bricklin
[Top] [All Lists]

RE: Chassis stiffness (revisited...)

To: Bricklin <bricklin@autox.team.net>
Subject: RE: Chassis stiffness (revisited...)
From: Phil Martin <pmartin@isgtec.com>
Date: Sun, 23 Nov 1997 14:33:10 -0500
On Sunday, November 23, 1997 2:45 AM, Greg Monfort 
[SMTP:wingracer@email.msn.com] wrote:
> >This thread has been pretty specific to my car and my resto/mod project,
> >but I've been keeping it public so that we can all learn something... I
> >hope it isn't boring anyone yet. ;)

> I've been bored with this subject since I helped design and build a 'A'
> Production Corvette 13 yrs ago, but what the hell....... :^))

Well, I'd like you to know that I really appreciate your help and sharing 
your knowledge & experience.

> >Thanks a bunch for the info - I was under the impression that poly 
bushings
> >were like 1/4 of the way between rubber bushings and heim joints 
(towards
> >the rubber end of the scale).
>
> The one's we just installed appeared to be the same hardness we installed 
on
> the 'vette in '85. Hard as a hockey puck straight from the freezer. If 
they
> make some that are only slightly harder than stock, go for it.

Maybe I could start with new rubber bushings and do something to them to 
harden them up a bit.  What if I bought both rubber and poly bushings, 
turned down the poly ones on a lathe to say 1/2 of their original diameter, 
then bored out the rubber ones and inserted the poly ones inside?  Is this 
an idiotic idea?  Probably ;)  What about just pounding some nails into 
them? ;)

> >Tell me how this sounds then:
> > 1) Go with the larger, stiffer wheels and tires.
> > 2) Replace the old rubber bushings with new (rubber) ones.
> > 3) Stiffen the frame as much as I practically can with bracing, 
gusseting,
> >etc.

> Sounds good to me.

Glad to hear it.

> >Do you think I'd gain anything significant with the extra width in the
> >rear?
>
> Yes, if you use softer rubber. Just keep offset to the inside so you
> actually narrow the track slightly helping turn in.

OK - thanks.

> >Is a stiffer rear bar reducing understeer by: helping front traction,
> >hurting rear traction, or both?
>
> It moves the polar moment of inertia forward (pivot point changes) 
slightly,
> improving front/rear weight distribution.

Forward or backwards?  If the weight is biased to the front, moving the 
polar moment forward would make things worse, wouldn't it?

> I'm afraid it's not that simple. Is your frame shop qualified to design
> front end geometry? If so, tell them what you want the car to do, then 
hope,
> assuming of course they don't want too much extra.

These guys have a shop that's primary purpose in life is a place for them 
to build cars that they race.  They do a bit of fabrication for other 
people to try to pay the bills.  I'll have an in-depth chat with them about 
the project.  It will certainly help to be able to share the thoughts of 
somebody who knows a lot about the Brick.

> I was basing it on stock heads. The only GT-40 heads I know about only 
fit
> Cleveland mills and Cleveland's won't fit in a Bricklin as far as I know. 
I
> don't keep up anymore; these TFS wedge heads which I assume are for the
> Windsor, have to be somewhat larger and I'm not sure you'll be able to 
get
> an exhaust system to fit.

Well, there are definitely GT-40 heads for the Windsor blocks, but I'm 
leaning towards the TFS parts.  They fit a 5.0 or 5.8 in Ford applications 
without moving either the intake or exhaust ports, ie: the original 
manifolds bolt right up.  If you're not too bored, have a look at:

http://www.trickflow.com/tfswjhdf.htm

I'm thinking that aluminum heads and intake, plus replacing the cast 
exhaust manifolds with headers should help me shave 50-70lbs off of the 
front.  Is that a pipe dream or is it realistic?

> >I have no doubt that a Brick can't put 350 hp to the pavement at 0-40 
mph,
> >but I expect that it would be hooked up and pull pretty hard at 60 and
> >above, wouldn't it?
>
> Even with the mods you're contemplating, I doubt it. That's why they 
added
> IRS to the 'vette so long ago. If they make really soft compound tires in
> the size you need, probably, but they'll be shot in 5000 MI.

OK - how about at 100 mph ;)  I wouldn't mind a car that pulls from 100 
twice as hard as my RX-7, as long as it could do it without getting 
sideways ;)  I've heard that the SV-1's handling strength is straight-line 
stability... How well-behaved are they at triple-digit speeds?

> >Yes, I don't want to sound like I think I can (or should) make the Brick
> >into something it's not.  I'm trying to get a feel for what mods have 
the

> That seems a bit different than your original stated  goals. :^))

Well... I guess you've got me there. ;)  The truth is that I'd prefer a 
sports car over a muscle car.  If the SV-1 is a diamond in the rough, then 
I wanted to get to work on polishing it.  If it's always going to be a pig 
rutting in the mud, well, I guess I'll get my slop bucket ;)

It would be easy to build a strong motor with a 5 speed and 9" live-axle 
rear behind it and just drop it in without considering improving handling, 
but I want to know what I can do to improve handling.

> You're on the right path now. You can improve the car in every measurable
> way without destroying it's character with the frame stiffening, wheels,
> etc. discussed. It will ride a bit rougher, but will feel more 'all of a
> piece'. It will always be tail happy, especially with more power, but
> shouldn't 'snap' like a stocker does, unless of course you're a real
> leadfoot like me. :^)) I forget who did it, but someone put a nitrous kit 
on

No comment ;)

> their Bricklin; lit it off at 50 mph and spun the tires all the way to 
100
> mph at which point the rear end hooked up and snapped him sideways. He
> removed it.

Who wouldn't? ;)

Thanks again,
--
Phil Martin                         pmartin@isgtec.com
"This room smells like Hotel Illness,
 The scars I hide are not your business."



<Prev in Thread] Current Thread [Next in Thread>