flak monkey
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| posted on 25/5/05 at 05:20 PM |
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quote:
Originally posted by kb58
And AFAIK the Elise aluminum frame is *not* welded, either bonded or riveted... as are aircraft frames. The welding is what does it in.
Yes the Elise chassis is bonded. My physics A-level teacher had something to do with the bonding method development.
Chassis looks good BTW Marc  
Sera
http://www.motosera.com
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mookaloid
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| posted on 25/5/05 at 05:25 PM |
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quote:
Originally posted by Liam
quote:
Originally posted by mookaloid
Just to say I have seen Marc's chassis and I have to say it looks very impressive. It is clearly designed with the material used in
mind.
Yeah crikey, that's bitchin!! Nicely made. Wonder if its any lighter than a steel chassis though?
oh yes its definitely a whole lot lighter than a steel one - I would guess half the weight.
Now for a car that only does a few miles per year on hill climbs fatigue should not be a problem mmmmmmm... still thinking
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JAD
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| posted on 25/5/05 at 05:50 PM |
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7075 cannot be welded & 6061 requires heat treatment subsequent to welding (the welding process anneals/softens the alloy).
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britishtrident
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| posted on 25/5/05 at 06:02 PM |
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Any light alloy part has a finite life no matter how low the loading. Contrast steel at low loadings is considerd to have an infinite fatique life.
The added complication with welding aluminium is the heat treatment goes out the window and you have no real control of the metallurgy within the
weld not exactly ideal especially critical as welds tend to be at corner joints.
The frame in the picture is well engineered but I can't see it being lighter than a book Locost space frame although it could be a good bit
stiffer. 30 years back Porsche built alloy space fames for Le Mans as one race specials they were very worried about fatigue cracking to the extent
the presurised the tubes and fitted schrader valves so they could check for cracks at pits stops.
[Edited on 25/5/05 by britishtrident]
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nick205
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| posted on 25/5/05 at 08:46 PM |
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Marc - any figures on the weight o the Ally chassis? I'd be very interested to see how it compares with a typical steel chassis.
Nick
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marc n
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| posted on 25/5/05 at 10:40 PM |
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if i get chance will weigh it tomorrow
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Peteff
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| posted on 25/5/05 at 10:58 PM |
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It would be a shame to cover that up with panelling, I'd have it like the Atom so everyone could see it.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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kb58
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| posted on 25/5/05 at 11:57 PM |
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quote:
Originally posted by Peteff
It would be a shame to cover that up with panelling, I'd have it like the Atom so everyone could see it.
Except it would need to be corrosion protected just like any other metal. After painting it would look like any other chassis... in fact it would
"appear" heavier due to the larger tubes.
[Edited on 5/25/05 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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Rorty
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| posted on 26/5/05 at 04:49 AM |
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quote:
Originally posted by britishtrident
30 years back Porsche built alloy space fames for Le Mans as one race specials they were very worried about fatigue cracking to the extent the
presurised the tubes and fitted schrader valves so they could check for cracks at pits stops.
Did anyone notice any helium tanks in their pits?
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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NS Dev
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| posted on 26/5/05 at 07:09 AM |
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Really have had enough of this debacle now, but has anybody actually looked at a motorbike frame (well, most of them!)
They are designed for road miles and made using a welded aluminium structure (in most cases)
I know about all the arguments against aluminium, but you design around these.
I know of many arguments against wood but Marcos made some extremely good plywood racing cars!
Alloy/Nomex honeycomb is really a development of an alloy clad plywood composite, I don't doubt that that is where the idea came from anyway.
You cannot just take a statement like "welded aluminium cannot be used as it will fatigue crack" and apply it to any situation without
further qualification of the design.
I don't work in the aluminium industry, I work for a steel tubemaking company, but I do know that there are plenty of welded alloy structures in
heavily loaded, cyclic stressed applications, where cracking is not a problem at a sensible life.
As an aside, many steel structures are designed outside their "infinite" stress cycle range anyway. We did some research as part of a
project looking at loading shovels at College when I was doing my degree and it was surprising how many parts were loaded such that their life was not
infinite. (the main machine looked at had an estimated life at critical welds of 5300 hours approx, based on a simulated heavy duty work cycle, by my
calculation, which cunningly (or fortunately!!) was not too far short of the machine's overhaul interval anyway!)
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MikeR
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| posted on 27/5/05 at 12:40 AM |
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perhaps the concileratory statement (or three) is this .........
Ali can be used in a wide number of situations, but like all materials you have to take its strengths and weeknesses into consideration in the
design.
A general rule is that steel space frames can not be copied in Ali without the likelyhood of failure occuring very rapidly.
There is little proof that the formula 27 chassis has been designed for a life as long as the steel locost chassis. (can't help thinking it
looks like the robin hood 2b chassis with the round tube used!)
.......... does that cover it before all too many toys are thrown out of the pram?
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u401768
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| posted on 27/5/05 at 12:00 PM |
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With out wanting to stir things up even me - welds on a steel chassis will fatigue, and fail long before any other part of the chassis. Even when
using MIG, the weld is contaminated, and also always comes out hard/brittle. So I would thing that given that the Ali chassis would have most likely
welded with TIG or similar, the differences in the fatigue rate of both types of chassis would not be that dissimilar. The Audi A8 chassis is welded,
and also made from Ali. I would thing that has a life expectancy of at least 15 years/200,000 miles, and has also been pointed out bikes have been
using this method for a long time with out problems. At the end there is not that much difference in the mechanical properties of the weakest section
(the welds) and it comes down to preference, experience and cost.
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Peteff
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| posted on 27/5/05 at 01:09 PM |
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Except it would need to be corrosion protected just like any other metal
I've not got anything on my bare aluminium panels and they seem to be standing up to the exposure alright. They don't get that much abuse
from the weather so neither would that.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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kb58
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| posted on 27/5/05 at 01:57 PM |
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quote:
Originally posted by Peteff
I've not got anything on my bare aluminium panels and they seem to be standing up to the exposure alright. They don't get that much abuse
from the weather so neither would that.
Then you must have "alclad" coating which protects the aluminum. Bare aluminum corrodes by getting all chalky looking and pits.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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flak monkey
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| posted on 27/5/05 at 02:07 PM |
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Aluminium will only corrode if its in an environment where the AL2O3 layer is constantly damaged. Otherwise the oxide forms as soon as bare ali comes
into contact with oxygen (its a very very fast reaction), the oxide is a very hard ceramic and if left untouched a peice of bare ali outside will last
for years. Oxidised ali is the normal grey/white that you see. Before oxidation it is very shiney.
Sera
http://www.motosera.com
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ned
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| posted on 27/5/05 at 02:10 PM |
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so those who keep polishing their ally side panels are actually reducing the life of the panels?!!
beware, I've got yellow skin
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MikeR
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| posted on 27/5/05 at 04:35 PM |
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must remember that for when i find a woman and get married, sorry can't clean the car, i'm damaging it 
now if i could just find a way to link that to dusting in the house ........
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