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Racebrewer
01-05-2011, 01:48 PM
Hi,

I was thinking about adding a rear anti-sway bar to one of my cars and rolling my own since it is a very simple design (H-beam rear suspension so its merely a straight bar that connects both sides).

Looking through what was commercially available, I found an aftermarket rear bar made of "Aircraft aluminum" which I'm assuming is 6061.

Its a 1" diameter solid bar so I was wondering what the equivalent steel bar would be?

I was also trying to figure out why someone would use aluminum in what is essentially a short torsion bar? I realize that it might be slightly lighter than the same strength steel bar, but is aluminum a good material for that application? I usually see 4130 or 4140 steel being used.

I'm going to ask the manufacturer, but I'd like to ask the question with some background knowledge in hand.

Thanks for any input,
John

lbhsbz
01-05-2011, 02:39 PM
I sway bar is a spring. I can't ever recall seeing any "spring aluminum" in existance. I suppose the aluminum bar could work, but it would have to be substantial enough as to allow absolutely no twist whatsoever.

Go with steel, either hollow chromoly or a thinner solid bar...aluminum I don't think has the memory necessary to act as a torsion bar.

boslab
01-05-2011, 03:02 PM
what has the highest modulus of elasticty [E] aka Youngs modulus
regards
mark

garagemark
01-05-2011, 03:40 PM
I thought most aircraft aluminum was alloyed 70 series.

dockrat
01-05-2011, 03:47 PM
I thought most aircraft aluminum was alloyed 70 series.

Yeah...me too

Toolguy
01-05-2011, 04:21 PM
I was a toolmaker at Boeing and Cessna for a few years at different times. "Aircraft Aluminum" is a highly overused generic term. The most common alloys used in the manufacture of aircraft are 6061, 2024 and 7075. There are several others used for specific properties. These alloys are usually tempered to T4, T5, or T6, or some variation like T6511. Some of the sheet stock is in an 0 condition which is dead soft so it can be formed without cracking. 6061 is the lowest strength of the common "aircraft alloys" but still pretty good material. 2024 is stronger, then 7075 has the highest tensile strength of the three, assuming equal tempers. 7078 is higher strength than 7075. The higher strength materials generally corrode easier than the lower strength ones. With dozens of alloys available, there are many caveats and exceptions to the general rules.

Willy
01-05-2011, 04:38 PM
What's aircraft aluminum? Is it like billet?:D
Common alloys used for aircraft are 6061, 7075, 2024.

The most common material used automotive spring material is high carbon steel oil quenched and tempered. 1075-1095 is both readily available and low cost. If you've got lots of money titanium has a better fatigue life but is actually not a cost effective alternative. There are of course other more expensive spring materials but unless you are contemplating a F-1 application I doubt you'll notice the difference unless you look in your wallet.:)

Guess why you don't see a whole lot of aluminum springs.
Fatigue life.

Edited to add: Toolguy types faster then me!

topct
01-05-2011, 05:42 PM
I think what the op is talking about is a panhard bar or track bar. It is not caused to twist like a sway bar it is put into tension or compression and is used to control roll.

The wrench you see them using through the rear window of a stock car is moving one end up or down in relationship to the body of the car. The other end is attached to the rear axle housing. The amount of angle determines the amount of body roll at the rear of the car.

http://en.wikipedia.org/wiki/Panhard_rod

6061 would be a good alloy for that application. It can be welded. And it would also be less un-sprung weight.

Willy
01-05-2011, 08:54 PM
I think what the op is talking about is a panhard bar or track bar. It is not caused to twist like a sway bar it is put into tension or compression and is used to control roll.

The wrench you see them using through the rear window of a stock car is moving one end up or down in relationship to the body of the car. The other end is attached to the rear axle housing. The amount of angle determines the amount of body roll at the rear of the car.

http://en.wikipedia.org/wiki/Panhard_rod

6061 would be a good alloy for that application. It can be welded. And it would also be less un-sprung weight.

