does anyone have any thoughts on an ali chasis build
im using the first book live axel design but i thought if im fitting a bike engine why not save even more weight i have acess to tig and im good with
it on ali but i cant quite get my head around the stress calculations needed i know it wont be as simple as just using 14 swg wall box or maybe it
will i know there are some very clever engineers on here so perhaps they might have some info to help with my crazy plan
thanks
Do a search, basicaly a bad idea (expect for manybe a very low millage car).. Problem with fatige failure.
Dan
[Edited on 28/12/07 by Bluemoon]
I'll give it an hour and this thread will fill three pages.
I'll get some supplies in
i also thought the same make it out of alloy. and i still think that it could be done. but then when you look at how light the steel frame is and how
quick you could put it all together i just went for the steel. plus its tryed and tested annd i no that when its all together i wont have to make
another one because its fell apart.
adam
The best explaination is, in order to make it as stiff as a steel chassis, it'll end up being the exact same weight... never mind the work-hardening/cracking concern.
i had completely overlooked the work hardening issues thankyou for all your info tho steel it is depending on how bored i get ill tig it mak it nice
and neat
many thanks
just to note that alloy and ally are totally different ideas, its not an interchangeable word!
what if you used enough supporting sheet aluminium wouldn't it be like an aircraft ??
quote:
Originally posted by JoelP
just to note that alloy and ally are totally different ideas, its not an interchangeable word!
quote:
Originally posted by macspeedy
what if you used enough supporting sheet aluminium wouldn't it be like an aircraft ??
quote:
Originally posted by 907
In all the time I've been reading Locostbuilders that's the first time I've seen that in print.
Paul G
lol
an aluminium chassis is a totally different animal, if you want a 7 in aluminum look at a robinhood, which seems to be a swear word around here.
Just a thought but ,robinhood did one and had all sorts of problems with sva, might be worth having a look at there site under( lightweight)
quote:
Originally posted by violentblue
an aluminium chassis is a totally different animal, if you want a 7 in aluminum look at a robinhood, which seems to be a swear word around here.
quote:
Im going to build one just to show you lot it can be done.......
just that it's dangerous if you do it wrong and there's no profit in
it if you do it right 
Plus..... it's already been done........ so hardly breaking new ground either..........
Phil
quote:
Originally posted by JoelP
quote:
Originally posted by 907
In all the time I've been reading Locostbuilders that's the first time I've seen that in print.
Paul G
is that because its too obvious?!
can anyone guess my other pet hate?!
A properly engineered aluminium allloy monocoque chassis will likely actually be heavier than a aluminium alloy skinned steel spaceframe.
(google for Lotus 25 & Lotus 24)
A welded aluminium alloy spaceframe is very likely to be lethal.
quote:
Originally posted by britishtrident
A welded aluminium alloy spaceframe is very likely to be lethal.
Okay I was wrong it took more than an hour.
Still on first page for me, you can have more than ten posts you know, unless you like loading new pages that is.
quote:
Originally posted by gazza285
quote:
Originally posted by britishtrident
A welded aluminium alloy spaceframe is very likely to be lethal.
Like this Le Man winning deathtrap..........
An aluminium alloy space frame may well be a difficult solution. But building from aluminium alloy isn't inherently a bad idea - its just that
the design needs to take advantage of the qualities of the alloy and allow for the weaknesses.
The latest generation Jaguars are aluminium alloy monocoque, they are lighter than the previous generation steel cars. So if it is lightness that you
are after it can certainly be achieved.
Before carbon fibre chassis became ubiquitous in F1 aluminium alloy composite panels were being cut and folded to form strong light and relatively
safe cars. Ok so the F1 gang have alot of money to throw at the problem.
But in the late 80's there was a cheap aluminium composite chassis in produced, the Formula Lotus. The chassis was of a similar size to a Formula
Ford frame but was cheaper to produce and had a terrific reputation for protecting its driver in a prang. IMO that should be the goal of a composite
chassis - better safety, easier build (well easier if you can't weld), and self jigging.
There is even a precedent for a composite 7 - the PRB http://www.prbaustralia.com.au/ That car had a
terrific reputation for both speed and safety. It wasn't designed to b cheap mind!
So that is my new years resolution - to design a 7 that uses honey comb composite and can be built for under £2k plus the running gear. How hard can
it be! Well I'll answer that when its done.
My advise ,as i am a aircraft sheetmetal engineer is to stick with the steel chassis .
sounds boring i know ,but if you start to get involved into the world of tempered alloys hope you have a very deep pocket and lots of knowledge of
stress engineering .best of luck
sorry to put a downer on it .
Thats why i think for years the kit car inds has stayed with the tried and test steel chassis.
quote:
Originally posted by JoelP
can anyone guess my other pet hate?!
quote:
Originally posted by martyn_16v
quote:
Originally posted by JoelP
can anyone guess my other pet hate?!
