Foaming the chassis

[Redd]

this is an interesting debate. i hope u all dont mind if i explore a bit more on this.

purely academic, of course. i am neither for nor against foaming. in fact, im a strong supporter of the "different strokes for different folks" movement.

right, foaming as pertaining to structural stability. both lee and necc have valid concerns and points, but too little is known about the foam to say if either one or the other is rights. bear with me.

crumple zones exist to absorb crash energy and to redirect that energy away from the passenger capsule where it might cause injury. they dont crumple just cos the car manufacturer decided they would like to sell u more spare parts. a lot of energy is expended when "deforming" a structure, ie crumpling it. this energy is then not transmitted to the cabin where it can cause harm.

so will foam in these crumple structures negatively affect rigidity of the structure that it will not crumple as designed? its certainly possible, but without knowing the material properties of the foam, its impossible to tell. for all we know, the foam can cure so hard that it becomes like steel, unneccesarily stiffens the crumple structure causing it not to deform - or deform insufficiently - and transmit crash shock into the passenger cabin. this is the necc's argument.

alternatively, it is entirely possible that the molecular structure of the foam has a relatively weak atomic bond. then it is likely that the foam can actually help absorb crash energy by disintegrating in a crash - the disintegration absorbs crash energy to break the bonds between the foam molecules - and can help reduce crumple damage in the structure and still divert crash energy away from the cabin.

it is not difficult to create a foam material with a very specific shear property whereby the molecules separate and the foam disintegrates when it encounters a certain amount of force - higher than chassis flexing force, but lower than crash force.

but we dont know enuff about the foam to say one way or another.

redd

 

[koryong]

Originally posted by E34EuroTouring@Jun 15 2005, 03:57 AM
Hey, none of us are Class A Automotive structural engineers right ?.

You're right about that .... EVEN IF we are, every car maker has very different perspectives about some safety factors and global governance of these parameters.

BTW, the foam that Kev used, normally cures in 12-24 hours but since it is in his crevices .... and not exposed to air, it may take 48-72 hrs but definitely no longer than that.

 

[wolverine]

Originally posted by E34EuroTouring@Jun 15 2005, 04:57 PM

Oh... I just have a thought. Maybe its a good idea to foam the darn house, that will stop creaking on the floor boards and stop those dreaded cocroaches hiding in the crevices....

:rofl:

 

[The F.Man]

in the name of science, physics and all the bulls.h.i.t that has gone on, i propose the necc and the lee both be crash test dummies in their own cars and do a direct 60kmh head-on.

i'm sure we're all interested to see the actual foamed vs unfoamed crumple zones.

and engaging the Sport button is optional.

 

[Lee36328]

Originally posted by The F.Man@Jun 16 2005, 02:36 AM
in the name of science, physics and all the bulls.h.i.t that has gone on, i propose the necc and the lee both be crash test dummies in their own cars and do a direct 60kmh head-on.

i'm sure we're all interested to see the actual foamed vs unfoamed crumple zones.

and engaging the Sport button is optional.

Err... Mr F,

Can you do a demo in ur car for me and The Necc as to what u mean?

:rofl:

However, this still wud not settle the debate conclusively, since no two cars (esp two that have been on the road for a while with different levels of metal fatigue and somewhat modified, summore one of them is an M3 wor & the oder only 328) are exactly the same....

If you can provide two factory-fresh cars of identical spec, I wud be happy to crash any or both of them for you, foam or no foam.... ok?

:rofl:

 

[Lee36328]

Originally posted by E34EuroTouring@Jun 15 2005, 04:57 PM
Lee,

Hey, none of us are Class A Automotive structural engineers right ?.

We are consumers of all things automotive to fulfill our desires with our interest/passion/sport/whatever. So mostly things that makes sense, we can accept. You have great points and a great car which you enjoy very much and loved to share your job of having foamed your car.

