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Understeer

Printed From: Official Baja SAE Forums
Category: General
Forum Name: Design Discussion
Forum Description: Discuss Design, Tech, Cost, and related issues
URL: http://forums.bajasae.net/forum/forum_posts.asp?TID=2790
Printed Date: Feb/16/2020 at 10:16pm


Topic: Understeer
Posted By: dajay
Subject: Understeer
Date Posted: Apr/11/2019 at 1:08pm
Our team is having an ackerman percentage of 82 % and with an inner lock angle of 43 degree but when trying to steer at low speeds the vehicle tends to understeer due to slipping of the front wheels. Should we increase the Ackerman percentage morebthan 100percent to avoid understeer?. Or is it due to less load distribution on the front tyres



Replies:
Posted By: RLM
Date Posted: Apr/15/2019 at 8:19am
the answer to this is very car dependent. it will be different for every team. for under/over steer characteristics, you need to look at the entire suspension and steering system as a whole and analyze and make changes from there. look at roll axis inclination as a basic starting point. 

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McMaster Baja Racing (09-Dec 2015)
Team Captain 2012-2015
Suspension Lead 2015-2016
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Posted By: dajay
Date Posted: Apr/15/2019 at 12:07pm

Rear roll centre is lower than that at the front. What effect can it have on understeer and oversteer.Does roll axis inclination have much effect on slow speed cornering?


Posted By: RLM
Date Posted: Apr/16/2019 at 8:18am
Originally posted by dajay dajay wrote:

Rear roll centre is lower than that at the front. What effect can it have on understeer and oversteer.Does roll axis inclination have much effect on slow speed cornering?

If you do not already know the answer to this, it may be time to put your design on hold while you do some more research and readings. I suggest Racecar vehicle dynamics by milliken. It contains the answers you seek.


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McMaster Baja Racing (09-Dec 2015)
Team Captain 2012-2015
Suspension Lead 2015-2016
All spoonfeed PM requests will be billed at $10 USD per reply, payable via paypal.


Posted By: but1ene
Date Posted: Jul/29/2019 at 9:29am
if your roll centre is higher than real.....while cornering your front tyres dont get much grip due to less weight transfer.....the main job of cornering is done by your front tyrs....try changing yoour roll axis so that roll centre is low at fron and relative near the cg at the rear



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