People randomly interchanging their, there and they're? Winds me up no end
so what does a steel book chassis weigh in at then ?
quote:
Originally posted by britishtrident
quote:
Originally posted by gazza285
quote:
Originally posted by britishtrident
A welded aluminium alloy spaceframe is very likely to be lethal.
Like this Le Man winning deathtrap..........
Did you know that the T70 was infamous for something called "the Lola Limp"
the lower wishbone pickup in was fully exposed in the drivercompartment just below the knee, in a front-end collision this broke of and hacked right in the back of ones knee.... ouch that gotta hurt. one than was "Lola Limp" when walking
quote:
But it wasn't built out of 25x25 extrusion a Porrsche went to great lengths to monitor the chassis for cracked welds durring the race. More than one car was pulled out with cracked chassis.
but that has had to do with the very soffisticated way the alloy round tube chassis was welded at the factory
foto of original Porsche 917's famous welding
Look at what RCR are doing nowadays with their alloy monocoques, those seem to be very strong. so it can be done
Grtz Thomas
[Edited on 29/12/07 by thomas4age]
[Edited on 29/12/07 by thomas4age]
[Edited on 2/1/08 by thomas4age]
JoelP - 29/12/07 at 11:46 PMquote:
Originally posted by martyn_16v
quote:
Originally posted by JoelP
can anyone guess my other pet hate?!
People randomly interchanging their, there and they're? Winds me up no end
nearly! your and you're (sorry paul)
iank - 30/12/07 at 12:08 AMquote:
Originally posted by dave r
so what does a steel book chassis weigh in at then ?
Page 53 of the 'and race it' edition has a picture showing Ron waving what looks to be a complete chassis minus brackets and panelling in the air. The claim is 'about 35lb'.
The spaceframe chassis really isn't the key to massive weight reduction. Maximum saving is only ever going to be a couple of kilo's.
cossey - 30/12/07 at 04:15 PMyou can make a aluminium spaceframe work but it will almost certainly require fully chassis heat treatment post welding and if your going to go to that trouble you might as well go for 4130 steel or similar.
if you want a better chassis use seamless round tube and use a large mix of tube sizes so that each section only uses what material is needed. also make sure the roll cage if you use one is an intergrated part of the chassis and can be used to reduce the weight of other structures
02GF74 - 3/1/08 at 11:10 AMIt is a fact of life that nearly all newbies ask this question, even me
Take a look at bicycles - nearly all are now made fgrom alloy (note - not the same as raw aluminium) which has replaced steel.
In the early days, must be about 15 or more years, there was some problems with frame fracture but volume of experience means that is no longer is the case. I daresay if the same was done with alloy chassis, the situation would be
same.
As said. there have been alloy frames as well as the aluminium robin hood monocoque so it is doable but you would need to know what you are doing.
In short, it is cheaper, easier and safer to go with a proven steel design - the weight saving not being enough to entice more buiders to use alloy, not to mention steel is easier to DIY repair.
britishtrident - 3/1/08 at 02:19 PMA push bike frame or motor bike frame can easy enough be heat treated -- heat treating an entire car chassis is a bit more problematic.
iank - 3/1/08 at 03:06 PMquote:
Originally posted by britishtrident
A push bike frame or motor bike frame can easy enough be heat treated -- heat treating an entire car chassis is a bit more problematic.
Indeed, also the aluminium bike frames tend to have 2-3" diameter round/oval tubes for far smaller loads than a car spaceframe made from 1" box will see. Frequency of vibrations will also be an order of magnitude different.
I suspect an average bike will also see fewer than a 1/10th the miles of an average kitcar, and if the frame cracks it's 1. out in the open so you can see it often as it goes bang, and 2. chances of someone dying/suing are much less.
Confused but excited. - 5/1/08 at 10:28 PMquote:
Originally posted by britishtrident
A push bike frame or motor bike frame can easy enough be heat treated -- heat treating an entire car chassis is a bit more problematic.
So the answer would appear to be; make the chassis out of push bike frames bolted together. This would give plenty of triangulation and make maintenance easier.
Triton - 5/1/08 at 11:11 PMquote:
Originally posted by Confused but excited.
quote:
Originally posted by britishtrident
A push bike frame or motor bike frame can easy enough be heat treated -- heat treating an entire car chassis is a bit more problematic.
So the answer would appear to be; make the chassis out of push bike frames bolted together. This would give plenty of triangulation and make maintenance easier.
The Halfords spesh.......
iank - 5/1/08 at 11:36 PMquote:
Originally posted by Triton
...
The Halfords spesh.......
Guy at work calls Halfords bikes BSO's (Bike Shaped Objects) but then he spent more on his bike (he's a triathelete in his spare time so what's not carbon is titanium) than I'm spending on my car.
gazza285 - 6/1/08 at 12:33 AMPush bike snob is he?
Halfords is not the place to buy a performance bicycle, same as it is not the place to buy perfomance car stuff.
But.
A cheap bike probably weighs 28-9lbs.
A £300-400 bike weighs 23-24lbs.
