iank
|
| posted on 11/1/08 at 12:59 PM |
|
|
You forgot 'cheap', both the material and the machine/technologies required to stick it together.
[Edited on 11/1/08 by iank]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
|
|
|
|
|
Puk
|
| posted on 11/1/08 at 01:07 PM |
|
|
Oh yeah - good point!
What about cheap in hours? Some folk enjoy the trip, personaly I'd like to get the car built quickly so I don't mind spending more time at
the design stage.
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
|
|
|
kb58
|
| posted on 15/1/08 at 02:16 PM |
|
|
Never mind, it'll work perfect...
[Edited on 1/15/08 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
|
|
|
Rogue Se7ens
|
| posted on 15/1/08 at 03:19 PM |
|
|
quote:
Originally posted by kb58
"Currently (contrary to the recommendations of a couple detractors) I am planning to fabricate an aluminum monocoque tub...
I would like to cheer you on. Even though there may be many reasons to avoid such a project, the end results should be rewarding. I look forward to
hearing more.
|
|
|
Puk
|
| posted on 15/1/08 at 06:45 PM |
|
|
Aluminium chassis - the case for
Go for it Mr.Bear!
And in case doubts should set in, rest assured that you're in good company:
This is the RCR GT40 chassis - a very low volume welded aluminium mono:
RCR
That promising upstart Aston Martin with their DB9 chassis (which has been in production since 2003)
AstonDB9
Then there is the Elise
Elise
Surely some one involved in the design of these cars must know that you just can't hope to use aluminium to build a car chassis. Don't
they pay attention to our forum!
Incidentally whilst on the RCA site check out their very tasty Superlight Roadster - 'tis a thing of beauty!
RCR Superlite
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
|
|
|
kb58
|
| posted on 15/1/08 at 07:48 PM |
|
|
quote:
Originally posted by Puk
Surely some one involved in the design of these cars must know that you just can't hope to use aluminium to build a car chassis. Don't
they pay attention to our forum!
I'd bet the first two examples are heat-treaded after assembly, and that the Elise has its aerospace adhesives properly cured at temperature and
pressure.
I would indeed like to see someone from one of the above companies tell us that no engineering skills are needed. If he's a professional
structures and/or materials engineer, I guess he may as well tear up his diploma, as it seems it's just a matter of sticking it all
together...
I don't think so. Of course, if 1/4" aluminum plate is used it can hide a multiple of sins, but good fabrication skills do not equal good
engineering skills.
[Edited on 1/15/08 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
|
|
|
Volvorsport
|
| posted on 15/1/08 at 11:25 PM |
|
|
quote:
Originally posted by Delinquent
quote:
Originally posted by britishtrident
I would say a GRP composite monocoque with some Kevlar and CF reinforcement would be a good option but trying to get it through SVA would be fun,
and I don't think it would be lighter than a spaceframe.
I've been having some fairly extended chats with the SVA chaps about this - and it might ... might not be as bad as it seems.
I've been given loads of tips from both the VOSA people and local SVA chap. The main outcome of the discussions is to show other cars that have
used very similar layup construction and been through the SVA without problems - i.e. GTM, or for more up to date Murtaya. Couple that with a full
photo build of the layups as proof... I've been told it "shouldn't be a problem" (yeah right...)
My current spare time is spent trying to get detailed info from current manufacturers regarding their layup techniques and materials... which is not
exactly simple, however if I DO ever get it built, and SVA'd, I would of course be more than happy to give detailed info on my own layup to
anyone that wanted a go at it.
BTW - re the Tour bikes, there are as many different materials and constructions as there are riders. My brother does the mountain stages when time
allows - last year he went steel frame with everything else carbon or titanium. Unfortunately the chap building it for him cocked up one of the
measurements at the fitting session so don't think that bike will be used again!
all modern darrian rally cars , have been SVA'd . British GT and national tarmac winners .
its a fairly easy modular GRP/Kevlar/carbon chassis , but with a full RAC msa spec roll cage bonded in .
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
Rogue Se7ens
|
| posted on 16/1/08 at 01:46 AM |
|
|
quote:
Originally posted by kb58
I would indeed like to see someone from one of the above companies tell us that no engineering skills are needed.
[Edited on 1/15/08 by kb58]
I'm sure engineering skills are indeed needed, but as with many parts of a build, I would think much of this is common sense. Multiple bends,
proper adhesives or welds should allow reasonable material thickness. If I remember correctly the RCR uses .125 Al and welded seams.
|
|
|
Dom9
|
| posted on 16/1/08 at 09:30 AM |
|
|
I'm a degree qualified materials engineer and an ex-Lotus employee...
