How to unbend aluminum bumper

[Sam_Fear]

This is apparently flimsy aluminum. I'm more concerned that you'll kink it in one spot instead of getting a smooth bend.

Would an English wheel work?

 

[BigR]

Hi All,

Got the bumpers FedEx today. They are thicker than I anticipated. I don't think there will be a problem of kinking them. Now to get the press and make all the wood blocks, supports, etc.

They look like they will really enhance the looks of the car, compared to the stock bumpers. What do you think?

John in Prescott Arizona

 

[Old Iron]

That's gonna look rally good
[P[P[P

 

[Sam_Fear]

Them's fancy! But that's a lot of curve to take out - good luck.

Take a lot of process pics!

 

[BigR]

Yesterday bought the 12 ton hydraulic press at HF. Went to Home Depot and purchased some 2 by 4s for the outlying tripods, which will support the ends of the bumpers. Push down in the middle and take out a bit of bend then work incrementally towards the ends is the idea. Another buy was some particle board to use for patterns.

Did a simple experiment. I pushed down on the center of the bumper with my hand and was able to take a couple of inched out of the bend easily.

I'm cleaning the garage now to make room for all the equipment. Picture will be forthcoming as I get it all set up.

John in Prescott, Arizoa

 

[BigR]

Update:

Made up the form from particle board for the rear bumper. I had to remove the brackets. After much adjusting sanding and cutting I think I have a nice curve pattern.

Just for grins I mocked up the still curved bumper and took pics. I think it will look good with the excess arc taken out. Will need to take a few inches off each end; don't want it to wrap around as much as the stock unit.

What do you think?

John in Prescott

 

[05snopro440]

Update:

Made up the form from particle board for the rear bumper. I had to remove the brackets. After much adjusting sanding and cutting I think I have a nice curve pattern.

Just for grins I mocked up the still curved bumper and took pics. I think it will look good with the excess arc taken out. Will need to take a few inches off each end; don't want it to wrap around as much as the stock unit.

What do you think?

John in Prescott

It's going to look nice and clean.

 

[BigR]

Got the press set up. I used a big block of wood for the pressure applier. Hole in the top for a big socket, two layers of foam board on the bottom.

I made a couple of triangle supports for the ends of the bumper. Marked the center and every three inches out on the bumper with blue painter’s tape.

There was quite a bit of spring back after the pressure was released. The throw of the press was about four and a half inches. I had to push down on the bumper and force it under the block before each session. One problem was that the spring resistance of the bumper was such that the whole press was raised off the ground when the pressure was applied. I guess that’s why the instructions said to bolt it to the floor. I wanted to keep it relatively portable.

As the bumper became straighter I had to keep blocking up the end supports. Eventually I was able to just use a 2 by 4 on the press itself without external support. You can see in the one pic how far the bumper was distorted during the process.

I worked my way from the center towards each side, using the masking tape markings for reference. The Volvo actually curved more towards the fenders than the arc of the VW bumper.

You can see the results on the car. I think with a bit of trimming this will look good. Now on to the front!

John in Prescott Arizona

 

[Old Iron]

[cl[cl[cl
[P[P[P

 

[Sam_Fear]

Wow! That looks like it worked great. How long did it take?

 

[BigR]

It took a couple of days to make the patterns, adjusting and fitting, then removing the old bumper brackets, etc. The prep work, assembling the press, cutting the wood, making the wood triangles, figgern' everything out took another half day.

The actual bending only took a half hour or so. I think I made maybe a half dozen tries. What surprised me was the amount of distance the metal needed to be moved before it took a set. These bumpers were nice and thick and I was careful to spread the pressure to the left and right of center, not working the same area over and over. Resulting curve is smooth, with no discontinuities.

Now I need to bend the ends more "inward" to conform to the curve of the car fenders. I want to keep the distance from the body consistent the full length of the bumper.

 

[smallfoot]

Does sound to me to be a good plan of attack!

 

[Bamamav]

I thought that would work. Just like reversing the eyes on a leaf spring, just not going as far. You do have to go past where you want it to let it spring back a bit.

 

[BigR]

Finished bending and cutting the rear bumper. I had to add more curve outbioard to match the fenders. This time I weighted down the press with a motorcycle jack, concrete filled coffee can and a bench vise.

Cut 5 inches off each end. Rounded off and polished one end then just had to put it on the car and take pics. Looks pretty good, if I do say so myself.