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]

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!)

[AshG]

planes are not welded for a start so there is no haz, they are made with screws rivets and glue. if you look back a bit into the history of planes there has been plenty of issues with ali fatigue look at the de Havilland Comet, they had a habit of falling apart in the air as did a fair few other planes that were conceived in the 50's. a lot of the new planes manufactured these days are made out of composite materials which are much stronger and lighter.

ali is a fantastic material but its really not suited to use on a chassis unless you can model it and do some fea to work out the issues due to the shortcomings of the material

[Wynand]

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]

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:D ..........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

[jerkins]

Aircraft actually take more of a hammering than a road car, its the buid philosiphy that makes it work.

I doubt whether an aircraft would hit as many potholes though... ;)

[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 !

[minicountryman1961]

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


On Page 53 of the second edition of Ron Champion's Locost book, he is shown holding an aluminum chassis up in the air. He wants us to think he is very strong, so he doesn't admit he is cheating.

[jerkins]

My brother is currently building an all-aluminium light aircraft (a Van's RV-4) - it's scary to see how flimsy each component is, and amazing to see how rigid the parts become when riveted together. Each fuselage & wing part is made of 1.0 - 1.5mm sheet aluminium alloy.

He will end up with a 200mph 2-seater aircraft that weighs over 200kg less than my Locost... :eek:

[TheArf]

Some ruskie pilot landed one of our corporate jets with the tail a bit close to the runway and scraped the tail end. Its now being braced up and brought back to the uk for us to fit new skins, keel section of engine beam frame and then back into the air.

[snapper]

Another problem to be aware off is the wishbone bush bolts going through aluminium brackets, or steel tube and aluminium together causing different metal electrolysis.
The Robin Hood lightweight was an ally monocoque designed as a one season race car, it needed a Hugh amount of re-engineering just to be strong enough to pass IVA.
A well designed steel chassis built with the lightest bits can be around 400Kg