Phil Martin wrote:
>
> On Tuesday, November 25, 1997 7:27 PM, John T. Blair [SMTP:jblair@exis.net]
> wrote:
> > Now as for stiffening the chassis. Had a discussion with Terry this
> > afternoon about some of this. So of what we discussed are summarized
> > here:
> >
> >
> > 1. Stiffening chassis - Tested and was the strongest frame of
> > any car made.
>
> There are lots of ways of measuring frame "strength" - it's not necessarily
> the same as stiffness. I don't know if there's much of a relationship
> between a frame's ability to be driven into a brick wall and it's ability
> to resist torsional flex, for example. Does Terry modify the frames in the
> high-horsepower vehicles he builds? Has he ever modified one while
> focusing on handling?
>
> > 2. Really can't lower the car. Initial ground clearence is
> > 4.5". Terry has lowered his to about 3". In addition the
> > front end geometry can get really screwed up, which will
> > cause all kinds of handling problems.
>
> I'd buy that.
>
> > 3. The Bricklin has been shown to be a better handling car on
> > most of the drivers. In 74, Road & Track did a comparision
> > of the 74 Vet and 74 Brick. The Vet out performed the Brick
> > on the streights. But the Brick did better than the Vet on
> > the cornering.
>
> Yeah, and a modern minivan will outcorner both of them. ;)
>
These are good points. If you are not going to drive your Bricklin in
an "aggressive" manner ( and I can't imagine why you wouldn't ) and keep
the stock engine, then you probably can keep the frame as it is. But
performance driving and more powerful power plants really require
frame/chassis/suspension improvements.
Stiffness and strength are not the same thing. A piece of spring steel
is quite strong ( up to its yield point) but not very stiff. In a car
you want both strength and stiffness. Stiffness also has the benefit of
reducing the magnitude of strain. Strain is how much a frame deflects
under load. The more it deflects, the sooner it fatigues under repeated
cyclic loading. Fatigue is the biggest killer of car frames next to
corrosion. A stiffer chassis will resist fatigue better at a given
level of loading.
Intelligent stiffening without adding unnecessary weight does require
careful planning and the Bricklin is heavy enough as it is. That is why
good drawings would be helpful. There are three principle types of
stiffness necessary for a car. On resists beam bending where the frame
flexes like a beam supported along its length a two or more points. I
feel there may be some need for increasing this type of stiffness at the
front and back.
The second is shear type stiffness where you clamp the back of the
frame and try to push the side of the vehicle. I suspect the Bricklin
is ok for this type of stiffness. The third, and probably most
important, type of stiffness, especially for handling, is torsional
stiffness. Imagine you clamp the back of the car and support just one
front corner of the frame and then push down on the unsupported corner.
The frame will twist a certain amount and the less it does the better.
This type of stiffness can, I believe, be improved on the Bricklin. A
fourth stiffness issue that is also important is flexing of the shock
towers. This type of flexing hurts handling and fatigues the tower and
the frame member it is attached to and really needs attention.
I hope this doesn't sound like mechanics 101! Phil is right, my mini
van corners better than the Bricklin and I suspect that if you took away
the T/A tires it would be a lot worse, but I believe the handling can be
improved considerably through frame stiffening and suspension
improvements.
George Schiro
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