Ackerman help

[jonnyjo]

Hi guys,
I was wondering if there is software available (preferably excel spreadsheet) that helps calculate ackerman angle for your vehicle (takes into account rack input etc)? I've searched google, and I was surprised to find very little on this. If you know of any websites or books that can illuminate the theory of ackermann it would be much appreciated.



"The best car safety device is a rear-view mirror with a cop in it".

[jonnyjo]

Hi guys,
I was wondering if there is software available (preferably excel spreadsheet) that helps calculate ackerman angle for your vehicle (takes into account rack input etc)? I've searched google, and I was surprised to find very little on this. If you know of any websites or books that can illuminate the theory of ackermann it would be much appreciated.



"The best car safety device is a rear-view mirror with a cop in it".

[Z]

Try the magazine "Racecar Engineering" V11N6/7/8 (ie. 2001 June/July/August).

Their website is www.racecar-engineering.com (http://www.racecar-engineering.com).

[Dick Golembiewski]

I highly recommend that series by the way. In fact, it's on a shelf right behind me as I type this.

The author is a whole 'nuther story! <GRINNING FROM EAR-TO-EAR>

[Z]

Yes, he is a long-winded old gas-bag, isn't he...

[clausen]

Hi,

Making your own spreadsheets to do this sort of thing is usually very educational. In this case it's not very difficult. Just some basic triangle geometry.

[D J Yates]

My team mate Tom (TomW on the forum) made a spread sheet to calculate ackerman angles. Apperently it's hard to calculate ackerman based on the difference of steer angles, so he'd calculate the steer angles based on the ackerman and an input steer angle, and use the Excel solve tool to iterate the ackerman until he got the steer angles he desired. He also did some somthing in the same sheet that calculated how much caster we needed to get sufficient tire break away warning...very clever.

[Alan]

D J,

I was just wondering how your teammate was able to quantify sufficient tire break away warning. This is something that has always interested me.

[fade]

self aligning torque ?

[DJHache]

If you've got access to a simple kinematics package (cosmosmotion or working model or just solidworks) you can make a simple model to figure out Ackermann.

Your break away warning comes from your tire behavior. Usually self-aligning torque of your tire will drop off before lateral force does so right before break-away there will be a period of "softness" in the steering. You can affect the amount of softness with caster angles and offset and kingpin offset. Check out Milliken&Milliken Race car vehicle dynamics for a good explanation of the tire's self aligning torque.