just wondering ?

[KAMBO]

how much less would a chassis weigh if built in 2mm wall ali box section ?

[monsterob]

have a search but i think the general concencus was ali is a different material and has different properties so wouldnt be suitable

[acra]

I'd expect Aluminium to show signs of fatigue stress a lot sooner than steel with worse results, based on when I was looking for a new push bike.

That said, it is used in aircraft structures, so I guess it's feasible? Damn expensive though I'd imagine!

[jerkins]

Originally Posted by acra

That said, it is used in aircraft structures, so I guess it's feasible?

Aircraft get stripped down and thoroughly inspected at regular intervals - and they tend not to get the same pounding as a road-going car.

This has been discussed many times in several forums - the general opinion is that aluminium will suffer from fatigue cracking very quickly. It also age-hardens, which wouldn't help. So - OK for race cars, but not for road-going ones.

[twinturbo]

It would most probably way more to retain the require strength. The design does not lend itself to the material.

TT

[leroybrown911]

Aircraft actually take more of a hammering than a road car, its the buid philosiphy that makes it work. Steel is more practical than ali for a road car (that does not have to fly!)

[Wynand]

Originally Posted by KAMBO

how much less would a chassis weigh if built in 2mm wall ali box section ?

Steel weigh about 8750kg/cubic meter and aluminum about 2600kg/cubic meter - thus ally is about 3.37 times lighter than steel. Sounds good, but to get to the same tensile strength as steel, you have to up the thickness to be on par with steel.
When I built/ designed ocean going yachts for a living before retiring, many designs were built either in steel or aluminum. But overall the ally went 30% in size, thickness etc to comply to the same scantling as steel, but still these yachts turned out much lighter than their steel counter parts....

Back to the subject at hand; since we use 25 x 25 x 1.6mm tube for the frame, a meter length will weigh about 1.256kg. The equivalent in ally to be used should be 25 x 25 x 2.0mm and a meter length will weigh about 0.52 kg.
But to be absolutely safe you can up the ally to 25 x 25 x 3.0mm and a meter length will weigh only 0.78kg and a frame built of this over sized grade will be much stronger than the std steel frame and still be 38% lighter!

[KAMBO]

Originally Posted by Wynand

Steel weigh about 8750kg/cubic meter and aluminum about 2600kg/cubic meter - thus ally is about 3.37 times lighter than steel. Sounds good, but to get to the same tensile strength as steel, you have to up the thickness to be on par with steel.
When I built/ designed ocean going yachts for a living before retiring, many designs were built either in steel or aluminum. But overall the ally went 30% in size, thickness etc to comply to the same scantling as steel, but still these yachts turned out much lighter than their steel counter parts....

Back to the subject at hand; since we use 25 x 25 x 1.6mm tube for the frame, a meter length will weigh about 1.256kg. The equivalent in ally to be used should be 25 x 25 x 2.0mm and a meter length will weigh about 0.52 kg.
But to be absolutely safe you can up the ally to 25 x 25 x 3.0mm and a meter length will weigh only 0.78kg and a frame built of this over sized grade will be much stronger than the std steel frame and still be 38% lighter!

I was thinking 2 to 3 mm myself...........wow 38% lighter ..........looks like a plan for my trackday car then

[TheArf]

It might be a good idea to listen to leroybrown he knows what he is talking about when it comes to aircraft and the hammering they take

Arfon

[flyerncle]

Suprisingly strong for the hammer they take considering the dimensions of the parts they are fitted to and the size of the fixings they use.

Personal experience of clattering onto a runway at 80 knots with all three wheels at once and near flattening the oleo's

Saw the rotor head removed from local plod helicopter and it was with a few "Jesus" bolts,youv'e guessed it. Jesus, is that all that holds that on !