On Sun, 20 Oct 2013 13:26:02 -0500, Ignoramus8008
wrote:

On 2013-10-20, Ignoramus8008 wrote:
On 2013-10-20, wrote:
But you can also
just use heat and water. Heating along the bulged side and then
cooling will shrink the metal, eventually pulling it flat. You could
use a big oxy-acetylene torch or a weed burner torch. I would use a
weed burner, actually a few of them, to heat the full length of the
bend all at once.

Eric, thanks. I have a big "Belchfire" fuel/air torch. I may give it a
try.

OK, so, the way to do that would be:

1) Heat along the whole length with a belchfire torch, to perhaps 500
degrees F (measured with pyrometer)

2) Cool rapidly with garden hose spraying water on top

right?

i
Red heat is best. The metal needs to be soft enough to move easily.
And then the hose. And for a large radius bend it is best if the
heated area is spread out over the bent area, with the center being
hottest. You would probably be best served by trying the technique on
a piece of scrap to get a feel of how thw metal is going to move. I
learned how to flame straighten in welding class years ago and like
anything practice helps. If you were doing the sheet metal on a car
then lower heat would be OK since you don't want drastic changes. By
the way, the legs of the Space Needle in Seattle were flame bent. They
just used torches and water.
Eric