MattWatson
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| posted on 13/12/02 at 04:47 AM |
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Aluminum Monocoque Chassis?
Other than time issues, are there any considerably difficulities building an aluminum monocoque using sheel aluminum with rivets for joints unseen and
epoxy or spot welds for the remaining?
Anyone know why more chassis like this are not made (other than cost) in the kit car markets?
Thanks
Matt Watson
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VW 1.6L SOHC Turbo Mid engined car
http://members.shaw.ca/wavindustries/
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Findlay234
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| posted on 13/12/02 at 08:32 AM |
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its probably easier to design a well handling space frame chassis. im only guessing there tho.
cheers
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Spyderman
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 posted on 13/12/02 at 01:33 PM |
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My opinion is that it is very costly and time consuming to build with Aluminium.
As discussed elsewhere on this site, rivets are not as strong as they could be unless you go the Aviation route. This puts up the cost
considerably.
Would you really be comfortable bonding panels together structuraly?
I think you would need to be really confident that you were using the correct materials under the right conditions.
Finally, welding aluminium is a specialist job. I'd give it a go and I am quite comfortable welding steel, but would not do it on any area that was
structural.
That is why there are not many aluminium cars about, even production models.
These are just my opinions though! Somebody prove me wrong please!
Terry
Spyderman
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Alan B
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| posted on 13/12/02 at 01:54 PM |
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Hi Terry, I think you have correctly mentioned the main issues.
Another big one...design.
There are a lot of spaceframe cars out there for us to go "hmm, yes 1" x 16g should be good here"....but very few monocoques. Spaceframes are
easier to analyse, they can be done on paper (and were done that way for many years) but sheetmetal structures are much harder to analyse without
FEA...(read Roark's classic works to see why)
So, that alone would put me off (even though I've designed machines and structures for 20 years)....and then as you say the cost and time come into
it..
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Stu16v
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| posted on 13/12/02 at 05:33 PM |
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I read a book by Allan Staniforth (the suspension guru) on how to design and build racing cars, but cant for the life of me remember what it was
called (Probably How to Design and Build a Racing Car... ) In this book he explains various methods and materials available for the home builder
utilising aluminium honeycomb panels for to make a monocoque tub. May be of use if you can find the book.....
Dont just build it.....make it!
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Alan B
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| posted on 13/12/02 at 05:40 PM |
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Stu, it is called.....Race and Rally car sourcebook....yes good book, but I don't know if you'd be a monocoque guru after reading it though
You would definitely have a much better understanding of the issues and techniques that is for certain.
Worth getting, it's a useful reference. It was a follow up to "High Speed Low Cost" which is another "must have" book....if you can find a copy
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Liam
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| posted on 13/12/02 at 05:48 PM |
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quote:
Originally posted by Alan B
Worth getting, it's a useful reference. It was a follow up to "High Speed Low Cost" which is another "must have" book....if you can find a copy
Ooh - never seen that one. Is it worth getting High Speed Low Cost if you already got RARCSB? Do they tread over the same ground?
Liam
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Alan B
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| posted on 13/12/02 at 07:12 PM |
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Liam,
There are some repeated diagrams etc., but more than enough extra stuff fo it to be worth having both.
Basically, "High speed low cost" is the story of the Terrapin mini based racing/hillclimb/sprint car...the world's cheapest 140 mph car
It covers chassis design concepts, theory and practice. Material selection. Suspension design including the legendary "string computer". The full
story and build up details of the car and much, much more
IMO it is a far more significant book than the "book"...
Most of the princples and techniques can be applied to road cars too. It was the first book that said to me"Hey, you CAN build your own car..."
If you can find one..get it...you won't be disappointed.
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fastenuff
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| posted on 13/12/02 at 09:13 PM |
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The Highspeed lowcost is very good reading and even though it is old it gave me some ideas on how to get around the suspensions adjustable and such.
It also shows a good pic of a string computer and rear susp and upright. The terrapin is about 60-75% of a locost weight so do have to beef up
somewhat.
