Foxxtron

iTrader: (1)

Yes, we did that exact test, and no creaking or misalignment on mine and the other test vehicle while the jack was loading one corner. It was not what I’d expected, however I was glad that I my expectation was wrong. As a matter of fact, I’ll do it again and see if I can videotape it. Some here do mention like results with their F-body that you’ve had with your TR7, however I would like to question their test methods. I would also like to mention that the door hinges may be weak as well, so that could effect the test results too (but if it was, it would’ve still dropped considerably).

I decided to try this due to my criticisim in another thread dealing with the proper method of SFC’s installation. If you perform a search you’ll come across a thread where a sponsor here installed SFC’s by using jack lift (essentially lifting the f-body in the air by their jacking points and letting the suspension hang off of the body, a la usual method for performing under car service), and he mentioned that it wouldn’t matter for the 4th gens, but was critical for 3rd gens. He too mentioned that when he did jacklift several vehicles and did opened and close their doors. Yes, it isn’t quite like the test you and I tried, however it was enough for my curiosity to phone up my favourite suspension manufacturer who sells and advocates SFC use. Guess what? They said it didn’t matter whether the suspension was loading the chassis or the chassis was loading the suspension. These testimonies kind of offered me some insight on this highly contested and debated subject.

NHRAMAN

iTrader: (1)

Gotta chime in again...all your arguments are well and fine,but in real world driving,any stiffening of the car will make it more enjoyable,and it will last longer than one that doesn't have SFC's,STB,BOXED CONTROL ARMS,better Sway Bars,better PANHARD,and POLY bushings...rubber degrades out too quick...the T-ROOF DOES INDEED make our cars less rigid....I replaced all these on my car after 2 months,and to this day it is better than new....100,000 miles..... [side note: anything welded is much better than bolted-in.]

Foxxtron

iTrader: (1)

Yes, as far as your mods for what you're doing (High HP Drag racing), I can agree, however be advised that when it comes to corner carving with boxed LCA's and Poly bushings, the heavy stiction from the poly binding will hurt performance. Also be adivsed that I have replaced the crummy factory rubber with Moog problems solver rubber bushings and they have enough hardness without all of the coldflow problems of poly.

As far as ALL F-bodies lasting longer with the SFC's and STB's, please elaborate since I too am curious how this is true with an example like the thread starter has mentioned. Not trying to be a wise ***, but I rather hear the complete evidence, rather than just I have been through X number of drag races @ Y number of tracks. Bear in mind that It's a lot more resourceful to mod as you need, rather than just modding for ease of mind.

Bear in mind that AX and RR is real world driving, and is much harsher than almost anything done on the street. Drag racing is brutal to any chassis also, however you're talking 1/4 miles done in like a few seconds at a time in straight line. Still brutal, but are you doing lots of speeding up, slowing down many times in at least 3 or 4 hours while cutting curves and dealing with nearly equally massive G forces from all 4 sides?

As I have mentioned, we are not just "keeping the lion in its cage", we are testing on circle tracks, closed circuit road courses, and mostly through AX courses. Don't think that AX isn't like RR? Ask Sam Strano or some highly experienced AXer's and they will mention the phrase, "if AX is any slower, it'll be RR." Sound strange and somewhat stupid, but it is indeed factual.

Foxxtron

iTrader: (1)

Got some nice news for your fallacy of info imprudent one. Floorpans and firewalls are not designed to be part of the "stress bearing" structures of the monocoque. The unit body term is really a misnomomer as it is not quite the body, but the fact that the stress bearing part is integrated into the overall shape of what will determine the exterior, or shape of the body. That's what doors, bonnets, fenders, and other exterior panels are really considered body parts. Some parts of the monocoque can include some exterior panels, but that still doesn't mean they're all parts designed to handle certain road stresses.

The one piece isn't necessarily a one piece structure as many cars have their floorpans and some other monocoque parts spot welded after the chassis is formed. F-bodies do as well.

Foxxtron

iTrader: (1)

Yes, the Mechanical Engineers specialising in Finite element analysis have explained and guess what? According to them, you're inaccurate. Once again, I have a Baccalaureate in Materials Science, so I am quite familiar, since FEA is fundamental to predicting material failure.

Here's a reminder of how it works:
http://www.sv.vt.edu/classes/MSE2094...s/history.html

You need to bear in mind that FEA doesn't always involve the acual measuring of the body itself, though with what we're doing it sure does. We use probes while both chassis's are at rest and also in motion, a motion that is seen in intense road racing. Vibration and Fatigue analysis is what we're using as of this moment.

