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Author: Subject: Building an Ultra Light-Weight Car
Rod Ends

posted on 2/2/09 at 06:38 PM Reply With Quote
Building an Ultra Light-Weight Car

An incredible way of producing your own vehicle

quote:

Alternative construction approaches to DIY one-off vehicles
Using fibreglass and aluminium honeycomb sheets to build a monocoque tub
Forming curves and bends
All done with hand tools!
The University of South Australia’s ultra light-weight electric car




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tegwin

posted on 2/2/09 at 06:56 PM Reply With Quote
Pretty cool... I would have thoght that a foam core laminated with Kevlar/CF would be lighter though?





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Volvorsport

posted on 2/2/09 at 09:04 PM Reply With Quote
ive posted several times on the advantage of building/fabricating this way .

load points do need to made through bonded in inserts to spread the load .

cant think why i didnt do it myself .





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Mark Allanson

posted on 2/2/09 at 09:05 PM Reply With Quote
Just need to add a few brass handles down the side to finish it off





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snapper

posted on 2/2/09 at 09:42 PM Reply With Quote
I love it, i think Colin Chapman used this type of material in his race cars.

If you presented one for SVA i think the examiner would have a pink fit unless you had some serious calculations available





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Turtle

posted on 3/2/09 at 10:23 AM Reply With Quote
In the Tony Pashley book "How to Build Motorcylce-engined Racing Cars" there is a nice section on aluminium honeycomb construction. Well worth a look, but like most of that book tends to wet the appetite but not provide quite enough to satisfy it.

-Brian.

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alistairolsen

posted on 3/2/09 at 01:41 PM Reply With Quote
nomex honeycomb in carbon kevlar is the way to go. unfortunately however maximum strength is in curved panels and the ortogonal joints in a homebuild flat panel contruction cause issues.

as Volvorsport said, load points such as suspension mounts etc also represent a bit of a headache.

finally it is worth considering that repair is virtually impossible

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ceebmoj

posted on 6/3/09 at 10:01 AM Reply With Quote
how much does this stuff cost is it prohbitiave because of the cost?

ceebmoj

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alistairolsen

posted on 6/3/09 at 12:08 PM Reply With Quote
nomex is bleeping expensive and good quality epoxy resins arent cheap either.

If you want to go really light you have to move away from glass and into carbon/kevlar/glass combinations which are very expensive too.

The reason most people wont ever build a car this way however is due to the design time to ensure sufficient strength and stiffness, and the time involved in making jigs etc, or complete molds if you want to take advantage of curved panel stiffness.

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Benonymous

posted on 20/3/09 at 03:49 AM Reply With Quote
quote:
Originally posted by ceebmoj
how much does this stuff cost is it prohbitiave because of the cost?

ceebmoj


This material, fiberglass skins over aluminium honeycomb, is approx $440AU per 1200x2400mm sheet. It is produced in Australia so you'd have to figure some damned expensive freight in as well. I'm sure there would be Brit manufacturers or US if not.

For a better book there is the Alan Staniforth "Race and Rally car" one which has a fair amount of detail with aluminium skinned honeycomb. The thing I like about the fibreglass skins is the relative ease of construction compared to ali . You need to make heaps of sheet metal parts and to use thousands of rivets to put it all together.

I agree with the impossibility of repair comment also. If you damaged the tub you'd have to chuck it.

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britishtrident

posted on 20/3/09 at 04:41 PM Reply With Quote
Back in the 1960s first people to use this were Ford on the J Car -- and Bruce McLaren on one of the early McLaren F1 cars, in the Hillclimb fraternity Charles Barter "improved" his Davrian saloon with similar methods.

It really isn't a practical way to build a racing car -- the biggest single problem being repair of even very minor accident damage. Nobody else really took it up and as soon as the Ron Dennis pulled the dust sheets off the carbon/kevlar composite MP4 everybody forgot about it especially after John Watson's famous shunt at Monza.

Although not sandwich construction Allex Issigonis's 1930's hill climb car The Lightweight Special used a balsa monocoque.

