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I don't need anything with excellent graphics just somethign where you can draw a couple lines and spits out numbers for you. It needs to be something to play with the suspension systems along with the chassis. And Preferably free or cheap.....Any help would be really appreciated guys!

Perhaps this should be moved to aero, chassis, suspension, but i have another question. If i know the coefficient of friction for a tire, As well as the contact patch?... I can then calculate the necessery suspension geometry correct? But I HAVE to start with the tires, I think....

I don't need anything with excellent graphics just somethign where you can draw a couple lines and spits out numbers for you. It needs to be something to play with the suspension systems along with the chassis. And Preferably free or cheap.....Any help would be really appreciated guys!

What are you trying to do? Drawing lines and spitting out numbers... is not suspension design. There are DEMO versions of kinematic sims, where you generally can't do much, and can't save anything. Kind of the ghetto approach. OptimumK comes to mind.

Or, if you know what you're doing, you can program up your own stuff. If you don't know what you're doing.. I'd suggest just reading Carroll Smith books and not getting in over your head with simulation.

If i know the coefficient of friction for a tire, As well as the contact patch?... I can then calculate the necessery suspension geometry correct?

Sadly, no. Not even close.

Fastback, here is a link our friend Carlos gently gave me a while ago.

http://www.eng-tips.com/faqs.cfm?fid=768

A good resume of the availiable softs.

Thank you!

Jersey Tom wrote:

I don't need anything with excellent graphics just somethign where you can draw a couple lines and spits out numbers for you. It needs to be something to play with the suspension systems along with the chassis. And Preferably free or cheap.....Any help would be really appreciated guys!

What are you trying to do? Drawing lines and spitting out numbers... is not suspension design. There are DEMO versions of kinematic sims, where you generally can't do much, and can't save anything. Kind of the ghetto approach. OptimumK comes to mind.

Or, if you know what you're doing, you can program up your own stuff. If you don't know what you're doing.. I'd suggest just reading Carroll Smith books and not getting in over your head with simulation.

If i know the coefficient of friction for a tire, As well as the contact patch?... I can then calculate the necessery suspension geometry correct?

Sadly, no. Not even close.

Care to elaborate then?

The first question is, what are you trying to do?

If you are assuming rigid suspension links, the trig to model a double wishbone suspension is not hard - I've seen second year students cobble together an Excel spreadsheet for this in less than 2 hours. If you want to include chassis roll effects, things become a little more complicated.

Please be more specific about your goals / desired outputs and what you have to work with:

1. What type of suspension are you working with ? Machpherson struts, double wish bone (A-arms) ?

2. What sort of vehicle/ racing formula? Off-road (loads of suspension travel) or track (open wheel or closed wheel)

In answer to your question about friction / contact patches:
Friction and the contact patch will determine the size of the loads going into the the tyre and hence the suspension. You can't calculate the suspension geometry from this info - the loads will determine the area / thickness / cross section of the suspension arms necessary to carry the loads BUT suspenion geometry will always be chosen by the designer as the best compromise between tyre movement (path of the tyre centre, camber change, bump steer (if present)) and the necessary packaging to make it fit with the rest of the car.

ReubenG wrote:
In answer to your question about friction / contact patches:
Friction and the contact patch will determine the size of the loads going into the the tyre and hence the suspension. You can't calculate the suspension geometry from this info - the loads will determine the area / thickness / cross section of the suspension arms necessary to carry the loads BUT suspenion geometry will always be chosen by the designer as the best compromise between tyre movement (path of the tyre centre, camber change, bump steer (if present)) and the necessary packaging to make it fit with the rest of the car.

Thats all the explanation i needed. Basically i don't have a project and im not trying to do anything at the moment except learn as much as possible about suspension kinematics and design. I really just wanted the program so as to help me understand specific inputs and outputs.

After reading carroll Smiths chapter on suspension geometry and a couple other books. I am beginning to realise that it is a system of give and take. But really the most important part is the tire and how well it is interacting with the road. In theory what i have come to realize is, if your tire is connected to the road with as much grip as you want you could have a suspension system made of pillows. (Just an anology I would never think that is a viable method)

Believe it or nto this stuff is really fun to learn about!

Everything is a tradeoff in motorsports. If you're just trying to learn, Tune to Win is probably the best starting point. The rest of the Carroll Smith books are real good as well for racecar-related stuff.

Paul Haney's tire book isn't bad... but there are some items I don't agree with.

Bottom line, suspension kinetic and kinematic design exist to control the distribution of load through the 4 wheels, minimize load variation, and control the wheel's position in 5 degrees of freedom.

You can get a long way without knowing specific tire data, and design a suspension that won't screw ya, and is going to be tunable "enough" to get you by.. especially when the driver is a bigger variable than anything. Trying to get that last few percent of performance is where very detailed chassis and tire data come into play.

I have been learning and trying to teach my self as much as possible this winter break.

So, i have come to the conclusion that, to have a suspension system working properly, you need to have a balanced system. (Okay the way i have it in my head sounds so much better but i digress..)

anyways in this system to optimise everything from rocker arms to push rods, you would best find it that a 1:1 ratio be best. While at the same time maintaining the correct spring rates.

Okay, this post sounds rediculous ,but it all makes sense too me. Anyone care to add more?