Forces Acting on a Vehicle

Title : Forces Acting on a Vehicle

Objective :

1. What should be the maximum speed of the motor used in an electric scooter capable to run at 90 kmph, if the fixed gear ratio is 7 and tire size is 90/100 R10 53J? How to read a tire?

Recalculate the same value if tire code is 90/90 R18 51P?

Solution:

To calculate Maximum Angular speed ,

we have

ω=G.V/r

where , G =7

V= 90kmph ; 90.5/18=25m/s

Now give tyre size is tire size is 90/100 R10 53J

D = 10inches ; 0.254m

then r = D/2 = 0.127

`Angular speed ω= G.V/r`

= 7. (25/0.127)

ω = 1322.83 rpm

Now as per new tyre code lets calculate new Angular speed

Give tyre dimensions :90/90 R18 51P

D = 18 inch ; 0.4572m

so, r= 0.2286

Angular speed ω= G.V/r`

= 7. (25/0.2286)

ω = 765.52 rpm

2. Prepare a simple excel calculator to identify vehicle propulsion power based on given inputs and outputs.

Inputs: Kerb Weight (kg), Payload (kg), Coefficient of rolling resistance, Air density (kg/m3), Width (m), Height (m), Drag coefficient, Speed

Output: Total power in kW

Solution:

What are the limitations of this calculation?

We have to put all input values manually. Also we have to put

Formulas manually to calculate desired values.

Ex. To calculate Air drag we have to put formula as follow

=0.5*B11*B13*B14*B16*B16 in excel.

These are all limitation of using Excel calculator.

3. Assuming that tire pressure reduction by 15% results in increase of rolling resistance effect by two times, how much will be the difference in total traction power keeping all other parameters same?

Solution:

If the tyre pressure reduces by 15% then rolling resistance effect is two times.

So in below image i have Vehicle 3 Rolling resistance by two times shown in Vehicle Column.

So as per this all the other values are changed shown in RED and Green box.

4. See the video of Range rover sport dragon challenge. How much is the gradeability? What was the average speed? Which are the forces acting on car?

Link to the video: https://www.youtube.com/watch?v=EUwzWHD3Htg

Solution:

Key Specifications of Land Rover sports