The Aston chassis was engineered by Lotus and is put together in the same way as the Elise chassis... I don't believe there was any heat
treatment after the chassis is assembled... The adhesive probably wouldn't like it!
I have spoken to Fran at RCR recently and I'm sure he knows exactly what he is doing and he is very well respected!
All F1 cars and most early Group C prototypes ran folded and riveted aluminium chassis at some point... Including the Porsche 956/ 962 which won just
about everything! I'm sure Porsche know what they are doing!
|
|
|
Puk
|
| posted on 16/1/08 at 09:53 AM |
|
|
Adhesive Bonds
Hi Dom, do you know any more about and are you at liberty to share with the forum further information about the bonding process?
There is a perception that bonding requires high levels of cleanliness, to high to be realistically achievable by the average Locoster. Whilst I
appreciate that Redux like products can demand expensive surface preparation to produce a suitable Al oxide for bonding (correct me here if I'm
way of track). Do you know if there alternatives available that might be more suited to our purposes?
I'm anticipating that the bonding process used at Aston and Jag must be capable of being applied on a regular production line. Which could imply
a tolerance for some surface oxides, possibly even an oil film and would probably preclude any elevated curing temps - with the possible exception of
the paint bake.
By the way I look forward to seeing the evolution of your car - ambitious!
Cheers,
Puk
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
|
|
|
Delinquent
|
| posted on 16/1/08 at 10:21 AM |
|
|
quote:
Originally posted by Puk
Hi Dom, do you know any more about and are you at liberty to share with the forum further information about the bonding process?
There is a perception that bonding requires high levels of cleanliness, to high to be realistically achievable by the average Locoster. Whilst I
appreciate that Redux like products can demand expensive surface preparation to produce a suitable Al oxide for bonding (correct me here if I'm
way of track). Do you know if there alternatives available that might be more suited to our purposes?
I'm anticipating that the bonding process used at Aston and Jag must be capable of being applied on a regular production line. Which could imply
a tolerance for some surface oxides, possibly even an oil film and would probably preclude any elevated curing temps - with the possible exception of
the paint bake.
By the way I look forward to seeing the evolution of your car - ambitious!
Cheers,
Puk
I've emailed my Dad about this (works in aircraft maintenance) as I'm a bit bemused by the cleanliness aspect - I've witnessed some
of the muppets bonding bits of aircraft together, cleanliness is most certainly not the first word that comes to mind...
|
|
|
britishtrident
|
| posted on 16/1/08 at 11:04 AM |
|
|
quote:
Originally posted by Dom9
I'm a degree qualified materials engineer and an ex-Lotus employee...
The Aston chassis was engineered by Lotus and is put together in the same way as the Elise chassis... I don't believe there was any heat
treatment after the chassis is assembled... The adhesive probably wouldn't like it!
I have spoken to Fran at RCR recently and I'm sure he knows exactly what he is doing and he is very well respected!
All F1 cars and most early Group C prototypes ran folded and riveted aluminium chassis at some point... Including the Porsche 956/ 962 which won just
about everything! I'm sure Porsche know what they are doing!
I don't think anyone has a problem with a properly constructed aluminium monocoque, indeed it should be a lot stiffer than a spaceframe but it
would be very unlikely to be lighter than a sparse spaceframe..
The Elise style chassis is interesting in that it is a hybrid of monocoque and deep ladder frame. The deisgn of the bonded and rivet joints is as
much the key to the cars sucess as the concept of using extrusions.
Aluminum spaceframe are a diffeent matter, I am reminded of an interview given by roll cage pioneer John Alley in a Magazine 30 years back, When
asked about light alloy roll cages he replied "Yes we do them but only if the customer insists don't recommend them."
In my professional life I spent a year sorting out problems in fabricated lifting machines made of light alloy. Welded joints in aluminum alloys have
to be carefully designed and specified, a lot of designers used to working in mild steel assume that aluminium alloys behave like a lighter weaker
steel they don't.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
Dick Bear
|
| posted on 16/1/08 at 11:13 AM |
|
|
Never argue with a ....
I'm sorry I wasn't able to see Kb58's full statement before he edited it out. I'm sure it was flattering.
What's the stir about? I come home from the shop at 3:00am, sign-in and find a war about aluminum monocoque vs steel tubes. This type of
construction is not new for goodness sakes it's being done everyday and although I won't claim to know everything about it my not knowing
won't lead me to believe blindly that it is impossible to accomplish at my own shop. Certainly I will need to learn more but the need to learn
more about everything is what keeps me interested in living. I guess some feel that they have gained all the knowledge there is to learn so their
ideas and concepts remain at a stand still.
