Relationship between camber link length and angle?

[Monkeysmate]

Can any one either explain or point me to a good (and simple) explanation of the relationship between camber link length and angle?
I short of understand the angle, but am somewhat confused by the affect of the length...
Anyone able to help please? Ta.

[danmurphy]

http://users.telenet.be/elvo/

Suspension page 3

Just read the last couple of paragraphs

[James]

Very briefly; longer link means more roll which means slower change of direction and for instance on the rear slower for the rear to snap away but still generates rotation due to the shift in weight. Shorter link rolls less, so again as an example on the rear it will make the car change direction quicker.

[Monkeysmate]

Thanks chaps.
So then am I right in assuming that the angle of the camber link changes the amount by which the camber changes under shock compression?

[Monkeysmate]

Ok. I'm getting there...
I understand the image below, but can any one please tell me what happens to the roll centre if the upper link effectively is angled upwards compared to the lower arm, and hence the two red lines never intersect?



And, does having a longer upper camber link have the same effect as putting washers under the inner ball connection? i.e. raising the roll centre = less roll?

[Robocop]

One of the best things to do is to go to your local track and try things on the car..

[markwilliamson2001]

Basically a rough guide:
Longer links higher on the inside for higher grip, smooth tracks
Shorter lower links on the inside for low grip tracks..

You can fine tune with the height of the link on the inside, changing the length of the link makes more difference. Raising the inner link lowers the roll centre (centre of gravity if you will)...

The rear inner hinge pin height, gearbox height, axle height and ride height all interact with each other though!

Lowering the rear link on the inside can make the car feel twitchy on high grip tracks, raising it can free the car up and cause some 'drift'.
Making the rear link longer makes the rear 'hold onto the turn' more. Shortening the rear link makes the car rotate more (useful for hairpins etc)

A lot of this is down to feel however.

My suggestion is to look up a few setup sheets and see what the common ground is on this, then tune on feel at the track :-)

[markwilliamson2001]

This video explains it well :-)

http://youtu.be/Wl1qcwe_ATU

[Monkeysmate]

Thanks RoboCop. I completely agree, but life means such opportunities few and far between... I'd like to really understand the mechanics of the geometry changes whilst I'm not at the track, to make absolute best use of the track time that we do get...

[Clive Loynes]

Originally Posted by markwilliamson2001

............. Raising the inner link lowers the roll centre (centre of gravity if you will)...

I'm rubbish at this lark but I would say that roll centre and centre of gravity are two different things.

Is it not the difference in height between the two that determines how much "roll" will take place? The CofG is the point at which the mass can be considered to act whereas the roll centre is the theoretical point about which the chassis can be considered to roll.

If the roll centre is low and the CofG high then it will lean like a sailing boat in a gale! If they were both at the same height then it wouldn't lean at all.

[Clive Loynes]

Originally Posted by Monkeysmate

Ok. I'm getting there...
I understand the image below, but can any one please tell me what happens to the roll centre if the upper link effectively is angled upwards compared to the lower arm, and hence the two red lines never intersect?

Just guessing but if you raise the inner camber link mount until it makes the two lines parallel then they intersect at infinity(or not at all) and your roll centre is at track level.

If you raise it still further then the two lines will intersect on the other side and your roll centre will be below track level.

Neither of these sounds good.

In addition, I think that it would make the tyres lean out a lot! If they are a rounded profile then that probably won't have much effect but if they are a flat profile then you would probably run out of tread.

[James]

Camber link angles change the rate of camber as the arm raises and lowers, hence you must remember that as a car corners the outer shock will compress as it loads up and the body leans, so changes in camber link angle mounting position create different reactions at different levels of shock compression - namely entering a corner, mid corner and exiting the corner.

Again, to keep it simple - lets take the front end - raise the inner camber link (lowering the roll centre) will give less initial turn in but more mid corner steering as the camber change is greater resulting in more tyre contact patch. Lower the link giving more turn in and a little less mid corner steering.

So the above relates to how much the car rolls due to link length as discussed above.

You can change the castor block height too to affect roll centre, so many things..
Centre of gravity affects roll too.. put a flat piece of lead under your chassis and your car will find it harder to roll as it's more weight to move. Put a strip on top of your topdeck and the car will roll more violently, but will centre more slowly.
It takes an awful lot of experience to get your head round all this I'm afraid.