The tests are a lot more accurate than you think. Any structure doesn't need to be always measure in motion because some evidence of shifting can still be present even after the vehicle is no longer moving. They chassis parts aren't designed like springs so it's very unlikely that they will return to its complete previous physical state.

We do include several gauges that do measure the torsional rigidity of certain areas of the monocoque in question.

Do yourself and others a favour and relax.

DONAIMIAN

iTrader: (18)

-95 T/A
Its one thing to dissagree with someone, its another thing to act childish and resort to name calling. I will not tollerate that AT ALL. If you cant act mature and have a civilized discussion on different thoughts I wont hesitate to get you on that vacation list.

-Donaimian
LS1Tech.com Staff

300bhp/ton

I agree with Foxxton here. I don't think it is chassis flex but strss transfer.

This would be the sameway arch damns work, and many structures in buildings, such as bridges and towers.

300bhp/ton

Foxxton - I would like to say thanks, for spending the time to explain, I have found it most interesting and enlightening.

I'll be honest, I haven't done the testing you have or indeed even have access to the equipment. But from my observations I would certainly agree that the STOCK 4th gen does indeed have a good chassis to start with. I'll admit my car is stock, although it is Euro spec so I'm not certain what the stock suspension actually is (I have a suspicion it isn't quite the same as a stock US Z28.) But I can confirm in stock trim it performs very well on narrow, bumpy uneven British roads. It could perhaps do with a little more body roll control at high speed (80-100mph cornering) but that's about my only complaint as a road car. And SFC's and even STB would do nothing in this respect.

So interms of chassis tuning and suspension setup I am 100% with you. I do intend to spend some time at the drag strip so I will probably get some lightweight SFC's anyhow. But this is partly because they are pretty cheap and because I'm in the UK so I only want to order things in bulk (better for postage).

Also I can't find any floors in your logic or reasoning, so sadly I have nothing else to debate.

I ask a question - You answered it.

As you are measuring forces and such, what sort of lateral g are you pulling? Would be quite interested to know.

Cheers.

Foxxtron

iTrader: (1)

And many thanks to you and others who participated with patience and prudence. As I would like to mention, this is still far from finished, so anything else can come up and also I don't rest on my laurels, so I can always be proven wrong either through my own findings, my SAE club colleagues, or through other participants. You see where the main focus of where this debate is.

My mad rationale is kind of fueled by the American "mythbusters" show, however this extends far beyond their simple trial and error analogies.

I haven't quite got to the chance to investigate what the Euro spec 4Gen Camaro is, however I can assure you that if it does indeed use DeCarbons, and they're old and never been replaced, you ought read this thread:

https://ls1tech.com/forums/suspension-brakes/421717-konis-qa-1-a.html

If you demand better handling for corner carving, then these are the threads to read:

1. https://ls1tech.com/forums/showthrea...ght=Sam+strano
2. https://ls1tech.com/forums/showthrea...ght=Sam+strano
3. https://ls1tech.com/forums/showthrea...ght=Sam+strano

Sam Strano is another interesting vendor with some great knowledge, experience, and has a network of people he knows in AX/RR and I believe in Drag racing as well.

BTW, if you shall need some SFC's and ones that are made well by a good businessman, you could try UMI. I will also mention that I have come across some F-body owners that were pretty good at TIG welding and mandrel bending with tubular steel thus fabricated their own.

So far, both mine and the other "shared" test vehicle (stripped with test instrumentation) are only at about .93g's on 275/40 ZR17 Kumho V710's with about 4/32 of "tread" on 17x9.5 OEM Z06 rims. My cheapo street tyres are considerably less. There could be more, however it's still a work in progress, because it is still something I want to be able to determine the limit of.

jam01

ive owned 10 camaros a 67,68,72,75,77,two 83"s 84 t/a, 89 convertible and my 02. i bought each of theses cars used. from my experience so far from the older models they would have benefited from having sfc's. my 02 is the only one ive put them on so far, i still own one of the 83's 84 t/a and the convertible.ive had body work done to the 83 to repair the stress cracks from twisting, and im not taking a chance with my 02. ill give you evolution on the camaro has improved from each model but facts are there just not a full frame car. even they twist, witch is why i bought the 3 point. i should have bought weld in's but my area lacks decent welders with lifts, plus the fact i like working on my own vehicles. my testing has been going on for 23 yrs plus. ive also owned other chevys too, but the last 10yrs or so have been camaros.