A £800-1000 bike weighs 22-24lbs.
A £5000 bike weighs 21-23lbs.
And just like everything else bullshit baffles brains, how much did he spend on his bike?
gazza285 - 6/1/08 at 12:37 AMquote:
Originally posted by iank
what's not carbon is titanium
Ask him why the Tour De France boys still use steel frames then......
Steel alloys I know before anybody calls me, but still more iron than anything else.
iank - 6/1/08 at 01:58 AMquote:
Originally posted by gazza285
Push bike snob is he?
Halfords is not the place to buy a performance bicycle, same as it is not the place to buy perfomance car stuff.
But.
A cheap bike probably weighs 28-9lbs.
A £300-400 bike weighs 23-24lbs.
A £800-1000 bike weighs 22-24lbs.
A £5000 bike weighs 21-23lbs.
And just like everything else bullshit baffles brains, how much did he spend on his bike?
Oh yes big snob, I suspect over £3k, but I've not asked.
iank - 6/1/08 at 02:06 AMquote:
Originally posted by gazza285
quote:
Originally posted by iank
what's not carbon is titanium
Ask him why the Tour De France boys still use steel frames then......
Steel alloys I know before anybody calls me, but still more iron than anything else.
I suspect like all things the tour guys have special requirements (robustness over days of competition under all weathers, surviving the odd crash, allowing some repair on the event etc.) For all I know there could even be regulations on what materials you can use.
As a counterpoint the velodrome events seem to all require carbon bikes these days, and a significant number of the triathletes use composite bikes from what I remember.
Doug68 - 6/1/08 at 05:08 AMThe Tour bikes are steel for comfort, it's a more 'springy' ride and less harsh than the other materials.
They do use different bikes for different days though and in the mountains I'd expect everyone to be all Carbon.
Back to the subject of Aluminium Chassis frames. Bluntly put just swapping out one material for another and building the same design is either going to leave you massively over designed or on the way to hospital.
Any design for any load bearing object needs to be designed with full thought to the material its being made from.
So for example if you do a Aluminium space frame you typically will end with much larger cross sections used which therefore have a much higher second moment of area this is important as tubes will fail in compression before they do in tension and looking at
Eulers Column Theory if you reduce the Modulus of Elasticity (by going from steel to alloy) you need to increase the Second Moment of Area to compensate or the tube will fail at a much lower load.
If you look at the picture below you can see the large cross sections used, this is the frame for the RCR Super Light Coupe which is a when respected manufacturer in the USA.
[Edited on 6/1/08 by Doug68]
crafty - 6/1/08 at 01:39 PMI like this a lot... http://www.teamlorenz.com/shannon_s2.htm
crafty - 6/1/08 at 01:56 PM... or how about THIS
http://www.gmtracing.com/carsforsale.htm
cymtriks - 6/1/08 at 11:34 PMAn aluminium space frame is never going to be as good as a steel one.
To be as stiff it will need to be made of tubes with three times the cross section of a steel tube. The aluminium has a density about three times less than steel so you end up back where you started. But you have spent more money, the welds will be harder to get right (or easier to get wrong) and the fatigue properties will be worse.
The only way to get it to work, as far as I can see, is to use bonded on aluminium panels to turn the chassis into a semi monocoque. The sheet material could replace all the spaceframe diagonals if you did this right. It could also be very stiff if the panels were added both sides of the chassis tubes which would turn them into very deep rectangular cross section beams. However by "bonded" I mean properly etch primed and glued using the correct kind of glue applied in the correct way, not stuff squirted out of a hot glue gun or, god forbid, bath sealant. You'll want to pop rivets aswell just in case the glue hardens and cracks over time.
Even then there's going to be corrosion. Aluminium may not rust but it certainly corrodes in salt or in the pressence of steel parts (like a lot of the cars parts will be).
The "spaceframes" made by mass manufacturers are actually more like multitubes or complex ladder frames (i.e. they are not triangulated). They get their properties partly from the large cross sections of the tubes and partly from the bonded on body panels. I don't know how much of the final strength and stiffness is due to either.
By the way a book chassis is nowhere near 35lbs finished, more like 180lbs if you strictly follow the book, which specifies a 16 gauge steel floor. Even with an aluminium floor and some lee way from the book I'd expect a finished and paneled chassis to be well over a 100lbs.
iank - 7/1/08 at 12:18 AMquote:
Originally posted by cymtriks
...
By the way a book chassis is nowhere near 35lbs finished, more like 180lbs if you strictly follow the book, which specifies a 16 gauge steel floor. Even with an aluminium floor and some lee way from the book I'd expect a finished and paneled chassis to be well over a 100lbs.
As I said picture that claims 35lb has no panels at all (I include the floor as a panel) or brackets. Since people on here have made floor panels in everything from 3mm steel though 1.5mm aluminium the range is huge.
