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Old 01-14-2007, 03:15 PM   #31
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Re: Structural Rigidity enhancement...

Quote:
Originally Posted by drunken monkey
What kind of scan did your car have?
Don't know my friend owns a body shop he just told me it came out good and clear. I know it runs a systems where the whole chassis is scanned an then the numbers are imputed into the computer an compared to the original or what should be numbers. He said they were on par to the original factory #'s.

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Originally Posted by drunken monkey
Why do you want a stiffer ride?
High speeds and Extremely winedy (Sp) roads...
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Old 01-14-2007, 03:17 PM   #32
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Re: Structural Rigidity enhancement...

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Originally Posted by GreyGoose006
my biggest argument is that if the foam cracks, you will be left with an unevenly stiff chassis.
you compared it to bone, and bone cracks pretty easily.

i guess i have to try the "great stuff" experiment.
If it cracks then I'll have it removed from the chassis and reinstalled until it happens again.
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Old 01-14-2007, 03:18 PM   #33
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Re: Structural Rigidity enhancement...

Try it and see for yourself. Experience is the best teacher...
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Old 01-14-2007, 03:21 PM   #34
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Re: Structural Rigidity enhancement...

you can walk the plank first, tell us what it's like.
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Old 01-14-2007, 03:21 PM   #35
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Re: Structural Rigidity enhancement...

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i doubt an aerosol of this foam will deliver the kind of rigidity you expect, if there is such a gain to be had, as shown by this GT-R i'd imagine they used some gear a little more "heavy-duty" than squirting a can of foam into the frame's hollows.
I'm sure it's a high grade of what ever urthane they use. Your thinking about it as if it were a base K-mart plastic. Isn't there is a difference between steel and forged magnesium...
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Old 01-14-2007, 03:24 PM   #36
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Re: Structural Rigidity enhancement...

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Originally Posted by 2.2 Straight six
you can walk the plank first, tell us what it's like.
You guys are going to have to sit on it for a while. I'm at college an building funds for my little racecar. High performance parts aren't cheap ya know or would you
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Old 01-14-2007, 03:28 PM   #37
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Re: Structural Rigidity enhancement...

I don't think that the foam was used in isolation either.
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Old 01-14-2007, 06:43 PM   #38
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Re: Structural Rigidity enhancement...

The urethane foam is nothing like the spray can of foam. I just mentioned that as something you could try at home. Imagine the urethane foam like the cheap spray can times ten.

If the car is truly compromised, then it won't work miracles, but the foam is very effective.
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Old 01-14-2007, 09:53 PM   #39
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Re: Structural Rigidity enhancement...

I have to agree with how strong the foam can be, and its follows that from if injected into a cars chassis it could make more rigid.

I can however think of a few problems.
Once its in, its NEVER coming out. Not unless you cut the car up completely destroying it in the process.

ANY moisture that gets trapped by the foam, will cause rust. Lots of it.
I wouldn't do this to a car I planned to keep very long as a road car.
Suitable for race only applications IMO, where the cars life is going to be limited anyway.


I also don't think it will be as effective as a lot of others think it will be.

In order to make your car more rigid you have to find out why its flexing to begin with.
90% of the time its not because the existing structures are strong enough, but because they are poorly placed, or there are not enough of them.
If the flex is occurring over a long length of the body, for example the from the base of the floor to the top of a pillar, simply making that pillar stronger often won't have much effect.
The amount of flex across that distance only has to be a very small amount, to cause a larger change else where, say to wheel geometery.
Increasing the strength of that pillar to to stop that small amount of flex may require an exponential increase, in its strength. Even making it out of solid round bar might not be enough.

Instead what is needed is extra bracing, or even a redisgn of the pillar.


Its been mentioned that the foam works by forum millions of little cross braces with in its expanded from.
Well a car body works in the same way.
Its much more efficient to find where the flex is occurring, and adding cross bracing in the right places, than it is to simply try and reinforce he whole car based on its existing structure.

The best refinement Iv seen done, was to a Lotus Elan.
The owner made a scale replica of the chassis, and used it to observe the weak spot. It showed him only a very small (about 300mmx300mmx300mm) triangle needed to be fitted on each side in a spefic location, and the chassis rigidity could be almost doubled.
While a Lotus Elan chassis is much simpler than that of an RX7, the same princiables apply.


Besides, while the foam may have a very large amount of strength over a wide area, put pressure onto a small point of it, and it will collapse.
It would only take a small collapse of the foam with in the chassis, for the whole procedure to be rendered pointless.
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Old 01-14-2007, 10:10 PM   #40
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Re: Structural Rigidity enhancement...

