Grassroots metal shaping: annealed aluminum

So we've been getting our 928 TT/HPDE car ready for next season and we are intent on fitting Porsche GT3 cup rear tires all the way around on 18x10" wheels. The only problem we're having is in the front. The offset isn't quite right so the tires are poking out about 3/4".

The fenders are annealed aluminum, and I've read that they can crack if you try to get too aggressive with the fender roller.

Any suggestions on how we can soften the metal and get busy with the roller?

When I rolled the fenders on my E30 I was easily able to flare them outward by over an inch and I'm hoping for similar results. Thanks guys!

I don't know if you can un-anneal something. But I have bent annealed aluminum tubing and if you are very careful you should be able to.

Annealing it makes it softer so you can work it. It most likely isn't annealed anymore, and would be a lot harder to work, and that's why it would crack. You want to anneal it again. You'll have to strip the paint off. Then the best way I've found is to take a Sharpie black marker and scribble all over the aluminum. Then go over the whole area with an acetylene torch with a rosebud tip until the sharpie lines just lighen up. If you do too much, waiting for the lines to disappear, you run the risk of melting the aluminum (big mess). After the lines lighten, then let it cool all by itself slowly and it will be annealed and much easier to work.

A lot of heat (couple of heat guns?) and some patience go a long, long way. Give it a shot and let us know what happens. Go until it cracks, then back it off one click. Really though, how much is another fender? It seems like this would be a perfect opportunity to get a used fender that might be in crummy condition (bad paint, minor dent, etc.) and bolt it to the car for experimentation. I bet after trying it on one used fender, you'd have a pretty solid idea of what you can get away with on the "pretty" ones.

Bryce

I forgot to mention that the car will be getting a paint job, so there are no issues with breaking out the torch

It's going to depend a lot on what type of aluminum alloy you're dealing with as well. When making the windshield for the Seven, I tried a bunch of different ones before I came up with a good metal that would take a nice bend. Unlike Dr. Hess, I find it works better if you burn that Sharpie mark right off. Getting your hands on a spare fender for practice is an excellent plan.

The way my books read you set the torch with little to no oxygen so you get a smokey sooty flame. coat the alum with the smoke / soot mix then add O2 and heat untill the soot burns off then slowly cool work it and repeat

44

Be ready to get right to work on the fender. Depending on the alloy, it may harden back up in a few hours, even if you don't do any work on it. Also, it may work harden after being bent a few times. So be prepared to keep re-annealing it as required.

I've annealed 6061 from T6 to T0, and it was a 6 hr heat/cooling process in my kiln: 2 hrs at 775F, then cool at 50F/hr down to 500F, then air cool. I needed to expand and taper some tubes for a custom manifold, the T6 simply fractured and split, the T0 was like 'butta'. Of course, when done forming it, I had to harden it back.

Will the rules/aesthetics allow you to space the fenders out 3/4" ??

That might be the easiest solution.

Rog

44, I've tried the soot method. I saw Jessie James do it on one of his first TV shows. After melting the aluminum, I tried the sharpie method. You can still screw it up, but it is a lot safer. And that line will never completely disappear, until the metal goes liquid on you, but it will lighten significantly.

Rolling the aluminum over this top rail took quite a bit of annealing and beating:

I think it turned out good, compared to all the other 7's I've seen, including ones built professionally. Most just cut the panel down lower at the corner and don't worry about it instead of forming that inside radius.

Using the bat roller method can be risky, and is not true metal shaping. Door gaps can open up, low spots can suddenly form in the fender etc. You are basically bending, pulling, and tweaking something that instead needs to be stretched to get more surface area. Depending on the alloy, you may be able to stretch without annealing... at least to start.

You can stretch using a ballpeen hammer backed up by a shot dolly ( basically a leather bag with sand in it). I have stretched fenders with a thrift store leather purse full of sand hanging over the outside of the fender, and a ball peen hammer from behind. You need to attack it in stages. Stretch, then smooth with a hammer and dolly, and stretch again etc.

A practice fender would be the way to start if possible. Getting a feel for this kind of work takes some time. My youtube videos show some of the work involved:

http://tinyurl.com/custom-metal

John www.ghiaspecialties.com

Nice work Dr. Hess! You really sweat the details! A plus one for the sharpie method and Nashco's get an old crap fender to practice idea. I'm new around here so I thought I'd try to be useful. It might help to know what annealing is so here's a simplified explanation:

Metal is madeup of crystals and the working of the metal (hammer-hammer-bang-bang-roll) moves those crystals and changes their relationship to each other. Done on purpose (think forged crankshaft) it can make a stronger part. It's called work hardening. Annealing is heating and cooling the metal to bring the relationship of the crystals back to their original state (or close to it), thus allowing you to work the metal again. How much heating and cooling will vary with the alloy, as will how many times you can work it before it decides you're an idiot and cracks, hence the experimentation on something that don't count.

An easy way to understand it is to think of shoveling snow because snow work hardens, too, and for the same reason. That's why the snow in the drive is easier to shovel than that pile of E36 M3 at the end of the driveway. The snow at the end of the drive has been work hardened by the plow blade.

That gives me and idea. Next time it snows I think I'll get a big torch and anneal the crap out that snow bank

GladlyTheCrossEyedBear wrote: That gives me and idea. Next time it snows I think I'll get a big torch and anneal the crap out that snow bank

I was loving the analogy right up to the part where you can't anneal the snow with a torch to make it easier to shovel again.

I've got a flame thrower / weed burner for that! Snow piles get to high at the end of the driveway for the wife to see over out comes the flame thrower and down the drain the snow goes...

Pee can anneal snow, too.

I knew I could be useful around here...Now excuse me while I anneal my name in a snowbank.