downest

I'm looking into making a few skidplates for some of my subaru customers as well as our shop RallyCross WRX, and I'm not sure what the best material to use is. I know of one company that uses 5052 for sure, but I've heard of both being used. I don't know much about the different alloys of aluminium, and I want to use the best one. As far as making the plates, I know both of them are easily worked and welded, I just want the strongest and most corrosion resistant material I can use (I assume the weight will be similar). Can someone outline the differences for me?

scartail

As I recall from school, the higher the series the better grade the aluminum. 6061 and 7K series are for aerospace apps. 2K-3K for soda cans.

9bells

Specifically 2024 and 7075 are used for high-strength applications. 6061 is also good, but it's main advantage is easy fabrication and weldability. 7075 and 2024 are considered unweldable for the most part. 7005 is weldable, as are a few of the 2000 series ones.
1000 and 3000 are very corrosion resistant, but not hard by nay means.
In all reality, aluminum is a terrible choice for skidplates as it is not very tough or hard when compared to steel. Stainless would be great, or even 4140 painted.

KFMRC

6061 is stronger then 5052. 6061 will also required much more of a radius if you decide to bend it to keep it from cracking. 5052 is also cheaper and can be bent with pretty sharp corners and not crack. Either would work and I would base my choice on availablilty and also the fabrication requirements. equipment available bends needed and things like that

5052 welds really well as does 6061. I use alot of 5052 in anything from .025 up to .188

6061 primarily for parts that will be machined.

you could also mix the 2 using the 6061 in areas where your going to machine holes as it machines nicer then 5052.

wade

iTrader: (1)

Took the words out of my mouth.

5052 is alot more malleable and easy to bend like said.
6061 doesnt like to bend and more prone to cracking and breaking. Its more 'brittle' to say.

tepid1

That all depends on the temper rating as well.

downest

Thanks guys, I ended up getting a sheet of 5052. It seems to be the "standard" for these things, and the cost is a plus too. I'll be making a few from this sheet, including the one for our RallyX car, so we'll see how it does.

I agree that steel would probably be a better choice, and I was pretty surprised the first time I installed a Rally Armour plate to find that it was aluminium. I don't think that will be an issue anyway, it seems like the vast majority of the Subarus with skid plates never see off-road conditions, most of them are shiny and clean, kissing the pavement. If we have a problem on the rally car I can easily repair it or replace it with a proper steel plate.

Seymour86

what he said. At my old job we used to mendrel bend 3 inch 6061 we would order it i 0 condition to bend it. Then when done with the welding send it out to be tempered to T-6 condition. 6061 in 0 condition was almost soft enough to scratch with you finger nail.

Here is a break down of the major alloying elements in aluminum alloys

1xxx = 99% or greater aluminum
2xxx = Copper
3xxx = manganese
4xxx = silicon
5xxx = magnesium
6xxx = magnesium and silicon
7xxx = magnesium, copper and zinc.



Actually soda cans are mad from 5k series, just fyi.

KFMRC

yes the temper does change the strength of an alloy. On the other hand 5052 when bought from a supplier is usually sold in H32 or half hard and 6061 is usually sold as t-6. This is why I didn't mention the heat treat. Not saying you can't get it in anything else but you have to ask for it and maybe search several vendors also. usually if you want something easier to work then 5052H32 you buy 3003 instead.

3003 is what many of the aluminum oil pans are made of.

Nick Z32

i still don't get why you would use aluminum for a truck and rally skid plate

DESTROYER

The same reason you would use aluminum anywhere.

mattminer

for this application the skidplate is more about protecting the oil pan and turbo manifold from debris and keeping the engine bay free of mud/dirt/crap. Its not for like scraping over boulders in a rock crawl competition.

M@

downest

Ok guys, I got one most of the way there, but I'm having a problem with warping. So far I've only welded on a spacer plate where it bolts in at the back, it's warped the large plate pretty bad. I haven't welded a ton of thick aluminium like this so I need some help as to what I'm doing wrong. Here's the plate, and how it's warped:





much more noticeable from this view:



I have clamped down thinner/smaller stuff before, but I don't know about this sheet. First off it's pretty damn big, and there's not really a good way to clamp it. Also, my table is pretty thin, and I'm using a fair amount of heat on this so I don't know how it'll hold up. My table is actually already a little warped from a lot of use... it's an old school desk with the laminate removed. Even if I get a big steel or aluminium top on there, I'm not sure how to clamp the plate down, if that's even the solution. I also have to weld a lip along the leading edge, the longer one shown at the bottom of the first two pics, where the arrow is pointing. The lip will be a 3-4" piece that runs the length of the plate, angled upward at ~45 degrees.

It's 3/8" 5052, welding on a Sync 500 current set to ~275A but I'm not using the whole pedal, AC balance slightly on the "penetration" side of balanced, no pulser, 3/32 thoriated tungsten, 1/8" 5356 filler.

essex

wow thats pretty thick to warp like that

KFMRC

It doesn't look like 3/8 think. Its a large flat surface and its going to move welding in the middle. 3/8 steel plate would move also. You can try to heat the plate up before you start welding. This may eliminate some or most of the warping. If you can get away with it try using buck(solid) rivets instead of welding when working in the middle of a large pc. The finished pc will be stronger since you won't destroy the heat treat. Solid style rivets when installed are very strong. Easy to install with an air chisel and the correct tip. You can buy these at mcmaster carr.

downest

What about welding on the leading edge there, will I see warping from that too? I mistyped, it's 3/16"... too many numbers going on there haha.

downest

Well, I ended up making a kind of steel jig, which seems to be keeping it from warping, and also lets me locate the mounting holes and front lip piece. I backed the heat down slightly, max current is down at ~220A now (though I'm using more pedal), I'm moving a little faster too. The front weld on this one is pretty inconsistent since I was playing around to get the feel of it, I probably won't sell this one anyway since it's warped. Anyway, here's what I came up with, didn't have any square stock so I welded angles together...





Yeah I know this weld is dirty, I didn't clean it much, just wanted to get some big "tacks" on the backside so it wouldn't pull too bad, just trying to show the lip thing in this one:


Gotta make this look better for the next few (I cut out 4 more blanks last night)

keons5

I know you already chose the material, but this site has helped me out in so many ways; maybe it will help you sometime. Awesome place to find material data in a jiffy.

Check out http://www.matweb.com and just search for 5052 or 6061.

downest

Forgot to update this...

Well I finished the first plate and ended up sticking it on our RallyX car which served as the 000 car for International Rally New York last weekend (23-25 October). It was very short notice, we had a few hours to go over the car and kind of prep it, a friend of mine called me wed night and the guys were up there the next night after running all over the place getting the car reg'd etc. Anyway, any worries about the material strength are gone now, they beat the **** out of it, jumped a couple of times and slammed the plate pretty good, and it came out fine, not even a dent or any warping:

before:


after:


the worst damage, a gouge right at the sticker, no big deal!



The course was about 300 miles total, mostly gravel and dirt roads, the car had no problems except it lost a couple of the mounting bolts for the plate at one point. I'll be making some more little goodies for it when we have time, some plates to protect the rear links/axles and some rotor scrapers for the mud. Here's the car at the Rally: