Flame Straightening has been used for many years for repair and
forming. However it requires a lot of skill in addition to an
understanding the basic principles of how it works. Only a few individuals
have mastered it fully. "Arc Straightening",
on the other hand, is not widely reported, is much easier to apply, and the
results are much more predictable and repeatable.
|The fact is when you are
welding you get distortion. That is thought of as the opposite of
straightening. However if you start with a curved piece and put the weld bead on
properly it will straighten!
|The following is an example used to
straighten the roll bar legs fabricated for our Street Rod.
the roll bar for the 1934 Pro Street, Street
Rod, 0.093 wall mild steel tubing was ordered. To allow UPS
shipping two pre-bent sections and some straight tubing was purchased.
Some tubing was ordered that slipped inside for a backing ring for the butt
joints. A simple fixture was made to hold the parts in place while tack welding
them together. The distance between the two legs was very critical since
the pipe stubs they would slip in were already
welded to the car frame.
| It was important to factor in the
distortion that welding would cause so as to have the proper final
dimension. That was done, but as expected it wasn't sufficiently
||Ruler in hand,
it was off by 3/16 inches! What to do? Having recently traveled to
Mexico where an earthmoving equipment manufacturer using "arc
straightening," that looked like the best alternative since it was predictable
MIG weld beads were placed toward the top of one leg on the side that needed
to move out slightly.
|Weld beads were placed as shown in the accompanying photo, With
each bead the results were measured and slowly but surely as the weld cooled and
shrank, the end of the bar moved. If it was desired to have the bar move in the
other plain as well, the beads could be placed further around the bar.
It is not easy to bend a 0.093 wall 1 3/4 inch steel tube but
"Arc Straightening" did the job. It took 5 weld beads and
the job was accomplished, the spacing between the bars was exactly that
||to achieve the final result the welds were just ground smooth. The finished
bar leaves no indication of the weld beads. For the mild steel tubing the
effect on the structural strength was minimal. Do not use this
technique on 4130 tubing, the extra heat-input will lower the strength.
Rapid cooling could also cause cracks to form.
This process is not widely known or used. It has the potential to solve
some unique problems with less heat input then flame straightening. It is
also much easier to apply and much more predictable. There may be an
application in your shop.
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One Page Summary of Gas Saver System