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Re: 64 leafsping
Posted by: 7004doorL ()
Date: November 30, 2018 06:41PM

I thought FC's are about 50/50 balanced front to rear?

And I have seen the "Drop" video and they bounce real good.

Mike
1960 Four Door

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Re: 64 leafsping
Posted by: moomba32 ()
Date: November 30, 2018 06:57PM

You know I thought he was wanting to carry more weight, he didn't say in the original post, interesting thread though.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: 64 leafsping
Posted by: MattNall ()
Date: November 30, 2018 07:00PM

FC's are rated for 1 TON!





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Re: 64 leafsping
Posted by: joelsplace ()
Date: November 30, 2018 07:09PM

3/4 not 1 ton

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Re: 64 leafsping
Posted by: putput ()
Date: November 30, 2018 07:22PM

I use it and haul things and like to play with the tubro plus I have the parts

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Re: FC leafsping
Posted by: MattNall ()
Date: November 30, 2018 07:54PM

Do it!





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Re: 64 leafsping
Posted by: JerryM ()
Date: December 01, 2018 08:20AM

7004doorL Wrote:
-------------------------------------------------------
> I thought FC's are about 50/50 balanced front to
> rear?
It nearly is but not the ideal polar moment - a topic for another discussion.


IMO a front stabilizer and 1-2 degrees of negative camber at the rear would improve things.



Edited 2 time(s). Last edit at 12/01/2018 08:25AM by JerryM.

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Re: 64 leafsping
Posted by: MattNall ()
Date: December 01, 2018 10:31AM

putput Wrote:
-------------------------------------------------------
> I use it and haul things and like to play with the turbo plus I have the parts.

=================================================

SO... are you want to haul more weight..... or handle better...





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Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
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..............................110-PG.................................................Webered-Turbo

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Re: 64 leafsping
Posted by: MattNall ()
Date: December 01, 2018 10:35AM

joelsplace Wrote:
-------------------------------------------------------
> I agree on the stiffer springs and big sway bar
> but the rear needs to be addressed also as Matt
> said.
> Are you sure about that Chet? I've just assumed
> they were different on the FCs but never actually
> compared them. That would be nice to use stock
> components for everything but the leaf. No
> problem to punch holes in a leaf to work with the
> stock mounts.
=======================================================

We have visual proof...Antkoto's restored GB...Factory installed on one side!

As far as 50/50 weight..... that does not make a good handler!





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Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
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..............................110-PG.................................................Webered-Turbo

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Re: 64 leafsping
Posted by: ensys ()
Date: December 01, 2018 08:22PM

Hmmm... At the risk of ruffling more than a few feathers, from where I sit, it seems that on this thread, good information is in short supply. I'm not surprised, as the swing axle has been fairly uncommon in the experience of most folks and is widely misunderstood, and it doesn't help that it has characteristics that most find counter-intuitive.

Unfortunately, there is a reason why there is an old saw that says "a little knowledge can be dangerous". For example, use of a conventional anti-sway bar on a swing axle is highly discouraged because it can amplify the fundamental weakness of the swing axle design and thus can incite disaster..

The transverse spring on the '64 is commonly called a "camber compensator" because it restores zero camber by compensating for the softer springs the Factory installed to reduce the rear roll couple, all to reduce the tendency to tuck the outside wheel. Its sole function is to carry the lost weight capacity in a static situation only. Hence, the single-action of the end points of the spring and its lack of a center connection, so that it will not interact with the axles in a turn.

Part two of this strategy is to stiffen the front roll resistance with stiffer springs and a fatter anti-roll bar.

Others have used this approach to the swing-axle problem, most notably the Porsche 356.

There are two alternatives to this device:

-The Zbar: It does little to carry weight, but is very successful at transfering the vertical force of the dropping inside wheel, to raising the outside wheel, thus eliminating tuck. While reducing the roll couple always helps, this solution does not require using softer springs.

-The double-acting, center pivot transverse spring (or Virtual Zbar): This device, said to have originated with George Follmer, also carries little weight, but is very efficient at transfering, via jointed connection to the axles/trailing arms thru a center pivot connection to the gearbox, inside wheel drop to produce outside wheel lift.

This device has proved to be successful in actual application by a fair number of users.


Both of these devices solve a specific problem well and eliminates the need to run excessive negative camber on the rear, which can induce various handling issues all its own.

Its all about mechanical geometry and the science of dynamics.

I conclude that GM chose not to use the car's camber compensator/soft spring approach on the van because:

1. It cost too much.
2. It was considered unnecessary on a truck that not expected to be handled like a car.

$.02 from the peanut gallery.

Keep 'em flying...

S.J.Szabo

From America's
Automobile Heartland

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Re: FC leafsping
Posted by: joelsplace ()
Date: December 02, 2018 05:30PM

I understand how the different devices work. The typical anti-sway bar does exactly the opposite of the z-bar and transverse leaf.
The question I have is that if you have a sufficiently stiff front anti-sway bar is the weight high enough in the rear to negate the need for a z-bar or transverse leaf?
BTW: I've never seen a sufficiently stiff front FC bar. The Addco bars were better than nothing but woefully flimsy.
The only picture I can remember of an FC in a hard corner showed a combination of not enough roll stiffness in the front and too much in the rear. I'm thinking it's possible that correcting the front roll stiffness might solve the rear.
I also realize that you can get too much overall roll stiffness but I don't think there is much danger of that so far...

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Re: FC leafsping
Posted by: JerryM ()
Date: December 03, 2018 06:22AM

joelsplace Wrote:
-------------------------------------------------------
> I understand how the different devices work. The
> typical anti-sway bar does exactly the opposite of
> the z-bar and transverse leaf.
> The question I have is that if you have a
> sufficiently stiff front anti-sway bar is the
> weight high enough in the rear to negate the need
> for a z-bar or transverse leaf?

It's the spring rate at the rear that is issue. A stiffer front bar is a step in the right direction to a point. The general rule of thumb for road cars is about 25% of the total front spring rate for the stabilizer.Stiffer comes with compromises. In racing there are some good reasons for going stiffer - until the inside front wheel is off the ground and the front track can provide no additional roll moment. That's where de-coupling roll of the rear wheel pair with Z-bars, transverse leaf and other like devices is an advantage.

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Re: FC leafsping
Posted by: joelsplace ()
Date: December 03, 2018 07:20AM

I'm sure there are some different dynamics for an FC's high cg compared to a car.
25% may be a good starting point if you have nothing but the bar stiffness you need is inversely proportional to the vehicles spring rate and also has to be adjusted for how sticky the tires are.
When I had the stock springs in my G-body I had my sway bars adjusted full stiff. I installed stiffer springs and ended up having to go full soft on the bars to get it to stick. My 65 has Crown bars that are worthless. They don't seem to be spring steel.

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Re: 64 leafsping
Posted by: EM-racer ()
Date: December 04, 2018 07:05PM

What I did about the front going down and the back up for my corvan before taking it to Helen Ga. a few years back for the autocross, its a short tight challenging coarse. I figured if the front is limited in down travel the rear would be more stable and not raise as much, I added spacers under the front rubber stops and it worked, they tried to get me to raise the rear tires I tried but could not do it. It handle on the road quit well until you hit a big bump. The corvan is now in Hot Springs Village Ark. sold it to my Grandson without the stops.
Gene Barr
Eustis, Fl.

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