Sway bar question

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08-14-2009, 05:14 PM
jeremiahkellam

Sway bar question

I guess some of you know the problem I was having with sway bar bushings at TWS. We thought we had fixed the problem by shortening the endlinks, and the car felt good in R4. Come to find out, we had actually lost the bushings on both sides (driver and passenger) instead of just the drivers side.

First question - would having one bushing missing on each end of the sway bar (which gives about 3/4" play) be somewhat similiar to running a softer bar??

2nd question - In my best attempt to measure the angles of the existing sway bar, I found that there is 3 degrees of deviation at the ends of the bar. In other words, when the passenger side bar end is parallel to the ground, the drivers side is lower (we're talking maybe 2-3 mm). Is this normal and can it be countered by properly preloading the bar?? Or do I need a new bar??

Thanks
08-14-2009, 05:30 PM
Wirtz

I have not really played with running endlinks loose in road racing except in the heavy rain and when I have too much time on my hands... Used to play with the links alot in autocross. Running extra slack in them would in effect help soften the car, at least on initial turn in. I would think once the car rolled and put load into both links, the roll rate is basically the same. I mainly remember using end link free play as a way to tune in for slaloms.

I would not think a few millimeters difference between sides is to be unexpected. Set your shim stacks for the endlinks with the car on the ground if possible, as you mention, you can get the left and right side balanced better.

Jeff
08-14-2009, 05:34 PM
David Love AI27

Quote:

Originally Posted by Wirtz

I have not really played with running endlinks loose in road racing except in the heavy rain and when I have too much time on my hands... Used to play with the links alot in autocross. Running extra slack in them would in effect help soften the car, at least on initial turn in. I would think once the car rolled and put load into both links, the roll rate is basically the same. I mainly remember using end link free play as a way to tune in for slaloms.

I would not think a few millimeters difference between sides is to be unexpected. Set your shim stacks for the endlinks with the car on the ground if possible, as you mention, you can get the left and right side balanced better.

Jeff

What did he say???? loose links??... shimmin stacks???
08-14-2009, 05:46 PM
jeffburch

...
08-14-2009, 06:09 PM
jeremiahkellam

Thanks Jeff (W)

One more question - is the torsion rate of sway bars linear or progressive??
08-14-2009, 06:19 PM
Rsmith350

Quote:

Originally Posted by jeremiahkellam

Thanks Jeff (W)

One more question - is the torsion rate of sway bars linear or progressive??

I would think it would be linear, wouldn't the bar have to be varying diameters and and thickness across the bar to be progressive?
08-14-2009, 07:15 PM
jeremiahkellam

I would think it would be progressive, but only fractionally. Think about anything you twist will eventually become harder to twist...

Ayway, I found this equation for sway bar torsional strength, first one to give correct answer gets a $1000

R = 5e6 x D^4 / (0.4244 x A^2 x L + 0.2264 B^3)

R = Torsion rate of bar
D = Bar diameter
A = Effective length of lever arm
L = Length of bar
B = Length of lever arm

note: I don't have any way of confirming answer, so you're screwed...
08-14-2009, 07:38 PM
edrock96GT

I would agree on it being progressive. You could twist it a couple inches or so by hand but it would take more force to twist it much more.

Also, I don't think the 3 degrees of offset will be noticable as long as you don't preload the endlinks.
08-14-2009, 07:50 PM
GlennCMC70

Quote:

Originally Posted by edrock96GT

I would agree on it being progressive. You could twist it a couple inches or so by hand but it would take more force to twist it much more.

Also, I don't think the 3 degrees of offset will be noticable as long as you don't preload the endlinks.

your reasoning for it being progresive is not sound.
a 700lb linear spring will require 700lbs to compress 1", and 1400lbs to compress 2". its still a linear spring even though it requires more force to for each inch you compress it.
i agree the swaybar is likely progressive but not much. its likely due to the angle of the lever changing as the force is applied, but the direction of the force doesnt. thus as the angle of the lever changes the distance gets shorter between the point of force to point of rotation. a shorter lever requires more force for the same given deflection.

i'm sure RP will chime in and point out my/our errors.
08-14-2009, 08:35 PM
David Love AI27

Quote:

Originally Posted by jeremiahkellam

I would think it would be progressive, but only fractionally. Think about anything you twist will eventually become harder to twist...

Ayway, I found this equation for sway bar torsional strength, first one to give correct answer gets a $1000

R = 5e6 x D^4 / (0.4244 x A^2 x L + 0.2264 B^3)

R = Torsion rate of bar
D = Bar diameter
A = Effective length of lever arm
L = Length of bar
B = Length of lever arm

note: I don't have any way of confirming answer, so you're screwed...

I think you made that shit up.... RICHARD?!?!?!?
08-14-2009, 08:43 PM
Hood

Re: Sway bar question

Quote:

Originally Posted by jeremiahkellam

2nd question - In my best attempt to measure the angles of the existing sway bar, I found that there is 3 degrees of deviation at the ends of the bar. In other words, when the passenger side bar end is parallel to the ground, the drivers side is lower (we're talking maybe 2-3 mm). Is this normal and can it be countered by properly preloading the bar?? Or do I need a new bar??

