Is there any problems that anyone knows of with making book chassis out of 25 * 25 * 3mm ali boxsection ? as its half a kilo lighter per meter than 25
* 25 * 1.6 mild steel ?
im sat here with my fingers crossed because i started my chassis yesterday and now ive got a complete chassis i.e. fully fabricated and welded sat in
my garage made from ali.
http://www.locostbuilders.co.uk/viewthread.php?tid=36920
I think it ended in basically its fine if you want to die?
quote:
Originally posted by rebelrider
im sat here with my fingers crossed because i started my chassis yesterday and now ive got a complete chassis i.e. fully fabricated and welded sat in my garage made from ali.
That's quite impressive........ but have you tried a search on here for aluminium chassis?........not good......
Looking on the bright side, consider it a dress rehearsal before tackling the chassis again usinig steel 
Obviously didn't work for Lotus, did it?
Just my two pen'th. 
Edit: Mind you, they glued theirs together instead of welding it.
[Edited on 21/10/07 by Confused but excited.]
I keep refreshing this page waiting for the sarcasm to flood in.
It just has.
Edit; No flood, just one drip. Doh! 
[Edited on 21/10/07 by Confused but excited.]
oh f@$k
does anyone want a pretty frame to put on there mantle piece what a waste of 10 hours grr.
now do i ignor everything and go for it like a stubern idiot or restart now ?
and if i do it and sva it and it breaks can i put all the bits on a steel frame when no one is looking ?
Aluminium monocoque - yes
Aluminium honeycomb planks like a formula vauxhall lotus - yes.
Design specifically intended for aluminium extrusions with cast nodes like an Audi A2 - yes.
Design intended for steel tubing.......
Nooooooooooooooooooo........................
All the best
IMHO, not the brightest idea...
Got any pics of this piece of ali art?
Weld an aluminium skin to both sides of it ?
Normally I'd say there's a million ways to do things and that you should do what you want. HOWEVER, I cannot do that in this case.
Just build a steel one. If you really, really must do aluminum, consider a *properly designed* monocoque, having an airframe engineer or equivalent,
design it.
I know it's mostly in the design but if the welding is good could it be that bad?
rebelrider has used 3mm box wall so stiffness will be improved over 1.6mm of the same material.
May be some well designed bonded ally gussets over the welded joints going past the heat affected zones (see Photo )
http://locostbuilders.co.uk/photos.php?action=showphoto&photo=9image002.jpg
And ally has also been used in bike chassis ( Welded and Bonded ) for years and these are designed to flex.
Ally skins both side of the chassis would be a good idea but bond them instead of welding them no HAZ from the welding.
Just some idea's not saying it's right or wrong but just food for the mind.
Jason
funnily enough, last week I was thinking there hasn't been a "can I make chassis from aluminium" post for a while, lo and behold there
is!!
(ps I also asked this when I was much a newbie 
)
a twsit would be can I make the chassis from carbon fibre?
No they're not, that's why they have suspension. Aluminium bike frames have all manner of reinforcement inside the spars and on the swing arms to stop them from flexing.
I thought a certain amount of lateral give in rear swing arms was normal and desirable since the suspension can't really cope with vertical wheel
acceleration when you've got your knee down in a bend. I could of course be wrong.
jk
quote:
Originally posted by rebelrider
and if i do it and sva it
As you have got this far why not figure out how to plate it by bonding and riveting then ask your local SVA for comments. Fatigue risk is an issue I
have a welded ally bicycle frame and it has cracks in the headstock, no one will go near fixing these,
Just a thought you may be able to use something like Lumiweld to put the panels on, this is a brazing technique with an aluminium alloy that melts
below aluminium melting temp but gives a structural strength joint.
10 hours is very quick I presume you have not got all the triangulation in yet? If you plate and fillet with reasonable thickness alloy you may be
able to omit quite a lot.
Failing this there will be some sucker on ebay who will take it off your hands probably for a lot of money!
Caber
Might wanna talk to this guy:
http://www.geocities.com/MotorCity/7630/chassis.html
It got thru SVA and is still on the road. The only difference with book chassis is that he glued honeycomb sandwich plates to the chassis to get the
torsional stiffness required.
You must also understand that if the chassis is very light and you add a light engine like a bike engine, that your overall weight will be very low
thus resulting in (much)lower stress on the chassis compared to a steel chassis with car engine where it was originally designed for.
