tjkj2002 wrote:
Just remember that to make a bumper out a aluminum which is a s strong as say the ARB it would weigh about the same weight or possibly more and the cost would be 1-2 times more.Plus when hitting/sliding on a rock you would want steel anyways since the steel will slide easier while the rock would dig into the aluminum and slow progress.
Being an engineer who designs machinery for strength, cost, function, etc, I eat up these topics, and I apologize in advance for my long winded replies...
There is something to your sliding concept, as steel is about 40% harder than aluminum, but I'm not sure you can directly say that a rock would dig one and not the other, it would all depend on the rock, and how much pressure you're applying. Anodize the aluminum and the surface will be harder than steel, by a considerable amount.
As far as an aluminum bumper weighing equal or more to achieve the same strength, if you assume they are using standard structural steel, this is just plain and simple not true. It may be true if you overcompensated due to being new to aluminum. Aluminum 6061-T6 is almost 3x lighter than steel, and roughly equivalent in strength to common construction grade steels.
It's true that aluminum plate can be expensive. Its much cheaper to buy extruded aluminum rectangles or tubes. Buying extruded aluminum is often equivalent in price to steel. It cost more by the pound, but weighs far less for the same shape. Typically I can buy flats up to 12 inches wide, which should be fine for most bumper pieces assuming you weren't forming it out of one big piece. For me to take a steel fabrication and convert it to aluminum, I'm probably going to spend 20-40% more to build it than I would have out of steel. I still might be able to make it cheaper than someone else could make the steel equivalent though. It often depends where and how much of the material you buy.
Aluminum is definitely harder to work with and more expensive to fabricate however. You'll scratch it a little more if handling it with / on steel objects, you'll have to grind before welding to remove oxidation, and it conducts heat so well that welding can be tricky. It also melts without warning (ie, turning red like steel) and at a lower temperature. Stronger aluminum sheets are tough to form because they'll crack at the bend. It all depends which kind you're using and your bend radius.
Bottom line:
If you know what you're doing, you could design and build aluminum bumpers and skid plates that were of equivalent
strength as steel components, and they would probably weigh about half as much. If they were equivalent
size, they'd weigh about 1/3 as much.
And they wouldn't rust.
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2005 KJ Renegade
Fabrications for sale:
Aluminum Roof Rack (See Page 9)Aluminum Gas Tank Skid --
Radiator Skid --
Front Strut ShimsComing Soon: Rear Bumpers with lots of options
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