Designing sway bar - very upset!

[Quickshoe]

Greg,

So that "plate" section on its' edge is the only factory roll resistance at the rear? This blue bar bolts to that plate and adds to its' rigidity? Are there clearance issues that would prevent a more common bar design? Why not add "lever arms" on this bar that attach directly to each trailing arm?

[Greg Amy]

So that "plate" section on its' edge is the only factory roll resistance at the rear?[/b]

Do you mean the vertical part of the beam? If so, yes. Those "plates" that attach the two trailing arms together are both structural items to keep the arms in place *and* torsion bars to resist twist. Anything you can do to increase the "torsion" of those plates will increase roll resistance in the same manner as an "anti-swaybar".

This blue bar bolts to that plate and adds to its' rigidity?[/b]

Don't get me wrong: yes it does. But, since it's not acting co-axially to the axis of bending of the trailing arm assembly, it's acting more in tension than in torsion (though, you MEs will argue with me that a torsion bar does, too. I hear ya).

Are there clearance issues that would prevent a more common bar design? Why not add "lever arms" on this bar that attach directly to each trailing arm?[/b]

Haven't been under the Professor's car in a while - most of my experience was in Rabbits - so I'll look next time I'm there. What I was basically trying to indicate is not that this bar is ineffective - it is - but it's not *really* doing the same thing that a torsion-based anti-swaybar does. This bar is acting more as a stiffener.

Another way you could re-create this action - as a "for example" - would be to use flat plate and make those triangular tabs one big plate across. You could then see that as the beam is twisted the plate would be "stretched". Then you could add a vertical angle on the front edge to increase its torsion, and you'd be effectively doing the same thing.

The Professor and I have discussed this, but given the whole rear suspension is one big anti-swaybar design, and rear swaybar are free, I think there's a LOT of clever things you can do with this that are well within the letter of the rules. However, I don't see the rear suspension design of this car as the limiting factor; you'd get a lot more performance out of trying to make the Mac front end work better...

[Knestis]

We added the Shine bar, in addition to the stock "GTI" bar that I think the base Golfs didn't have, and THEN added a separate more conventional bar that hangs under the beam. The latter is made of Speedway Eng. NASCAR parts, with a 1.25 OD x.25 wall tube and splined arms.

Cameron Conover has what he calls the "Happy Bar" modification that does what Greg describes, plating some portion of the open side of the transverse beam. He's experimented with MkII's, varying the length of the plate to tailor the "size" of the virtual rear bar that creates. I don't know but I think that approach is more efficient, since torsional rigidity is so influenced by diameter.

Left to start over, I would indeed invoke the "sway bars are free" clause and modify the stock beam heavily, trying to add less weight than our ERBB* has caused. I've even sketched on napkins what I might do if I could build one from scratch.

K

Do your part to help fight Embarrassing Rear Bar Build-up.

[Grumpy]

I am considering hollow sway bars for my car to lose weight. I have removed every legal item, and am still 108 pounds over. ... The weight savings from two one inch solid bars would be substantial.

Chuck
S.E. Region
#34 ITA
[/b]

If I read this correct, you have done everything legal to reduce you weight, and now you are looking for "other opportunites?

Just askin'

[RacerBowie]

If I read this correct, you have done everything legal to reduce you weight, and now you are looking for "other opportunites?

Just askin'
[/b]

It sounded more to me like he has unbolted every legal item to lose weight, and now is starting to think about replacing components with lighter but still legal components. Perfectly legal and WELL within the spirit of IT!

[Grumpy]

Thank you.

[Quickshoe]

Thanks Greg, I am now up to speed.

Effectively this Shine bar isn't twisting along its' centerline but trying to push one end forward as it twists (co-axially) and resisting an increase in length (tension).

Do the racers that use this bar have issues with the fasteners bending/breaking?

I like Kirk's supplemental tubular bar idea.

How "FREE" are swaybars in IT? Can they be of the blade type lever arms common in formula cars and cockpit adjustable?

[lateapex911]

Thanks Greg, I am now up to speed.

Effectively this Sine bar isn't twisting along its' centerline but trying to push one end forward as it twists (co-axially) and resisting an increase in length (tension).

Do the racers that use this bar have issues with the fasteners bending/breaking?

I like Kirk's supplemental tubular bar idea.

How "FREE" are swaybars in IT? Can they be of the blade type lever arms common in formula cars...[/b]

yes, they can....

and cockpit adjustable? [/b]

but no, not that.

[Conover]

I can't for the life of me find my C. Smith "to Win" books, four years and two moves after I last saw them! This is getting VERY serious...

Can someone out there help me out with the formula for tubular anti-roll bar rates, while I decide where else I might look - or if I need to order new copies.

Thanks

K
[/b]

Dood, they are all on the shelf at my shop, haha, I reminded you that they were here last time you were down here and you said something to the effect of "Good, you'll probably use them more than I will."

You want me to ship them to you?

[Greg Amy]

Dood, they are all on the shelf at my shop, haha, I reminded you that they were here last time you were down...[/b]

DOOD, welcome to 2008...! (check the date of Kirk's post in your quote above...exhuming old dead threads has its own unique dangers...)

;)

[Conover]

Haha, I knew it was sorta old, but I didn't realize it was THAT old. I just thought that Kirk was forgetting his:

[Knestis]

I found them long after that post and then dropped them at CMS World HQ...

K

[timo944]

Gents,

Another related question: What is the guideline for the ratio of spring rate to sway bar rate? I am undergoing the same exercise and don't eally know what spring rate to design the sway bar to.

And I guess as spring ate goes up, the ratio goes down???

[Fastfred92]

kirk,,

i found it.......

FWD=(rear bar as big as you can get it)/more rear spring