Best Flat Belly/Skid Plate Armour?

[Donk]

So what are you all using material(s) and thickness wise for doing a flat belly/under armour? Be interested to hear thoughts on lighter weight rigs say sub 3k lbs like SXS or Trackick VS heavier full bodied rigs in the 5k lbs+ range. As always pictures are a bonus

 

[Provience]

AR plate is designed for this kind of stuff if you can get it.

something like 1/8" is probably plenty for a lightweight rig.

aluminum is a terrible choice.

plastic cutting boards seem to work really well, just need to be considered replaceable UHMMW ultrahighmolecularweight plastic sheeting. seems people use more than 1/8" and often with a backer, sure you could use AL for a backer if you want to save weight.

i'm planning on being >4k lbs and using 3/16" AR-400 or so.

 

[vetteboy79]

I used 3/4" UHMW on mine, with countersunk 1/2" allen bolts. Even during race use it's been OK mostly unsupported aside from the perimeter.

Used a 1/2" 45-degree wood router bit on my router table to bevel the edge all around as well.

 

[arse_sidewards]

Build a steel skid plate and add plastic later if you want it to be more slick. 1/8 or 3/16 for steel thickness depending on how much space you have for reinforcement, reinforcement spacing and how much deflection you can tolerate.

 

[Yotota]

The other guys pretty much covered it. It will also depend on where you're driving. Jagged sharp rocks VS round smooth rocks VS dirt VS snow.

AR plate is the hardest and toughest, but expensive. If you need sharp rock or constant grinding rock protection it can't be beat.

Real UHMW plastic (don't assume all hard plastic is real UHMW) is a good lightweight alternative. It's not structural and should be backed with something, and treated as consumable. But on a lighter rig or round rocks it's a good choice.

HDPE plastic (cutting board material) might work for certain uses but it's much softer and floppier than UHMW.

Aluminum is soft and brittle unless you pay for high dollar grades. Could be useful for snow/sand, but that's about it. A rock impact will either gouge the hell out of it or crack it.

Good old mild steel works for maybe 75% of uses and is cheap. For the average trail rig we don't need much more than this.

 

[Donk]

Cheers for the input so far.
So depending on rig weight the following thicknesses would be reasonable?
Steel 1/8"-1/4"
Aluminium 1/4"-1/2" (Not reccomended)
UHMW 3/4"

Weight wise those materials come in as follows:
Steel 0.284 lbs/in^3
Aluminium 0.098 lbs/in^3
UHMW 0.034 lbs/in^3

So based on 20 sq/ft of skid plate you'd be looking at the following weights
3/16" Steel - 153lbs
3/8" Aluminium - 106lbs
3/4" UHMW - 73lbs

From a quick look a 10'x4' sheet of 3/4 UHMW is roughly 1/3 the cost of a sheet of 3/16" AR400 and non food grade UHMW (sometimes referred to bed or bin liner) is cheaper than food grade

vetteboy79 How wide of an unsupported span have you got there? How much of a hammering has it had?

I figured it this could be a handy thread but my personal reason for the question is I'm considering having a crack at Trials (cone dodging) and for the stock class you're limited to 33"s and no LSD/lockers unless they're factory fitted. So I'm looking into something like a 2nd/3rd Gen SWB Montero which came with factory rear lockers over here but are IFS so there will definite belly dragging going on.

 

[Wulf]

FWIW I am running 3/16" steel skids on my Tacoma and after abusing them for 5 years they are bent to the point that installing them requires a floor jack and BFH to get things close to lining up.

Next set will be 1/4"

 

['84 Bronco II]

FWIW I am running 3/16" steel skids on my Tacoma and after abusing them for 5 years they are bent to the point that installing them requires a floor jack and BFH to get things close to lining up.

Next set will be 1/4"

Assuming they are A36 then?

 

[YotaAtieToo]

FWIW I am running 3/16" steel skids on my Tacoma and after abusing them for 5 years they are bent to the point that installing them requires a floor jack and BFH to get things close to lining up.

Next set will be 1/4"

Why not 3/8 or 1/2? ​​​​​​

5 years is pretty good for a wear item. I didn't realize the skid plate I brought for my 3rd gen 4runner was 1/4", it's stupid heavy. It's not a pure rock crawler though.

