Blade Type Swaybars

[swong46]

Hey everybody,

I was wondering how you would go about calculating the stiffness of a swaybar system using blades and its setup angle.

I know I can load it up in Solidworks but wondering how I could do it by hand or in excel?

[Adambomb]

For starters, just to keep it simple, I'd look at the softest case and the stiffest case, and figure that whenever I'm actually adjusting them at the track the amount I decide to adjust them will be "just a little bit."

Although linearity of adjustment, i.e. how much it changes if I'm going "just a little bit" when it's nearly full soft, or "just a little bit" when it's nearly full stiff, or somewhere in the middle, might be nice to know as well.

[Zac]

I'd recommend just running through a couple angles in FEA, and doing a hand calculation for the full soft or full stiff case as a sanity check. Trying to do a closed form solution of a rotated blade seems like it would be hard.

I should also point out that in my experience (measuring different blade settings on a kinematics and compliance rig) the adjustment is pretty far from linear.

[Rotary Sprocket]

I would agree that the adjustment is far from linear.

The method I used for designing our blades was as Zac recommended, by doing FEA at a few angles I determined the stiffness of the blade. As this is not completely accurate once I got in the ballpark of where I wanted the stiffness range I had a pair machined and verified the stiffness on a test rig. I then fine tuned the design from there until I acheived the desired stiffness range.

[swong46]

Thanks for the input guys. I just ran one FEA with just the blade and a mock up "holder" tube.

What kind of force are you guys applying on the end of the blade at worst case scenario?
Is the force simply wheel rate*swaybar motion ratio?

[sbrenaman]

Instead of a force, don't you have a maximum displacement boundary condition? IE; the rocker is only going to move X degrees before it bottoms out the damper.

[aalves2]

Hello, I am designing the blade arms, and I was wondering what material is commonly used to make the them?

[AxelRipper]

Whatever material you figure suits your needs. Somewhere between fishing line and Unobtanium is usually advisable though