Patch panels metal ?

[DRJDVM's '69]

I'm getting ready to start cutting rust and replacing with patch panels, smoothing the firewall etc as well as box my rear frame before I put the trunk pan in. I need to pick up some steel for the areas where it will have to be fabbed vs. I can buy pre-made panels.

So it looks like most of the sheetmetal is 18-19 ga and the rear frame rails are 16ga.

So I called up the only steel supply place around and asked about prices.... the first question he had was..... what kind of steel ???

So.... would it be best to get hot rolled, cold rolled, galvanized etc etc etc ???

The 4x8' cold rolled 16ga was $53... which is kind of expensive and really more than I need, but they only sell it in big sheets unless they happen to have some remanants.

This is my first attempt at a job like this, so I'm looking for some guidance...

[astroracer]

Head to a junk yard. Pick up a hood from a truck or anything that is big and flat. 2nd gen Montes and Eldorado's had Huge hoods. If it's got a few dents & dinkles in it the cheaper you should be able to get it...
Mark

[Ralph LoGrasso]

If you're notching and boxing the rear frame rails, you'll want to use 1/8" steel instead of 16ga. For my rails, I used 1018 cold rolled 1/8 plate.

[LSRS7]

Try calling D&J Rosa welding their in Manteca, ask for Dave. He sometimes has some scrap pieces.

Jason

[parsonsj]

notching and boxing the rear frame rails

I'd use .188 material for that (3/16), rather than .125.

CR material is easy to machine and fit, and welds very nicely. Its only problem is due to how it is manufactured. Cold rolling induces lots of stress into the steel. Welding can have the effect of releasing those stresses, aka warpage.

The use of a big-ass hood is a great idea. I wish I'd thought of that!

jp

[DRJDVM's '69]

The frame in a Barracuda is 14 ga.... whats the point in adding a piece that is thicker than the majority of the frame ??

Since I MAY notch the frame on the side for tire clearence (IF I do a minitub, I'm not sure yet), I was going to close in the top of the "U" frame now since I have the trunk pan out of the car.

Next question.... whats the difference between sheemetal and steel plate ??

[toxicz28]

The frame in a Barracuda is 14 ga.... whats the point in adding a piece that is thicker than the majority of the frame ??

When notching the frame, you are removing some of the strength of the area notched. By adding a thicker piece, you would add some of the strength back.

Since I MAY notch the frame on the side for tire clearence (IF I do a minitub, I'm not sure yet), I was going to close in the top of the "U" frame now since I have the trunk pan out of the car.

Good idea, since this will add some rigidity to the area.

Next question.... whats the difference between sheemetal and steel plate ??

The thickness.

[parsonsj]

whats the point in adding a piece that is thicker than the majority of the frame ??

No point, unless you are reducing the cross-section of the framerail. Most strength properties of tubes are based on the cross-sectional area. If that is reduced via a notch, you try to put some of it back with thicker steel.

jp

[astroracer]

Adding "thicker" steel is okay IF you can get the proper welds... Welding thick to thin or vice-versa is a problem because it is very difficult to get a consistant weld between two materials that are over 20% different in thickness. You will almost inherently end up with a too cold weld on the thick piece or to hot (read as blow through or holeing) on the thin. It is usually better to weld like thickness to like thickness. With weld consistency and quality a factor you will generally have the strongest assembly going this route.
Mark

[parsonsj]

Adding "thicker" steel is okay IF you can get the proper welds.

Obviously true, and is true with all fabrication involving welding. If one can't properly weld, then the structure will not have the desired strength. Welding thick to thin is more difficult, but we're not talking about welding 20g sheet to 1/4 plate. We're talking about welding .125 to .188.

One might also argue that the thicker material now causes a non-linear response to stimuli, but then again, so will the notch.

In general, don't notch. If you must notch, be sure you are well-versed in welding technique and have the proper equipment. Be aware that notching in and of itself compromises the rigidity of the frame rail, and that filling the notch will not not recover that strength. If the ultimate strength of the original framerail is required, other means are necessary, such as thicker metal or additional triangulation or bracing.

jp