Spotted this today: (Yes I know its Marc from MNR selling it 
)
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=100921&item=4551975923&rd=1
Is this one of those made by MK a while back? ISTR discussion about it on several occasions.
Might be ok for a race/sprint car thats going to be checked regularly, wouldnt use it on the road though....
David 
The description refers to it as a Formula 27 chassis. Either way I agree about using it on the road 
yep chassis defintely f27 38mm round tubular durol chassis, looks pretty impressive
think the mk one was done in inch by inch box in standard alloy
best regards
marc
Not convinced an ali space frame is such a good idea....one shunt and it's a goner
One word - FATIGUE - aluminium will always fatigue and crack eventually can't be avoided.
It works OK in aircraft because most parts are 'lifed' in hours and replaced/scrapped after that time expires.
[Edited on 25/5/05 by JAG]
There are a number of offroad racers that lead much harder fatigue lives than a "second" road car ever will and have tubular alloy
spaceframe chassis.
An aeroplane's fuselage and airframe are not routinely replaced (don't know whether they are lifed but some 747's have been around a
long time if they are!)
I know about the MK ally chassis but as was said, that was a replica of a steel one!!!!! You have to tailor the design to suit the material, look at
an F1 car or mountain bike FFS!!!!!!!!!!!!!
Maybe thinking before answering would be good.
quote:
Originally posted by marc n
yep chassis defintely f27 38mm round tubular durol chassis, looks pretty impressive
think the mk one was done in inch by inch box in standard alloy
best regards
marc
quote:
Maybe thinking before answering would be good
JAG, do you have any accurate numbers to back up what you're saying, assuming say 6061 or 7005 T6 alu*, properly welded and treated?
and of course in various different configurations, compared with steel of many flavours.
I figure, if you want a decent fight about this crap, it may as well have some proof to it.
*picked out of the hat due to many years of mountain biking on frames made of these alloys
Just looking at the 6061 frame of my mountain bike that I came to work on this morning..........................better nip up the corridor and get the
dye penetrant aerosols out then!!
Steels between ~0.3 and 0.6% C show a fatigue limit if loading is loads are kept below a certain level. Which means cyclic loadings can go on forever
and it will never fail. Other steels do not have fatigue limits and will eventually break due to fatigue.
Most if not all ali's do not have a fatigue limit. And most will fail under much fewer cycles than steel.
(Materials courses can be handy sometimes )
You can ignore HT on most chassis as when you weld you destroy the effects of any HT on the surrounding area. Of course if you can heat treat the
whole chassis without resulting in any distortion etc, then that problem wouldnt exist.
An ali chassis designed correctly will not have too many problems. But it will more than likely fail before a steel one due to fatigue.
David
quote:
Originally posted by NS Dev
Just looking at the 6061 frame of my mountain bike that I came to work on this morning..........................better nip up the corridor and get the dye penetrant aerosols out then!!
Taking my bike on the track on Friday, should I check for stress fractures before I go.......
John
Well maybe you ought too!
A seriously used ally downhill frame is generally considered to have a life of only 3-5 years. Not too sure about road racing ally frames, but
i'd have thought only about 10,000 miles. But then you'd have to be a serious racer to cycle a frame to the point of failure in that time
(assuming no bad crashes). You and me could probably keep a decent ally frame for many years, or at least as long as our commitment to ride lasts!
I dirt jump on a 7005 frame and it feels bulletproof, but i'd always check it after a bad landing. My friend had a similar frame and broke a
headset bearing and the steerer tube on a bad landing without damaging the head tube/gussett at all. (But i'd still feel better with a steel or
Ti frame!)
As NS Dev says it is the design that is important. An ally aircraft fuselage can be designed to last 30+ years despite the material. Similarly for a
car chassis. The important thing is that an ally structure is stiff as any bending will fatigue the ally very fast.
As for an ally copy of a locost steel chassis - that is definately NOT stiff and will fail relatively quickly. That F27 frame seems much better but
who knows its fatigue life? Probably not even the designer.
And that's the problem with one off ally car chassis - unless the design is rigorously analysed and tested (which it mostly isn't) you never
know the date it will start falling apart around you on the road. This is NOT the case with aircraft and, to a slightly lesser extent, bike
frames.
Liam
[Edited on 25/5/05 by Liam]
Huh huh!!
Just read the add...
"One of only 3 ever made."
"Believed to be the only one left now."
Says it all!!
Liam
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.
Could make a very interesting hill climb car, mmmmmmm.... now there's a thought!!
Cheers
Mark
heres one
Rescued attachment alloy-chassis-1.jpg
and another
Rescued attachment alloy-chassis-2.jpg
and another
Rescued attachment alloy-chassis-3.jpg
another
Rescued attachment alloy-chassis-4.jpg
finally
Rescued attachment alloy-chassis-5.jpg
sure i've seen one of that design on ebay before, i remember the rear irs bulkhead plate arrangement..
Ned.
I you bend a piece of steel back and forth slightly (staying in the non-elastic mode) you can do it a really long time. Now do the same with
aluminum. The very act of bending the aluminum causes it to work-harden, to get more and more brittle, finally reaching a point where it will crack
at the welds.
And AFAIK the Elise aluminum frame is *not* welded, either bonded or riveted... as are aircraft frames. The welding is what does it in.
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.
gonna wade throught the emails tonight
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.
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?
7075 cannot be welded & 6061 requires heat treatment subsequent to welding (the welding process anneals/softens the alloy).
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]
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
if i get chance will weigh it tomorrow
It would be a shame to cover that up with panelling, I'd have it like the Atom so everyone could see it.
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.
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.
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!)
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?
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.
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.
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.
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.
so those who keep polishing their ally side panels are actually reducing the life of the panels?!!
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 ........