Spreadsheets

[Frank]

I can't help myself..

I love spreadsheets, and i like sharing them.

http://www.uq.edu.au/fsae/Suspension_Statics.xls

[BCIT_James]

Any chance I could get a basic explanation of the best way to use this spreadsheet. Email is jamescannon@hotmail.com
Thanks

[Frank]

I’ve been getting a quite a few emails asking about the old UQ spreadsheets for suspension, traction control, and CG measurement.

I’ve put them on a Google hosting space.

Measuring the CG
https://docs.google.com/file/d...TTg/edit?usp=sharing (https://docs.google.com/file/d/0B1Nm8Xe9BT3uN2tqaTJNZUhrTTg/edit?usp=sharing)
Suspension V1
https://docs.google.com/file/d...ajQ/edit?usp=sharing (https://docs.google.com/file/d/0B1Nm8Xe9BT3uQkhLRHhkSl9BajQ/edit?usp=sharing)
Suspension V2
https://docs.google.com/file/d...MUE/edit?usp=sharing (https://docs.google.com/file/d/0B1Nm8Xe9BT3ud0RqUzY0X3E2MUE/edit?usp=sharing)
Traction
https://docs.google.com/file/d...YUU/edit?usp=sharing (https://docs.google.com/file/d/0B1Nm8Xe9BT3ubEdIN3l2azJDYUU/edit?usp=sharing)

A few points
They are all locked, but there is no password.

Traction control refers to the old Motec M4 unit. I never had this confirmed by the big men at Motec, but two sales/tech guys from Motec said that they thought the diagram accurately described the algorithm, as they understood it.

I know nothing about newer Motec units. I have heard some people say they are set up differently.

The CG measuring is a bit difficult to understand. There is an example given, and a working area for your calculation. The drawing supports the example. The example is a front heavy car.

The suspension sheets are the same, except one version is “driven” by natural frequencies, the other version is “driven” by spring rate.

I generally use driven by natural frequency in the design phase, when I am picking a motion ratio to suit the particular shock absorber.

I generally use the driven by spring rate spreadsheet once a car is built, and we are making adjustments.

A few people asked what the “internal reaction” is about. This is difficult to explain without a diagram. But I will try. The equations for distribution of sprung mass elastic weight transfer are based on “the stiffer path takes the load”. The formula most people are use to using assume:
1. Rigid Tyre
2. Chassis Infinitely Stiff, to enable the “perfect distribution”, proportional to roll resistance ratio F/(F+R)

If you use equations of this form, with a non-rigid tyre, there is another equation for how the chassis resists a difference in roll angle between the front and rear (ie there is a torque in the chassis). You can model this in an FEA package quite easy, using spring elements, and get the results to confirm.

Some general important points:

Although quite a few people have checked various parts of the math in these spreadsheet, please consider them NOT CHECKED.

I have, from time to time, found mistakes and updated the version with a date at the bottom.

The starting numbers are fictitious. DON’T use these numbers to design a car. This is not a design template.

This is collaborative work; I’d like to thank a few people from UQ for working out equations, and checking equations. Thanks to:

Daniel Burt
Mark Fenning
Adam Karl
Micheal Atherden
George Cummins

Enjoy

Frank Evans UQ 2001-2005

[ChristianChalliner]

Frank you have a PM http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Big Bird]

Frank, you are a legend. Thank you for sharing, this is the true spirit of our community.

And did you sort out that oatmeal on your bib, mate??

http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Frank]

Thanks Geoff,
I got my bib wiped!

If anyone does find errors, please PM me, and I'll have them fixed.