Foxxtron

iTrader: (1)

Again, the 4th gens are in question. There's no boubt that the 67 - 92 are in definite need of SFC's as I've AXed several 3rd gens. If you must, weld-in, but again the reason I mention this is because many make claims based on ownership, but never acutally based on complete facts, just owner and witness tesitimony, which are useful testimony, but again don't convey the actual physics at play.

If you note correctly, Monocoques are never as stiff as their "equal weighted full-frame counterparts", no doubt about that. That doesn't necessitate that all monocoques are absolutely flimsy enough to warrant any type of added structural reinforcement FOR every F-body, under EVERY circumstance. Quite the contrary. There have been monocoques stiffer than frame cars, however for the weight involved, it yields a much heavier chassis. What I am trying to do is again test the efficacy of SFC's on 4th Gen F-bodies. That means if it's doing what it's supposed to do, under what circumstances do they work.

Many also neglect to note that their suspensions aren't even tuned correctly for what they're doing. Of course, a sloppy suspension is going to transmit much noise and much vibrations, but you you think that a solid chassis is going to solve that? So far it makes the NVH worse. What SFC's can do is stiffen the chassis, but again my posts are aimed at the efficacy at the 4th Gens.

The statement that ALL Monocoques need SFC's really neglects to specify which ones, because if you take note of some of the recent hyperexotics, their carbon-fibre monocoques not only exceed a torsional stiffness to weight ratio as compared to a tubular steel frame or box steel frame, but exceed their torsional stiffness as well. I know that's stretching it a bit, however WHICH monocoque need SFC's is really what should be asked. That's what I'm asking of the 4th gen, where, when, and how.

Again all chassis' made of steel will flex, regardless of being monocoques or box steel or tubular steel frames. The placement of the steel is what could make a difference, which tubes (with enough thickness, overall diameter, and proper geometric placement) are definitely stronger than sheet pressing (depends on thickeness and placement once again). Again, how much flex are 4th Gen's really exhibiting? Enough to warrant SFC's or not, and under what circumstances.

Again, the history of flexing observed while parked in the shop. Is this only though seeing what's going on with the suspension alignment, done by one's eyeballs alone, or would this be through measuring the overall chassis geometry through a machine like the Cheetah 360? If it's done with one's eyeballs, then is the history taken into account with an honest claim?

I'd prefer to offer more than a simple placebo, and owner testimonies.

Foxxtron

iTrader: (1)

Well, again since this thread was started with a generic enquiry (a useful enquiry nevertheless) I'll merge another thread into this just give you an example of another person's experience with credible evidence.

https://ls1tech.com/forums/showthrea...highlight=Koni

BJM

iTrader: (1)

I find it hard to agree with this. Okay I don't agree at all. If body-on-frame cars were a more mass efficient means of building cars of a given stiffness, then that is what we would all be driving. OEMs builds this kind of car because it provides a lighter car. Cars are built as uni-body or even monocoque construction because mass is saved for a given stiffness, particularly in torsion. Connecting a body to a frame using rubber bushings by necessity gives up a lot of stiffness in favour of NVH and the body is designed to hold itself together only and not designed as a load carrying member since the frame carries the real loads.

As far as SFC's go I do agree that they may not be necessary but they are so easy to add and they do not weigh very much so people add them. In my case I am not looking to add handling capability, my convertible will hopefully pick up some torsional rigidity with a 3 point SFC underneath.

Foxxtron

iTrader: (1)

Read this:

http://www.autozine.org/technical_sc....htm#Monocoque

It provides for a more space efficient vehicle, not necessarily a lighter vehicle, or less overall mass. Again, most designs provide for a poor rigidity-to-weight ratio.

BJM

iTrader: (1)

That page says the same thing I did.

Excerpting

Ladder Chassis

Since it is a 2 dimensional structure, torsional rigidity is very much lower than other chassis, especially when dealing with vertical load or bumps

Monocoque


the rigidity-to-weight ratio is also the lowest among all kinds of chassis bar the ancient ladder chassis.


This is what I stated. The other frame types are nice but are not used in any kind of car I will ever own.

Foxxtron

iTrader: (1)

Then I will state that for the same type of metal used, their rigidity-to-weight ratio is less than a TSF.

Bear in mind that if they were designed to be light, then they can, however there are safety requirements that are to be met, so they can only make it light enough to accomidate the required crumple zones and thus stiffness can be compromised in those area.

Also, bear in mind that it's space efficient (volume for use of things, not amount of molecules for the material, or mass) as far as where certain items can be placed (installed in or on the car, or placed as cargo). It is not necessarily overall mass efficient for how much material is used and where it is used.

