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attn Maurizio (I think you have done this already).


I would like to build a tubular front sway bar for my 3.0 milano.
I would like my bar to have a similar spring rate to the 27mm or 28mm solid bars that are offered by some of the vendors.

The options I have found (at Speedway Engineering) are the following:

1in OD with .095in or .120in wall thickness

or

1.25in OD with .095, .120, .188, or .250 inch walls

The site I am looking at has spring rates for these bars with various arm lengths (rated at 5 degrees of twist on the bar). Therefore, I could match them if I knew the specs on the bars that I am trying to match. (again, 27mm or 28mm solid)

I also dont know, offhand, what the arm length or bar length is on milano/75 front sway bars. Can anybody tell me? I cant measure mine right now.

I am guessing that the 1.25in OD bar with .095in wall will be the one.

A quick check is looking at the moments of innertia of the round tube.

For a solid tube Iz = 0.25 * pi * R^4
For a hollow tube Iz = 0.25 * pi * (R^4 - r^4)

R= OD/2
r = ID/2

So for your plan 14^4 = ((1.25*25.4)^4 - (r^4))
al dimensions in mm's

Thanks Maurizio,

I have calculated the Iz for the closest options:

Baseline solid bars
27mm, Iz = 26,087
28mm, Iz = 30,172

hollow bars
1.25in w/ .095in wall, Iz = 24,103
1.25in w/ .120in wall, Iz = 28,634
1.25in w/ .188in wall, Iz = 37,961

It seems that the .120in wall will put me in between the 27mm and 28mm solid bars.

Maurizio,
Do you recall what your length was on your bars? I measured the stock bar on my Platinum and it seemed to be about 34in (86cm).
The bar is of the bent rod type. I think I might be able to have one that is slightly shorter. A shorter bar might increase tire clearance. Does anyone know if this is even an issue?

I plan to bend the arms myself in a press. Will it be necessary to have the arms heat treated after the bending? Or is that past the point of diminishing returns?

Thanks for the help

Zambon,
i posted a question regarding this a few weeks ago.
interesting to see it come up again so soon!
i recently bought a hollow bar made by schroeder off ebay.
it is gun drilled ( not sure what this exactly means) but the the hollow bar reportedly has the same stiffness as the equivalent solid bar!
i cant report on how it goes yet as i havn't received it yet.
have a look on ebay as there is a bit of that stuff floating around.

keep me posted on how you go with the set up as im interested to compare notes when i get mine fitted.
hope this helps.

ben

here is the link for schroeders web site.

hope this is of use.

ben

here is the link for schroeders web site.

http://www.schroedersteering.com/HomePage.html

hope this is of use.

ben

on my AR bar iI did weld the knives. So maximum clearance to the wheels, I don't have exact number at hand. But the bar just fits the chassis.

I wouldn't bend the bar, first the tube will collaps and the original bars are probably hot pressed into shape.

Ben,
After I posted this, I saw your thread with the nearly identical topic. Thanks for the link. Keep us posted on your project.

M,
I am talking about bending the arms only, not the bar it self. I am wanting to use a splined bar, eliminating welds from the setup. I could have some arms bent to suit me and I could change the bar if I didnt end up happy with my rate.

Here is a link to a site selling arms of the type I am describing:
http://www.stockcarproducts.com/susp22.htm

Stock car guys swear by splined sway bars. They claim that they are more consistent than welded arms. Further, I have been told that drilled bars are more consistant still compared to solid splined bars. This is due to the heat treatment acting on the inside of the hollow bar.
Most likely this is all way beyond what I have the ability to notice while behind the wheel...

I am talking about bending the arms only, not the bar it self. I am wanting to use a splined bar, eliminating welds from the setup. I could have some arms bent to suit me and I could change the bar if I didnt end up happy with my rate.

OK misread, the arms on my bar are cold bend, no heat treatment afterwards.

Not interfering with the building of the bars, I'd just like to remind the IMHO most sensible way to stiffen the anti roll bars.

Move the attachment point on the control arm outwards.

In the original setup where the attacment point is 190 mm from the inner axle and the length of the control arm is 315 mm, only 36% of the AR bar stinness actually reaches the wheel.

Moving the attachment 10 mm outwards increases the effective stiffness by 11%. A 3 cm movement by 34%. 5 cm 60%. I'm sure you get the point by now.

The effect is in practice even bigger as the flexing of the bushes and fastenings are relavively smaller.


Else, I think hollow bars is the way to go for weight/stiffness ratio. I'm considering making one myself.

a nice one. Just need a new attachment point in your A-arm.
Micke note: tubular a-arm needs several mounting points for ar-bar

I did also use 2 rubbers on each side to mount the AR-bar onto the chassis (under the radiator).
A: To spread the load to the chassis more.
B: To increase the stiffness in the chain.
The round part of the bar is pre-loaded against the the body at the top. (I grease the ar/body contact area reguarly). A sleeve bearing would be better.

Been there - done that.

Drill. Thread. Done.
The cast A-arm is so huge drilling a hole in it is not a problem.

No problems with wheel clearance?

Nope.