[Edited on 20/3/09 by britishtrident]





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RK

posted on 20/3/09 at 06:10 PM Reply With Quote
Well that pic shows the aerodynamics of the Berlin Wall so of course it won't work!
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Benonymous

posted on 23/3/09 at 12:36 AM Reply With Quote
The thread starter made a link to the complete article if you follow it you'll see that the car turned out very slippery with its completed bodywork. It's rare to see a really appealing chassis apart from an Atom and a couple of the superb home made middies on this forum.
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Benonymous

posted on 23/3/09 at 12:42 AM Reply With Quote
BTW. Dennis is building his DP-1 with honeycomb sheet.

http://www.dpcars.net/dp1v8/da.htm

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Theshed

posted on 23/3/09 at 03:07 PM Reply With Quote
So am I - see my photos!

approx 6000 rivets in and about 500 to go....(8 years)

I would not do it again....well not straight away.

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hexxi

posted on 23/3/09 at 06:21 PM Reply With Quote
"Theshed", can you give the specs of the rivets and glue you have used? Which grade of aluminium are the panels(the reinforcements) and the honeycomb plates? Basically the whole recipe interests me.
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Theshed

posted on 23/3/09 at 08:32 PM Reply With Quote
What I have done and what I would do if I started again are not the same!

I should really put up some decent pictures but I have not worked out how yet.

The main panels of my tub are commercial grade - the skins are 1.2mm NS4 equivelent with 1/4" cells and 19mm thick. That material is reletievly easy to bend when cut with a router on one skin.

7 years ago it was £200 per sheet of 1250 x 2500mm.

The front tub and center spine and now some other bits is a bit more high tec it is 7075t6 skins - hard and strong as hell. Again the core is commercial 1/4" cells - a mistake . The big mistake is that the shins were really hard to bend to make the somplec sub- structure you can see. the skins are just 1mm and the material 10mm in total. More mistakes beacuse where 2 rivets meet from either side they clash. This sheet was expensive - £400

I am using 2 types of adhesive - for lap joints and such I am using Araldite 420A/B apart from needing digital scales - swiped from the kitchen - it is easy to use. For "potting" in top hats - bushes and inserts - I ham using "Epocast". Both of these glues are expensive at about £100 for 1.4kg - I have used 3 tins!! I abrade the aluminium with coarse scotch brite and/or abrasive paper and clen with MEK and just plain soap and water.

Rivets are mainly blind rivets - I am just getting the hang of solid rivets. I started using Advel monoblok rivets. Actually they seem fine but for reasons of a silly e-bay purchase and a desire for aircraft grade rivets I have progressed....Most rivets are Huck double action rivets installed with a fancy gun (I have now the worlds collection) most are Monel with a Cres stem - they are very strong. In addition there are some cherrylock rivets - they need a different gun often availsble as surplus on e-bay £3500 to the taxpayer about £80 to me brand new! If I started again I would use Cherrymax rivets available surplus in the USA.

I have used 2014T4 for most of the internal paneling and joining strips - that is alclad with pure aluminium for corrosion ressistance - that is very nice to work with but needs a bending radius of 4t+.

If I started again and wanted to go the honeycomb route I would use 25mm thick panels all over with 2014t3 skins and 1/8" aricraft grade honeycomb. I would also spend a lot more time designing before buiding. The panels are all made to order and it would not cost much more to have all inserts bonded in.

I really wish that I had thought of cnc routing before I built my car - the pictures of the DP car make me want to cry! However gluing but no riveting at all..hmm

I tested a 1" square bonded only test piece by nailing it to my shed and hanging from it it was fine. However in peel - bending it over - i snapped it by hand - the key is in joint design - place the loads in shear seems to be the key to bonded joints.

I think that a honeycomb locost with thick honeycomb panels at either side joined by sheet and a solid front bulkhead would be very easy to draw up.

My car is not locost - I am not sure that it will really work. It should do but cowerdice might mean I keep adding weight. It now boasts a northstar engine and the gearbox from the cadillac LMP car. It will not be underpowered.....

The point of contact with "the book" is that I stole the dimensions for the footwells and seating area from uncle ron...

I believe that the fear of repair is perhaps overstated as a knock out argument. It depends on the purpose of the honeycomb. In a road car it would be a brave choice but good enough for Ferrari...Also the choice of many LMP cars. For home construction aluminium skins are probably easier than Carbon/kevlar although I do not know for sure. A locost chassis with aluminium honeycomb floors and side panels would gain huge amounts of stiffness - assuming that that was wanted. Side impact protecction a useful bonus.

Just thinking aloud...

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filiperosa

posted on 24/3/09 at 03:49 PM Reply With Quote
its just the future
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