Skid plate: steel vs aluminum

I hear you. I went w/all steel w/the budbuilt '3 pc.' set, front IFS, belly pan and t.case is 1 skid, and a rear x-memeber that supports the rear of the b.pan. The 40 lbs in weight diff. wasn't enough to compel me to spend hundreds more

 

I went with BAMF full set of Aluminum skids. They look to be built pretty stout and possibly the strongest aluminum option out there. Havnt got a chance to use them yet.

been waiting patiently to hear about a gas tank skid from them but I think they may have forgot about it.

 

Right on, looks good. I just checked out their site again, good stuff. Much less than other manufacturers for the aluminum options I noticed this time. I looked once and stopped, I have a 1st gen., they don't make skids for them. Yours look great! Good, lighter weight option.

 

You are right there is aluminum that bounces back. It’s 7075 and nobody makes skids for 3rd gens made from 7075. Rci more than likely uses 5052 which is relatively weak as it’s not hardened like 7075. If you have ever drilled through 7075 it’s like drilling through hardened steel. Only issue is 7075 can’t be bent like the 5052 which is why it’s not used.

 

Try a composite . Use 1/8" steel outer plate backed with 1/4" Polycarbonate plastic sheet? use backing washers and bond the two and see how it works?

 

That’s great and all but it doesn’t slide very well on a truck going slow and 1/8 steel ain’t shit on these trucks. I had a piece of uhmw on my samurai which weighs 2600 lbs and it didn’t slide worth a damn. Impacts felt better but that’s about it. I now have a piece of 1/4 7075 as a skid and it’s slides better but not nearly as nice as the steel that it replaced. This is for rocks, dirt doesn’t matter nearly as much.

 

For reference here is a 1/4 steel BAMF skid. For those of you that play or are going to play in rocks you need steel and thick. Can’t tell from the picks but this only has 6-7 harder trails on it and it’s bent in about 5-6 spots. The aluminum skid I replaced this with was bent so bad that you could see the outline of the front diff and it was so beat up when I pulled it off the bolts basically shot out and the skid would not line up to reinstall it no matter how many dents I beat out of it. So for the cost and strength steel wins by a long shot. The skid picture had been painted many times and major gouges were ground down with a flap disk. This is 2 trails since the last paint job.

 

I have the 4xinnovations skid plate and it's made of steel, it's a good item and I'd recommend it. It is pretty heavy, though, so it was a bit tricky to install (I basically just laid down with the plate on top of me and scooted under the truck to bolt it up). The weight of steel skid plates is their primary issue, IMO. I like everything else about them, but their weight is just an inherent issue of the material. Aluminum plates are significantly lighter, but they can't endure the carnage that steel plates can.

"No solutions, only compromises" and all that, I suppose.

 

went w/steel, thank you for the pic

 

Went w/steel for skids. Looking at sliders form 4xinnov. thx!

 

I have weld-ons from 4x. Great sliders.

 

Why do so many people make the blanket assumption that an aluminum part is not as strong as a steel part? It is possible to make an aluminum part that is the same strength as a steel part by making it bigger/thicker/etc and the aluminum part will still be lighter.

That said, it’s not at all clear to me if the various aftermarket aluminum skid plates are equal strength to the steel versions from the same manufacturer. I’m not an engineer, but I can google the tensile strength of aluminum and steel and see values of 276 MPa and 505 MPa respectively (I realize not all aluminum and steel is the same) . That suggests to me that an aluminum skid needs to be about twice as thick to be equal in strength to a steel skid. The aluminum skids I am familiar with are only 33% thicker (1/4” vs 3/16”) thus I assume they are not as strong. The caveat is that there might bracing involved.

EDIT: one other thing... AFAIK aluminum oxidizes but that process forms aluminum oxide which is a very hard material that prevents further oxidation.

