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Roll axis inclination

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=2728
Printed Date: Jun/18/2019 at 8:47am


Topic: Roll axis inclination
Posted By: Rishav
Subject: Roll axis inclination
Date Posted: Jun/19/2018 at 11:59pm
I am designing my suspension geometry for a baja buggy. I want to have a negative understeer gradient for my vehicle. Mine is a rear mounted vehicle. What should be my roll axis inclination?
The front roll centre should be higher or the rear roll centre should be higher?
Please guide



Replies:
Posted By: RLM
Date Posted: Jun/20/2018 at 7:55am
please read a vehicle dynamics textbook. put in the leg work to read it and it will guide you on this and many other things related to suspension design

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McMaster Baja Racing (09-Dec 2015)
Team Captain 2012-2015
Suspension Lead 2015-2016
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Posted By: Rishav
Date Posted: Jun/26/2018 at 7:49am
I read a book as you said sir. But still its not getting clear. Can you please help me out.


Posted By: RLM
Date Posted: Jun/26/2018 at 7:57am
which book did you read? this is laid out in books such as racecar vehicle dynamics. 

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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: Rishav
Date Posted: Jun/26/2018 at 8:02am
I read in RCVD by Miliken sir. And also fundamentals of veh dyna by Gillespie. I came to know that the roll moment is transferred due the moment arm i.e. the distance between CG and RC. But how does the direction of roll moment is decided i couldnt guess. Guide me please sir


Posted By: vin2000
Date Posted: Jun/27/2018 at 10:01am
The roll axis just joins both the roll center's , you only need to figure out if you need a higher roll moment at the front or rear. If you ask me how to do this, find out your CG first and put the equations to use from the books you have mentioned.
To be specific to your query, find out the degree of roll at front and rear in a particular direction for a particular lateral load and this will lead to the answer of your question!


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RVCE-BAJA
2011-2015
www.thrbaja.com


Posted By: sujandinesh
Date Posted: Jun/27/2018 at 11:47am
Originally posted by Rishav Rishav wrote:

I read in RCVD by Miliken sir. And also fundamentals of veh dyna by Gillespie. I came to know that the roll moment is transferred due the moment arm i.e. the distance between CG and RC. But how does the direction of roll moment is decided i couldnt guess. Guide me please sir
Any moment is a factor of a force and its moment arm. The moment arm is a scalar so the direction of the moment just depends on the direction of the force. This is just basic physics. 


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RVCE BAJA: 2011-2015
General Motors: 2015-2016
Tyre Testing - University Racing Eindhoven: 2016-2017
Tyre Dynamics - TASS International: 2017-2018

Tyre Engineer - Apollo Vredestein
The Netherlands



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