I'd wouldn't disagree with your estimate for a fully panelled chassis (without running for a calculator
britishtrident - 7/1/08 at 08:26 PMThe 35 lbs weight is roughly the weight of a bare early Lotus Seven S2 chassis.
These chassis have a lot less tubes than a Locost (or later Lotus or Catherham) and were made of 1.2mmr round tube.
A very bare Locost chassis is more than twice that, many builbs nearer to 100 lbs.
chrisg - 7/1/08 at 08:37 PMIt's worth noting that the chassis that Ron is holding up in hat picture IS an aluminium space frame - one of the experimental frames made by MK Engineering.
My Locost frame (with a steel floor) was 94.5 lbs.
Cheers
Chris
Puk - 9/1/08 at 10:10 AMI agree with Cymtriks, to take advantage of aluminium's properties would mean abandoning the space frame and replacing it with a monocoque. Employ a couple of deep sides planks running from the front suspension pickups to the rear and tie the planks too each other with transverse bulkheads between the front wheels, behind the engine and behind the seat backs.
What you'd end up with is a wider version of this:
Check later post for the picture - teething problems :-(
But would it be lighter - can't promise that.
Would it be cheaper - well probably. If you cost in the hours spent cutting and welding tubes into a space frame and compare tht to the cost of buying a composite panel that has been CAD routed to shape then I'll bet the composite solution come sout cheaper. I did the cost analysis on the car above and it was cheaper than a Formula Ford car.
What about the bonding - this is the weak spot. To date creating structural bonds has been difficult but since Jaguar started gluing pieces of aluminum together to make XKs and XJs things have moved on. These cars are built on a production line, so the adhesives used must tolerate a less clinically clean environment than aircraft and race car chassis are built in. Plus there must be solutions for making repairs to crash damaged cars outside of the Jag factory. If there weren't then the insurance companies would have charged exorbitant premiums, and you can trust Ford to have consulted with them before launching the XJ.
The composite aluminium monocoque has one card left to play - they absorb impacts progressively. A space frame is very stiff whilst all of its members are still straight - but once one member gets buckled the whole thing becomes greatly weakened. That Formula Lotus chassis in the picture had a terrific reputation for protecting its drivers in a crash. The composite 7 built in Oz (PRB) had a similar reputation.
Right I'll get off my soap box and get on the phone to Jaguar to see if I can cadge a pot of glue of them.
[Edited on 9/1/08 by Puk]
[Edited on 9/1/08 by Puk]
02GF74 - 9/1/08 at 11:07 AMquote:
Originally posted by cymtriks
An aluminium space frame is never going to be as good as a steel one.
To be as stiff it will need to be made of tubes with three times the cross section of a steel tube. The aluminium has a density about three times less than steel so you end up back where you started.
without looking up the specs. I seem to recall that the strength (I usethe work in the most non technical sense) was 1/2 but density as you say is 1/3 so to get the same as steel, there is still a weight savving.
Otherwsie why use aluminium on aircraft? It would be more bulky for the smae strength as steel.
re: the RC chassis photo - that really is aluminium???!?!?
Doug68 - 9/1/08 at 12:42 PMHere's a Titanium aircraft...
Here's a Stainless Steel one...
Here's one that mostly plywood...
The point is that these structures are Engineered to make best use of the chosen construction material.
Puk - 9/1/08 at 05:26 PMThis is a picture of the Formula Lotus chassis - basically two composite aluminium planks tied together by transvers bulkheads. It was a simple and cheap car that was strong in a crash:
Rescued attachment FormulaeGMLotus300.jpg
scootz - 9/1/08 at 09:04 PMThat's my chassis!
PS - Wasn't that cheap... still cost just under £20k back in the late 80's!
[Edited on 9/1/08 by scootz]
Puk - 9/1/08 at 09:19 PMThat what they sold for, believe me they didn't cost that much to make! But that is why Adrian Reynard used to arrive for work in a helicopter :-)
[Edited on 9/1/08 by Puk]
scootz - 9/1/08 at 09:30 PMVery helpful chap is Mr Reynard - I made an enquiry about the chassis design on his business website and I got a reply directly back from him... not often that happens!
flak monkey - 9/1/08 at 09:35 PMquote:
Originally posted by 02GF74
quote:
Originally posted by cymtriks
An aluminium space frame is never going to be as good as a steel one.
To be as stiff it will need to be made of tubes with three times the cross section of a steel tube. The aluminium has a density about three times less than steel so you end up back where you started.
without looking up the specs. I seem to recall that the strength (I usethe work in the most non technical sense) was 1/2 but density as you say is 1/3 so to get the same as steel, there is still a weight savving.
I wasnt going to post, but I can't resist tempatation.
Stiffness, not strength they are very different things, as I am sure I and other have mentioned many times. Ali is 3 times less stif than steel. So to get the stiffness back you effectively need to use 3 times as much material in the construction of the frame.
The best way to achieve this is through the use of much larger tubes, e.g. 75x75mm.