I don't believe he is talking about a panhard bar, as an H-beam rear suspension, like a leaf spring rear suspension, has no need for a panhard bar.

bob ward
01-05-2011, 09:20 PM
.....aftermarket rear bar made of "Aircraft aluminum".....
John

Talking about marketing hype which we weren't, on the wasteland that is 2am cable TV, I've recently seen ads for exercise equipment made from 'professional quality steel tube', a glass ornament made from 'optical quality' glass and some other gizmo made from 'plumbers quality' copper. All good for a giggle.

Anyway, back to suspension components.

jep24601
01-05-2011, 10:41 PM
No grade of Aluminum is really appropriate for a real torsion bar because of it's fatigue properties. The stress would have to be limited to such an extent that the application in aluminum would be uneconomic.

tdmidget
01-05-2011, 10:49 PM
So, what is an "H beam suspension"?

Joel R
01-05-2011, 10:55 PM
Go with steel. Here's a selection of the reasons:

They'll be similar in weight: steel is roughly 3 times heavier than aluminum, and roughly 3 times stiffer. If you want to shave weight, make the largest diameter bar you can, with a minimum wall thickness that will withstand unexpected impacts or events. Torsional stiffness varies by an exponent of 4 with diameter.
Steel has an 'endurance limit', a stress value at which a near infinite (10^6 normally) number of cycles can occur without failure, assuming an initially flawless bar. Aluminum alloys do not possess this property... every cycle reduces the strength of the aluminum. Jep24601 touched on this already. Expect a lot of cycles. Since the bar will be designed for stiffness, stresses may be low anyways, however, better safe than sorry here.
The harder steel bar will take impacts from rocks, cones, or whatever else you run over better.

Willy
01-05-2011, 11:12 PM
So, what is an "H beam suspension"?

This will explain it in better detail than I can.:)

http://uk.ask.com/wiki/Twist-beam_rear_suspension

tdmidget
01-05-2011, 11:21 PM
Since the link implies that the proper name is "twist beam" and there is nothing there that remotely suggests the letter "H", why call it that? The only part subject to torsional force is the large square box section. Any thing between that and the stub axle centerline will be subjected to tension, as the distance between the longitudinal members will increase when one moves. The large square box performs exactly as the torsion bars on the old VW Beetle, which at least was adjustable.

Racebrewer
01-05-2011, 11:58 PM
Hi Guys,

Thanks for the input. It confirms what I was thinking. The link to a 'H' beam explanation was great except it didn't show the two coil springs (view from above):

A A
I I
I I
I___________I
I I
I I
__I0 0I__

"A" is where the H beam connects to the chassis
"0" is where the coil springs go between the H beam and the chassis as well as where the stub axles/wheels/tires mount. As the car corners and leans over it causes the center of the H to twist. Anything that gets added to the center piece stiffens the H beam and acts like a rear sway bar resisting the twist of the H beam stiffening the rear suspension.

I was just surprised to see the torsion bar made of aluminum.

Thanks for the input. Any other thoughts?
John

topct
01-06-2011, 09:06 AM
Well after my first blunder :o, I almost hesitate to add anything further, but I wonder if the factory might have offered a "towing" package that included a bar.

If it did, a trip to the wrecking yard might yield one.

Racebrewer
01-06-2011, 10:04 AM
Hi Gene,

Actually that is a great suggestion and I picked up a larger front bar by "mixing and matching" that way. No rear bars that I can find even though there are mounting holes already in place.

So I'm just working on the rear bar now.

I'm glad to see that the use of aluminum by this aftermarket company left everyone scratching their heads, as I was....

John

topct
01-06-2011, 10:35 AM
I might try to find out if they used the same part on another model. Does the factory list one? If so what other cars might they have used it on? Sometimes part listings will show what other models the same part fits on.

tdmidget
01-06-2011, 10:37 AM
Where does this bar fit into the suspension shown in Willy's link?

vpt
01-06-2011, 11:46 AM
I would suggest chromoly tubing with adjustable arms. This next summer I will be building one for the rear of my excursion.

http://www.clubcobra.com/photopost/data/500/sway_bar.jpg

lazlo
01-06-2011, 11:58 AM
Since the link implies that the proper name is "twist beam" and there is nothing there that remotely suggests the letter "H", why call it that?