I hear you bro, I hear you... B)

 

[jarance]

Originally posted by The F.Man@Jun 16 2005, 01:36 AM
in the name of science, physics and all the bulls.h.i.t that has gone on, i propose the necc and the lee both be crash test dummies in their own cars and do a direct 60kmh head-on.

i'm sure we're all interested to see the actual foamed vs unfoamed crumple zones.

and engaging the Sport button is optional.

F-man... I think they rather see you be the crash dummy before they do it in their own car.. :nyehehe: :nyehehe:

 

[E34EuroTouring]

The newer technology is already being experimented by Audi in "foam" like honey combed aluminium chassis components. Less mass but more rigidity.
Heck, carbon nanotubes are the utilmate way to go in future. Consider this 5X stronger than steel and 1/10th the weight.

In 10 or 15 years car manufacturing will go this route and I am sure Lotus and Jaguar are better positioned for such technologies. I would not count out the Germans since they tend to catch on very fast and will have the *best* quality eventually. Not necessarily the best price though.

I can envisage my little girl 15 years from now, wanting that SpaceFrame nanoTub Porsche!. She will get a 30-40 year old Porsche 911 .... will still be a classic Porsche in that era!!!. PSM rigged for novice mode!.

 

[Jules]

wah veli hot topic one here......

Lee, must take a ride in ur car-loh......

Guys,
If I may speak from an Engineer's point of view......i think foaming will do wonders for NVH issues and as mentioned by a forumer, required for ICE fans.

For chassis strutural rigidity improvement, IMHPO minimal advantage will be gained. Foam, in the forms I know has a lower modulus of elasticity/compression(E)/shear(G) than steel, hence deflects more, shears easier than steel.

Placed inside the cavity of a car chassis - as said above I can expect minimal assistance to the structural strength of the chassis - if they are strategically placed on load bearing members. ( ie. if you do it inside the doors, zero improvement for chassis rigidity due to the support system )

In terms of improving the crash resistance with foaming - minimal again is the gain here. Personally, making a "solid" car can actually kill the occupants since the crash energy is at best dissipated to anything other than the occupants - Redd already explained this more scientifically than me.

Whilst I am also trying to understand how foaming can give all the wonders the forumers have listed - can it be that the MUCH reduced NVH has not given you the sensory input ( especially the less NOISE ) that the car is more rigid, secure & handles better? Foaming may have dulled also some vibrations, all good things to achieve in a car.

Having said all the above - if your butt and SENSORY receptors perceives this to be a good mod, by all means. It's at the end your money, your ride, pride & joy.

Anyway, where's Bundy? He's the better engineer than me and may have another opinion...

cheers & surely just my 2 cents.

 

[Lee36328]

Jules,

come, come... since we are so near to each other.... can try my car anytime... free for lunch?

 

[Zoggee]

Originally posted by The F.Man@Jun 15 2005, 01:36 PM
in the name of science, physics and all the bulls.h.i.t that has gone on, i propose the necc and the lee both be crash test dummies in their own cars and do a direct 60kmh head-on.

i'm sure we're all interested to see the actual foamed vs unfoamed crumple zones.

and engaging the Sport button is optional.

well...I'm willing to take you on !!! My 5.7 Yellow Monster coupe..this time, how about 70kmh head on...toward you..!!! :aggressive: cipek..!!! :nyehehe:

let us learn from here...not fanning them ma... If the comittee wants to ban me...ban lar!!! Cipek la lu Fman. !!! :aggressive:

 

[jarance]

well said.. zoggee... :yahoo: :yahoo:

 

[The Necessary]

Lee,

thank you for your admission, it takes more balls to stop a fight than to start one. But the prom queen always goes home with the winner, alas.

Hahaha.

No hard feelings.


Anyhows, my take on the entire foaming thing is that IT WORKS. It works to "strengthen" and "stiffen" the hollow chassis by the distribution of incidental force over a wider area- ie. it's like standing on thin ice and laying belly down, both same weight, but someone's going to get wet. I have no doubt it works, I've sat in a close friend's car who has had the whole treatment done by the Desmond too.