It is possible to make a chassis from aluminium, and one that works very well (just look at the lotus elise) BUT you have to design for the specific properties of the material. Spaceframe chassis do not lend themselves to construction with aluminium as they tend to use lots of small tubes to spread the load. The better option for an aluminium frame is either a monocoque or a beam chassis (a la elise) to take full advantage of the massive stiffness gains through using much larger second moment of area (moment of intertia) sections without the weight penalty.
A direct aluminium copy of the locost chassis will be abismally floppy and at a guess wouldnt last 1000 miles of road use before it started falling apart at the seams (literally).
Any strutural welded aluminium construction needs to really be heat treated (both stress relieved and age hardened) to avoid the potential of fatigue cracking. Some of the best strength aluminium alloys are not weldable (not impossible, but very difficult!) as they just crack on cooling. IIRC its the 5 and 7 series ones, the ones that strength wise are equivalent to a good alloy steel which is another major drawback. but what they do lend themselves to is bonded constructions or monocoques!
I didnt write a thesis on aluminium chassis for my 3rd year uni project, honest...
David
scootz - 9/1/08 at 09:38 PMRight - that's ali dealt with...
So what would be the optimal material to use for a lightweight spaceframe assuming money was no object... titanium?
flak monkey - 9/1/08 at 09:41 PMquote:
Originally posted by scootz
Right - that's ali dealt with...
So what would be the optimal material to use for a lightweight spaceframe assuming money was no object... titanium?
Have you tried welding that stuff?
The ultimate chassis material if money is no object is carbon fibre, in a monocoque construction.
IMO for proper spaceframes, for stiffness to weight, you'll have a hard job beating old fashioned steel.
scootz - 9/1/08 at 09:58 PMNo
Bit of a PITA is it?
That aside... I understand that Titanium is both stronger and lighter than steel.
flak monkey - 9/1/08 at 10:04 PMquote:
Originally posted by scootz
No
Bit of a PITA is it?
That aside... I understand that Titanium is both stronger and lighter than steel.
Titanium is a pig to weld, not impossible, but a pain. I shant type it out, I'll just let you read this:
http://www.twi.co.uk/j32k/protected/band_3/jk24.html
The UTS of unobtanium is about the same as steel, but its 45% lighter. So strength to weight its much better than mild steel.
Stiffness wise its a little bit less than steel (116GPa compared to about 121GPa), but again, for the weight its much better than steel.
David
scootz - 9/1/08 at 10:07 PMDavid... step away from the books and go to the pub - you need to get out more!
flak monkey - 9/1/08 at 10:10 PMquote:
Originally posted by scootz
David... step away from the books and go to the pub - you need to get out more!
You aint wrong
907 - 9/1/08 at 10:22 PMActually titanium is gorgeous to weld. It flows like a dream.
The problem is keeping out the oxygen from the surrounding air. Ideally the weld should stay silver, straw is OK, but blue is a no no.
I've used all sorts of masking techniques and followers on the torch and it therefore is very time consuming.
I have done shapes that have had 6 argon lines running at once.
Paul G
scotmac - 10/1/08 at 06:34 AMquote:
Originally posted by gazza285
quote:
Originally posted by iank
what's not carbon is titanium
Ask him why the Tour De France boys still use steel frames then......
Steel alloys I know before anybody calls me, but still more iron than anything else.
A good many of the tour bikes are carbon and titanium. eg, remember that Lance Armstrong was sponsored by Trek...All Carbon All the Time!
scootz - 10/1/08 at 09:23 AMSo... if you were to make a Ti space-frame would it be safe to assume that the Ti tube thickness could be the same, or slightly thinner even, than that used on an identically proportioned steel-chassis car?
Benonymous - 10/1/08 at 10:58 AMNice academic conversation. Ti is a superb material but completely impractical for a 'low-cost' home made clubman. when the subject of light weight and lightening comes up I always remember a lovely story I heard once. The story concerns a guy involved in production motorcycle racing in the late 70's. It was the era of the Kwakka 1000 and other behemoths. The racer had drilled holes in everything that looked like it could use less weight. This activity culminated in the heavily drilled gear lever snapping off mid-race. The dejected rider was sitting in the pit feeling sorry for imself when an old guy, who'd been racing for years, stopped by to lend a sympathetic ear. He scanned the machine and offered this advice, "instead of drilling holes in everything to lose some weight, take my advice, just have a big sh!t before the race"
scootz - 10/1/08 at 12:41 PMWell aware that no-one's going to spunk out the thousands required to get the necessary Ti materials, but hypothetically speaking...
britishtrident - 10/1/08 at 01:46 PMI 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.
Doug68 - 10/1/08 at 02:08 PMMean while back in the real world Ducati won the Moto GP world championship using a steel tube frame.
And I think their budget would stretch to whatever material they felt like.
This isn't a GP7 but their WSB which is close enough in its frame deign to get the idea...
[Edited on 10/1/08 by Doug68]
crafty - 11/1/08 at 01:50 AMquote:
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.
