steering problem!!

[snoop]

hello all !
i have a problem at my planning our first steering sys. we are a new group ' we haven't the tire data and we don't know which sys. build if pro/anti ackermann . also, we have only 95mm between the steer wheel location and the front axis.
so my question is if because that i plan a anti ackermann' then i have a space to do that what i haven't if i want to locate the pro.
ty Snoop http://fsae.com/groupee_common/emoticons/icon_smile.gif

[snoop]

hello all !
i have a problem at my planning our first steering sys. we are a new group ' we haven't the tire data and we don't know which sys. build if pro/anti ackermann . also, we have only 95mm between the steer wheel location and the front axis.
so my question is if because that i plan a anti ackermann' then i have a space to do that what i haven't if i want to locate the pro.
ty Snoop http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Chris Craig]

Firstly
this is very hard to understand

Secondly
if you have no tyre data, you cant really have a usable simulation model so therefore where is your justification for anti ackermann

and Finally
use 'Find', it works wonders

[snoop]

Sorry, but i don't understand why anti ackermann it's the solution chosen?
If i get at futures the tire data what affect of my decision if it's going to be anti/pro?
ty

[Bemo]

I think what Chris wanted to say is that as long as you don't have any tire data you can't simulate or calculate anything and your design is just a guess.

[Goost]

Snoop, I'm having a hard time understanding what you want to know. The reason you want shouldn't use true Ackermann steer ratios is because in a turn the outside wheel is loaded (weight transfers) and so the peak slip angle for the outside and inside tyres are different (only true at high lateral accelerations, of course). Since your car should be seeing significant lateral g-force, and <STRIKE>peak tyre slip angles typically decrease with increased load</STRIKE>[edited 12/4: should read 'peak tyre slip angles typically increase with increased load'], your car should probably have parallel steering or better reverse Ackermann (meaning Delta_outside &gt; Delta_inside) If you don't already have it get/borrow a copy of RCVD. a quick read through chapter 19 could help you considerably.

Austin G
Auburn University
War Eagle Motorsports
Suspension Kinematics

[Mehul Botadra]

Speeds arent that huge to reach the peak slip angle unless you're using softer springs that allow more weight transfer. I'd prefer 4-5% more over Ackerman(100%) but it changes from driver to driver!

[exFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mehul Botadra:
Speeds arent that huge to reach the peak slip angle unless you're using softer springs that allow more weight transfer. I'd prefer 4-5% more over Ackerman(100%) but it changes from driver to driver! </div></BLOCKQUOTE>

Since when does spring stiffness change your global weight transfer?

Likewise with speed affecting "peak slip angle." You most certainly can saturate the tires on these cars.

[Mehul Botadra]

Sorry I meant roll, my bad!

[Goost]

This is true, exFSAE.
Mehul, I would think roll shouldn't really affect slip angles unless your car has pretty extreme Roll-Camber...

Also, snoop, I mistakenly said that "peak tyre SA decreases with increased FZ." this obvious contradicts my correct statement that the outside tire should have a greater steer angle (Delta_outside) than the inner one (Delta_inside). Sorry!

[snoop]

ty all, but we just ordered the tire data so i think it's going to be easier for us.
I appreciate your help..