But in my opinion, I feel the fact that it works is what makes it so "dangerous", as now, the crumple zones will not absorb the forces in a crash, instead they will transfer those forces into the passenger compartment- a bit like the weakest link theory, if you know what I mean. In this case, the weakest link IS you. The crumple zones have now become "stronger" and more resistant to crumpling without a resultant increase in strength/rigidity of it's down/up stream components.

Just a little side note; the said friend of mine who's had the entire chassis foamed (ala Lee), has recently suffered a rather catastrophic suspension structural failure, and you know what? He blames the foaming. Why? The foaming has stiffened his chassis to the extent that it does not "give" anymore, placing more load on various suspension components, wearing them out quicker and causing the failure that has happened. Probably. Because, remember, our cars were made and engineered to function as a whole... none more so than the chassis/suspension components, which is why the new E60 rides horribly on run flats (not designed for them) and why 318s on 19" bling bling wheels handle like elephants.

 

[Lee36328]

Yes, the suspension will be worked harder since the chassis is stiffened and does not flex to help absorb the stresses as before.

This is the conclusion of Kevster as well... his suspension feels soft now...

I am monitoring my suspension closely (Eibach on Bilstein) to see whether they can take the added stress or not... Desmond has recommended a harder setup, like H&R, for precisely this reason.

It's that perenial and inescapable engineering balance and compromise...

 

[ALBundy]

Hahahaha...just discovered this thread..guys don't stop!! :rofl:

Anyway back to topic, I would seriously take a look at the numerous "dumb crashes" done by the auto manufacturers and actually see how the crumple zones work. I think they showed these crashes sometimes on Discovery channel

My personal opinion, the A, B and C pillar actually forms part of the safety cell to protect the driver and passengers and it should be as rigid as possible and the crumple zones should be left untouched ie; the frontal side fenders, shock towers and etc. Well, that's my opinion after looking at slow motion pictures of how a car reacts when its it crashed towards a wall at 80km/hr.

And if I wanna do forming, it will purely be for NVH reasons.

 

[Zoggee]

hm...thats more like it.. at least I get to know more about foaming.. :nyehehe: heheeee... :nyehehe:

 

[The Necessary]

Lee... you actually want to change to STIFFER suspension??? For what? To place EVEN MORE stress upon your mounting points?!?!?!

Furthermore, HOW CAN your current suspension feel "softer" after foaming? It should feel "harder" if anything, because a previously semi-compliant part of the system (ie. your chassis) is not "working" anymore... and your suspension will have to work harder as a result (more force transmitted?).

See... this is what I mean when I say you don't DO THINGS RIGHT... *sigh*.

 

[The F.Man]

Originally posted by The Necessary@Jun 18 2005, 07:28 PM
Lee... you actually want to change to STIFFER suspension??? For what? To place EVEN MORE stress upon your mounting points?!?!?!

Furthermore, HOW CAN your current suspension feel "softer" after foaming? It should feel "harder" if anything, because a previously semi-compliant part of the system (ie. your chassis) is not "working" anymore... and your suspension will have to work harder as a result (more force transmitted?).

See... this is what I mean when I say you don't DO THINGS RIGHT... *sigh*.

unless you have an automotive engineering background, now is the time to shut up.

When you keep quiet, no one can accuse you of being stupid - chinese proverb.

points to keep in mind when in discussion on foaming:

-chassis / body flex. By your logic, the more flexible/softer the chassis, the better handling the car 'cos the entire chaissis acts as a suspension component??? so that your "real" suspension dont have to work so hard???? This must be the most amazing "fact" i've ever heard. If that's the case why do they always try to make the convertible versions as stiff as the coupe versions at the expense of weight and god forbid - safe crumple zones??

the suspension mounting points are also one of the strongest points in a car - have a look at yours. They're reinforced and doubly welded. Perhaps you meant the mounting bushes??

I think you are mistaking body flex (which is what foaming aims to reduce) for the safety-related crumple zones.

And please do not feel compelled to reply to this. Remember the proverb.

 

[Jipster]

....................... (chinese proverb)

 

[zaskar]

I think he refers to, stick and stones...................