swaybay

[Martin]

Hi I need a front sway bar for my gt40 I am building,is the a univesal bar I can buy?I have inclosed the diamentions
Thanks martin

 

[Mick Ridley]

Hi Martin,

With this chart, you should be able too make your own..

I have never tried it, but it was originaly posted by Eglitom

View attachment SUSPENSIONCALCULATIONScoreccted.xls

 

[Frank Catt]

Firstly, you need to know what you want out of the car. There are two types of "sway" ( anti roll ) bar. Firstly a solid bar that acts as a torsion bar, twisting over its length to give a progressive resistance to roll on the loaded wheel, and a tubular bar that acts as a transfer from the loaded to the unloaded side of the car. In essence most road cars would probably use torsion, whilst race cars would use a tubular transfer bar, but of course it gets much more technical than that the more you get into it, and there will no doubt be a lot of individual advice on this subject, Frank

 

[Seymour Snerd]

I may have forgotten some physics but what I remember says a tube and bar can both be torsion bars, that is, transferring torque as a linear function of the angle of twist, and that therefore hollow and solid do exactly the same thing, that is resisting lean and transferring "weight" from the inside wheel to the outside, but all else being equal (Length, diameter, material, etc.) the tube simply has a somewhat lower rate than the solid bar. To put it another way if the rates are the same, the car has no way of knowing whether it's tubular or solid, aside from weght difference. What part of the physics am I missing?

 

[Martin]

Thanks ,I am building a road GT40,just need a standard bar,cant I just buy one somewhere?

 

[Dimi Terleckyj]

Hi Martin
If you need swaybars check out speedway car suppliers in the USA as they have a great range of universal bars in all sizes and lengths that are splined on both ends and they also have a great selection of different length arms to suit in both steel and alloy which are also splined.

I needed some for my 40's and the cost is good and the service was excellent.

Much cheaper than trying to source here in Oz.

Dimi

 

[Clayton]

Hi Martin
The front looks similar to an RF, give Paul a call at Roaring Forties.
Roaring Forties - Replica GT40s
Open the 'quoting tool' and you'll find a anti roll bar kit, p/n 40-12.

Clayton

 

[flatchat(Chris)]

Do yourself a favour and talk to Kmac or send 'em a sketch of what you want and they will make / supply it with no BS ---probably start with a 22 mm dia bar up front ??
If you're trying to control chassis torsion --you probably don't need an anti roll bar :worried:
K-MAC Tuning hints

 

[John Milmont]

I dont know whats available where you are, but it shouldn't be too hard to find a custom length sway bar for your application. It doesn't matter if its a solid bar or a tube, the car just sees it as a spring. Tubes are more efficient as sway bars though since virtually all of the torsional force is concentrated at the outside of the bar, not the center. So tubes will be lighter for a given rate.

Here in the states, we can just call up Hoerr racing and order a bar to whatever spec we need, as long as it doesn't have custom bends that is.. Genesis Technologies Cockpit Adjustable Race Car Sway Bar Kits
this one is cockpit adjustable, you wont want that unless your a hardcore racer.

You should also know that one does not just go ordering sway bars and installing them. There's some engineering involved to calculate the correct rate so you don't have to guess and check with a ton of different rate bars. The best bet is to ask someone else who has the same car.

Needing or not needing a sway bar is a matter of preference and suspension design. Cars with roll centers much lower than their CG will tend to need sway bars while cars with CG's and roll centers at the same height may not need them. You may also want them if you just want a simple way to tune the handling balance of the car.

The bar you need will be custom built for your car. It will be a straight bar with the ends splined. Any shop that builds real race cars should have a source for these...

 

[EGLITOM]

I may have forgotten some physics but what I remember says a tube and bar can both be torsion bars, that is, transferring torque as a linear function of the angle of twist, and that therefore hollow and solid do exactly the same thing, that is resisting lean and transferring "weight" from the inside wheel to the outside, but all else being equal (Length, diameter, material, etc.) the tube simply has a somewhat lower rate than the solid bar. To put it another way if the rates are the same, the car has no way of knowing whether it's tubular or solid, aside from weght difference. What part of the physics am I missing?

Alan,

thanks for that, saving me writing a similar comment :thumbsup:

All can be calculated with my chart attached above.

For example i´m looking for replacing my solid bar with a tubular bar to save weight. Now that i´m knowing that my swaybar rate is working fine, i just have to find the tubular bar and arm lengts dimensions giving the same rate as my solid bar arrangement. So probably bar will have a bigger diameter and action arms will be shorter ( and made out of aluminium instead of solid steel), thus resulting in the same rate but lower weight ( which partialy is unsprung weight)

I did the quick simulation in my chart:
CURRENT SET UP : 1" solid bar 34" length, 12" Action arms = swaybar wheelrate 108 lbs/inch
ALTERNATIVE SET UP: Tubular bar 1" OD, 0,75" ID; 10" Action arms = swaybar wheelrate 107 lbs/ inch and probably around the 1/3rd of the weight ( with aluminum arms).

If you don´t trust my calculator check and compare here
swaybar.xls



TOM