Suspension layout

[PaulB]

When I built my suspension parts, I asked myself, why do they put no gurneys on the suspension parts. That must be a great advantage. I did not find a term in the regulations which forbid that.

[Jersey Tom]

By rule, suspension components need to be symmetric in profile and thus neutral for aerodynamics, do they not? (I'll admit, not my specialty... but I thought this was the case).

[Giblet]

Suspension arms must be neutral, but not the brake ducts. This seems to be where they add the little flips or more DF.

I would imagine suspension arms that produce varying levels of downforce would be very hard to dial in a good spring rate with or to fully undertand what is actually going on in the corners of the vehicle.

[mep]

It would just increase drag and vorticies.
You need a high angle of attack to get an advantage of a gurney.

[olefud]

I would imagine suspension arms that produce varying levels of downforce would be very hard to dial in a good spring rate with or to fully undertand what is actually going on in the corners of the vehicle.

Less so than conventional aero since nominally half of the downforce would act directly on the wheel, i.e. on the unsprung portion of the suspension.

[MIKEY_!]

I don't suppose this would be legal. Grey lines are suspension arms. Left black square is the nose, right one is the wheel/tire. Only the lower suspension arm would be worth having a gurney.



This gets the 'wing' we've created much closer to the ground for more DF.

[allstaruk08]

sure wouldnt like to jump a curb with that lower suspension arm

[Jersey Tom]

I don't suppose this would be legal. Grey lines are suspension arms. Left black square is the nose, right one is the wheel/tire. Only the lower suspension arm would be worth having a gurney.



This gets the 'wing' we've created much closer to the ground for more DF.

That lower control arm would snap in half in the first corner. Not being straight defeats the whole benefit of an A-arm.

[godlameroso]

Agreed 90 degree angles are structurally weak angles. Notice almost all suspension components avoid 90• angles? Same with modern jet fighters. Triangles are simpler and stronger structurally than rectangular shapes. Even stronger are circular shapes, old Egyptian civilization used wheels instead of straightedges to make distance measurments and look how long their structures have lasted, same with the Incas and Mayans. Maybe that's why we can't replicate their structures using our "modern" techniques.

[mep]

Even stronger are circular shapes,

hmmm I tend to disagree. Triangle should be the strongest shape but it might depend on the application. Circular shapes are prebuckled and therefore less stiff.

[MIKEY_!]

So raise the arm to about 100mm height (the front wing survives at 75mm) and make it more curvy (or thicker if we really must). The point is whether it's legal. I have my doubts but I can't quote the regs or anything.

[mep]

Those arms have to be straight not curvy.
Thats a absolute basic principle.
You would not get them in ground effect.

[MIKEY_!]

Why not? Is the chord too small? And why must they be straight. They will act in the same way as a normal arm so long as they don't flex.

[PaulB]

Why not? Is the chord too small? And why must they be straight. They will act in the same way as a normal arm so long as they don't flex.

I'll draw you a mechanical picture tomorrow to show, why straight arms are the best in suspension way. Curved arms are from the mechanical way a desaster.

btw. Thaks for that interessting discussion and comments.

p.s. okay, it's after three o'clock, so the drawing will come today.

[Jersey Tom]

They will flex, and they will snap with ease, because they are in massive bending rather than tension/compression (as they would be if they were straight).

The significance? Here's a real world example:

Go outside and find yourself a few sticks. First, try breaking them by literally pulling them apart. Grab both ends and have a tug of war with yourself and see how much effort it takes to try and rip them apart by tension loading.

Then, try breaking them by bending / snapping them in half and note how trivially easy it is.

Hence why things like a-arms and pushrods are straight.