im going to build a space frame out of aluminium
i just what to know what grade people think i should use
im using 3 1/2" tube 3mm thick wall
thanks

the grade i would suggest is steel.

its been discussed loads on here, and generally isn't a good idea.

stress fatigue is a main cause. to make it strong enough if would need to be very thick, by which time its about the same weight as a steel one would be

consider the response from your last thread about this BAD IDEA

[Edited on 3/9/09 by blakep82]

dont go there lol only joking you will have to think of ali being brittle and for you to get the same strenth of steel you will have to make it as heavy as steal. better making it as a monocoque out of alley

[Edited on 3/9/09 by aaron bassett]

quote:

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Originally posted by aaron bassett
dont go there lol only joking you will have to think of ali being brittle and for you to get the same strenth of steel you will have to make it as heavy as steal. better making it as a mono cock out of alley

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What are your reasons for wanting it ally? Is it just weight saving?

Can I have your engine and gearbox after it looks like spaghetti and you've given up?

^ ah, heat distortion? hadn't thought of that

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Originally posted by deezee
Can I have your engine and gearbox after it looks like spaghetti and you've given up?

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Tell owners of ferrari 612s and 360s that ally spaceframes arent a good idea!

How do you intend to mount the suspension?

As I recall the robin hood lightweight was red flagged at SVA because it was discovered the ali brackets were not up to the job.

Personally having looked into this unless your going the mono cock route I'd advise using steel.

quote:

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Originally posted by jambojeef
Tell owners of ferrari 612s and 360s that ally spaceframes arent a good idea!

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quote:

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Originally posted by deezee

quote:

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Originally posted by jambojeef
Tell owners of ferrari 612s and 360s that ally spaceframes arent a good idea!

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LOL ok, you send em around and I'll tell em. Although I can only half tell em, cos half their car is monocoque. Even though compared to the 355 the 360 is only 30kgs lighter. Not a lot more in a 1400 kg car.

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Why settle for aluminium when, with the same amount of research, and for possibly much less risk of fatigue failure, you can go for Carbon Fibre and really have bragging rights - and end up with a lighter chassis.

motorbikes r made out of ali they dont brake or bend etc
i just wanted suggestions of grade to use
not
steels better bla bla bla

quote:

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Originally posted by philipcurtis100
motorbikes r made out of ali they dont brake or bend etc
i just wanted suggestions of grade to use
not
steels better bla bla bla

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Do you have the same heat treating ovens as Ferrari, to normalize the chassis once it is all tig welded together?

Also do you want to bend and twist the first one to see how it handles stress?

quote:

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Originally posted by philipcurtis100
motorbikes r made out of ali they dont brake or bend etc
i just wanted suggestions of grade to use
not
steels better bla bla bla

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this is a wind up OR you work in the office and you have miss understood your more technical colleagues advice.

Trust me they didn't mean for you to build an ali space frame. A motorbike chasis is not a spaceframe. A casting is not a spaceframe

EDIT
An ali motorbike frame isn't a spaceframe

[Edited on 3/9/09 by liam.mccaffrey]

quote:

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Originally posted by philipcurtis100
motorbikes r made out of ali they dont brake or bend etc
i just wanted suggestions of grade to use
not
steels better bla bla bla

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I don't want to poo poo your idea, but I worked for 5 years in a welding and fabrication workshop. I have welded both cars and bikes.
There are cars that have used aluminium chassis but the problem with it is that it is a crystaline metal which means that it fractures easily compared to steel.
To get over this, the ali is thicker or cast into required shapes.
The structure bending under welding is also an issue as it seems to pull more than steel.
For the amateur builder, stay with steel, because you will not even notice the power to weight gain from a slightly lighter chassis.

If it was a viable option, then you can bet your boots that most kit-manufacturers would be selling them right now.

When metal solidifies it forms into crystals that are more or less equal in shape and size.
Diagram A shows this in simple form. Aluminium in this form is low in tensile strength. (Soft)

When it is made into usable shapes in the mills it's rolled and extruded while it's cold,
and this squashes the crystals as in diagram B.
In this form the tensile strength is much higher. In sheet form this is what is termed "half hard".
Further cold working increases the tensile strength even more, like the ali angle that you can buy in Homebase for instance.