First of all 2-3 mm is negligible considering ALL the components in our cars are compromises to make the series affordable (no F1 stuff here). Wirtz addressed the preload issue (use shims to make up the difference but be sure that this is measured with the drivers weight in the seat) and as far as linear vs. progressive, linear would be correct answer (think about it like a torsion bar type suspension). Also, in the equation, the assumption is made that the bar is solid (which is probably correct for the Ford bar... GM bar that I use is hollow) otherwise a wall thickness comes into the mix.
08-14-2009, 11:05 PM
edrock96GT

Quote:

Originally Posted by GlennCMC70

Quote:

Originally Posted by edrock96GT

I would agree on it being progressive. You could twist it a couple inches or so by hand but it would take more force to twist it much more.

Also, I don't think the 3 degrees of offset will be noticable as long as you don't preload the endlinks.

your reasoning for it being progresive is not sound.
a 700lb linear spring will require 700lbs to compress 1", and 1400lbs to compress 2". its still a linear spring even though it requires more force to for each inch you compress it.
i agree the swaybar is likely progressive but not much. its likely due to the angle of the lever changing as the force is applied, but the direction of the force doesnt. thus as the angle of the lever changes the distance gets shorter between the point of force to point of rotation. a shorter lever requires more force for the same given deflection.

i'm sure RP will chime in and point out my/our errors.

You are right. that is the theory I had in mind since it takes it takes a little force to move partway but more to move it further. From what I could find, that is the definition of linear, being that it required a "linear" application of more force to move it further.

Googling Hooke's law will explain it in detail.

F.Y.I...if you google "sway bar", you're going to get more than just hits about car parts :lol:
08-14-2009, 11:52 PM
David Love AI27

I haven't checked but I guessing it is almost a swinger bar... not swingin' just swayin'???
08-15-2009, 01:57 AM
Rsmith350

Re: Sway bar question

Quote:

Originally Posted by Hood

Quote:

Originally Posted by jeremiahkellam

2nd question - In my best attempt to measure the angles of the existing sway bar, I found that there is 3 degrees of deviation at the ends of the bar. In other words, when the passenger side bar end is parallel to the ground, the drivers side is lower (we're talking maybe 2-3 mm). Is this normal and can it be countered by properly preloading the bar?? Or do I need a new bar??

First of all 2-3 mm is negligible considering ALL the components in our cars are compromises to make the series affordable (no F1 stuff here). Wirtz addressed the preload issue (use shims to make up the difference but be sure that this is measured with the drivers weight in the seat) and as far as linear vs. progressive, linear would be correct answer (think about it like a torsion bar type suspension). Also, in the equation, the assumption is made that the bar is solid (which is probably correct for the Ford bar... GM bar that I use is hollow) otherwise a wall thickness comes into the mix.

That's exactly what I was thinkin :)
08-15-2009, 08:25 AM
AI#97

F'n Nerds.... :lol:
08-15-2009, 05:51 PM
Hood

Quote:

Originally Posted by AI#97

F'n Nerds.... :lol:

Just because you don't understand something is no reason to HATE! :lol:
08-15-2009, 07:32 PM
David Love AI27

its a friggin sway bar... bigger, tighter.. smaller, looser
08-15-2009, 08:41 PM
GlennCMC70

Quote:

Originally Posted by David Love AI27

its a friggin sway bar... bigger, tighter.. smaller, looser

thats for the front.
can you do the one for the rear too? :P
08-15-2009, 10:29 PM
AI#97

Quote:

Originally Posted by GlennCMC70

Quote:

Originally Posted by David Love AI27

its a friggin sway bar... bigger, tighter.. smaller, looser

thats for the front.
can you do the one for the rear too? :P

It's opposite. Easy!

Now if you can explain how to tune the suspension on a front wheel drive car that would be great! ;)
08-15-2009, 10:44 PM
GlennCMC70

Quote:

Originally Posted by AI#97

Quote:

Originally Posted by GlennCMC70

Quote:

Originally Posted by David Love AI27

its a friggin sway bar... bigger, tighter.. smaller, looser

thats for the front.
can you do the one for the rear too? :P

It's opposite. Easy!

Now if you can explain how to tune the suspension on a front wheel drive car that would be great! ;)

thanks David Love..... :roll:
08-15-2009, 11:00 PM
edrock96GT

Quote:

Originally Posted by AI#97

Quote:

Originally Posted by GlennCMC70

Quote:

Originally Posted by David Love AI27

its a friggin sway bar... bigger, tighter.. smaller, looser

thats for the front.
can you do the one for the rear too? :P

It's opposite. Easy!

Now if you can explain how to tune the suspension on a front wheel drive car that would be great! ;)

Front wheel drives like it stiffer in the rear...a little softer up front.

That's how they roll.

Here's proof: http://www.houseofthud.com/cartech/swaybars.htm
10-05-2009, 03:10 PM
jeremiahkellam

If any of you SN95 owners are working on your cars anytime soon, can you give me a measurement from hole to hole on the front sway bar?? Or if you have an extra laying around the shop.

Thanks