It may be interesting to some to find that learning and skill development aren't concluded when they are issued their degree or whatever they
base their authority upon.
Aren't we fortunate that someone thought it just might work to fill a rubber tube with air and attach that tube to a wooden wheel. My goodness,
we had wooden wheels for centuries .... that will never work!
I'll end this and say no mare about it with a quote that I feel sums it all up quite well. iank's signature says it best, "Never
argue with an idiot. They drag you down to their level, then beat you with experience. Anonymous
Now back to making things .........!
Dick Bear
www.marketpointproductions.com
|
|
|
iank
|
| posted on 16/1/08 at 11:50 AM |
|
|
This thread started as the traditional substitute aluminium tubes for steel into an unmodified spaceframe discussion.
For some reason (probably to do with the RH lightweight debacle) gets taken by some people to mean that no chassis can be made out of aluminium -
it's obviously not true, aeroplanes and elises obviously prove counterexamples.
Whether properly designed aluminium chassis are lighter than a steel spaceframe for the same strength/stiffness/fatigue characteristics/whatever is
debatable without anyone, here, really having the expertise and experience to definitively end the discussion. WW2 bombers were the original source
for the spaceframe IIRC and current bombers don't use it so there is a datapoint that spaceframes aren't the perfect answer to
construction.
Opinions on the suitability of the material for safe home construction of a chassis seems to be the trigger to the current spat.
[Edited on 16/1/08 by iank]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
|
|
|
Dom9
|
| posted on 16/1/08 at 12:20 PM |
|
|
Elise bonding methods
quote:
Originally posted by Puk
Hi Dom, do you know any more about and are you at liberty to share with the forum further information about the bonding process?
There is a perception that bonding requires high levels of cleanliness, to high to be realistically achievable by the average Locoster. Whilst I
appreciate that Redux like products can demand expensive surface preparation to produce a suitable Al oxide for bonding (correct me here if I'm
way of track). Do you know if there alternatives available that might be more suited to our purposes?
I'm anticipating that the bonding process used at Aston and Jag must be capable of being applied on a regular production line. Which could imply
a tolerance for some surface oxides, possibly even an oil film and would probably preclude any elevated curing temps - with the possible exception of
the paint bake.
By the way I look forward to seeing the evolution of your car - ambitious!
Cheers,
Puk
Puk, have a look at these links and this website in general:
http://www.sandsmuseum.com/cars/elise/thecar/chassis/index.html
http://www.sandsmuseum.com/cars/elise/information/misc/pdf/index.html
http://www.sandsmuseum.com/cars/elise/information/technical/asauto.html
There is plenty of good information there but I can remember very little detail off the top of my head from 7-8 years ago!
Can you make an identical spaceframe chassis substituting aluminium for steel... No! Can you make an aluminium chassis by one method or another...
Yes!
Will it be lighter and just as strong as a steel spaceframe... Well... Porsche etc seem to think so! As do Lotus, Audi, Jaguar, Ferrari, Ford and a
fair few aircraft companies!
Remember the Porsche 917 was a spaceframe and they tried both aluminium, which failed and magnesium tube (!!!), which failed... Not sure if they tried
Ti though! However, the 956 went to an extremely successful, strong and light ally monocoque.
|
|
|
Dom9
|
| posted on 16/1/08 at 12:22 PM |
|
|
By the way...
I pointed Fran Hall of RCR in the direction of this thread and he emailed me after reading it. I won't post his reply here as it was a personal
email and I am sure he could register here if he wanted to join the debate. But suffice to say that he is highly qualified and very happy with his
choice of ally in his construction.
|
|
|
Puk
|
| posted on 16/1/08 at 12:37 PM |
|
|
Hi Dom 9- thanks for the links.
I did actually design a aluminium mono chassis whilst at uni. Ran a bunch of load cases on it using ANSYS and got it to the point where the torsional
stiffness was more than adequate. With a bit more time I'd have liked to try and simulate some crash loads.
The process taught me a couple of important lessons - firstly FEA is a blunt instrument and requires skill to be useful. At the time I was able to
lean on a chap that had done his PHD thesis on FEA (this was early 1990s -I guess that people don't get awarded doctorates for that sort of
thing now).
The other realization was that creating a structural bond first time every time was not something that the adhesives then available were going to be
able to guarantee without stringent surface prep and/or elevated curing temps.
