Roll resistance calculations error?

In summary, the conversation is about calculating weight transfer and roll resistance for a vehicle using a specific formula. The person is struggling with understanding the units of measurement and is seeking help on a forum. They are also recommended to read a specific post on a mechanical engineering forum for further guidance.
  • #1
Jas1159
19
0
Hi,

I am trying to calculate weight transfer from the front to rear of a vehicle and have already calculated the total sprung weight to be transfered.

I now need to calculate the Roll resistance generated by the springs using the following forumula and this is where the error occurs.

(SF/(WmF/SmF)^2) x TF^2 [ x ] 2 x ∏ / 180 = ArF

In laymens terms

SF = Front Spring Rate
WmF=Front Wheel Movement
SmF=Relative Front Spring Movement
TF = Front Track
ArF = Roll Resistance of Front Springs

Now i can't figure out if the x i placed in brackets [ ] is supposed to be / (x or /)?

The example is as follows;

(175/(1.00/0.75)^2)xTF^2x2xPi/180 = 2889.77 in.lbs per degree (roll resistance of front springs)

you will notice that the formula does not equate to the answer and to obtain the answer i must devide... which present me with a problem as my understanding of this particular aspect is clouded by my understanding of the units...

I realize this is probably a 'suck eggs' moment but can somebody explain in practical terms what is meant by in.lbs per degree... the amount of in.lbs per degree of roll but in.lbs is both a distance and a weight...

Any help with either or both of the above problems will be much appreciated.

Regards
Jason
 
Last edited:
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  • #2
hello and Welcome
suggest you read Race car suspension Class
on t his mech eng forum posted Jul29-09

page two has calc for spring ratesmerry Christmas
rm
 

1. What is roll resistance?

Roll resistance is the force that opposes the motion of a rolling object. It is caused by the interaction between the object and the surface it is rolling on.

2. How is roll resistance calculated?

Roll resistance is calculated by multiplying the coefficient of rolling resistance (Crr) by the weight of the object and the acceleration due to gravity. The Crr is a value that is specific to the object and the surface it is rolling on.

3. What factors can affect roll resistance calculations?

There are several factors that can affect roll resistance calculations, including the surface type and condition, the weight and shape of the object, the velocity of the object, and the temperature and humidity of the environment.

4. What are some common sources of error in roll resistance calculations?

One common source of error in roll resistance calculations is inaccurate measurement of the coefficient of rolling resistance. Other sources of error can include changes in surface conditions during the experiment, variations in velocity, and human error in data collection and calculations.

5. How can roll resistance calculation errors be minimized?

To minimize roll resistance calculation errors, it is important to accurately measure the coefficient of rolling resistance and to carefully control and record all variables in the experiment. It is also helpful to perform multiple trials and take an average of the results to reduce the impact of any outliers.

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