Developing a Proper Suspension Model

[ToyoburuBRZ]

Originally Posted by fika84

This thread is awesome! Great work so far gathering information.

No one wants to measure the suspension points of the car??

I used to work at OptimumG and have used OptimumK quite a bit. I've been very tempted to put the car up on jack stands and measure the points the old fashioned way so that I could have a good baseline to start with before I start doing suspension modifications. But it's a lot of time consuming work.

I contacted Bob Simmons over at Morse Measurements (http://www.morsemeasurements.com/), who has actually done some K&C testing on a BRZ, and has all of the suspension data, but he was reluctant to give any sort of deal (he wanted ~$1,600 for the data).

EDIT: Also very happy to see so many people saying "Damping" as opposed to "DampENing".... drives me crazy

Here is a link to the suspension points on the car. They were posted on this forum somewhere. Not sure how accurate they are either but it is a start.
https://docs.google.com/spreadsheet/...rive_web#gid=0

I've been thinking about applying to Optimum G (FSAE alumni here). Can't make up my mind

[Shankenstein]

Originally Posted by ToyoburuBRZ

Here is a link to the suspension points on the car. They were posted on this forum somewhere. Not sure how accurate they are either but it is a start.
https://docs.google.com/spreadsheet/...rive_web#gid=0

I've been thinking about applying to Optimum G (FSAE alumni here). Can't make up my mind

Yep! That's my spreadsheet.

It's not accurate. I started with the track width, then looked at alot of pictures of the geometry to get a rough estimate. Things like wheel/tire size and offset helped a bit for scaling.

Using the rough estimates, I ran the kinematic model and made some minor tweaks to get the curves to look halfway normal.

If anyone has better data, I've left the read/write access on that spreadsheet wide open for anyone to contribute.

[fika84]

Yeah, I saw that and then read the rest of the post.

One of these days when I'm bored I'll jack the car up and measure points with string, chalk and the concrete floor with reference points for front and rear so that people can adjust for different ride heights, wheels and tires.

Originally Posted by Shankenstein

I've started a spreadsheet of the suspension coordinates.

Very few points are correct yet. The front has been approximated based on pictures and specifications. The rear has not been configured, and is simply the program defaults. I'll fill these in shortly.

I'll leave this publicly viewable. If anybody wants "edit" capabilities, just PM me.

[eric6]

I just wanted to offer a word of caution with the suspension coordinates in the google document on the first page. It would be wise to double check the work .

Great ideas, a ton of excellent information and work in here!

[cdrazic93]

ahhh cant wait until I can finally start using SolidWorks in class. Ill actually be able to participate in this discussion and know what Im talking about lol

[fika84]

Originally Posted by cdrazic93

ahhh cant wait until I can finally start using SolidWorks in class. Ill actually be able to participate in this discussion and know what Im talking about lol

Unfortunately SolidWorks won't really teach you anything about a proper suspension model. You need to read books like

[ame="http://www.amazon.com/Race-Car-Vehicle-Dynamics-Experiments/dp/0768011272"]http://www.amazon.com/Race-Car-Vehicle-Dynamics-Experiments/dp/0768011272[/ame]

and

[ame="http://www.amazon.com/Fundamentals-Vehicle-Dynamics-Thomas-Gillespie/dp/1560911999/ref=sr_1_1?s=books&ie=UTF8&qid=1415724849&sr=1-1&keywords=vehicle+dynamics"]http://www.amazon.com/Fundamentals-Vehicle-Dynamics-Thomas-Gillespie/dp/1560911999/ref=sr_1_1?s=books&ie=UTF8&qid=1415724849&sr=1-1&keywords=vehicle+dynamics[/ame]

and

[ame="http://www.amazon.com/Vehicle-Dynamics-Application-Reza-Jazar/dp/0387742433/ref=sr_1_3?s=books&ie=UTF8&qid=1415724849&sr=1-3&keywords=vehicle+dynamics"]http://www.amazon.com/Vehicle-Dynamics-Application-Reza-Jazar/dp/0387742433/ref=sr_1_3?s=books&ie=UTF8&qid=1415724849&sr=1-3&keywords=vehicle+dynamics[/ame]


These books teach you what equations and theory is needed to understand and implement a suspension model. SolidWorks can help you visualize the system, but without understanding of why points are where and what moving them does to your system, SolidWorks is useless.

[DuroSquad]

Originally Posted by cdrazic93

ahhh cant wait until I can finally start using SolidWorks in class. Ill actually be able to participate in this discussion and know what Im talking about lol

Lol tell me how that goes. What school are you at? A basic solid works class teaches you nothing more than how to use the tools within solid works. It's still up to the user to understand wtf is going on.


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[cdrazic93]

Originally Posted by DuroSquad

Lol tell me how that goes. What school are you at? A basic solid works class teaches you nothing more than how to use the tools within solid works. It's still up to the user to understand wtf is going on.


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Not currently in my school yet, but solidworks was the only CAD program that came to mind lol

[DuroSquad]

And so it begins....

I'm still waiting on the actual book to arrive


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[plucas]

Originally Posted by DuroSquad

And so it begins....Attachment 95797

I'm still waiting on the actual book to arrive


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That is a good book. I have all three that are listed above. Another good one is Chassis Design

[ame="http://www.amazon.com/Chassis-Design-Principles-Analysis-R-206/dp/0768008263/ref=sr_1_1?ie=UTF8&qid=1416168491&sr=8-1&keywords=chassis+design"]Chassis Design: Principles and Analysis [R-206]: William F. Milliken, Douglas L. Milliken, Maurice Olley: 9780768008265: Amazon.com: Books[/ame]

[Amaya]

I was going to go to sleep two hours ago, but I started reading this thread. Curse my love of knowledge.
But otherwise, awesome stuff!

[redlined600]

Ive searched but couldn't find it. Has anyone measured and graphed front and rear camber curves and toe change.

[fika84]

Originally Posted by redlined600

Ive searched but couldn't find it. Has anyone measured and graphed front and rear camber curves and toe change.

Not that I've seen anywhere.

[Shankenstein]

Originally Posted by fika84

Not that I've seen anywhere.

If anyone has those curves, it would be a huge service to the community for choosing the "optimal ride height." I use quotes because you can always set the static values of camber and toe... but if it changes quickly under the normal weight transfers of racing, we might have to tweak the geometry.

Some guy from the WRX world posted this up, but it comes with no context or guarantee. I assume that 1 and 2 inch are the levels of drop. 10, 20, 40 might be wheel spacers (or offsets).