FV sway-bars

[jpetillo]

hmmm....I need to check my calculator....

I'm coming up with about an 18% difference at 2" bump from horizontal. Perhaps that is still insignificant over the amount of travel.

I started with an effective trailing arm length (c to c) of 4.75" at 2" bump it's effectively 4.375" and 3" it's 3.75" (60% stiffer)

Daryl, for my numbers I was using a trailing arm length of 6.5" (the torsion arm alone has close to a 6.25" radius - just measured it).

Let me correct my previous statement. I incorrectly stated that it was a rate change when I should have said that it was a force change (I just edited it above). I get a 5% vertical force change at 2" and 13% at 3".

For the trailing arm length of 4.75" that you mentioned, I get 10% change at 2" and 30% at 3".

Just to make sure we're on the same page, how do you come up with an effective radius arm at horizontal of 4.75"? John

[Rolling Stone]

Greg,

That car looks awesome! Do you have any more pictures of the suspension setup that you would like to share? Did you see any advantages to this setup? Is that what they used to call a zbar suspension I don't know forgive me as you know that stuff was before my time?

"green" wheels beats PINK anyday

[Steve Davis]

I would also think that the spring pack would be *significantly* NON-LINEAR. It's not like a constant rate, spiral wound spring like we use on the back. The only way I can think of to determine the rate change would be to measure it.

Am I off the wall on this one? IS it, in fact a CONSTANT (or nearly so)??

Steve, FV80

[jpetillo]

Steve, generally torsion springs are pretty linear in torsion. However, our stacks of leafs are hardly a typical torsion spring. My very-non-precision measurements showed it to be relatively linear. John

[Daryl DeArman]

The amazing part is that you can get an FV to handle really well in spite of the suspension system. For dollar spent, FV is the best deal in road racing.

Agreed.

[Daryl DeArman]

Daryl, for my numbers I was using a trailing arm length of 6.5" (the torsion arm alone has close to a 6.25" radius - just measured it).

Just to make sure we're on the same page, how do you come up with an effective radius arm at horizontal of 4.75"? John

Admittedly, I don't have an arm here to measure. I had the information written down from when I was experimenting with front spring rate measurements. This is how I measured:

[Diamond Level Motorsports]

Daryl,

Not sure where you got those dimensions but it is real close to 6" center to center.

[Daryl DeArman]

Can't argue with that....who knows maybe I was using hundredths of a smoot

[FVRacer21]

Can't argue with that....who knows maybe I was using hundredths of a smoot

Your dimensions looks like edge to edge , but center-line to center-line is normal measurement.

Of course we are not twisting a traditional one piece torsion bar either.

Once upon a time, I took a old link pin an welded a nut onto it. Clamped it in and did torque measurements with a degree wheel. Notes are probably long gone....

All things being equal - rate will increase as arm gets to horizontal and as it passes it starts to decrease. Although with soft spring rates, the difference is minor.

Constant or decreasing rates are easier on the driver - increasing rates seem better for the car - especially if ground effects - which I hope we do not have..

ChrisZ

[Daryl DeArman]

Your dimensions looks like edge to edge , but center-line to center-line is normal measurement.

Of course we are not twisting a traditional one piece torsion bar either.

Once upon a time, I took a old link pin an welded a nut onto it. Clamped it in and did torque measurements with a degree wheel. Notes are probably long gone....

All things being equal - rate will increase as arm gets to horizontal and as it passes it starts to decrease. Although with soft spring rates, the difference is minor.

Constant or decreasing rates are easier on the driver - increasing rates seem better for the car - especially if ground effects - which I hope we do not have..

ChrisZ

They would have been center to center.

As the arm goes towards horizontal it's effective length is increasing (softer rate) once it swings through the horizontal it's effective length is decreasing (stiffer rate).

The spring rate is irrelevant as to the effect, it is completely dependent upon the length of the lever arm.