Now I have a feeling that this may no longer be the case - what with Jags being produced using riv-bonded joints. This might imply that there are
crash shops that repair them - and I expect that their levels of cleanliness may be achievable by the stubborn amateur. And as Delinquent suggests
modern glues may be tolerant of muppet skill levels. Come on mate - I'm holding my breath here!
Got my Dom's and Tridents confused - apologies.
[Edited on 16/1/08 by Puk]
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
|
|
|
Doug68
|
| posted on 16/1/08 at 01:15 PM |
|
|
I'd agree that there has to be a method for bonding alloy without it being a surgically clean job.
From my time at BAE I learned that fuel tank sealant (sorry forgot the correct designation) for example has very good tensile strength, doesn't
need heat to cure it and spends it's life submersed in Kerosene.
To illustrate how strong the stuff was I was once told by very experienced Engineer how it'd been used on the bolted joint face of the engine
pods of a VC10 to prevent fretting. When the bolts were removed to have the pod taken off it stubbornly refused to move, the fuel tank sealant needed
to be chipped out by a guy armed with a steel rule before it could be separated.
That same Engineer also told me he'd never fly in a plane that wasn't riveted as well as glued mind you, but that was back in 1990.
Doug. 1TG
Sports Car Builders WA
|
|
|
Puk
|
| posted on 16/1/08 at 01:24 PM |
|
|
Adhesive is great in tension and shear but crap in peel - the rivets take care of the peel. Also during assembly the rivets can align the joints and
provide the pressure to promote the bond cure.
The devil is in the detail!
Interesting clues in the articles that Dom 9 provides links too:
"The adhesive is a single-part, heat-cured epoxy paste (XB 5315) which is more often used tar bonding oily steel. It has a tensile strength of
35 MPa and an E-modulus of 2,700 MPa. Curing takes about 40 minutes at 200°C. Until cured, it has a paste-like consistency and is very
stable."
Not sure how to achive 200°C - I wonder what temp powder coating ovens run at.
Arhh - another hopeful quote - "The curing oven is an expensive nuisance. Adhesives technology is evolving and within a few years cold-cure
adhesives will become available for this type of application" the article was written the year that the Elise was launched - when was that
'95? I suspect that they must have cleared that obstacle to enable them to sell the solution to Ford (Jag)
The other little gem was "The assembly of the complete Elise chassis is performed by Hydro in Denmark" - which is coincidentally where I
am based at present. Wonder if I can get a site visit!
[Edited on 16/1/08 by Puk]
[Edited on 16/1/08 by Puk]
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
|
|
|
britishtrident
|
| posted on 16/1/08 at 01:58 PM |
|
|
Yes at the ends of bonded joints peel forces are generated --- hence the rivets.
The caution with using rivets and adhesive bonding is that the rivet can clamp the parts of the joint too firmly together and squeeze out the adhesive
before it cures. For a strong bond a minimum thickness of adhesive is required.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
Puk
|
| posted on 16/1/08 at 02:11 PM |
|
|
Hydro use 0.5mmm ridges on the surface of the Elise extrusions. Another solution is to mix glass beads in with the adhesive which achieves the same
affect.
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
|
|
|
kb58
|
| posted on 16/1/08 at 03:07 PM |
|
|
quote:
Originally posted by Dick Bear
What's the stir about? I come home from the shop at 3:00am, sign-in and find a war about aluminum monocoque vs steel tubes.
It all depends on the application. For a show car, material doesn't matter.
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
|
|
|
Dick Bear
|
| posted on 16/1/08 at 04:06 PM |
|
|
Anyone have cheese and bread to go with the background w[h]ine? Or is that the sound of sour grapes?
Dick Bear
www.marketpointproductions.com
|
|
|
Delinquent
|
| posted on 16/1/08 at 04:15 PM |
|
|
Well the response from my Dad was a little on the short side - he'll go to go into more detail "later" which I presume to mean
"not while I'm at work with a load of aircraft awaiting sign-off"
He did say the need for surgical cleanliness appears to be long gone. They used to have to have all parts to be bonded anodised (the process for which
cleans in itself) before bonding, whereas now they simply "buff" the surface with an abradisc, apply a substance called
"boegel" which acts as a cleaning agent then apply a bonding primer. If the boegel hasn't done it's job then the primer simply
will not take, if it does, you're good to bond.
As I say, a little thin on the ground at the moment, I'll press him on it further over the weekend
|
|
|
Puk
|
| posted on 16/1/08 at 05:47 PM |
|
|
Much obliged - if you are anything like my son then don't stop nagging until he gives in.
I've put a call into CIBA to see what they recommend and whether I need to buy by the tank load. Lets see
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
|
|
|
