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Bumper straightening

Posted: Mon May 18, 2009 5:13 pm
by jmvv
When I went to rescue the 67 sunroof Beetle from its eminent grave, I had to drag it out from between the cars on either side.

Flat tyres and cars wedged tight meant that 4x4 low range on the Jeep had to get the job done. It worked, but the bumper paid the price.

This afternoon we decided to try our hand at bumper straightening and the following is the result.

Before (I had the chrome removed in an acid bath beforehand)
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After

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The bumpers will be painted for the Twobucks project, so a skim coat of body filler will make it perfect.

Re: Bumper straightening

Posted: Mon May 18, 2009 5:47 pm
by Blitzkrieg
Excellent. I'm going to print this post out for future reference. I intend to do the same to a set of type 3 bumpers for my white fasty, when i get eventually get round to fixing it up. Would like to paint them a high gloss black, called finishing black. I see that after the acid dipping the surface is still shiny. Will there be any problems with the paint and primer not sticking?

Re: Bumper straightening

Posted: Mon May 18, 2009 6:18 pm
by bugspray
Came out quite good. Is it better in real?? How'd you manage to do it? I've got 2 front bumpers that are in need of straightning

Re: Bumper straightening

Posted: Tue May 19, 2009 8:54 am
by jmvv
Blitzkrieg

When the chrome was removed, the base metal came out with all rust etc removed. When the acid gets washed off, you immediately get a very slight layer of survace rust formed.

If you follow the correct procedure for filler you should have no problem with the adhesion of paint.

What I'll do here is to first sand the whole bumper with 600 paper to remove the layer of surface rust. I'll wipe that down with a tack rag to remove grease from finger prints. I'll follow that with a layer of body filler (mixed properly). I use BASF CAR SYSTEM filler. That will get sanded with a long board with 600 paper again. High spots will be knocked down and low spots filled. The plan is to not have more than 0,5mm of filler on the finished project. Then I'll apply sealer after a wipedown with a tack rag, follow that with spray filler, sand that down and then apply the carbon fibre finish folowed by a few layers of clearcoat with a bit of flexing agent mixed in to resist chipping.

This is the route I follow and so far it's worked for me.

Re: Bumper straightening

Posted: Tue May 19, 2009 9:09 am
by jmvv
bugspray wrote:Came out quite good. Is it better in real?? How'd you manage to do it? I've got 2 front bumpers that are in need of straightning
It came out very nice. I would not send it for chrome plating as is as there are some minor imperfections that will show through, but nothing that cannot be filed smooth with a metal file.

I used the basic tools as found in the Adendorf's and Midas panel beating sets.

I used a selection of flat head hammers (to limit metal stretching) and some picking hammers with the relevant dollies to gently work the metal back into the original shape. (Banging with a hammer on some metal "gently" is an oxymoron, I know, but use your imagination)

We finished it off by "twisting" the bumper to get the correct "set" and level curve.