Welding on pre-existing tabs:

844 Views 6 Replies 4 Participants Last post by d.b. cooper, Oct 17, 2021

d.b. cooper

Discussion Starter · Oct 12, 2021

Will welding on pre-existing tabs already attached to a rear axle cause the axle housing to go out of alignment?

Now, we know that welding tabs onto a rear axle housing will generally tend to bend out of alignment.

However, if weld on an existing tab, such as:

Ladder Bar Housing Bracket Fits 3-1/2" Axle Tube ⋆ S&W Race Cars

Part# 40-206-350 Ladder bar housing bracket, 1/4" mild steel, fits 3-1/2" axle tube, 7-1/16" center to center of 5/5" diameter mounting holes

swracecars.com

For example, to establish a place to mount a coilover shock.

Would this pull the axle tubes out of alignment? Again, we are welding on the tab, but not the actual axle tube. Of course, the tab is directly connected to the tube, which is why i'm asking.......

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ericnova72

· #2 · Oct 12, 2021

Welding to a tab you won't change the tube.

The reason the tube changes is inside the weld bead to tube interface itself, the stress that bends the tube when it cools is only in that area that the weld is in direct contact with the tube. Called the HAZ - Heat Affected Zone,

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d.b. cooper

Discussion Starter · #3 · Oct 13, 2021

ericnova72 said:
Welding to a tab you won't change the tube.

The reason the tube changes is inside the weld bead to tube interface itself, the stress that bends the tube when it cools is only in that area that the weld is in direct contact with the tube. Called the HAZ - Heat Affected Zone,

Good to know..........buuuuut will the tab itself bend?

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kso

· #4 · Oct 13, 2021

When metal distorts by welding it's because it expands as it gets hotter...creating stress...it would shrink back again to the starting size if cooled except, once it gets up to red-hot it loses its' strength and that expansion force collapses, then as it cools it will contract back in from there and be to a new different shape. Of-course a good penetrative weld will bring the base material up to red-hot. If the critical component here i.e. the axle tube didn't get red-hot while the attached bracket was being welded on it won't warp. If the bracket happens to distort a little from being welded on it's no big deal, whack it back into place.

If you ever warp an axle tube by welding on it, applying similar heat (usually w/ a gas torch) to the opposite side can even it out, kind-of an art which does leave usually-insignificant internal stresses.

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d.b. cooper

Discussion Starter · #5 · Oct 13, 2021

kso said:
When metal distorts by welding it's because it expands as it gets hotter...creating stress...it would shrink back again to the starting size if cooled except, once it gets up to red-hot it loses its' strength and that expansion force collapses, then as it cools it will contract back in from there and be to a new different shape. Of-course a good penetrative weld will bring the base material up to red-hot. If the critical component here i.e. the axle tube didn't get red-hot while the attached bracket was being welded on it won't warp. If the bracket happens to distort a little from being welded on it's no big deal, whack it back into place.

If you ever warp an axle tube by welding on it, applying similar heat (usually w/ a gas torch) to the opposite side can even it out, kind-of an art which does leave usually-insignificant internal stresses.

Yeah, i kinda figured brackets can be fairly easily bent back to original position.

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johnsongrass1

· #6 · Oct 14, 2021

It's not really a concern to worry about. You won't put enough heat into those to matter.

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d.b. cooper

Discussion Starter · #7 · Oct 17, 2021

johnsongrass1 said:
It's not really a concern to worry about. You won't put enough heat into those to matter.

Ok , thanks.

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