Turning Radius Minimization using slip angle theory

[brij1501]

Hi, I am working on decreasing the turn radius of the car,to as minimum as possible , approach i am using is -
getting the tyre data, for the given velocity ,finding the lateral loadsthan finding the slip angle , than for the assumed turn radius
(required) getting the steer angle ,including slip angle (for a given track width and wheel base ) , from instantaneos centre approach ,
Now , for some steering ratio (say for calc as 15:1), Now I want to ask1. Whether my approach is correct to fing total steer angle
2. Further approach to decide geometry, as I am getting toe out for inside tyre (different steer angle for two front tyres) to achieve
minimum turn radius
P.S.- I have searched it on forums , not found any relevant (if u find ,provide link :P ), please don't be rude & help me .
DEADLINE - Today , I want to complete this .
So, please don't be rude & help me .Also main aim is to minimize turn radius .

[acedeuce802]

Your approach sounds very similar to what I did. This article helped me out quite a bit with it:

http://www.optimumg.com/docs/SteeringGeometry.pdf

I found some of the equations to not be spot on (maybe the slip angle formulas, if I remember correctly, but those are simple geometry) so be sure to double check the formulas, and check the units.

Also know that you should design past the "optimal" max steering angle, to account for understeer and such.

[exFSAE]

Deadline today... good time to be asking whether your conceptual approach is correct.

[Claude Rouelle]

Similar response than ExFSAE but with other words.

Every time you want something in life you have 3 criteria: cheap, quick and good. You can't have 3; pick 2

What is cheap is not good, What is good in not cheap. What is quick delivery is not cheap either

So the question I have for you is: how much money do you have? You are a student so probably none.

I guess you have the conclusion from here....







W

[acedeuce802]

At least he stated his approach, instead of just saying "plz inform me to create steering system." http://fsae.com/groupee_common/emoticons/icon_smile.gif

[MCoach]

Also know that you should design past the "optimal" max steering angle, to account for understeer and such.

It's also a good thing to consider how much compliance is in your suspension. Tolerance stack ups are no laughing matter over the width of a vehicle connected by several linkages (think steering rack). Also, tire compliance becomes quite a factor in fine tuning everything and can lead to surprising results if it's not looked at during the original design.You may plan for -1 of camber during your simulations but end up with +3 during testing (or worse, toe!).

An overriding account for all of this is donut steer angle. You can get some wicked tight and quick donuts in these cars. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[acedeuce802]

Originally posted by MCoach:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Also know that you should design past the "optimal" max steering angle, to account for understeer and such.

It's also a good thing to consider how much compliance is in your suspension. Tolerance stack ups are no laughing matter over the width of a vehicle connected by several linkages (think steering rack). Also, tire compliance becomes quite a factor in fine tuning everything and can lead to surprising results if it's not looked at during the original design.You may plan for -1 of camber during your simulations but end up with +3 during testing (or worse, toe!).

An overriding account for all of this is donut steer angle. You can get some wicked tight and quick donuts in these cars. http://fsae.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>
Scary compliance!

[MCoach]

Yes, that would be some seriously scary compliance and an extreme example.

On the camber side, with how floppy these tire's sidewalls seem to be and the low pressures that can be run, I wouldn't be surprised if someone actually achieved those values...

On the toe side, for the love of driver safety, I hope those values haven't been seen for front nor rear...

[Pennyman]

If you drift around the corner your turning radius doesn't have to be very big at all, but it requires counter-steer.

Seeing as your design deadline has passed, if you get a chance to put some data aq on your car, try doing some tests with average steering angle for a given corner. If you can measure your average speed through that section of your test, you might be onto a good empirical method for evaluating your steering geometry.