Is it possible to straighten Pre A bumper guards ?

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Daryl Bertram
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Is it possible to straighten Pre A bumper guards ?

#1 Post by Daryl Bertram » Mon Nov 08, 2021 9:24 pm

I would like to straighten my February '54 Cab's rear bumper guards which got a bit pretzeled in a rear end collision late '50's. Is it possible to unbend them without damaging them further? Thanks!
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Donald Zingg
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Re: Is it possible to straighten Pre A bumper guards ?

#2 Post by Donald Zingg » Tue Nov 09, 2021 12:10 am

It is possible.
First, strip the anodize surface treatment. Caswell sells stripper that works well.
https://caswellplating.com/anodize-chro ... 3-gal.html
Then, anneal the guards before attempting to straighten out the damage.
I did a quick search but couldn't find Richard Miller's old tech article about restoring aluminum guards.
He described how to use an oxy/acetylene torch to anneal the aluminum.
Or find a friend with a heat treat oven. Doublecheck these numbers, but 650 - 700F degrees for 30 minutes should work.
Let the parts cool down in the oven.

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Joris Koning
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Re: Is it possible to straighten Pre A bumper guards ?

#3 Post by Joris Koning » Tue Nov 09, 2021 1:39 am

Don,

What I have done to anneal is to cover the part part in the soot from a pure acetylene flame. Carefully burn the soot of with the torch. When you have burnt the soot of, thee part is annealed
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Rick Albro
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Re: Is it possible to straighten Pre A bumper guards ?

#4 Post by Rick Albro » Tue Nov 09, 2021 1:40 am

I have seen people anneal aluminum with a torch but you can also end up with a molten glob of aluminum... the craftsmanship needed is a rare skill these days... I would suggest using an annealing oven where the temperature can be more precisely controlled... I think Don is right on in the process... the excerpt from the bible on heat treating is posted below... The question is do you want to gamble with your rare parts? Be sure do it right... Daryl, I think you know Spencer Harris. Spencer has a metal guy that can do the torch method... I have a small furnace that I anneal aluminum in but I don't think a bumper guard will fit...

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Harlan Halsey
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Re: Is it possible to straighten Pre A bumper guards ?

#5 Post by Harlan Halsey » Tue Nov 09, 2021 6:22 am

I have also used the welding torch/carbon soot method mentioned by Joris. It is one of those operations where a little practice on some scrap aluminum, if at first you are experimenting, will pay dividends. After a little practice with the soot and torch, it is easy. Convertible D windshield trim, and Carrera bumper decos are two other areas where annealing is very helpful.

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Mike Wilson
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Re: Is it possible to straighten Pre A bumper guards ?

#6 Post by Mike Wilson » Tue Nov 09, 2021 12:20 pm

I'd be willing to bet Jose at Christensen's Chrome Plating in Vernon can restore them.

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Daryl Bertram
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Re: Is it possible to straighten Pre A bumper guards ?

#7 Post by Daryl Bertram » Tue Nov 09, 2021 12:43 pm

Thank you all. I have the torch but not the skill so I've e-mailed Spencer to find out who his guy is that has experience with this technique. Mike, thanks and I'll keep Jose in mind as well.

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Mike Wilson
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Re: Is it possible to straighten Pre A bumper guards ?

#8 Post by Mike Wilson » Tue Nov 09, 2021 1:04 pm

Glad to be of help.

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James Davies
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Re: Is it possible to straighten Pre A bumper guards ?

#9 Post by James Davies » Tue Nov 09, 2021 6:56 pm

Daryl, not to rain on your parade, but those aluminum guards are not original to your early 1954 cabriolet. Yours would have had steel bumper guards that rusted to nothing. They were probably replaced with the mid-1954+ aluminum ones you have. FYI.

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Daryl Bertram
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Re: Is it possible to straighten Pre A bumper guards ?

#10 Post by Daryl Bertram » Tue Nov 09, 2021 10:54 pm

Don't worry about "raining on my parade" James. Spencer gave me that info earlier today. The cab was whacked front and rear in the mid fifties and the aluminum guards are replacements. That's why the original owner took the car back from his college kid and sold it to my friend in summer 1959. FYI; our cars don't have to be original to be appreciated for their history.

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Harlan Halsey
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Re: Is it possible to straighten Pre A bumper guards ?

#11 Post by Harlan Halsey » Wed Nov 10, 2021 4:44 am

Indeed, the un-originality is often an interesting part of their history.

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Re: Is it possible to straighten Pre A bumper guards ?

#12 Post by Eric Lenius » Wed Nov 10, 2021 10:04 am

Harlan Halsey wrote:
Tue Nov 09, 2021 6:22 am
I have also used the welding torch/carbon soot method mentioned by Joris. It is one of those operations where a little practice on some scrap aluminum, if at first you are experimenting, will pay dividends. After a little practice with the soot and torch, it is easy. Convertible D windshield trim, and Carrera bumper decos are two other areas where annealing is very helpful.
Do you leave them in annealed condition after working?

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Rick Albro
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Re: Is it possible to straighten Pre A bumper guards ?

#13 Post by Rick Albro » Thu Nov 11, 2021 12:44 am

Leaving the aluminum in the dead soft condition exposes the part to potential distortions and dings... Ideally the part should be heat treated. However this is not a clear black and white question nor is there a clear and defensible answer... geometry webbing and other factor all play a part in the life cycle of the heat treatment... the hardness changes in time and with accumulated stress... aluminum tends to form an oxide layer kind of like a natural anodize... however that is not really true either so...

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Harlan Halsey
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Re: Is it possible to straighten Pre A bumper guards ?

#14 Post by Harlan Halsey » Thu Nov 11, 2021 4:40 am

Yes Eric,
I leave the parts in the annealed state. It's a tradeoff between not being able to do the job at all, or hoping the annealed parts will survive, and age harden in place. Window trim and bumper decos need to be bent in place. Hard to get around that.

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Martin Benade
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Re: Is it possible to straighten Pre A bumper guards ?

#15 Post by Martin Benade » Thu Nov 11, 2021 10:51 am

The way these cars are used soft bumper guards (only attached to sheet metal bumpers) should be fine. One would hope they are never touched by another car.
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