Body Armor Musings (little long, sorry)

[JeeperMatt]

I'm a DIY guy, so I've decided to build my body armor panels. Before getting too deep into designs and whatnot I had a couple questions to throw out there for y'all's opinions, experiences, and so on.

1. Weld-on vs bolt-on. I know the sheetmetal is pretty damn thin, and I don't want to go blowing holes all over the place. If welding them on is alright, I plan on tacking then welding in small sections at opposite ends to minimize warpage and other issues.
Bolt-on would alleviate the warpage/hole blowing issues entirely. I do a ton of metal-work on a regular basis (airframer in the Navy), so counter-sinking holes and whatnot is something I'm quite proficient at. Bit more tedious, considering that some panels would require disassembling the interior to access the backside for bolts. Also, sealing the panels to the body to prevent water-intrusion. The bolt-on method also ties into the material selection I address below (I know you can't weld aluminum to steel without a bonding strap, and that's way over my intended budget)

2. Steel vs aluminum. Again, thanks to my job I have access to a ton of scrap aluminum (let me specify, this is scrap metal that we can no longer use on the aircraft). My main thought here is weight-savings as I know steel can add up in the heft department fairly quickly.
I've done some research on what's on the market already, granted it's pretty much Wrangler-exclusive. However, the alloy of choice seems to be 6061 compared to the 5056 that I have access to. This doesn't seem to be an issue as overall tensile strength for 5056 is nearly double that of 6061 (42000psi compared to 17000). There's a good variety of metal thickness and tempering available as well.
Suggestions on what thickness and tempering would be best? The majority of what I can get is T3, with a good amount of T6 thrown in too - all in the typical thicknesses. I just don't want to go through all the effort only to have it gouge and chunk off on the first hit.

Appreciate any ideas, suggestions, and thoughts y'all can throw my way!

- M@

 

[SleeperXJ]

I like the idea of using Al for weight savings.
T6 is very tough but I think you'd have some trouble forming it.
I have some experiance with 6061 T6 and it's impossable to bend
(tends to break before it bends).
The ideal process would be to form it first, then heat treat to T6 condition.
Another potential problem is dissimalar metal corrosion. The combination
of steel alloy and aluminum alloy will pose this problem if the mating surfaces
aren't properly treated.

 

[FlexdXJ]

If it needs armor, i don't think it matters what it weighs. Aluminum would be cool but the cost would be ridiculous.

 

[JeeperMatt]

...
T6 is very tough but I think you'd have some trouble forming it.
I have some experiance with 6061 T6 and it's impossable to bend
(tends to break before it bends).
This is one of my main concerns using Al as well. I can think of two good points that relieve this concern a bit,
1) They'll be large pieces, and the body panels on the XJ aren't that curvy
2) I can try to form the curve with the grain, similar to making bends so the likely-hood of cracks is lessened. This pulls another point up, if the Al is under stress from the curve already, will it be more prone to cracking upon impact?
The ideal process would be to form it first, then heat treat to T6 condition.
This is what I was thinking as well, there's a ton of T3 available which will form better and easier, then heat treat it. I'm worried that the metal will warp during the process, as it will have a curve and thus can't be weighted down to prevent warping.
Another potential problem is dissimalar metal corrosion. The combination
of steel alloy and aluminum alloy will pose this problem if the mating surfaces
aren't properly treated.
Way ahead of ya on that one. Primary advantage is my body panels are in great shape paint-wise, so there isn't much prep needed other than some scuffing. The Al would get some scuffing up to water-break free, then an alodine treatment, then primer and paint

If it needs armor, i don't think it matters what it weighs. Aluminum would be cool but the cost would be ridiculous.
I'm not looking for some massively thick, literally bulletproof protection, just something to help ward off light smacks with rocks, trees, etc.
As for cost, I mentioned in my original post that I'd be using left-over scrap metal that is no longer suitable for use on aircraft - either too small, too many tool marks, light gouging, etc. No cost to me.

 

[Ronbo]

We use black HDPE sheet at work as low friction slides for heavy equipment. It's tough, flexible, easy to machine, lighter than steel and cheaper than aluminum. Not sure who our supplier is, but McMaster-Carr sells it.