And his car was using heavy sierra parts and DOHC engine, so using escort/cortina (alloy) parts and Bike engine with lightweight body (he used a very
heavy form of body) you should end up somewhere around 400kg? Or even less?
[Edited on 22/10/07 by Werner Van Loock]
All Bike Chassis flex ( and car ) ally or steel even if they are designed to not
Tul-aris is a prime e.g this even has parts of the rear suspension designed to flex ( it is now patented ) and has been used for a few years with no
problems this part is Ti but the same facts apply
http://locostbuilders.co.uk/photos.php?action=showphoto&photo=exotic-1.jpg
Put simply 2 Chassis of the same design made of 2 different materials will behave differently due to different Material behavior. You can make a
chassis too stiff so much so that the tyres will not cope in this case flex in the chassis is a good thing.
"Frame stiffening as discussed will in most cases significantly reduce the stress levels in frame members as well as stiffening the whole
structure, but there are occasions where the stiffening of one part of the frame may lead to increased risk of failure in another unstiffened area. A
flexible frame acts as a spring and can absorb and reduce the effects of some types of loading, if only parts of the frame are stiffened then we may
pass more load through to the unstiffened areas which may deform locally more than before even though the whole frame deforms less. Well, now you have
a rigid frame to work from, but that's all it is at the moment. Handling will probably have improved somewhat already but to get first class
results you must start the fine tuning process. That is, selecting spring rates, matching tyres, changing geometry by moving the fork sliders in their
yokes, etc. the list is endless. But that is all another story" A Quote With Thanks To Tony Foale
If it don't bend it will..........
Any way it's what make it all so fun different ideas and people willing to try different stuff. If we all stuck to the same ideas we would all be
driving/riding the euro box
Jason
quote:
If it don't bend it will..........
Any way it's what make it all so fun different ideas and people willing to try different stuff. If we all stuck to the same ideas we would all be driving/riding the euro box
Jason
If I may I'll add my 2p
When aluminium is rolled into a sheet or extruded into a shape (i.e. box section) it gains it's strength from being work hardened.
When it's then welded it is annealed back to it's soft state and the addition of gussets just moves the soft area further along the
section.
This local annealing could be why the rungs of extension ladders are never welded in.
Paul G
Even Rossi can't accelerate with his knee down in a bend I ride a bike and spend time at the bike shop and if there is lateral movement in a
swingarm it fails the MOT.
Jason, what is Ti? If it's steel then the same rules do not apply. Aluminium has a finite lifespan which is greatly reduced by flexing. The quote
you give there shows the benefit of stiff frame leading to more predictable handling because the suspension is able to do what it was designed to do.
quote:
Originally posted by Peteff
Even Rossi can't accelerate with his knee down in a bend
Peteff
Play in any joint connected to a chassis is a different issue and will all ways fail SVA/MOT bike or car.
I used a race a Norton commando along with a few other bikes and in an attempt to make it handle stiffened the chassis so much it handled worse then
for a bit of fun put some slicks on it and it then was much better than it ever was so flex is the chassis was good for this e.g as in that class we
were not aloud slicks.
Ti is Titanium.
All materials have a life span with regards to flexing and will be reduced by being flexed.
Take a valve spring on a standard road car in an attempt to improve performance you could reduce the load it puts on the cam thus reducing friction
and increasing performance. In standard from the spring is designed to " flex " and should run for a fair few miles. If we reduce the wire
size of the spring it will ( if we go to far ) reduce the life of the spring and it will fail. The same applies to any material in any shape
A good e.g is a kart chassis which is designed to flex some modern ones have torsion bars so the chassis can be tuned for different conditions i.e
make it flex more or less. And as tyres have become more gripy over the years the chassis need to flex less ( be stiffer ). But in the wet more flex
will give you more grip. So we design more flex into the chassis.
Ally box chassis have been done ( see Werner Van Loock post for link ) and have worked before. I would build one but my ally welding is just not as
good as it could be for a chassis so for now will not attempt a chassis in ally box. I would if money was no object do a bonded ally honeycomb
chassis.
rebelrider have you any photos? I for one would be pleased to see them.
And good luck with the build
Jason
[Edited on 23/10/07 by short track 123]
Karts are made to flex because they have no suspension.
The main reason to have a stiff frame and let the suspension do the work to keep the tires in/under control is that suspension is "easily"
damped and tuneable while the flex in a frame is not.
If you stiffen the frame you will have to retune your suspension as it is now working under totally different circumstances.