Your profile pic reminded me of this
Delinquent - 11/1/08 at 11:46 AMquote:
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!
Peteff - 11/1/08 at 12:05 PMNot 16g mild steel though, and the engine is the main stress bearing member with the frame bolted to it to hang the steering and seat on. If they used aluminium it would need to be bigger section and make access awkward. Different designs need different materials as already put forward.
Puk - 11/1/08 at 12:21 PMIts been stated several time that different design objectives need different solutions. So what do folk feel are the objectives of a 7esqu frame? Being light is probably the one that drives the suggestion to try aluminium, but there must be others too. How about, and in no particular order of importance:
Light weight.
Easy for a novice to build without any high level of expertise - and get right first time.
Good ratio of stiffness to weight.
Acceptable to SVA/VOSA (or who ever the grown ups are in your part of the world)
Materials readily available.
Able to withstand temperate climate (and road salt ?).
Already proven fabrication technique.
Already proven chassis design.
Every now and then people talk about crash worthiness, but we always seem to come back to 'its safer than my motorbike' or 'its an acceptable fun/risk compromise'.
Anything else, anything to remove?
iank - 11/1/08 at 12:59 PMYou forgot 'cheap', both the material and the machine/technologies required to stick it together.
[Edited on 11/1/08 by iank]
Puk - 11/1/08 at 01:07 PMOh 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.
kb58 - 15/1/08 at 02:16 PMNever mind, it'll work perfect...
[Edited on 1/15/08 by kb58]
Rogue Se7ens - 15/1/08 at 03:19 PMquote:
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 - 15/1/08 at 06:45 PMGo 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
kb58 - 15/1/08 at 07:48 PMquote:
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]
Volvorsport - 15/1/08 at 11:25 PMquote:
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 .
Rogue Se7ens - 16/1/08 at 01:46 AMquote:
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 - 16/1/08 at 09:30 AMI'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 - 16/1/08 at 09:53 AMHi 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
Delinquent - 16/1/08 at 10:21 AMquote:
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 - 16/1/08 at 11:04 AMquote:
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.
Dick Bear - 16/1/08 at 11:13 AMI'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
iank - 16/1/08 at 11:50 AMThis 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]
Dom9 - 16/1/08 at 12:20 PMquote:
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 - 16/1/08 at 12:22 PMI 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 - 16/1/08 at 12:37 PMHi 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]
Doug68 - 16/1/08 at 01:15 PMI'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.
Puk - 16/1/08 at 01:24 PMAdhesive 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]
britishtrident - 16/1/08 at 01:58 PMYes 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.
Puk - 16/1/08 at 02:11 PMHydro 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.
kb58 - 16/1/08 at 03:07 PMquote:
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.
Dick Bear - 16/1/08 at 04:06 PMAnyone have cheese and bread to go with the background w[h]ine? Or is that the sound of sour grapes?
Dick Bear
Delinquent - 16/1/08 at 04:15 PMWell 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 - 16/1/08 at 05:47 PMMuch 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
airframefixer - 16/1/08 at 06:48 PMDelinquent
I believe your old man is referring to AC130 sol gel treatment.
You can buy from pacific coast composites. comes in a two part kit which gets mixed and applied to the surface. The bond primer is big dollars last time I checked and it has a really short life. they mainly use heat cured film adhesives with this system, which necessitate a hot bonder (a machine that schedules and applies a current to a heat blanket in vacuum bag).
Keep in mind though that this is a repair method, it might not pass muster for manufacturing. Carrol Smith even said it "bonding is not for us". For myself at least, I can think of few places were the dollars would go a lot further than being able to bond metal. driver training and tires come to mind.
Andrew
Puk - 16/1/08 at 07:09 PMquote:
Originally posted by airframefixer
Delinquent
I believe your old man is referring to AC130 sol gel treatment.
Keep in mind though that this is a repair method, it might not pass muster for manufacturing. Carrol Smith even said it "bonding is not for us".
Andrew
Ok - well I'll chase that up. Also got a lead on some adhesive from a company called Lord.
Structural Adhesive
Any one interested in car design will be familiar with Carol Smith and would be foolish to disregard his advice. That said he was writing at least 10 years ago, Tune to Win dates back to '78. He might not feel that glues aint for us if he were writing today.
Whist we stand on the shoulders of giants we don't need to slavishly copy the - after all Enzo used to insist that the "horse comes before the cart" and Porsche always put his engines out the back.
Delinquent - 16/1/08 at 07:55 PMquote:
Originally posted by airframefixer
Delinquent
I believe your old man is referring to AC130 sol gel treatment.
You can buy from pacific coast composites. comes in a two part kit which gets mixed and applied to the surface. The bond primer is big dollars last time I checked and it has a really short life. they mainly use heat cured film adhesives with this system, which necessitate a hot bonder (a machine that schedules and applies a current to a heat blanket in vacuum bag).
