Roll Camber

[apoorv]

Hello everyone.
I am Devansh Batra from SRM University, India. Our team will be participating for the first time in FSAE Italy this year. For our first vehicle, I had some problem upon simulation of our suspension geometry in Optimum Kinematics. I am giving the value of roll as input but the camber angle corresponding to any value of roll is remaining constant; same value as that of the static camber = -1 degree. It is varying in heave but not in roll. Can somebody point out where exactly i am going wrong.


Thank You:)

[CWA]

Perhaps I have misunderstood, but this sounds like a valid situation. Doesn't it indicate that you have 100% camber compensation in roll? With 100% 'CC' your wheel would retain its static camber angle (w.r.t the road/ground) when the chassis is rolled, but the camber would change when the chassis is heaved.

What makes you consider this as incorrect?

Do you have an image of the suspension type / parameters you have chosen?

[apoorv]

That would have been true but i even changed the pickup points altogether a few times and simulated the geometry to see if i doing something wrong. Turns out that even then there was no change in camber indicating that i am missing something. The roll center positions changed but camber angle remained the same which somehow doesn't make sense to me. We are going with a normal pushrod suspension , unequal and non parallel double wishbone setup, with static roll center positions above the ground and with an inclined roll axis.

[Claude Rouelle]

I bet you do no create a simulation at all. You are just looking at the static initial kinematics. Have you been using OptimumKinematics before? The best way to solve your problem is to send your file to OptimumG. If you are a customer (are you?) you will get an answer within 24 to maximum 48 hours.

[apoorv]

Thankyou Sir for your reply.
Yes I am totally new to this software and as you pointed out I am only doing a quick run by entering the hard points. As you said I'll send the file OptimumG.

[Claude Rouelle]

Devansh
1. Are you an OptimumG customer?
2. Did you read the help file?

[apoorv]

Sir,
I am not a customer as yet. I am using the trial version for now.
I went through the help file once. Maybe, as you pointed out, I need to create a proper simulation with multiple steps instead of just going with the quick run in order to get detailed results.

[Claude Rouelle]

If you input your suspension pickup point coordinates but you do not create a motion, of course you won't have any camber variation in roll, or heave or pitch or steering. As many students on this forum, whether it is about software use or more general questions,it seems you showed impatience by asking a bit too quickly your question without making your own introspection / homework and in this case basic reading of the help file.

[ChristianChalliner]

As Claude has said, the OptimumK help file will give you the answers to the most common questions and is to be honest a good read, I actually read (properly not just skim read) all the help files for the various OptimumG software pieces. They're quite informative and are a great place to start for people completely fresh to simulation.

They must be among the handful of help files I've ever read with regards to programs.

Anyway, back to the initial question. As Claude has said you need to create a motion, there's a tab for this somewhere, in the motion you have 4 graph lines if i remember correctly, roll, pitch, heave and steer angle, you simply create points on these lines which define your criteria, I think you can use the mouse to move the points but I always just used the table inputs to create the profiles.

You can do multiple criteria at once or just singular movements, however, I would advise the pairing of certain movements. For example, how could you possibly induce a roll angle without having a steer angle to induce it (on a flat road)? Similarly, you're unlikely to have perfect heave of the car, but it is somewhat useful if you have considerable aerodynamic downforce or if you are simulating only one end of the car at once. However, I think you learn more by running a simulation whereby you can visualize the whole platform movement, certainly it will show how the roll axis moves much more clearly.

If you do some reasonably basic calculations for things such as weight transfer during braking/cornering you could input the relevant pitch and roll angles to show exactly how you expect the platform to move. I say expect because you can be certain it probably wont move like that in reality.

P.S Oh, once you've created the motion then you have to create a study? the program will ask you what vehicle setup you wish to use and the movement you wish to use, then just click play. Correct me if I am wrong Claude?
The software also allows you to run movements whilst sweeping a parameter through a certain range, this is very useful for finding a tie rod/rack position for minimizing bump steer.