Ingmar
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MattWatson
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| posted on 13/12/02 at 09:30 PM |
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The thing I am looking at here is essentially designing a tub out of card paper, then transfering that onto aluminum ect.
However, price isn't really a big deal for aluminum here. As I live in Canada, the metal prices are VERY cheap and aluminum sheet for a chassis
wouldn't be all that much in excess of the total steel to do a chassis.
Likely, I will use steel, but I was wondering what the feasability was for a monocoque.
I had also looked at going the aluminum honeycomb route, but I currently have not located a manufacturer anywhere close to me.
Matt Watson
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VW 1.6L SOHC Turbo Mid engined car
http://members.shaw.ca/wavindustries/
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MattWatson
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| posted on 13/12/02 at 10:01 PM |
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Something like this:
This is just a mockup that I threw together using some 3d software I own.
[Edited on 13/12/02 by MattWatson]
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Alan B
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| posted on 13/12/02 at 10:07 PM |
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Matt, it is probably worthwhile joining the locost north America and locost theory lists on Yahoo if you aren't already. Both good resources as well
as here.
I hope I don't seem negative about the monocoque idea, but just to bring to your attention what's involved
It is certainly feasible, just not very practical unless someone has exsisting monocoque design experience...IMO
I would be the last person on here to discourage taking the less troden path.....
My build is hardly conventional for a locost
http://www.desicodesign.com/meerkat/
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MattWatson
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 posted on 13/12/02 at 10:15 PM |
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I am most likely going for a steel space frame, but thought it might be cool to try something different.
Thanks for the advice!
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Liam
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| posted on 13/12/02 at 11:12 PM |
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It's certainly cool to try something different (can I tempt you with 4WD? ) and I reckon doing a monocoque tub is *just* within the capabilities of
the average amateur home builder - construction wise. I considered it myself initially - a tub with removable steel tube sub-frames for front and
rear transmission/suspension. But unless you know *exactly* what you're doing designwise, it's rather daunting territory and you could easily end
up with something dangerous. What kind of background do you have?
I decided I didn't have enough knowledge to do a tub and didn't want to spend ages acquiring it (not for my first ever build anyway), so I'm
sticking with good old steel tubes. I'm keeping my head aching with 4WD and an engine that looks twice as big as my engine bay - I knew that
'Tardis Design' module at uni would come in handy.
Cool - you're in Canada. You must know my cousins Aeron and Byron Pope - they live in Canada too .
Liam
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stephen_gusterson
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| posted on 13/12/02 at 11:23 PM |
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I am wondering what a mono tub actually does for you?
If its weight, to be as radical as making a composite tub to save a few lbs, you would need to be as radical everywhere else to make it worthwhile.
Just pick up a wheel and hub/upright. Heavy. You have four on the car. I would guess that one or two would weigh more than the basic space frame.
Lets say a normal 'frame with a alu floor, but without panels weighs 140lb as a guess, and you reduce it to 70lb - a 50% reduction. In a car that
typically weighs 550kg (1200lb) thats not a ballistic saving.
You would need to think radical all through the design.
The problem with being radical, is that its seldom possible to get everything right first time. If you screw up on a one off car and something fails
on the road, the consequences could be bad. There isnt a lot of scope for testing.
Hence Alans theory of if you have seen it on other cars, its more likely to be 'ok'.
My car isnt exactly standard, but I havnt taken what I think are 'out on my own' risks.
If the alu is to save cost as its cheap locally - it wont. The cost of the chassis and panneling can easily be outstripped by a decent set of shocks
and alloys!
Building the spaceframe is one of the cheaper parts of the car to build.
atb
Steve
[Edited on 13/12/02 by stephen_gusterson]
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Spyderman
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| posted on 13/12/02 at 11:52 PM |
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quote:
Originally posted by Alan B
...(read Roark's classic works to see why)
Alan, was he one of them Greek Philosopher blokes?
Don't think we covered him at school!
