if it breaks it breaks
ill just do it an see
hi im phil
i wanna build a space frame for a mini fiberglass shell i wanna make it out of aluminum what size tube should i use and what wall thickness
i think i'd really advise against aluminium tube space frames.
Have a quick search on here for threads on alloy chassis...
IMHO, no manufacturor makes a space frame alloy chassis... they are all welded/bonded monocoques.....
A well thought out steel spaceframe can be as light and as stiff as a similar alloy tub, unless you have a LOT of experience and know where to save
weight on your alloy chassis!
i think i seem to remember a comparison between a steel chassis, and an equivalent aluminium space frame chassis, and there was no weight saving.
i think...
There's very little to be gained from the use of Ali in a well designed chassis. Most of the members should be in compression or tension, and
therefore, especially with the relatively thin walled, large dia, tubes used, Ali will offer little gain, for an increased cost. Ali also has much
greater fatigue problems, which make long term use a pain.
Ali can be much better for use in bending situations. Most common materials have similar E/density, thus for a given mass, they'll have a
similar specific E, but the incresed material needed for lower density materials affords much better designs.
The best chassis would be a CFRP shell, modified a bit for extra stiffness where needed. Either that, or wood's better than ali and steel.
i have decided to make it out of ali but i dont know what size tube and wall thickness to use
i was thinking 3 1/2" tube with 3mm wall thickness would this be ok?
thanks
phil
Everyone is telling you the same thing. Ali is harder to weld and won't weigh less for a spaceframe. There are fatigue issues as well.
However considering the tube size you just mentioned you geting very close to a size that could be used in a simple X braced ladder frame. Weight for
weight and with the right choice of tube size you might beat most steel spaceframe this way. Ladder frames are no where near as bad as some would have
you think and going to Ali would tip the balance in your favour. However to do this you would need to select the right tube size and weld it up
properly and consider the fatigue issues and any corrosion issues and any issues from Ali being in contact with steel bits (which makes ali rot away).
One option for determining tube sizes may be to equate it to a similar steel item. Either a similar weight, or use sutible specifications for a steel chassis or cage, maybe FIA specs and then use equivilant spec Ali.
Speaking of welding it correctly, what specs will be used for heat-treating the chassis? If this is unknown, it's a sign that serious reading is
in order.
Speaking of that, asking here about something as serious as aluminum chassis design is an iffy proposition. That's somethat that should be
researched in books, not asking strangers about something where your life will be on the line...
I'd like to see the chassis fatigue life calculations on the chassis before it's started, if you don't mind.
[Edited on 8/23/09 by kb58]
its only a bit of fun
if it breaks it breaks
ill just do it an see
Cool - good luck with the project. Love your enthusiam.
Out of curiosity, what will you do when it breaks, you crash into a bus stop full of people and kill a few of them?
Perhaps you'll be on a track and demolish someone else's car whilst skidding out of control - hopefully you won't kill them, will you
rebuild their car for them?
Yeah, i'm being harsh - but consider the implications of your actions on others as well as yourself. I'd put a wager on the fact you're
not an expert otherwise you wouldn't be asking these questions. Everyone is telling you its complicated and you need to read up more - either
follow the advice and make an educated decision yourself or make it out of steel.
(i'm in a grump, i've got a pounding headache from welding steel all day and breathing the fumes).
Oh, read up on porsche race cars - they made one out of Ali (907 / 913? not sure) and read about the problems they had.
edited to add - its the 917
and to correct myself, the 908 is where they started ali frames
[Edited on 25/8/09 by MikeR]
[Edited on 25/8/09 by MikeR]
Out of curiosity, what will you do when it breaks, you crash into a bus stop full of people and kill a few of them?
Perhaps you'll be on a track and demolish someone else's car whilst skidding out of control - hopefully you won't kill them, will you
rebuild their car for them?
it would be tuff they shouldnt get in the way
it prob wont be finnished i get bored easily
i have been told by collegues that ali is what i should make it out of
we make ali castings for automotive firms (aston martins, jags, metc, bmw, ford,etc)
so i think ali is perfect
Stunned silence
quote:
Originally posted by philipcurtis100
it would be tuff they shouldnt get in the way
it prob wont be finnished i get bored easily
i have been told by collegues that ali is what i should make it out of
we make ali castings for automotive firms (aston martins, jags, metc, bmw, ford,etc)
so i think ali is perfect
quote:
Originally posted by Staple balls
If you worked for a bakery, would you be making it out of bread?