That's what it is acutally explaining. I understand how the statement you refuted isn't completely correct, however your statement appears to confuse overall vehicle mass with space efficiency (volume of usable interior space(s)-to-mass of material used).

EDIT: TSF instead of TSB

Foxxtron

iTrader: (1)

They could serve their purpose, provided they're used for a correct purpose, however if you must buy them and pay someone to install a 3-point correctly, it can run upwards of ~200-250 USD total (can't remember what it is in CAN since it's been 13 yrs. after emigrating to the US), and if the SLP boxed ones are used, then prepare for it to be time consuming as attention to detail is required. If you must have 3-points, then I would compare UMI's to SLP's and see which one you'd would benefit from.


A convertible already uses an SFC, however it appears kind of weak, but were not researching that, yet.

Foxxtron

iTrader: (1)

Hate to dissect this, but as I looked further,

Space efficiency which would be volume, not necessarily the amount of material used, which is mass.

That’s a bit general, as there have been needs to increase the rigidity, thus the weight ends up being more, since the manufacturing efficiency needs to be achieved as opposed to the effective and efficient use of the material itself, which leads to more inefficient use of mass.

Sorry, but your explanation seems to be confusing that the fact of chassis stiffness is primarily affected by the use of which materials for body attachment method, in which is it mostly down to where the load of the body is applied on the chassis itself, and how much is applied. If a chassis isn’t stiff enough to begin with, then the chassis imperfections will reveal itself not through use of specific materials per se, but where the loads are actually applied and again how much. Rubber per se may absorb some of the loads applied, but it’s really down to the chassis or load bearing component themselves.

What is experienced with the scenario above is down to the bushings durometer, not the chassis’s stiffness. That type of stiffness is overall vehicle stiffness, not specific chassis stiffness, which indeed matters for overall response, however doesn't deal with the issue of SFC's and their efficacy to stiffen the load bearing components themselves. Bear in mind that I and the other vehicle are using parts with many spherical bearings and heim joints, and very little amounts of links using rubber and poly.

BJM

iTrader: (1)

Boy, you really hate to have mistakes pointed out. I am not looking for an arguement, honest.

Space efficiency has little meaning. The car must envelope the passengers, cargo, and drivetrain. They all do that with very similar shapes. Take two as near as identically shaped cars as possible of the same stiffness. One is body-on-frame, the other is uni-body. The uni-body car will have less mass. That is all I was saying. Primarily, this is due to the mushy interface between the frame and body.

And yes there are many competing factors driving the design, like crash worthiness, repairability, manufacturability, and on and on.

I also did agree that SFC's may not be needed but won't hurt and for myself I will have fun putting them on myself as a small project. In my case the cost is not the issue.

Foxxtron

iTrader: (1)

I’m not either, however you seem not to state this correctly, so I must reiterate the facts.

I hope to remind you that if space efficiency has little meaning, then why did you mention the what the car must envelope? The article I supplied states it well. In your definition you appeared to confuse volume for mass. Space efficiency has much meaning for the monocoque as you state they must envelope all of what you mention. Again better volume for the mass used is space efficiency, not necessarily less mass.

Again, the unit-body will can have more volume for its “container”, but again, that doesn’t mean less mass. It’s not only due to amount of what material(s) are used, but how that material (or those materials) is used for optimal strength. Again the body-on-frame is too generic. Ladder type is the only a lesser design stated, however all other types of body-on-frames (except carbon fibre of course) have a much better capability to yield less mass, however they sacrifice the space efficiency. That's why you really can't just say body-on-frame vs. monocoque, because there are many variations to either of those designs.

Interface between body and frame isn't appropriate if you're talking about a monocoque. A monocoque is a chassis yielded to a shape of the body. How that chassis is designed is what yields its torsional rigidity, not where "body panels" and "stress bearing structures" meet per se. If those two identical designs must have the same torsional rigidity, then obviously the monocoque will have more mass, since the material being used isn't used efficiently.

If you read the advertisements from Acura, the reason the mass can be reduced is due to use of different materials other than steel, and the better use of the steel itself (in their case, high tensile strength of steel through good materials science), which they then can reduce the mass.

This thread may not be concerned with that fact, but you are not stating correctly. Again, the monocoque will not have less mass necessarily, just not great use of the mass of material used, hence mass efficiency.

Please give me a URL where what you mentioned is positively stated in exactly the way you mention, otherwise I will not concede any mistake in this matter unless you can specifically explain and completely support what you mention.

No problem, however I’d like to state the figures involved.