suspension design

[abhijit swami]

hi,

Can anybody tell how to start with design of suspension for FSAE car. My team is participating in FSAE 2011.

1) how to select the wheelbase,track width.
2) hoe to decied the Aarm length,camber angle,KPI,castor angle

[t21jj]

http://www.sae.stuorg.iastate.edu/zenphoto/zp-core/i.php?a=formula%2F2001-2002-formula&i=notsure-1.jpg&s=595

If so please read these threads.

http://fsae.com/eve/forums/a/t...607348/m/72110779141 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/72110779141)

http://fsae.com/eve/forums/a/t...607348/m/48310896441 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/48310896441)

[Luniz]

Why did I know instantly, with only reading the topic, that this comes from india?

[The_Man]

1)Look at the rules. See your limitations. See other FSAE car specs online from team websites try thinking why they would have selected a particular value.

2) Go through a a book on basic suspension design. A comprehensive list exists as a pinned post on this forum.

While you are at it, read the other pinned posts too and the posts called teams from India. That will help you understand a lot about suspensions and the way this forum works.

Sorry if I am being a bit rude here but trust me it could be worse. Just google for wheel base selection, there is a thread on this forum too about it. Use the find button on top.

Go through these:
WheelBase (http://fsae.com/eve/forums/a/tpc/f/125607348/m/4286037842?r=4286037842#4286037842)
Teams from India (http://fsae.com/eve/forums/a/tpc/f/125607348/m/48310896441?r=243104723#243104723)

[Thomas MuWe]

Maybe, you should start with reading books and the rules.
Please do not think that there is written:

1. Best wheelbase for Formula 1: 3150mm
Best wheelbase for FSAE: 1650mm
etc.
Read between the lines.

Then you should visit some FSAE websites: There is written what wheelbases are used. You will see some difference between Stuttgart and Delft or Oregon. Why?! Think of some other parameters which are important.

Before I conclude....maybe you should start with choosing your tire....there is a tire test consortium which can provide you with data from FASE tires. But I think that you can understand the values of tires which were measured you should know them which leads me back to the books.

[PatClarke]

Here you go Abhijit Swami, the info you need is in this thread.
http://fsae.com/eve/forums/a/t...607348/m/48310896441 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/48310896441)

Pat

[exFSAE]

With each one of these posts, my fears of engineering positions being outsourced to India becomes less and less..

[Mikey Antonakakis]

I'm gonna go ahead and give a reply.

Minimum wheelbase is 60" so I'll let you take a wild guess at what most teams try to run for a wheelbase.

Track width is trickier, you have a center of mass above the ground so at some amount of lateral acceleration your car will roll over. Make sure this doesn't happen by picking a track that corresponds to a roll over lateral acceleration that is greater than what your tires can provide. I'm not going to talk about what your tires are capable of, sorry. Also important, read the section of the rule book that explains the tilt test. Make sure your track is sufficient to ensure you pass the tilt test. I'm gonna take a wild guess and say that your track probably should be less than your wheelbase. So at the simplest level, you want your track to be wide enough to ensure your car passes tilt and won't do a barrel roll in a turn (which one of those two actually matters is up to you to decide). You also probably don't want your track to be more than your wheelbase, so I don't think there is a team out there that runs a track more than 60". I'm gonna take another guess and say most teams run tracks at least a few inches less than 60".

Then go read the rest of the rule book. Several times. We all do. Know the rules. Do everything you can not to break them. Build a car that will be able to finish the endurance race and you will have a better car than I think 70% of the teams at Michigan this year. First year cars can finish endurance. But not if they roll over, break the rules, or explode.

Once you know your track, a-arm length is easy to determine. You know how far apart your wheels are because you've picked your track width. If you read the rule book, you'll find that your chassis has to have a minimum width. Your a-arms therefore shouldn't be longer than the distance from your wheel to a mounting point on the outside of the chassis. Simple stuff, right?

All I'm going to say about camber is that you generally don't want it to be positive on a race car on asphalt. If you want to find out more, read any one of a number of vehicle dynamics books. Googling "Vehicle Dynamics" will probably yield a useful link or two. Or go to Amazon and search for books on the subject. Read one. They're fun.

Same thing goes for KPI and castor, I'm not going to talk about that, other than saying that if you take a paper plate, attach it to a pencil such that the pencil is a pivot point, put the plate on the table like it's a wheel, and tilt the pencil different ways, you should see that the plate leans when you rotate it about the pencil. This should tell you that KPI and castor have something to do with camber change as you corner. Don't underestimate the power of pencils to do things other than write. Feel free to laugh at an innuendo.

Read the rules, read a vehicle dynamics book, read the forum, play with pencils, learn something.

[jrickert]

no

[move]

i think any vehicle dynamics book will help!!!

[Homemade WRX]

go figure, I'm searching for some suspension stuff as it isn't my niche of expertise and must say this thread made me crack up, Luniz's comment the most.

[Spetsnazos]

I first read the subject.

I then saw the username.

and then in my head I said, "yea....".