New for Suspensions!

[melkohil]

Hey guys,

I am new for suspensions design and I have two questions: How to adjust the ride height? what are the consequences if I raise it beyond the normal?

Thanks!

[Zac C]

How to adjust the ride height?

You probably need to make something either shorter or longer.

what are the consequences if I raise it beyond the normal?

The car will flip and you'll (probably) kill your driver.

[Pat Clarke]

Melkohil,

It is good manners to firstly introduce yourself and your school.
Then it is considered good manners to do a modicum of research before posting questions.
Failure to do so usually gets dismissive answers as above.

Pat Clarke

[JT A.]

Give this thread a read

http://www.fsae.com/forums/showthrea...highlight=eggs

[Claude Rouelle]

Melkohil,

What about introducing yourself? Just a question of being.....not even courteous....simply polite.

So unimpressive...

As far as your question, you wrote "...if I raise it (the ride height) beyond normal" How do you define and quantify "normal"?

[P^squared]

Raising the ride height beyond normal will give you better acceleration times from a standstill.
Because higher CG --> greater load transfer --> more grip at the rear --> less wheelspin
( just in case no one's following the FSG thread )

[Claude Rouelle]

P^squared,

1. Just a note: if you have a FWD or a 4WD (which is the case of more and more Electric FS cars) your consideration could be slightly different.

2. All other things being equals you are right in principle on a RWD for acceleration consideration: but...... then why not having 500 mm of ride height for acceleration? What is the limit? Is the rear tire longitudinal grip linear with the vertical load? What would be most efficient: vertical load or slip ratio control or tire pressure or tire temperature or toe or initial weight distribution, launch control loop, or aerodynamics parameters or simply mass, power, traction control, damping. ....? Or simply practical consideration such as ride height adjustability limit? If you do not have at least a theoretical answer for the influence of these other parameters stay away from intuitive or emotional (kind of the-winner-do-this-so-it-must-be-right" considerations): this is an ENGINEERING Design competition Also stay away from any multi input parameters simulation that is not backed up by comparative test data validations.

3. Do have the same thinking process for braking efficiency?

[P^squared]

Claude,
I suggested ride height adjustment to improve performance only after all the design and manufacturing has already been done. That is the reason to have any kind of adjustment built into a system.

I wouldn't follow the same thinking process as long as we have All Wheel Braking instead of just one axle.

I don't think FSAE suspensions are designed to allow such amounts of travel : 500 mm , let alone keeping the tyres properly oriented at such extremes, I.e. if you want a lowish CG for other events

[Claude Rouelle]

P^squared,

Ride height and ride height variations are 2 different things, except that for a given suspension stiffness the higher the CG the more suspension movement you will need. You kind of elided my questions or observations. 500 mm was used a provocative number; I could have said why not 50, 100, 150, 200 or 250 mm or 1 meter! How do you make that choice?

Claude

[P^squared]

What I meant was that while having a low ride height for Tilt and other dynamic events, it won't be possible to increase the ride height for acceleration above a limit , as the wishbone pivots will only allow a limited change in wishbone inclination.( unless you've made provisions to take care of that )

The theoretical upper limit to this kind of crude adjustment would be till the car " pops a wheelie " ( all weight transferred to the rear axle )

The lowest ride height would be that where you're confident in the sprung mass not touching the track under any dynamic maneuver. This, when you don't have an undertray/ wing in ground effect.

For most of the dynamics I'll aim for the lower ride heights