Go on do it, will give the IVA inspectors something to talk about during the tea break. Then you can try to rebuild the whole thing again from scratch from steel before the retest period expires.
quote:
Originally posted by Mark Allanson
Stunned silence
quote:
Originally posted by philipcurtis100
i have decided to make it out of ali...
well the entertainment is very good from this topic
but i think ill make it and see what happens for myself
unsubscribe
what do you mean
i have joined for some usefull info and all i get is use steel
has anyone used ali
im just after usefull info about ali
if you only know steel dont reply
I think it's quite obvious a lot of people here know plenty about aluminium, which is why you're getting told to use steel.
You could use aluminium, no doubt, but it's expensive, unsuited to the job, and all round a bad idea, hence everyone telling you to use
steel.
Now, you're either incapable of seeing sense and building a car that'll work, or terrible troll. I'd suggest you toddle off and do
something else, duplo might be more suited to your level.
im after info about ali so thanks for the useful reply 
If you want to go ahead and use ally thats fine. I cannot see anyone chipping in on a project that might go horribly wrong and come back on them!
youll much better off building the chassis out of prefab honeycomb sheet and bonding that into the mini shell .
even if your incompetent at GRP , it will still be easy to bond it in with a few pointers , with local strengthening of attatchment points .
youve not said if you can actually weld aluminium , so id have to advise no .
quote:
Originally posted by prawnabie
If you want to go ahead and use ally thats fine. I cannot see anyone chipping in on a project that might go horribly wrong and come back on them!
quote:
Originally posted by Volvorsport
youll much better off building the chassis out of prefab honeycomb sheet and bonding that into the mini shell .
even if your incompetent at GRP , it will still be easy to bond it in with a few pointers , with local strengthening of attatchment points .
youve not said if you can actually weld aluminium , so id have to advise no .
You can lead a horse to water springs to mind
quote:
Originally posted by philipcurtis100
quote:
Originally posted by Volvorsport
youll much better off building the chassis out of prefab honeycomb sheet and bonding that into the mini shell .
even if your incompetent at GRP , it will still be easy to bond it in with a few pointers , with local strengthening of attatchment points .
youve not said if you can actually weld aluminium , so id have to advise no .
i can weld ali
quote:
Originally posted by philipcurtis100it would be tuff they shouldnt get in the way
it prob wont be finnished i get bored easily
i have been told by collegues that ali is what i should make it out of
we make ali castings for automotive firms (aston martins, jags, metc, bmw, ford,etc)
so i think ali is perfect
quote:
Originally posted by philipcurtis100its only a bit of fun a learning thing about cars making one from scratch i want it out of ali dont care if it breaks it will b my fault dont care if its an expensive way of learning
ok lets say i was to make it out of steel what steel would i use
what size of tube
How long is a piece of string?
All depends what you're making, for a sevenesque car, mostly 1" box section works pretty well (read the books, websites and look at
cymtriks' work)
Course, if you're not building something sevenesque, 1" box might not be suitable, and you could be better off with different tubing.
I have made horse boxes etc from both steel and aluminium section. I found many more failures in the aluminum, with cracking occuring in the material
next to the welds, so I stopped using it, even though it saved time in painting and some weight, and generally looked better(it was a good selling
point). I think that is the main reason here about not using aluminium for a chassis is to do with the dangers of material fatigue failure. Its also
much easier to get a 'good enough' weld in steel.
If you want to do a space frame for a CF/fibregalss mini, have a look at www.kimini.com- (by kb58 one of the contributors on this thread) which will
give you loads of information precisely that design.
Hope that helps
Hugh
quote:
Originally posted by hughpinder
I have made horse boxes etc from both steel and aluminium section. I found many more failures in the aluminum, with cracking occuring in the material next to the welds, so I stopped using it, even though it saved time in painting and some weight, and generally looked better(it was a good selling point). I think that is the main reason here about not using aluminium for a chassis is to do with the dangers of material fatigue failure. Its also much easier to get a 'good enough' weld in steel.
If you want to do a space frame for a CF/fibregalss mini, have a look at www.kimini.com- (by kb58 one of the contributors on this thread) which will give you loads of information precisely that design.
Hope that helps
Hugh
No, I've gone through this with other builders who know better with their "outside the box" engineering. I guess I'm getting
better at handling this sort of thing... pulling the plug before getting irritated.
[Edited on 9/9/09 by kb58]