You could also do 3/16" again and either add bracing to the back and/or laminate areas that get the most abuse with 1/8"

Or AR plate

 

[Slander]

FWIW I am running 3/16" steel skids on my Tacoma and after abusing them for 5 years they are bent to the point that installing them requires a floor jack and BFH to get things close to lining up.

Next set will be 1/4"

What's up with tacoma fags and worrying about bending and denting skids??

I had/have 3/16 skids and had to use a floor jack, but am happy that they didn't weigh a thousand pounds. I would stick with 3/16, let them get dented to hell, beat them back or build new ones or drill the holes out a little bigger evrey few years.

 

[Eric]

1/4" steel with a little extra steel. 80 lbs.

 

[Dan]

Anybody try using Hardox? I have seen some very well used dump beds still holding up after years of dumping rocks.

 

[Provience]

Anybody try using Hardox? I have seen some very well used dump beds still holding up after years of dumping rocks.

hardox sounds like a brand name of some level of Abrasion Resistant plate. if it works on a dump bed, it will certainly work on a belly skid

 

[arse_sidewards]

1/4" steel with a little extra steel. 80 lbs.

Like this but with 3/16 and a tighter grid of reinforcing webs and a bunch of little holes so shit drains.

 

[Eric]

Like this but with 3/16 and a tighter grid of reinforcing webs and a bunch of little holes so shit drains.

These photos were before I drilled all the holes. What a fawking nightmare that was! Only reason I used 1/4" was to keep the bolt heads flush.

 

[YotaAtieToo]

hardox sounds like a brand name of some level of Abrasion Resistant plate. if it works on a dump bed, it will certainly work on a belly skid

It is exactly that. I'm going to guess it's a version, or at least pretty similar to AR plate.

In my experience AR plate isn't common below 3/8" i think I found 11 g (1/8") but it was special order.

 

[gozuki]

Anybody try using Hardox? I have seen some very well used dump beds still holding up after years of dumping rocks.

Hardox is the commercial name for AR500. AR plate product numbers range from 200 to 500 and indicate the hardness of the material: AR200, AR400, or AR500 are examples. In the case of AR400, the plate's hardness would equal about 42 Rockwell C (HRC) or approximately 400 on the Brinell Hardness scale, while AR500's hardness would be around 50 HRC or roughly 500 on the scale. AR plate is a higher carbon alloy, for a harder surface, somewhat at the expense of strength. Use it as the surface of skids, but back it up with milder structural steel.

 

[Wulf]

What's up with tacoma fags and worrying about bending and denting skids??

I had/have 3/16 skids and had to use a floor jack, but am happy that they didn't weigh a thousand pounds. I would stick with 3/16, let them get dented to hell, beat them back or build new ones or drill the holes out a little bigger evrey few years.

We'll see who's laughing when your dick is in my mouth






Its not a huge issue in the grand scheme of things but having to spend 30+ min installing the skid is a barrier to doing any kind of maintenance that requires a skid drop. Feel free to call me a lazy _generation you hate_

 

[Bebop]

Current one is 3/16 on buggy. Way too small, even with reinforcements.

I'm going to make another one then plate it with AR.

 

[SLOWPOKE693]

In my experience AR plate isn't common below 3/8" i think I found 11 g (1/8") but it was special order.

Yup. I made corner armor for a Samurai out of 1/8" Hardox plate and had to special order it at the local supplier. Their stock started at 1/4" and went up from there. The price I paid for that 1/8" sheet was absolutely stupid. That stuff is tough as nails but what a bitch to work with. It took a huge press brake and many slight bends to get that shit to wrap around the back of the body. Welding the tube fenders on also sucked. I had to preheat the plate to keep the welds from cracking. It's great for skidplates but horrible for body armor.

 

[Mr Stubs]

I used a flat piece of 1/4 AR 400 for my skid. Welded angle iron to it ( |___| ) and drilled holes and attached with bolts on a horizontal plane. Works killer.

I used 3/16 AR 400 for my front/rear ram mount skids and also plated the bottom/sides of my axle pumpkins.

As for price you need to look around more. The small fab shops are third and fourth party sellers and mark up according. My 4x8 sheet of 3/16 AR cost me $300. I had other quotes at and above $500.

