How is the roll centre used during braking?

  • Thread starter Thread starter nb89
  • Start date Start date
  • Tags Tags
    Braking Roll
Click For Summary

Discussion Overview

The discussion revolves around the application of roll centre in calculating weight transfer during braking, acceleration, and cornering in vehicles, particularly focusing on a three-wheeled car and four-wheeled vehicles. Participants explore the relationship between roll centre, centre of gravity, and weight transfer, as well as the implications for vehicle stability and suspension design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether the roll centre should be used in weight transfer calculations, noting a lack of formulas incorporating it.
  • Another participant suggests that roll centre height affects the distribution of overturning moments during cornering.
  • A participant raises the specific case of a three-wheeled car, questioning how weight transfer occurs between the wheels and the role of the roll centre in this scenario.
  • There is a discussion about the difference between roll centre and centre of gravity, with emphasis on their distinct roles in weight transfer calculations.
  • One participant inquires if the roll centre can be used to determine the angle of body roll.
  • Another participant expresses uncertainty about calculating weight transfer for motorcycles and suggests waiting for more knowledgeable contributors on that topic.
  • Participants discuss the objective of determining the correct spring size to handle maximum weight transfer during cornering.
  • There is mention of using the formula F=kx for selecting spring size, indicating a connection to weight transfer calculations.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and agreement regarding the role of roll centre in weight transfer calculations. Some participants propose methods for calculating weight transfer, while others question the applicability of these methods to different vehicle types. The discussion remains unresolved with multiple competing views on the topic.

Contextual Notes

Participants acknowledge limitations in their understanding of roll centre calculations, particularly in relation to different vehicle configurations, such as motorcycles and three-wheeled vehicles. There is also uncertainty about the specific formulas and their applicability to various scenarios.

Who May Find This Useful

Individuals interested in vehicle dynamics, suspension design, and weight transfer mechanics, particularly those working on or studying automotive engineering and related fields.

nb89
Messages
37
Reaction score
0
I'm calculating the weight transfer experienced by a car during braking, accelerating and cornering. So far i have been using moment equations with the centre of gravity height. I've used some suspension software to determine the roll centre and was wondering if this is meant to be used when calculating weight transfer? I've read about the roll centre but have not found it being used in any formulas anywhere. Is the roll centre mainly found to make sure it is not far off from the centre of gravity height? Thanks.
 
Engineering news on Phys.org
i recommend you look at post in mech engineering forum
Jul22-09, 11:03 AM titled
Race car suspension Class
and get back with me..
 
Ranger Mike said:
i recommend you look at post in mech engineering forum
Jul22-09, 11:03 AM titled
Race car suspension Class
and get back with me..

Thanks for that, I read through the roll centre section and saw this:

'Roll center height determines what percentage of the overturning moment (inside to outside weight transfer) will be distributed onto the tire contact patch a downforce, and what percentage is received as lateral loading against the tires tread face'

Does this mean the roll centre height should be used when calculating the weight transfer during a corner? I have been using Weight transfer = (Lateral acceleration x Weight x Height of CG) / Track width.

I am actually assessing the stability of a three wheeled car (1front, 2 rear wheels). I am wondering if during the weight transfer, would only the outer rear wheel receive the transferred weight because the single front wheel is located at the centre? I assume the front of the car would not have a roll centre?
 
Roll center and CG are two different points and can not be interchanged in the formula...
a percnetage of the sprung weight is transferred thru the roll center..the amount is a function of the length between the CG and the RC and acts as a moment or lever in this case
i am sure motorcycles have roll centers as they have suspensions...right?? You need to find out how to calculate the RC of a motorcycle..i have no desire to do this my self...also you should be able to find RC of a Tryke as well..good luck
 
Last edited:
Ok i think I'm kind of getting it. Would you have to use the weight at the rear of the car multiplied by the length between CG and the rear RC to find the % of weight transferred through the roll centre? And then same with the front weight and front RC? Is the RC also used to determine the angle the body has rolled by?
 
good questions all.. regarding this post..are you designing a vehicle from ground up? or does the vehicle already exist?
I can address the amount of weight transferred with regard to a four wheel vehicle but i can not address motorcycle questions..
i suggest yo u wait for other posters who know bikes in detail to assist you on this matter...
 
The vehicle already exists. Could you answer the question with regards to a four wheeled vehicle then, just so i can make sense of it. Thanks
 
Ok We can work this out...but..let us agree on the objective you desire which is..i believe..not the amount of weight transfered..but, the
What is the correct size SPRING required to properly handle maximum weight transferred when cornering...
correct??
 
Yes that is one of my objectives, I've done some calculations already on weight transfer, but how would i select the right spring size? Would i have to use F=kx?
 
  • #10
I think it will be beneficial to all if we move this post to Mechanical Engineering forum
Race car set up help
 

Similar threads

  • · Replies 15 ·
Replies
15
Views
7K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 9 ·
Replies
9
Views
8K
  • · Replies 13 ·
Replies
13
Views
7K
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
8
Views
2K
  • · Replies 17 ·
Replies
17
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K