 

[wheelinscott]

Since you can do the Aluminium for free, I would defiantly go that route. Please Take some pics.

 

[aintright]

why not take some of the scrap pieces of aluminum and smash it with some rocks, hammer, big piece of steel, anything heavy and hard really.

it'll at least give you some idea of the abuse it may be able to take.

for the armor though i'd suggest some 1/8 steel and just take it on in a bunch of places, but drilling and bolting is another viable option too. you can get some self anchoring nuts to bolt them down with. but that could get pricey. either way you go with welding or bolting you'll want to run some type of silicon sealant around the entire edge

 

[JeeperMatt]

Well I talked to one of the guys back home (currently deployed myself), and apparently the scrap bin consists of a ton of T0 and some T3, so aluminum is out for now.

We use black HDPE sheet at work as low friction slides for heavy equipment. It's tough, flexible, easy to machine, lighter than steel and cheaper than aluminum. Not sure who our supplier is, but McMaster-Carr sells it.
Thanks for the heads up, I poked around on their website to get some preliminary information, and it looks very promising. I need to price out the amount of steel and see how the prices compare. I found some UV-resistant VHMW (apparently offers better impact resistant over HDPE, 60psi per inch of thickness), and it sells for $228-ish for a 48"x96" sheet of 3/8" thick material. I figure that should be enough to do both front fenders, rear quarters, and maybe some boomerangs behind the cargo windows. I really appreciate you suggesting this, I'd never have thought of it.
Edit** So I just got off the phone with McMaster-Carr and they directed me to a table chart. The VHMW impact resistance has a 'No Break' listed, which means during their impact resistance testing they were not able to break it. Sweet baby Jesus I think I found my armor, lol!

why not take some of the scrap pieces of aluminum and smash it with some rocks, hammer, big piece of steel, anything heavy and hard really.

it'll at least give you some idea of the abuse it may be able to take.

for the armor though i'd suggest some 1/8 steel and just take it on in a bunch of places, but drilling and bolting is another viable option too. you can get some self anchoring nuts to bolt them down with. but that could get pricey. either way you go with welding or bolting you'll want to run some type of silicon sealant around the entire edge.
Well it's looking like aluminum is out for now. I'm going to poke around online and price out some 1/4" countersunk bolts, washers, and self-locking nuts. I've got a close friend (prior military in my squadron) that works at Fastenal distribution by Modesto in Cali, so I should be able to get them at a friend-price. I'll be giving all panels a thorough washing and drying, with the armor install followed up by a bead of RTV Ultra black to keep moisture at bay.

 

[stroked88]

Well I talked to one of the guys back home (currently deployed myself), and apparently the scrap bin consists of a ton of T0 and some T3, so aluminum is out for now.

id suggest using autobody sealer rather than silicon. If you decided you wanted to paint over it, silicon will fisheye while the autobody sealant is paintable

 

[JeeperMatt]

id suggest using autobody sealer rather than silicon. If you decided you wanted to paint over it, silicon will fisheye while the autobody sealant is paintable

Ooo that's a great point, that's for pointing that out bud! :wave:

 

[O-Gauge Steamer]

We use black HDPE sheet at work as low friction slides for heavy equipment. It's tough, flexible, easy to machine, lighter than steel and cheaper than aluminum. Not sure who our supplier is, but McMaster-Carr sells it.

This is great stuff! It is uses as the bearing for the track on a snow mobile... I'm thinking of sheathing my stock tank skid and rock rails with the stuff.

 

[xjtrailrider]

The problem I see with the HDPE is that you would not be able to make your tail light boxes as part of the quarter guard.

I'm building mine out of 1/8" steel. i was going to go 1/4" but decided that would be too heavy and overkill.

 

[stroked88]

yeah, learned that one the hard way. used RTV when i folded my quarters and had hell painting anywhere even close to that area. it looked just like oil and water haha

 

[Phil]

I believe Ben H. had plastic quarter guards on his old rig. You may try PMing him.

 

[srimes]

I'd try the aluminum as it's free.

I'd also consider just gluing it on. Maybe try a test panel to see how it holds up. I bet 3m window urethane would work. The main concern would be an exposed edge.