smart51
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| posted on 22/4/08 at 08:59 AM |
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carbon fibre tubular chassis
I was looking here: Link to Polyfibre price list and saw that they sell carbon
fibre tubes for reasonable money. The largest tube is 1" OD and 16 SWG thick. It is available in 5 metre lengths and sold at £10.75 + VAT per
metre.
Who reckons they could make a locost chassis from it? (that would be strong enough for the road, obviously)
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tegwin
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| posted on 22/4/08 at 09:07 AM |
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The question is, how do you bond the tubes together to give any strength?
And IMHO, a CF space frame would not work so well.....CF doesnt work well in compression...
I would feel safer with a properly engineered lightweight steel chassis!
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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02GF74
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| posted on 22/4/08 at 09:14 AM |
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quote:
Originally posted by tegwin
And IMHO, a CF space frame would not work so well.....CF doesnt work well in compression...
Be it correct or not, I'll use the allorgy of bike frames. These are subject to both compression and tensile stresses and have been
successfully manufactured from steel alloys, alumimiun alloys, bamboo (no really), titanium, carbon fibre and magnesium alloy using tube jointing
technique by lugs, brazing, welding and glueing.
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smart51
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| posted on 22/4/08 at 09:16 AM |
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quote:
Originally posted by 02GF74
bike frames ... bamboo
That I would like to see.
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StuartBJ
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| posted on 22/4/08 at 09:20 AM |
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yes and CF bikes still readily fracture, (yes they do ive seen it happen more than once) and they are not carry a 200KG engine and gear box at 150
mph. I too would rather have a steel chassis than a bonded CF structure. The bond line is always the failure point!
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TimC
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| posted on 22/4/08 at 09:25 AM |
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quote:
Originally posted by smart51
quote:
Originally posted by 02GF74
bike frames ... bamboo
That I would like to see.
Have you ever seen scaffolding in Hong Kong? Wow!
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Puk
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| posted on 22/4/08 at 09:31 AM |
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If you could design a joint then I guess you'd end up with something that is lighter and stiffer. But if you had a prang (and lets face it -
this is a race car) how would you be able to tell whether the chassis had been damaged beyond use? Steel can deform and bounce back with no weakening.
Deform and not bounce back is different but is also visible. CF may deform and shatter (easy to spot of course) or deform and recover but, unlike
steel CF can be significantly weakened. That IMHO is the brittle nature of CF is its Achilles heal. The aerospace industry mitigates against this by
performing regular NDT inspections - but that is not an option for the average amateur. I wonder if the need for NDT is what makes the Maclaren
F1's annual service £30k?
You could sensibly use CF in non-Jesus bolt applications - where its failure would not be catastrophic for the vehicle. Bodywork, seats, etc - where
the weight saving justifies it.
How about using CF for the drive shaft? Light weight and in that use you can control the loads that the tube sees far more easily. If it fails the car
just stops and at least it is encased. Donkervoort have done one.
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.
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02GF74
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| posted on 22/4/08 at 09:52 AM |
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quote:
Originally posted by StuartBJ
yes and CF bikes still readily fracture, (yes they do ive seen it happen more than once) and they are not carry a 200KG engine and gear box at 150
mph. I too would rather have a steel chassis than a bonded CF structure. The bond line is always the failure point!
But so do steel and aluminium bikes.
I don't quite follow your argument about the extra weight and speed as you would increase size and or/ numbers of tubing to cope.
Just like you woudn't make a car chassis out of 0.6 mm double butted tubing ?
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mcerd1
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| posted on 22/4/08 at 09:54 AM |
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quote:
Originally posted by TimC
quote:
Originally posted by smart51
quote:
Originally posted by 02GF74
bike frames ... bamboo
That I would like to see.
Have you ever seen scaffolding in Hong Kong? Wow!
well bamboo is basicaly a natural composite tube......
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Mr Whippy
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| posted on 22/4/08 at 10:13 AM |
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carbon my big bottom  rather use tinfoil!
 
Rescued attachment FerrariF1Crash.jpg
Fame is when your old car is plastered all over the internet
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907
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| posted on 22/4/08 at 10:18 AM |
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I've broke a few fishing rods in my time...
That's just casting 6oz of lead off Dover harbour wall. 
Paul G
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Paul TigerB6
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| posted on 22/4/08 at 10:43 AM |
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quote:
Originally posted by smart51
quote:
Originally posted by 02GF74
bike frames ... bamboo
That I would like to see.
Here ya go then mate.......
bamboo bike
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kendo
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| posted on 22/4/08 at 11:15 AM |
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Broken ferrari
The broken ferrari shown in the one of the previous responses was later discoverd to have ben made incorrectly. All the ply joints were in the one
place rather than distributed around the tub so not a good illustration.
The problem with using carbon in frame like structures if you are using premade tubes is the need to joining pieces at each interface obviously these
can become very complicated. The advantage of using a moulded carbon chassis is that you don't necessarily need to then add the bodywork that
would be required on a spaceframe.