"The twist-beam rear suspension, also known as torsion-beam axle is a type of automobile suspension based on a large H or C shaped member. The front of the H attaches to the body via rubber bushings, and the rear of the H carries each stub-axle assembly, on each side of the car. The cross beam of the H holds the two trailing arms together, and provides the roll stiffness of the suspension, by twisting as the two trailing arms move vertically, relative to each other."

Racebrewer
01-06-2011, 12:19 PM
With the H-Beam rear suspension, any additional torsion bars are usually bolted to the twist or cross-beam to stiffen it and resist twist.

They are bolted to the - section of the H. It makes for a very simple modification as no bending is needed. The add-on torsion bar is simply a straight bar which has bolt holes on each end.

John

JRouche
01-06-2011, 12:58 PM
Hi,

I was thinking about adding a rear anti-sway bar to one of my cars and rolling my own since it is a very simple design (H-beam rear suspension so its merely a straight bar that connects both sides).


I realize that it might be slightly lighter than the same strength steel bar, but is aluminum a good material for that application? I usually see 4130 or 4140 steel being used.

Thanks for any input,
John

I used steel. Never saw an aluminum torsion bar personally. JR

Here is my set-up..

Rear sway bar...
http://img.photobucket.com/albums/v366/Jrouche/Steves%20Nova/Rear%20rebuild/Final%20pics/a.jpg

http://img.photobucket.com/albums/v366/Jrouche/Steves%20Nova/Rear%20rebuild/Final%20pics/c.jpg

Front sway bar..
http://img.photobucket.com/albums/v366/Jrouche/Steves%20Nova/Front%20rebuild/zn.jpg

tdmidget
01-06-2011, 03:29 PM
Nice workmanship Jroushe. I don't agree with the design but obvious pride in ones work.
I still don't understand the OP's question. If the beam or Box is mounted to the chassis, then any transverse member connecting the longitudinal members between the box and stub axles will be in tension when one of them moves. That might make aluminum useable but the under car environment also needs durabililty so steel would be my choice.
BTW what is the vehicle?

Willy
01-06-2011, 03:39 PM
JRouche, I don't want this to sound kinky, but....nice rear end buddy.:D

Very clean and professional fabrication and rear suspension.
Looks like a very nice car, any chances of an overall pic of the rest of the car?

Dave P.
01-06-2011, 05:31 PM
John,
Keep in mind that the compliance in the bushings that connect to the
frame may prevent any gain in roll stiffness if you just stiffen the
H frame.
I'd suggest the typical anti roll bar connecting as outboard toward
the axle ends as possible and to a solid frame member if available.
Are you doing this to try to change the overall roll stiffness of
the chassis or the front/rear roll couple?
(Edit, as in reducing understeer?)
And as for the original question....aluminum....I don't think so.
Dave P.

topct
01-06-2011, 07:38 PM
Not an aluminum sway bar. But a Watts link that could be made out of straight pieces of 6061.

http://www.chevycruzess.org/forums/showthread.php?87-Watts-link-torsion-beam-rear-suspension-video

vpt
01-06-2011, 07:38 PM
How about an in cockpit adjustable on the fly sway bar?

http://2.bp.blogspot.com/_opiCXWcCWoM/TBa15KNdLLI/AAAAAAAAA1A/ixx4CS_wUKw/s1600/sway1.png

JRouche
01-07-2011, 12:00 AM
JRouche, I don't want this to sound kinky, but....nice rear end buddy.:D

Very clean and professional fabrication and rear suspension.
Looks like a very nice car, any chances of an overall pic of the rest of the car?


Thanks. Still a MAJOR work in progress.. JR

http://img.photobucket.com/albums/v366/Jrouche/Steves%20Nova/mugu%20pics/a.jpg

http://img.photobucket.com/albums/v366/Jrouche/Steves%20Nova/mugu%20pics/k.jpg

CompositeEngr
01-07-2011, 12:23 AM
Most aluminum alloys will turn brittle and break if used as a spring. Steel is where its at.

