Vehicle Dynamics

Question 1

Coordinate System

Answer 1

x = from centre to front +ve
y = centre to left +ve
z = down +ve
all rotation anticlockwise

Question 2

Force driving in a straight line

Answer 2

F = Rd + Rr + Rg + aW/g
Rd - Total Rolling Resistance
Rr - Rolling resistance due to tyre deformation
Rg - effect of gravity due to gradient
a - acceleration
W - weight of vehicle
g - gravity

Question 3

Rolling Resistance

Answer 3

Rr = frW
fr = coefficient of rolling resistance
W - weight

Question 4

Coeffitient of Rolling Resistance

Answer 4

fr = 0.01(1+V/147)
V = velocity

Question 5

Drag

Answer 5

Rd = (rho/2).Cd.Af.V^2
Cd = Coefficient of drag
Af = frontal area

Question 6

Maximum Velocity

Answer 6

(2P/rho.A.Cd)^^1/3
A = frontal Area
Cd = drag coefficient
P = Engine Power

Question 7

Engine Power

Answer 7

P = Fd x v
Fd = drag force
v = velocity

Question 8

BMEP - Brake Mean Effective Pressure

Answer 8

Brake work per cycle / Cylinder volume displaced per cycle
Pb.nr/Vd.N = 2.pi.nr.T/Vd
Pb = Brake power
Vd = volume displaced per cycle
N = Engine Speed
nr = number of crank revs per power stroke per cylinder (2 for 4 stroke engine)