Down to the Wire and Going Round the Bend

SimonWright · **Posted:** Tue May 01, 2007 10:25 am

OK, cute subject just to get your attention...

I'm leaving for Rally Tennessee very early on Thursday so I have little time to fix this. After installing the new long tube header on the rally car we find that the skid plate does not clear it. It contacts the bottom end of the header where the flange connects to the cat. Not good. If we bounce on anything with the skid plate (its purpose in life) then the force is transmitted to my nice new header and it'll crack for sure.

I've added spaces to the front mount of the skid plate to generate the necessary clearance but now the skid plate is too low at the front. I don't want to lower the rear any either.

So I think I need to get the skid plate bent somewhat so that I can use the existing mount points, keep the front end of the plate up and avoid the header flange. Assuming I can drill fresh mounting holes in the plate (since they'll move) who can I get to help me bend the aluminum plate - it's thick (1/4" I think) and there's no way it can be done manually.

Prompt advice appreciated.

Thanks.

Simon

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

Is there a way to remove the metal that contacts the header to give it more room? A Dremel would solve things, but I'm unsure of what rules you're having to work around.

SimonWright · **Posted:** Tue May 01, 2007 10:39 am

Good idea Wes, might try that. But it will only give me maybe 1/4 - 1/3 inch - need more.

Simon

Aaron Buckley · **Posted:** Tue May 01, 2007 10:42 am

Aluminum will stretch with enough heat. I would mark the area that needs to 'droop' a bit and pull out a torch. Heat plus a ball peen hammer will do wonders. - AB

Kevin Allen · **Joined:** Thu Aug 28, 2003 6:42 pm **Posts:** 3479

And this new fancy header is going to make you how much faster?

+1 for heat and hammer.

SimonWright · **Posted:** Tue May 01, 2007 10:52 am

Hmm, heat-n-hammer. I might give that a shot. If I leave it bolted to the frame (off the car) when we do that - perhaps it'll keep the original mount points in place.

As for going fastar with the new header: at least it'll help me get out of the corners and up some hills better. There were times that would have helped some. Top speed and corner entry speed is controlled by the pucker governor. I'm trying to adjust that too.

Simon

Ashraf Farrag · **Posted:** Tue May 01, 2007 11:23 am

SimonWright wrote:

who can I get to help me bend the aluminum plate - it's thick (1/4" I think) and there's no way it can be done manually.

Aiee! 1/4" thick - definitely would require a sheet-metal fab shop's assistance and I imagine something with a fairly large hydraulic arm.

I'm no so sure about the heat/hammer approach. Apparently it can crack. I've also gotten aluminum hot enough to melt through but that's probably 250+ amps of welding current for 1/4" plate and I don't think that a torch would have that much. If you do heat...be careful...it conducts heat very well and the input heat (going on my welding experience) required as you heat the metal "next-door" to where you just heated will be lower as you add heat to the work.

Somewhat technical Google result to read:
http://www.cnczone.com/forums/archive/i ... 22965.html

Regards,
--Ashraf

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Simon - Give Carquest on Germantown road a call. They have an extensive machine shop and I would be really surprised if they didn't have a beefy sheet metal brake that can bend 1/4" thick aluminum. Explain your situation and offer to throw a logo on the car!

When I made a custom skid plate for my E30, I had some guys at the IBM machine shop bend the plate for me with a large metal brake. Keep in mind that a brake can only take a relatively flat plate side-to-side -- if there are any "longtudinal" bends in it already it may not work on the brake.

Only other garage-shop idea I can think of is to grind/drill a hole in the skidplate where it's hitting the flange, let it dangle loose.

I'll offer my lift and an evening of help if you think it would be useful. I have lots of tools including a press and now a tubing bender but no easy way to bend sheet, it probably wouldn't fit inside either frame.

Chuck Frank · **Posted:** Thu Jun 07, 2007 5:35 pm

I wish I had seen this sooner, I would have been more than glad to "adjust" it for you. I have had a lot of experience with shaping aluminum, so it would not have been a problem.
For others benefit: Never try to work aluminum while hot it will crack apart. You will need to anneal the area to soften it before (and possibly in the middle of the process depending on how much stretching and working you'll be doing) working it. The proper way to anneal aluminum sheet is with a Ox-Ac torch. If the piece is thick and/or the area is large you may want a rosebud tip for the torch, otherwise use the largest tip you have. First coat the entire area with a layer of carbon by lighting the torch without turning on the oxygen. Play the sooty flame over the surface until it has a solid coat of black. Now add oxygen until you have a soft flame with two short cones in the center. Play the torch over the surface, keeping it moving, until the metal gets just hot enough to burn off all the carbon, NO MORE! There is a relatively short temp difference between annealing temp and melting, and Al does not turn color with heat, it just suddenly drops to the floor in a puddle!
As soon as all the carbon has been burned off, turn off the torch and set the metal aside until it cools to room temp, DO NOT force cool it with air or water. It is now ready to be shaped. There are a lot of shaping methods that can be used, but in this case since a soft shallow form was required I would likely have used a HMW plastic torpedo mallet over a sandbag to bulge the panel where needed. Aluminum also torch welds quite nicely maybe even better than tig welding!

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Down to the Wire and Going Round the Bend

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