Who wrote the "High Speed, Low Cost" book? ISDN?
Didn't Staniforth Write another book about suspensions or something? Is that one any good?
GTM built a semi monocoque chassis with the old coupe made out of folded steel.
A very succesful car who's only major problem was rust.
Come to think of it their later cars are all monocoque. Albeit made from glassfibre!
Terry
[Edited on 13/12/02 by Bull]
Spyderman
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Alan B
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| posted on 14/12/02 at 12:05 AM |
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quote:
Originally posted by Alan B
...(read Roark's classic works to see why)
Alan, was he one of them Greek Philosopher blokes?.......
May as well have been for the sense it made to me
Don't think we covered him at school!
Who wrote the "High Speed, Low Cost" book? ISDN?............
Mr Staniforth again, ISBN 0 85059 120 1
Didn't Staniforth Write another book about suspensions or something? Is that one any good?........
"Competition car suspension", yes very good too
GTM built a semi monocoque chassis with the old coupe made out of folded steel.
A very succesful car who's only major problem was rust.
Come to think of it their later cars are all monocoque. Albeit made from glassfibre!
...................
Yes you are correct, Studying one of theirs would give many pointers
Terry......
ALAN
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Spyderman
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| posted on 14/12/02 at 12:23 AM |
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Alan,
Do you know of any good online bookshops that might have the "High speed, low cost" book?
Other than Amazon, I keep forgetting to bookmark them.
I have "The Rally Source book", so is "Competition car suspension" worth getting as well?
Cheers
Terry
Spyderman
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Alan B
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| posted on 14/12/02 at 03:26 AM |
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quote:
Originally posted by Bull
Alan,
Do you know of any good online bookshops that might have the "High speed, low cost" book?
Other than Amazon, I keep forgetting to bookmark them.
I have "The Rally Source book", so is "Competition car suspension" worth getting as well?
Cheers
Terry
Sorry Terry no idea where you could get "High Speed Low Cost" from, other than secondhand.
I thought that "Competition car suspension" had enough new or different content to be worth buying. Sure there is some repetition, but not too much,
and some of the new stuff is very interesting, like active suspension for instance.
It is actually quite ironic that the least technically useful car book I own is....well I'm sure you can guess
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bob
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| posted on 14/12/02 at 08:28 AM |
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ONLINE BOOKSHOP
I use these these people,and have so far managed to get every single motoring book i've wanted.
http://www.chaters.co.uk
Doh!! except this one,site says its out of print but you can back order and its £25.
New ISDN 0 85059 037-X
Published by Patrick Stevens
[Edited on 14/12/02 by bob]
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johnston
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| posted on 15/12/02 at 11:31 AM |
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if u really want to try a monocoque why not try a 50/50 approch first look into to build a chassis with a backbone lotus elan style (i think)
then use a tub for the cockpit
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Mark Allanson
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| posted on 15/12/02 at 10:31 PM |
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Dont be afraid of using adhesives, I work in a VAG approved bodyshop and we repair A8's and A2's on a regular basis. They use a combination of
bonding and rivets in their construction. The rivets are not the pop variety, but compression and need a special tool to apply, but could be done with
a hammer and dolly if you have a practiced swing!
The adhesive is 3M structural bond and was used to 'glue' together the 6R4 body shell amongst others as it does not stress fracture like a spot weld
would.
I think the Elise uses the same stuff for the side rails, with a single rivet at either end of the adhesive fillet to prevent shearing.
The strength of this stuff has to be seem to be believed, because the bonded are is greater than a row of spots, it is much stronger, and I think it
may be stronger than a seam weld in mild steel because there will be no HAZ (heat affected zone) which is the weak part between the weld and the base
material.
The only problem is the cost, its about £30 a pair of tubes and needs a special mixing applicator (£100), but it is BLOODY GOOD!
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johnston
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| posted on 17/12/02 at 11:21 PM |
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mark
seen as you work at vag how the hell do u get a interior door panel of a '96 A4
(guess wat i was at 2nite)
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