 

[subybaja]

We'll see who's laughing when your dick is in my mouth

I had to read that 3x, and then

 

[Isdtbower]

!/4" 7075 - t6 aluminum to 1/2" Black (recycled/harder) UHMW. 5/16 flat heads to hold sandwich together. 3/8 flatheads to hold the sandwich to the frame.

Some UTV skid suppliers have some pretty trick indented washes to hold to the frame.

Skids are GREAT catchers of WEIGHT (Mud/rocks?etc) plan a way to let that stuff out if possible.

 

['84 Bronco II]

Hardox is the commercial name for AR500. AR plate product numbers range from 200 to 500 and indicate the hardness of the material: AR200, AR400, or AR500 are examples. In the case of AR400, the plate's hardness would equal about 42 Rockwell C (HRC) or approximately 400 on the Brinell Hardness scale, while AR500's hardness would be around 50 HRC or roughly 500 on the scale. AR plate is a higher carbon alloy, for a harder surface, somewhat at the expense of strength. Use it as the surface of skids, but back it up with milder structural steel.

Good information, but your comment about strength isn't entirely correct. AR500 plate for instance has a yield strength of ~200,000PSI which is nearly six times higher than the yield strength of your typical mild steel. The problem with using AR plate in structural applications (especially the harder grades) is that it is very brittle, so you will get very yielding before complete failure and it has low impact strength (AKA toughness). You are correct though, you will want to reinforce/back it with a more ductile material since a large unsupported span of AR plate will be prone to cracking and breaking.

Also, there are AR600 grades available, but I don't know useful they would be for out applications since they are just even more brittle and hard to work with than the lower AR grades.

 

[Isdtbower]

Good information, but your comment about strength isn't entirely correct. AR500 plate for instance has a yield strength of ~200,000PSI which is nearly six times higher than the yield strength of your typical mild steel. The problem with using AR plate in structural applications (especially the harder grades) is that it is very brittle, so you will get very yielding before complete failure and it has low impact strength (AKA toughness). You are correct though, you will want to reinforce/back it with a more ductile material since a large unsupported span of AR plate will be prone to cracking and breaking.

Also, there are AR600 grades available, but I don't know useful they would be for out applications since they are just even more brittle and hard to work with than the lower AR grades.

Can you anneal a bend line in AR plate?

It seems like we are talking about stiffness not toughness. Wanting those bullets to ricochet off instead of dent. But, have you ever picked up a 300M Race case or transmission? That stuff sure seems heavier! I would also prefer the muffling effect of UHMW over AR. Just other thoughts.

 

[Donk]

Can you anneal a bend line in AR plate?

It seems like we are talking about stiffness not toughness. Wanting those bullets to ricochet off instead of dent. But, have you ever picked up a 300M Race case or transmission? That stuff sure seems heavier! I would also prefer the muffling effect of UHMW over AR. Just other thoughts.

Most steels are within 0.002 lbs/in3 of each other and 300m is just a fancy ChroMo so I doubt there's any real difference.

AR only stretches around 12% at the point of breaking vs 20% for mild. AR is a high carbon alloy which is why it's both hard and brittle. It can be bent but it needs a minimum bend radius of 10x the thickness and to be bent across the grain so it doesn't split during bending.
​​​​​

 

[gozuki]

Can you anneal a bend line in AR plate?

No, bending AR is problematic at best

 

[Provience]

outside of style points, i can't think of a reason to want to bend a skid plate, UHMW or AR.

if looks matter that much, make one out of CRS and just expect it to wear out faster

 

[arse_sidewards]

outside of style points, i can't think of a reason to want to bend a skid plate, UHMW or AR.

if looks matter that much, make one out of CRS and just expect it to wear out faster

Torching an H-shape in a plate and then bending the "tabs" down and welding in a filler is an easy way to fabricate bump-outs for when you have stuff like the sump of an E4OD pan or the very bottom of any cast iron 4spd case that you need just a little bit of extra clearance around.

Of course you can just cut and weld.

 

[ScottRS]

My Jeep is kind of fat I'm guessing (probably 5k-ish pounds, haven't weighed it) and I did the skids with 1/4" aluminum and 1/2" UHMW. So far so good. Prior car was about 4500 pounds, had 1/8 and 3/16 steel with 3/8 UHMW over that, and it wasn't enough to keep from deflecting skidplates.