Fundamentaly you need deep pockets and know what you are doing to make it worthwhile.
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Bluemoon
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| posted on 22/4/08 at 11:31 AM |
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Humm bambo 7
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iank
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| posted on 22/4/08 at 12:12 PM |
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Bamboo is stronger (for some values of stronger) than carbon or steel.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Mr Whippy
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| posted on 22/4/08 at 12:37 PM |
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I've watched documentary’s that show the bamboo scaffolding, quite impressive
Thing to remember about carbon is its strength is all in tension, in compression it is quite bad and tends to crumble. You can see this in crash test
of F1 nose cones where the energy is dissipated by the disintegrating shell literally turning to dust. In a crash a tubed chassis is libel to snap
from the shock and produce dangerous sharp poles which could impale you. It's a good material but that doesn't mean it can be used in
everything.
Fame is when your old car is plastered all over the internet
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smart51
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| posted on 22/4/08 at 01:59 PM |
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I'm sure another aluminum space frame thread would have generated more heat than this. Is there a bit of Mondayness going on?
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iank
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| posted on 22/4/08 at 02:52 PM |
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quote:
Originally posted by smart51
I'm sure another aluminum space frame thread would have generated more heat than this. Is there a bit of Mondayness going on?
You are a mad scoundrel who's idea of using a different material for a spaceframe construction is mad to the point of recklessness. Think of
the children you will maim, disfigure and kill with your monstrousness machinations.
Happy now?
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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DIY Si
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| posted on 22/4/08 at 03:16 PM |
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And won't someone just stop and think about the kittens!!!
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Mr Whippy
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| posted on 22/4/08 at 03:16 PM |
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I'm sure newspaper first coated in wall paper paste and wrapped up really tight would offer a locost alternative to expensive steel. The plastic
joints used in tents could be used to join them, Airfix glue should be used here. Plus paper mache body panels would make a good environmental
alternative to nasty glassfiber.
Fame is when your old car is plastered all over the internet
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StuartBJ
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| posted on 22/4/08 at 03:37 PM |
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I`m not trying to dishearten you by any means, its just the fact of the matter that CF for novice applications is best left to non structural
appications.
Yes steel and aluminium frames fracture also, usually at the weld point, where you have to exceed the weld strength (another topic for another day)
and not the bond strength or peel ply layer in CF.
Also if you do damage it you will more than likely get some form of ductile/plastic deformation (see the recent bending wishbone thread) in steel and
ali, as opposed to a brittle faiure from a CF component.
My point is, I would not like to be applying whopping bending moments, and tensile/compressive forces to a very unforgiving material. CF is not the
be all and end off of materials, yes its stiffer, and slightly lighter (modulus of stiffness) than ali but even advanced aerospace companies don`t
know how to accuratly model and design to fully utilise the material. If you are in the position where you have the FEA suites, and advanced pre-preg
and processing equipment to fully consolidate your composite then you will probably be ok, but not always. I recently examined some korean prepreg
sample, with quick release fastners installed and even though the panel looked ok, the installation of the fasteners had caused the material to be
next to useless due to micro cracking. The cracks for aerospace regs state that the cracks can not exceed 0.35mm in length and inmitiate no further
than the 2nd ply layer, due to the fact that above those values the life expectency of the sample it greatly reduced to unsafe levels (for aerospace).
Drilling into CF weakens it due to nano/microcrack formation, hence bonding it tends to be used.
The cracks occurred from a simple drilling and installation proceedure and that was using some of the most uptodate techniques and best materials
avaliable.
I can forsee it being a bit painful if your lovely CF bike frame splinters in two, but just imagine that happening in a car if your crack has
propergated and a critical failure occurs. The likelyhood of this happening is far greater with poor materials and inexeprience.
PLUS all the cost!!!!! ££££$$$$££££
I`ll stick to steel thanks.
Sorry for the rant
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Alan B
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| posted on 22/4/08 at 04:45 PM |
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Stuart...dont apologise, it all made good sense and needed to be said...it just is not a good amateur material.
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Daimo_45
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| posted on 22/4/08 at 05:33 PM |
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My bikes carbon. Has a nice big crack at the bottom bracket which is setting me back £1500. STRONG but BRITTLE.
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Daimo_45
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| posted on 22/4/08 at 05:34 PM |
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and my wheels
seatpost
stem
handlebars
water cages
pedals
soles of my shoes
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D Beddows
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| posted on 22/4/08 at 08:02 PM |
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I'm confused now..... I was under the impression that pointing out the potential practical problems (not to mention cost) associated with
fashioning something out of unobtainium and suspending it from sky hooks in your lean to shed was very un PC on here nowadays and that someone would
almost instantaneously pop up to brand any non believers as negative luddites who should shuffle off to finish reading this months edition of The
Automobile........ must have dreamt that happening then judging by this thread
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