When stiffening a frame, care needs to be taken that transitions from stiff to less stiff sections are made gradually. You want to avoid
"hinge" effects that concentrate the bending action (and the stress) to a small part of the structure.
To use another material effectively you should redesign taking all the properties of the material in consideration. Substituting one material with an
other has spelled disaster many times before. Aluminum alloys are very different, to state that a frame is made of aluminum is like saying it is made
of metal.
The properties of Al-alloys also vary with heat treatment/temper.
So bottom line: If you undertake such a feat, do so with proper equipment, materials and know-how. Talk to (a lot of)people who do structural work in
Al-alloys, most likely you find them in aerospace or the higher echelons of motorsport.
You can do anything in a number of ways, but there is a difference between doing it right and just getting away with it.
Surely the aluminium frame in the link was realy just a lightweight framework to which to bond the honeycomb panels (which actually formed the main
structural component of the chassis) rather than any form of space frame chassis.
If you look at the end of the page it didn't end up being an awful lot lighter than a properly triangulated steel spaceframe either! stiffer
though.....
The whole saving weight in the chassis thing is less valuable than people think anyway. A steel locost chassis is <10% of the weight of the
finished car before you even step into it.
Better to do the safe stuff, i.e. fit carbon bodywork, aluminium diff casings, triming bolts to exactly the right length etc etc etc before getting
into shaving a couple of kilo's off the chassis.
To design with a material with different physical properties requires a different design. It's not a complicated concept is it? As ^^^ different
grades/alloys of aluminium will need different designs between themselves to work.
Bringing Titanium into the argument is missing the point as it has completely different properties to both aluminium and steel.
Stunt riding stuff, you're not accelerating while the wheel's spinning. There's an avatar on here with someone doing it one handed. You
will only accelerate when the tyre grips and if you're still leaning it will spit you off the high side. Been there done that, took an hour to
get the bike out of the ditch, too old and chicken for it now. There's at least one killed a week round here in Summer from trying to do it and
getting thrown into oncoming traffic up Matlock. The amount of grip available from your tyre was not like the superbikes now have. A friend of mine
still has a TZ and they are like pram tyres compared to Blade and ZX9 rears.
I had a blank there on the ti sorry Jason. Round here it stood for Tube Industries. I used to work in a foundry in the 70s where we cast titanium,
mostly turbine rotors. It was relatively experimental then and it was lighter and stronger than steel but the brittleness (is that a word?) was a
problem then till it had been heat treated. As with steel you can make springs from it but I've not seen any made from aluminium. Old Norton
frames were never renowned for their stiffness, some of my friends had them and claimed they were better after they had been crashed. The name
"Featherbed" was one that immediately sprang to mind as my uncle had one.
[Edited on 23/10/07 by Peteff]
I know what you mean by they were better after being crashed I was never shore if it seemed to improve because i had crashed or because it got stiffer
as i repaired it each time. That's why I went over the top with the stiffening. I have bonded plates to ally bike chassis to make them flex less
but was never able to tell if it made them better or not ( not as good at riding them as I could be )
Jason
I didn't say spinning I said sliding more like the feeling of walking, I'd describe it as and quite controllable.
Also I think you're thinking of the old 1980's TZ's the tyre size I ran on the rear was a 160 which I think is close to whats still
being run at world GP level today in the 250 class.
Below is a picture of the bike in question note the 'frilly' edges of the tyres.
BTW I am definately not trying to insinuate I'm any sort of riding legend in Australia I was graded as a 'C' grade rider which I think
was right. I'm sure anyone else who's raced motorcycles for any length of time particularly on slicks will be able to relay the same
experiece.
Rescued attachment BikeRear.jpg
If it's leaving black lines it's spinning up, that's why the edge is frilly. Should have said Stoner as an example, sorry
Anyway... back closer to the subject of the thread...
A quote from Peter Elleray, the Chief Designer for the 2003 Le Mans winning Bentley EXP LMGTP:
"As regards the overall level of stiffness, it is an order of magnitude higher than the roll stiffness of the suspension, which is usually a good
rule of thumb to work to…"
Which I take to mean if the force to induce 1 degree of roll is X then the frame stiffness should be 10X as a minimum.
Quote came from here
"As regards the overall level of stiffness, it is an order of magnitude higher than the roll stiffness of the suspension, which is usually a good
rule of thumb to work to…"
Which I take to mean if the force to induce 1 degree of roll is X then the frame stiffness should be 10X as a minimum
We would have solid bars instead of springs if it was the other way round.
Jason