Body Armor Aluminum vs. Metal

[jomobco]

Aluminum underbody armor is not quite a good as steel for several reasons beyond just strength.
1. Aluminum is much louder! It reflects any engine/tranny noise right back into the cabin, and when do you do grind over things, it's quite loud, perhaps even a bit alarming
.

Explain to me how aluminum is louder than steel? In one instance (this) you're saying the softer material reflects more noise. In the second instance (your #2) you're saying the softer metal is stickier - that I might believe. Slightly. I'm curious where you got your data, please explain...

 

[JPK]

Personally, I have found the aluminum skids to be no louder than steel skids when landing on them or scraping them. I used to have steel skids on my LJ, I notice no difference. The aluminum skids did squeek a little when the Jeep was flexing or off camber when the were new, but that lasted a week or two and since then they have been quiet.

Aluminum skids definitely are stickier. Their surface is not as hard as steel and so the rocks stick some when there is weight on the skids. That is why many KOH and hard core guys who choose aluminum also choose the ultra high molecular density, sacrificial plastic skins. I didn't think they were necessary for my aplication, but if I did a lot more rock crawling I would go with them.

JPK

 

[nwoods]

Explain to me how aluminum is louder than steel? In one instance (this) you're saying the softer material reflects more noise. In the second instance (your #2) you're saying the softer metal is stickier - that I might believe. Slightly. I'm curious where you got your data, please explain...

I never said softer.

1. Aluminum "grain" hangs on rocks more than steel. You are just gonna have to believe me.

2. Aluminum is more brittle than steel, combined with it's lighter weight, resonates at a higher harmonic frequency and produces prodigiously more noise.

I just made up that last part, but seriously, whack a sheet of steel with a hammer and then whack a similar size sheet of aluminum what that same hammer. It's not just louder, it's WAY louder. I have used both. I had AL sheeting on my Land Rover, and if there was any sort of vibration, say, you are at idle at a stop light with the car in gear, it would rattle something fierce, and the difference in in-cabin noise level when accelerating with the plate on or off was significant and bothersome. That is with the fasteners tight and torqued. I found that with the AL plating, I had to regularly retighten everything, because of that natural frequency vibration would rattle loose the bolts over time. I eventually used rubber mounts, nylocks and acoustimat insulation to tackle the problems and it helped, noticeably.

Steel, no problems. If you bend it, take it off and bend it back, throw it back on. Nothing special, no fine tuning, no noise, no vibrations, no problems.

 

[JPK]

Dude, you had some crappy skids. Maybe too thin, maybe not shaped right with bends for stiffness, maybe not supported right, maybe too close to your exhaust - which will cause a rattle with any skid material according to RROR, but you had some crappy skids. No rattles, no vibrations, no extra noise with my Jeep. No loose fasteners either.

BTW, they make gongs and symbols out of steel, for a reason. They don't make gongs and symbols out of aluminum, for a reason.

JPK

 

[nwoods]

BTW, they make gongs and symbols out of steel, for a reason. They don't make gongs and symbols out of aluminum, for a reason.

JPK

LOL, don't confuse frequency and tone with volume

 

[antiheroxp]

Aluminum is the best as far as skid plates go(so my dad says who started off his fabricating career building Dakar type race buggies and trucks) mainly because it's lightweight and it doesn't rust. It's lighter weight not keeps the overall weight down but it also helps with maintenance, as it is lighter it will be a lot easier to remove from underneath the truck than a big heavy piece of steel would be. Also aluminum is PLENTY strong enough under there, even though it is weaker than steel, with proper support(gusseting and ribbing) it will be perfect, it will hold up flawlessly to rocks being scraped along it. It may not hold up to driving off a cliff onto your undercarriage but it's plenty strong for bumps, high centers, scrapes and other hard landings!!