Modifying a sway bar?

[mrn2obelvedere]

Hello all,

Just curious. I would like to add some adjustability into my rear sway bar. What if I cut the standard bushing style ends off of the bar and then welded a tube over the end? I know this would change the properties of the material, particularly in the region of the weld, but I don't think it would really affect the material properties throughout the whole bar. Any thoughts on this?

[Lowend]

What kind of an application are you working with? There are already some known solutions out there

[LowBuckX]

I made these bar ends (BTW these started as 2" round stock turned milled and drilled)

Cut off stock smashed eyelets drilled the solid 7/8 bar and pressed then welded my ends on


I didnt like the stamped uchannel mount with the muffler clamp that was supplied so I made some solid Aluminum blocks and used 1/2 u bolts.


Then I didnt want heims top and bottom to eliminate any sound transfer to the chassis via solid connections so i made these links.

[John Wright]

I know this would change the properties of the material, particularly in the region of the weld,

This depends on what material was used to make the bar.

David Pozzi has made several adjustable rear bars by starting with an off the shelf bar and cut the ends off and welded his own with several holes for adjusting the rate. Search for "adjustable sway bar"....you'll propbably run across several threads with pics of his work. Fartherest hole out towards the end of the bar was the softest and the rate got stiffer as you moved inward.

Longer the lever = softer the rate

[Norm Peterson]

Jon Aadland came up with a slightly different solution a few years back. I'll just say that the range of stiffness adjustment probably is 2:1 or thereabouts and leave it at that.

http://www.frrax.com/rrforum/index.php?&showtopic=3730



Norm

[John Wright]

David Pozzi's modified swaybar ends....

[mrn2obelvedere]

Ok guys how about this:

Will it be worth it to add in the slot for infinite adjustment or am I overdoing it? I'm not sure which will be less expensive but I am thinking the holes will be a bit less and also I am thinking that from a performance perspective that the slots are a bit overkill.

As far as how much stiffer something like this makes a torsion spring, in theory the moment arm will have to be variable by at least 50% to achieve a stiffness adjustment ratio of 2:1. Also I would imagine that at some point you would go into plastic deformation if you made the ends too short (too much angular deflection would permanently bend the bar out of shape).

[John Wright]

I'd stick with the holes.....I'm thinking the slot will weaken your new addition to the bar.

[John Wright]

Just a thought....if you are worried about welding on the bar.....you could thread the ends of the bar(if using a solid bar) and then thread the new bar ends so that you could screw them onto the ends of the bar and use a jam nut to secure them. Just make the sleeved portion a little longer than in your model so that you could get enough thread engagement.

[mrn2obelvedere]

Can you tell the difference when you move the rod end by one position?

[mrn2obelvedere]

Nah...I'd rather weld the ends. I don't think that the welding will really affect the stiffness of the bar too much.

[Norm Peterson]

Ok guys how about this:

Will it be worth it to add in the slot for infinite adjustment or am I overdoing it? I'm not sure which will be less expensive but I am thinking the holes will be a bit less and also I am thinking that from a performance perspective that the slots are a bit overkill.

It depends on how long the bar 'arms' are. It doesn't take much change in arm length to SIGNIFICANTLY change the bar's stiffness. There is a limit as to how close you can put discrete holes before you might as well just make a slot, and I'm sure that this would get in the way on a bar with short arms.

Suppose you find that having the bar in one hole is not enough and in the next one it's too much, and you don't have enough room to drill another one in between without snagging one or the other of the existing ones?

As far as how much stiffer something like this makes a torsion spring, in theory the moment arm will have to be variable by at least 50% to achieve a stiffness adjustment ratio of 2:1.

Nope. Bar stiffness vs arm length isn't linear like it's so easy for people to think.

Actually, it's pretty close to 'inverse square', and to get a stiffness ratio of 2:1 a first cut at the effective arm length ratio required would be about 0.7:1. Don't forget that in addition to the effect that leverage has on the force required, it also affects the amount of bar end deflection. IOW, the "leverage" counts twice, just like any other motion ratio where stiffness is being investigated.

Also I would imagine that at some point you would go into plastic deformation if you made the ends too short (too much angular deflection would permanently bend the bar out of shape).

It's certainly possible to overstress the bar, as well as other related things such as endlinks and chassis-side bracket mounting. You would have to have some idea about how much roll could occur in order to estimate the stresses in these things.

Did I mention that Jon A is an engineer out at Boeing?


Norm

[John Wright]

Here is another idea that Dave @ PTFB used to make his 7/8" rear bar adjustable.....





Dave says that the rate is adjustable from 214 lbs up to 502 lbs. Which is a nice wide range IMHO.

BTW for reference, a stock 7/8" bar has a rate of 365 lbs.

[JRouche]

LOL!!!! And Im laughing cause buddy. You surprise me just about every time I see one of your build threads. You come up with some great stuff. Its like WHAT!!! Another neat idea. Keep them coming. Some solid ideas and some nice machine work. JR

I made these bar ends (BTW these started as 2" round stock turned milled and drilled)

Cut off stock smashed eyelets drilled the solid 7/8 bar and pressed then welded my ends on


I didnt like the stamped uchannel mount with the muffler clamp that was supplied so I made some solid Aluminum blocks and used 1/2 u bolts.


Then I didnt want heims top and bottom to eliminate any sound transfer to the chassis via solid connections so i made these links.