 

To make an aluminum skid the same strength at steel the aluminum would need to be 6061 at minimum but preferably 7075 which is not cheap, doesn’t bend very well because it’s heat treated and when you weld to it you mess up the heat treating and it will always crack at the weld. You could make a 5/16 thick piece of 7075 close to the strength of 1/4 steel like I did for this Jeep. It has a 2x2 .188 wall steel crossmember on the back another smaller brace in the middle of the skid to stop deflection. But aluminum doesn’t slide as good as steel in rocks so there always a compromise. You want to save 30-40 lbs but have something that gouges and bends fairly easy and doesn’t slide as easy? Not me. Btw most skid manufacturers use 5052 aluminum because it’s easy to weld, not heat treated and bends nicely without cracking. The problem is it bends easy, doesn’t slide very well and gouges. Even if you welded gussets all along a piece of 1/4 5052 it still wouldn’t be as strong as 1/4 steel with no gussets. That being said. I run a 1/4 7075 Aluminum skid on my samurai, and most jeeps I build get 5/16 or 3/8 6061 or 7075 aluminum skids. But I can get away with it because my samurai is very light and the jeeps are fairly light as well and have a lot more clearance than a Tacoma. The belly height of the rig pictured is 22 inches which is inches higher than most Tacoma sliders.

 

I’m not sure what your point is. My point is that you can make a skid plate out of any of those aluminum alloys and, as long as you make it thick enough, it will be the same strength as a 1/4” steel skid plate. agree or disagree?

 

Not really, I said close to as strong and using far stronger aluminum that what the skid manufacturers use for Tacoma’s . So unless you were to make a complete subframe that braces the aluminum and then use 7075 skids fairly thick they would be close or as strong if the correct materials are used but at that point you’re not a ton lighter and you would spend far more money for something that doesn’t slide as good. There almost nothing you could do to 5052 to make it as strong as a 1/4 steel skid and still be practical.

 

I think we might just be talking past each other. Let me use a simple example.

Given these 3 materials:

5052 aluminum 195–290 MPa (lets use 250 to make the math easy)
7075 aluminum 572 MPa (lets use 500 to make the math easy)
A36 steel 400–550 MPa (lets use 500 to make the math easy)

https://en.wikipedia.org/wiki/5052_aluminium_alloy
https://en.wikipedia.org/wiki/7075_aluminium_alloy
https://en.wikipedia.org/wiki/A36_steel

Make bars of these dimensions:

5052 aluminum bar 1m long by 1cm wide by 2cm thick (note that this bar is twice as thick)
7075 aluminum bar 1m long by 1cm wide by 1cm thick
A36 steel bar 1m long by 1cm wide by 1cm thick

Put them in a jig such that we can apply a force to the center of the bar until it fails.

Do you not think that all 3 bars will fail at about the same load? If not, please explain.

 

Im sure they will based on math.
I know how strong 5052, 6061, 7075 and A36 plate steel plate are. I’ve used them all for skids, built them myself tested out in Johnson Valley. 7075 and A36 steel hold up to abuse the best. The reason I use 7075 because when it bends for the most part it springs back and it’s light. If you actually go out and beat on these materials I promise you will find the strengths and weaknesses of each. 5052 doesn’t hold up to rocks. You’re also applying direct controlled force. Take that skid and drop it on a rock from 1 foot and trust me shit changes.

 

You are going beyond the scope of what I was trying to say, but I agree with you that there is more to the story than tensile strength. For example, like you have implied, aluminum and steel fail in different ways. Ronny Dahl has a good demonstration of this:

https://m.youtube.com/watch?v=lWM3o2v46KI

BTW, force is force. There is not "direct controlled force" and some other type of force.

EDIT: another possibly important difference for a skid plate is material hardness and I believe steel will generally win that battle.

 

True force is force, but it is very much controlled force in a Press. Dropping off a ledge and landing on the point of a rock is far different from 8-12 inches then it’s going to be in a press. Honestly I would rather have a 5/16 thick 7075 skid on my truck vs the 1/4 steel. The problem I’m having now with my 1/4 steel skid is the elastic deformation of steel. If I were to have a piece of 7075 my skid would more than likely not be bent and stay bent whereas my steel skid is bent and stays bent which is more annoying than anything and not causing a problem at this point. But getting 7075 skids to work is just too much work for my right now. We have a piece of 3/16 high strength steel on our 4800 car and it’s crazy strong but just too hard to work with. That would be sweet to have that as a option for Tacoma’s.

 

At the risk of offending you, the only obvious difference I see between my example with a jig and a press and your example of dropping on a rock is that mine is a example of a controlled scientific experiment and yours is not. That said, all my comments are based on (well established theory) and yours on experiment. I have not built skids out of various materials and put them through a test of strength and durability.