Keep in mind though that this is a repair method, it might not pass muster for manufacturing. Carrol Smith even said it "bonding is not for us". For myself at least, I can think of few places were the dollars would go a lot further than being able to bond metal. driver training and tires come to mind.
Andrew
May do, he specified Boegel as the brand name only. The bonding primer and bonding adhesive do indeed go out of date reasonably rapidly, though in that instance is of course to meet aviation standards which are (understandably!) overly stringent to say the least.
They don't generally use film adhesive or any form of hot bonding there, all cold cure mixes so one less thing to worry about!
kb58 - 16/1/08 at 08:09 PMWith all the discussion on liquid adhesives, has there been enough advancement in double-sided tapes that they could work, too?
That said, I could see a practical problem of how to line up the panel "just right" before letting it touch the chassis. I wonder if the stuff could grab onto the panel so hard that it would get destroyed pulling it off - if it went on misaligned.
Regardless of adhesive type is the implications of coolant/brake fluid/oil/gas dissolving the adhesive, tape or otherwise. I still think a few rivets in the corners are good insurance.
I was thinking the same thing about Carroll Smith. The guy knew everything, but his comments were based upon the adhesive technology at the time. It's natural to assume that newer better adhesives are out now. However, his comments on metal properies apply as much today as they did then.
[Edited on 1/16/08 by kb58]
I-man - 16/1/08 at 08:45 PMHi Guys,
Here is a link of a dutch guy who built a 7 with an alum chassis,
Hope it helps your discussion
http://www.geocities.com/MotorCity/7630/chassis.html
I-man
Joe T - 26/1/08 at 03:17 PMPondering on this I think I would also need some sort of mechanical backup in the event of a bonding failure, I am sure manufactureres will have calculated and compensated etc.
But if I was experimenting with my own stuff, I would build that in.
Most that have seen the RCR chassis in the flesh have marvelled at its design, weld quality and complete lack of distoriton. As for weight I think it would depend on the application, but to me they seem no heavier than equivellent spaceframes when we have had to move stuff around.
scotmac - 9/3/08 at 03:39 PMI have long finished the chassis of my RH L/W, fully strengthened and bonded.
I have not yet done any torsional rigidity testing, nor weighed the chassis, so i will not join the steel vs aluminum debate just yet.
However, in terms of bonding adhesive, i am using Fusor 112B/113B from (The) Lord . It has a lap-shear-strength of 18.6 MPa and a Torsional Impact Resistance of 106 in-lb. It is made for putting together auto body panels.
The specs for them can be found here:
http://www.lord.com/Home/ProductsServices/Adhesives/FusorAutomotiveAftermarketProducts/Products/MetalAdhesives/tabid/3400/Default.aspx
In terms of prep, all i do is run over the sections to be bonded w/ an electric sander w/ coarse paper on it. This gives me a nice metal to metal adhesion, which is really all they require for this adhesive. The adhesive is made w/ small glass beads to ensure the correct optimal bonding distance between the metal. It has a "work time" cure of 70 minutes at 70deg(f) and a full cure of 8 hours at 70deg(f). They have a "quick curing" version that has a "work time" cure of 40 minutes, but still requires 8 hours for full cure.
scotmac - 9/3/08 at 04:00 PMSorry, let me amend that. The lap-sheer rating of 18.6 MPa was an adhesive failure point. However, the 106 lb-in Torsional Impact Resistance was w/ "No adhesive failure". ie, the actual value is unknown, somewhere *greater-than* 106 lb-in.
Specs:
http://www.lordfulfillment.com/upload/UI3002.pdf
Puk - 9/3/08 at 04:20 PMHi Scotmac - can you let us know what materials you bonded and how did you support the bond during the cure?
Cheers,
Puk
scotmac - 9/3/08 at 05:53 PMThe adhesive works for almost any metal. It will even bond aluminum to steel. But all my strengthening was done w/ 6061-T6. I supported via rivets, bolts, and clamps. At this point, i now have a great selection of about 10 different clamps, almost of which are the rachet style or a high-clamp-force screw style.
[Edited on 10/3/08 by scotmac]
scotmac - 9/3/08 at 06:08 PMAnd note, the RH L/W is only a debacle in the un-strengthened form. It is actually a good "base" for an aluminum monocoque. What you do w/ that base is up to you.
Wragie - 24/8/08 at 11:00 PMJust caught this last post but the LW is not a good start. It's a good example of how not to cut holes or rivet and a few other things in aluminium. There are a lot of things that would have to be fixed if you hope to make it last. And none of this has to do with strength just the way they did things.
It's too bad though if done right it could be what they claimed.
Joe T - 26/8/08 at 09:31 AMAt the moment I have a bare RCR70 Aluminium moncoque chassis sitting on my wheelfree ramp, if anyone wants to come and inspect it they are more than welcome.
Did anyone have a good look at the new Lotus Aluminium chassis at the motorshow, any thoughts, comments?
Cheers
Joe T
Theshed - 26/8/08 at 02:13 PMHaving lurked I have plucked up the courage to show how you can spend six years going off at a tangent.