Willy
01-07-2011, 01:36 AM
Thanks. Still a MAJOR work in progress.. JR


Thanks for posting the photos JR.
Not wanting to draw attention away from the OP, sorry my fault.

But thanks again, it's nice to see someone take pride in every facet of his project.....it definitely shows. A very clean example of a modern Hot Rod.
Not gaudy, very functional, clean and well engineered.
Hey, and that's from a Mopar guy.;)

JRouche
01-07-2011, 02:14 AM
Thanks for posting the photos JR.
Not wanting to draw attention away from the OP, sorry my fault.

Not gaudy, very functional, clean and well engineered.
Hey, and that's from a Mopar guy.;)

Hahaha!! And yes, Im solly John for the side track on your thread, not my intention.

Mopar! Hell yes, I love them ALL. I just cant afford them. They are pricey down here. Mopar is a BIG part of automobile history here in the states. Many car guys will have a sweet spot for Mopar cars, I do anyway. Give me an Elephant and Im a happy man. JR

Racebrewer
01-09-2011, 01:07 AM
Hi Guys,

Beautiful suspension photos!

JR, sidetrack all you want! Nice work! What are your sway bar arms made of and do you have any issues with the clamps slipping?

And, the adjustable blade sway bars are really nice. I have another sway bar project and I may use that design. Any more photos?

The current project is a 2011 Mazda 2. It was a joint design between Ford (their Fiesta)and Mazda. 'Identical' cars with only 4 identical parts. I have a larger front bar from a Fiesta that I'm going to install along with an H&R coil over suspension and need a rear bar to balance the front.

A good explanation of this type of suspension can be found if you Google 'Edmunds Ford Fiesta Suspension Walkaround'. Sorry, but I couldn't link it.(????????????)

Mentally, I find it hard to contemplate a 'flexible' suspension member, but that is what the cross member in a 'H' beam rear suspension is. Anything you do to stiffen it increases roll resistance and stiffens the rear. Thus increasing oversteer/decreasing understeer. I think that there is an error in that article in that it talks about stiffening the H beam with a 'U' shaped traditional sway bar. With the 'H' beam you merely need to stiffen the cross beam.

Thanks for all of the input.

Maybe we need a car machinist/fabricator forum?

John

vpt
01-09-2011, 11:14 AM
Hi Guys,

Maybe we need a car machinist/fabricator forum?

John


That would be neat but I don't think there are that many car machinist/fab guys here.

Where do you race? Road or auto-x?

Racebrewer
01-09-2011, 04:28 PM
There may be more racers/builders/fabricators on here than you know.<LOL>

I recognize a lot of names from other racing forums.

Personally, I should have one of those "Still Plays With Cars" T-shirts. Started auto-X with a 240Z in 1971. Roadraced enduro karts for 20 years at NHIS (both tracks), Watkins Glen, Pocono, and Summit Point until neuropathy from diabetes caused me to lose feeling in my feet. Had a brake failure at the uphill turn at NHIS and didn't realize it for a couple nanoseconds, so I decided it was time to pack it in.

Still blueprint and modify 2-stroke kart motors and do post-race tech inspection for a karting organization(WKA) traveling from Daytona to Road America. I also play around with our family cars including the Mazda 2 and an Integra Type R. Suspension mostly on the first and suspension/engine on the latter. Just picked up a cheap pipe bender so I can bend up simple sway bars. The photo of that adjustable blade sway bar has me thinking, thanks for posting it.

John

vpt
01-09-2011, 04:40 PM
Sounds like allot ofgood times behind a wheel!

Since you have a type R you might be one of the few here that would apreciate the crx I built from the round up.

http://img38.imageshack.us/img38/2048/centercaps011s.jpg

http://img31.imageshack.us/img31/4747/wheel034.jpg

http://www.youtube.com/watch?v=Ikbl60T5xZk&feature=player_embedded

JRouche
01-10-2011, 01:14 PM
JR, sidetrack all you want! Nice work! What are your sway bar arms made of and do you have any issues with the clamps slipping?

John

Thanks. No slippage, the bars are splined. The arms are aluminum. JR

http://www.1speedway.com/Swaybars.htm