/\ Very good points. Well the car won't be driven as a DD only to shows and races an most of the time if it requires long distances it will be trailered no doubt.

As far as the bracement issue I know what your talking about an the key flex point is under the engine atleast from what I've been told. I want to make a custom titanium X brace as done by this owner.



What do you think?

Like moppie said the only thing I'm worried about is if it cracks it will be rendered useless. If the urthane was removable somehow (please tell me) then it would be a definite go ahead.

Moppie ~ Do you have more stuff on the Elans project I would like to see photos an such just to get Idea's.

Thanks
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Old 01-14-2007, 11:10 PM   #41
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Re: Structural Rigidity enhancement...

Quote:
Originally Posted by jcsaleen
Don't know my friend owns a body shop he just told me it came out good and clear. I know it runs a systems where the whole chassis is scanned an then the numbers are imputed into the computer an compared to the original or what should be numbers. He said they were on par to the original factory #'s.
So he did a measurement check and it came out okay?

Did he check for popped spot welds? Cracks? Crumpled members?
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Old 01-14-2007, 11:26 PM   #42
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Re: Structural Rigidity enhancement...

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So he did a measurement check and it came out okay?

Did he check for popped spot welds? Cracks? Crumpled members?
With what else a tape measure

Yes, There were poped spot weld in the front end past the front wheel pillars an since then they have been removed an a clip has been installed.

No cracks the only crumpled zone was the front right directly under the rad support an has been pulled an straightend to be brief. Structurally speaking the car is fine.

It was inspected tooth an nail.
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Old 01-14-2007, 11:27 PM   #43
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Re: Structural Rigidity enhancement...

Quote:
Originally Posted by jcsaleen

Moppie ~ Do you have more stuff on the Elans project I would like to see photos an such just to get Idea's.

Thanks
'


Sadly I don't know of any more details.
But the Elan chassis is just a simple back bone.


Ultimately I don't think there is any substitute for finding where the flex is, and fixing it properly with well engineered bracing.
It doesn't have to be complex, the above example of the cross brace looks very over the top to me. It may in fact make the problem worse, but over stiffening the front in relation to the rest of the car.

Also consider what sort of work the car will be doing.
You only really want a super stiff chassis if there is going to be a lot of hard cornering and fast direction changes on a nice flat track, and you have a lots of control over suspension set up.
I know people who have taken strengthening out because its made the car too stiff, and to twitchy.

And of course if your going to be racing in situations where the car may turn a corner at more than about 35mph then you need a roll cage. Even more so if there are other cars on the track.
Its doesn't take much to flip a car, and the more you race, the higher the chance it will happen.
You have to think of your own safety as well, and of course a cage, if built properly can do wonders to chassis rigidity.


I put emphasis on the built properly though.
I know of a car that was rolled up a bank (yes, UP the bank), then landed hard enough on its rear axle to break a wheel, disk and hub in half, and bend the rear axle, housing the lot.
Yet the cage held the car together in such good shape that we simply replaced the axle, wheel etc, and away it went again. (with some body work to the roof and front).
Yet that same cage allowed the car to flex enough that the A pillar separated at the base of the front window.
(of course a cage should be designed first to protect the occupants, which this one did).
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Old 01-14-2007, 11:51 PM   #44
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Re: Structural Rigidity enhancement...

I'm more into stright line speed but not 1/4 times though more or less 1 -2 mile sprints actaully (topspeed). I would do cornering but there aren't any real tracks here in N.Y (Atleast downstate). The other thing is it is mostly a track car for all purposes intended but I do like to take her out on joy rides as well as some nice cruises an meets. Also to nice occasions just going to the movies thats why I'm trying to find alternate ways instead of a roll cage. Not for anything but I like my car to have a stock look in the interior (No guages except a boost gauge a digital blitz Icolor 5 in one display on one screen), I'd hate to cut up anything my interiors its mint. Basically I use the car to take to shows, meets, races and also to treat a girl on a nice occasion. I'm not pushing major numbers (300-325 rwhp @ 12psi) but while the cars apart I'd like to do it, this way it will save me labor an time in the long run.

As far as vibration through the chassis I'm not worried I'm ordering the new Nexus GT ride control adjustable coilovers. They adjust stiffness as well as ride height where as most just have a pre-set rigidity.
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Old 01-15-2007, 09:47 AM   #45
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Re: Structural Rigidity enhancement...

If there is an issue with the area under the engine, I can't see how it would cause your doors and boot not to close when on a slope. If anything, your doors and boot not closing suggests to me that it is a longitudinal flex problem and an x brace under the engine isn't going to help this much; a brace here would be targeting torsional rigidity across the front axles.
what you need is a brace that spans the length of the car.
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