The photo is of my build which started off with locost dimensions. It will have a rear mounted Maserati V8 knocking out 375 bhp through a sequential dog box - Locost it has not been! Suspension is from a Lola champ car.
I make all my own machined parts in my shed - very very slowly!
This is the central tub. There is a sub-tub at the front. The rear will end in a machined plate thereafter a tube or two to support the transaxle.
Main panels are honeycombe. Internal panels stiffeners etc are all 2024T3 Alclad. Panels where not folded (a nightmare) are joined by bonded joiners using araldite 420 and riveted with Aerospace rivets - mainly monel. I do spend a lot of time cleaning off any oxide and abrading with scotch-brite and/or wet and dry and then clean everything up with Mek. I did a test strip and a 1 inch lap joint (with no rivets) tore at the metal before the joint broke. Not all that scientific though!
Its probably obvious but there is a glass fiber bit that covers all you can see.
For what it is worth if I was starting again and/or building a roadcar I would never go this route - it is too lonely by half.
I am reasonably confident that this will not fall apart too quickly. I have one suspension pick up that makes me nervous to look at....
I am not convinced that "surgical" cleanliness and an oven are essentials. I could however be spectacularly wrong!
I have given up answering questions on when this will be finished but I have gone far too far to give up!
Oh bugger - a forum virgin how do I attach a photo??? I have stuck in in the photo section under Theshed - Incidently in the background is the shed itself!
John
mr henderson - 26/8/08 at 05:14 PMHi John
Welcome to the forum. I haven't looked at your pics yet, my broadband is down to dialup speeds and those are some big pictures!
Regarding posting pics, there are some tutorials on the forum but I find it much easier to open a photobucket free account, then you can upload your pics and resize them (something under 100k is more friendly) then link to them in your posts here
John
Theshed - 26/8/08 at 09:01 PMYes - sorry about the photos I will try and re-size them- sounds like a good diversion from work!
I have stuck a few pics of what was at the time a half completed sub-tub to which most but not all of the front suspension is mounted. That bit is now very nearly finished and I am just about to join the two big bits together. Exciting bit!!
Wragie - 26/8/08 at 09:32 PMquote:
Originally posted by Theshed
Yes - sorry about the photos I will try and re-size them- sounds like a good diversion from work!
I have stuck a few pics of what was at the time a half completed sub-tub to which most but not all of the front suspension is mounted. That bit is now very nearly finished and I am just about to join the two big bits together. Exciting bit!!
That is very nice. I see you have the flanging, corners and so on done the proper way. Aviation background?
what are you paying per sheet for the panels? Last time I was brave enough to check the balsa core was about $1000 a sheet.
Dave
Theshed - 26/8/08 at 10:21 PMNo aviation background (bodge it and bang it is my usual fare) but next project might be a plane = swiftly followed by a divorce I suspect. I did get a lot of info from home build aircraft sites.
I have gradually learned more as I went along - the thicker honeycomb is "commercial grade" and was £200 for an 8' x 4 ' sheet with 1.2mm NS4 skins and 1/4 cells. Plan A was to make tubular front and rear sub-frames. For reasons that I now forget I decided to make a front sub-frame in honeycomb. I got a taste for the exotic so the thinner honeycomb is 7075 t6 shins 1mm thick with 1/4 cells ( that cost £400 for a sheet). Having learned something about this stuff I now know (hindsight is great) that I should have had much thicker sheets with smaller cells and thinner high grade skins.
Whilst I agree with all those who have warned against the exotic in favour of the proven I could not ressit the challenge of something daft....if it collapses under its own weight I will be the first to admit to stupidity....
I butted in to join the debate on bonding and riveting. I do not think that riveting would ever squeeze out all of the glue. If you look across a riveted panel it is slightly wavy. I suspect that by aviation standards the bond is shocking in that it varies in thickness. However for mere mortals I know that you need a chisel to force such a joint apart.
I am not sure that the fact that you cannot undo a bonded panel is a major downside. Most of my joints were pinned for months or even years before being finally bonded - it is a slow process! You spot mistakes before they are irreversible - usually...
My "sub-tub" is accurate to a few thou in most places. It is all made from one piece of material bent into the shape you see. I really made a mess of that first time around....long story!
Whilst I have struggled (and made some serious errors) I do think that a "locost" could be made with two side panels of honeycomb. Side impact would be improved (has anybody ever seen a t-boned locost?). Serious thought would need to be given to suspension loads. Could be fun!
John
Wragie - 26/8/08 at 10:41 PMDon't worry about taking it apart that's not as bad as you think. Just get a heat gun, looks like a hair drier on steroids, and a paint scraper. Most adhesives let loose around 150-200c (depends on brand of goop used). Gently heat, and pry a section at a time. As long as you keep the temp under about 300c it doesn't affect the aluminium.
The panels are very strong, we used balsa cored panels for cargo floors. The alum core stuff you used is even stronger.
Dave
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