Page 55 - Final Report - KAUSC Team

KAUSC Team

3.2 Motor selection

After getting the approximated weight and shape of the car. The motor calculation comes
second to design the transmission system.

 Rolling Resistance Force
The rolling resistance is caused by the tire.

RR = GVW x Crr (4)
RR = Rolling Resistance
GVW = Gross Vehicle Weight
Crr = Co-efficient of Rolling Resistance

Table 35 Values of Co-efficient of Rolling Resistance

0.017 x 100 x 9.81 x 4 = 66.708 N

 Drag Force
The drag force is caused by the speed of the car into the wind

Fd = 1 2 (5)

2

Fd = drag force (N)

cd = drag coefficient
ρ = density of fluid (1.2 kg/m3 for air at NTP)

v = flow velocity (m/s)

A = characteristic frontal area of the body (m2)

0.5 x 0.5 x 1.2 x 11.11^2 x 0.48 = 17.77 N

 Acceleration force
The acceleration force is the inertia of the mass to be accelerated.

Fa = m a (6)

m = mass of the vehicle

a = required acceleration (0.741 m/s2)

0.7 x 200 = 148.2 N

54 | P a g e