get clogged, throw them out.

Copper and Brass radiator materials give you many more practical and
far easier assembly methods - you can form the tank from brass sheet
and TIG-weld the tank corners and attach hose fittings and trans
cooler fittings, and TIG the copper core tubing to the brass header
bases (high temperature process), and then you use soft solder (low
temp) for final assembly of the tanks to the headers without worrying
about the other joints coming apart.

For a small engine like a lawn tractor, you might be able to
repurpose an air conditioning condenser, a heater core or a
transmission cooler. Or the little radiators off a Quad or
Motorcycle.

Making a curved radiator core will be a real problem, unless you can
repurpose a chunk of condenser out of an air conditioner that was
factory made as curved - you can make tanks or headers to convert it
from single-flow to multi-pass.. They are made of thinwall tubing
that kinks and restricts coolant flow, and really thin fin material
that will kink and restrict airflow if you look at it funny.

-- Bruce --