ackermann calculations articles by eric zapletal required

[raj_fsae]

hello friends
i found two excellent articles by eric zapletal on 1 steering axis
2 toe in and toe out
however it seems there is a previous one more article by him on ackerman calculations .i desperately need it as i m working on the steering system of our car.someone who has it .........please give it to me.i would really appreciate ur help
raj
aious formula racing team

[exFSAE]

What do you need for Ackermann calculation? Should be pretty easy to deduce from geometry. Make a sketch in your favorite CAD program of your steering assembly and see what it does.

[raj_fsae]

i have confusions regarding toe in and toe out.......i have given a slight toe out to the front wheels for good cornering and toe in to the rear wheels for straight line driving stability .........however i m confused over how to adjust this toe out......?whether to increase the length of the tie rods or give an offset to the pivoting points of the steering arms.

[exFSAE]

Be careful with "toe out giving good cornering." It may promote good turn in, but near the limit you will be driving the unloaded inside tire at a higher slip than the loaded outside tire. May not be what you want.

Which is where Ackermann steering comes in.

Adjusting toe is typically done by shortening or lengthening the steering tie rod, which is threaded right-hand on one end and left-hand on the other end.

Static and dynamic Ackermann steering effects are set by the angles of the tie rod relative to the line from the kingpin axis to steering joint pickup.. and the angle of the tie rod relative to the chassis centerline (respectively).

That is to say.. you have a ton of variable effects going on. For example, you can have a steering setup that starts pro-Ackermann around 0 steer, moves to parallel steer, and the goes to reverse Ackermann at full lock! Or the other way around, or parallel steer that stays constant, or any number of things. If it sounds confusing.. it is! But it gives you a lot of options. If its what your tires wanted, you could have a setup that was toe-out and near parallel steer around 0 for good turn-in and then rapidly went to reverse Ackermann at lock to get the most out of the inside and outside tires.

[raj_fsae]

ok sir
now that ur words have finally begun to enlighten me i would bother u a little more........the wheel base of our car is 1900mm and track width is 1220 mm ......although on our part we are doing our calculations ....i would like ur opinion on wat would be best positioning of our rack and pinion.and length of our tie rod with ofcourse considering in mind the slight toe out i have given to the front wheels
raj
aious racing team

[exFSAE]

That is entirely dependent on what kind of Ackermann you want. Doesn't really matter where you put the rack so long as (a) its rigidly mounted (b) it gives you the steering you want (c) it doesn't give your suspension crazy bump steer.

Of course that's all ideal case. Sometimes it just comes down to putting it where it will fit!

[Chris Lane]

Originally posted by raj_fsae:
ok sir
now that ur words have finally begun to enlighten me i would bother u a little more........the wheel base of our car is 1900mm and track width is 1220 mm ......although on our part we are doing our calculations ....i would like ur opinion on wat would be best positioning of our rack and pinion.and length of our tie rod with ofcourse considering in mind the slight toe out i have given to the front wheels
raj
aious racing team

Be careful designing in toe-out. It creates an unstable situation as the car wants to steer itself. Design in stability-inducing toe-in if anything.

Use a kinematics program to position your rack and determine steering link length.

[ben]

Originally posted by Chris Lane:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by raj_fsae:
ok sir
now that ur words have finally begun to enlighten me i would bother u a little more........the wheel base of our car is 1900mm and track width is 1220 mm ......although on our part we are doing our calculations ....i would like ur opinion on wat would be best positioning of our rack and pinion.and length of our tie rod with ofcourse considering in mind the slight toe out i have given to the front wheels
raj
aious racing team

Be careful designing in toe-out. It creates an unstable situation as the car wants to steer itself. Design in stability-inducing toe-in if anything.

Use a kinematics program to position your rack and determine steering link length. </div></BLOCKQUOTE>

Toe out at the front and toe in at the rear's a fairly normal setup is it not?

Pro-ackerman's dynamic toe-out and anti-ackerman's dynamic toe-in no?

Ben

[Chris Lane]

Static toe settings, dynamic toe (ride/roll steer or 'bump steer'), and ackermann-induced toe are all different situations.

Static toe is set during set-up.

Dynamic toe is a function of your toe/steering link lengths and pickup heights (suspension geometry).

Ackermann induced toe effects are a function of steering geometry.

I think it is safer to design a suspension that toes in very slightly during ride to ensure the front of the car doesn't wander excessively under braking. Static toe settings can be decided once the car is actually built and tested.

My opinion anyway

[Chris Lane]

Oh and raj_fsae, ensure that your rack is positioned such that your steering linkages can't invert. Pretty much a crash and rebuild car situation.

[Dan B]

This was on the RaceTech web site around 2000. I don't have the article to go with it.

http://mysite.verizon.net/triaged/files/ackermann.zip

[Gian]

Hello friends,
I would like to establish a contact with Mr. Erik Zapletal regarding a suspension system patent. Can somebody tell me his e-mail or his fax number?
Thanks, regards

[Mike Cook]

I'm not sure of his email my I know he is still kicking around. He had an article in RCE a few months ago.