When metal is welded it re-crystallizes from B back to A, and also the surrounding area, the heat affected zone. (HAZ)

Aluminium is a fantastic conductor of heat so the HAZ is huge, so in a welded fabrication we have high strength areas
and very soft areas, the red bits in diagram C.

This is why cars that use ali in there construction are riveted, bolted or glued, and not welded. e.g. Lotus.


It's more complicated than this but this may go some way to explain.

Cheers
Paul G

forget aluminium mono cock, make it from tit anium.

F*ck it - go make it out of gold

It seems you're looking for an answer that you want to hear, rather than the right answer.

If so, why ask the question in the first place?

I'll ask my dog and see what grade he suggests.

Edit: my dog says to use steel....

[Edited on 4/9/09 by 200mph]

quote:

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Originally posted by 907
...Aluminium is a fantastic conductor of heat so the HAZ is huge, so in a welded fabrication we have high strength areas
and very soft areas, the red bits in diagram C...

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There are heat treatable aluminium alloys and precipitation hardening (age hardening) aluminium based alloys,
aircraft are made from them, but as far as I know normal (pure) aluminium is not heat treatable,
well only to soften it. (annealing)


Cheers
Paul G

The OP said

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im using 3 1/2" tube 3mm thick wall

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unless you have shed loads of cash salt baths and temper treatment ovens forget it buy the best quality steel nice welder nice mitre saw and get busy forget the ally root you cant really use welding this will just snap around the weld .so you have to go the nut bolt root your working in tubing too all those fittings you will have to make up.

Lots of negativity here! Can I mention the Lotus Elise? Extrusions bonded and then (apparently only for PR) screwed with self tappers?? Welding is only one way of joining metal. Aircraft do not (often) fall out of the sky and they use rivets - as did most formula 1 cars of the 70's.

I have a welding book somewhere where the author uses a tig welded cobra chassis as an example. RCR make a very nice Lola T70 from welded aluminium.

Most motorbikes do not exclusively use castings they use castings welded to extrusions.

Having said all that.....steel is obviously easier and from an engineering point of view better! On the other hand if some other nutter wishes to join me and build a car from aluminium - why not! (errm time money and mainly ....lonelyness!)

quote:

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Originally posted by Theshed
Lots of negativity here! Can I mention the Lotus Elise? Extrusions bonded and then (apparently only for PR) screwed with self tappers?? Welding is only one way of joining metal. Aircraft do not (often) fall out of the sky and they use rivets - as did most formula 1 cars of the 70's.

I have a welding book somewhere where the author uses a tig welded cobra chassis as an example. RCR make a very nice Lola T70 from welded aluminium.

Most motorbikes do not exclusively use castings they use castings welded to extrusions.

Having said all that.....steel is obviously easier and from an engineering point of view better! On the other hand if some other nutter wishes to join me and build a car from aluminium - why not! (errm time money and mainly ....lonelyness!)

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quote:

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Originally posted by Theshed
Lots of negativity here!

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"It is wrong to assume negative = wrong"

I didn't! I was trying to say that whilst I would be the first to say that an aluminium chassis is many many times harder to build and has very few, if any, advantages over a steel spaceframe it is not an impossible task.

Very obviously starting with a pile of 25mm square ali tubing and welding up a locost style chassis would be very silly. However there are many examples of welded aluminium cars out there on the net. Probably fair to say that the term "spaceframe" is stretched a bit. I would describe the lotus as a spaceframe. Another example is the Shelby Mk1.

I did not read the initial poster's "other thread" so please do not take any of this as a defence of any attempt to fabricate an aluminium frame by copying processes that work in steel. In that respect negativity is richly deserved. On the other hand out of the box thinking is surely to be encouraged?

I have just read the other thread...........Now I understand!

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Originally posted by Theshed
Probably fair to say that the term "spaceframe" is stretched a bit. I would describe the lotus as a spaceframe.

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Originally posted by Theshed
I would describe the lotus as a spaceframe.

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..or Audi's description of the A2 chassis

Please don't feed the troll, this isn't the only forum he uses as a lunch table.

Alan...

Possibly the most comprehensive discussion on the matter:

http://locostbuilders.co.uk/viewthread.php?tid=79918

Long and short of it is the chassis needs to be designed for the material you are making it out of. A spaceframe by its very design doesnt lend itself to aluminium construction. Other types of chassis (monocoque, twin beam etc) all do, but require a considerable level of knowledge and expertise to get right.

thanks