Challenge

Vehicle Ride 2

DDeepak Raj17 Sept 2020

Total weight= 1900Kg

Total mass front= 0.55*1900=1045Kg

unsprung mass front=90Kg

Sprung mass front=1045-90 =955Kg

Total mass rear= 0.45*1900=855Kg

Unsprung mass rear=60Kg

Sprung mass rear=855-60=795 Kg

i) Sprung mass critical damping

Front

c=2*sqrt(Kr*ms)

Kr=Ks*Kt/(Ks+Kt)

=20*250/(20+250)

=18.51N/mm

c=2*sqrt(18.51*955)

=265.91N-s/m

Rear

c=2*sqrt(Kr*ms)

Kr=Ks*Kt/(Ks+Kt)

=30*250/(30+250)

=26.79N/mm

c=2*sqrt(26.79*795)

=291.82 N-s/m

ii) Unsprung mass critical damping

Front

c=2*sqrt(Ke*mus)

Ke=Ks+Kt

=20+250

=270N/mm

c=2*sqrt(270*90)

=311.76N-s/m

Rear

c=2*sqrt(Ke*mus)

Ke=Ks+Kt

=30+250

=280N/mm

c=2*sqrt(280*60)

=259.23N-s/m

iii) Sprung mass initial damping coefficient

Front

Damping ratio=0.7

Front sprung mass initial damping coefficient=damping ratio*front sprung mass critical damping

=0.7*265.91

=186.14N-s/m

Rear

Damping ratio=0.7

Rear sprung mass initial damping coefficient=damping ratio*rear sprung mass critical damping

=0.7*291.82

=204.3 N-s/m

iv) Unsprung mass initial damping coefficient

Damping ratio=0.2

Front unsprung mass initial damping coefficient=damping ratio*front unsprung mass critical damping

=0.2*311.76

=62.352N-s/m

Rear

Damping ratio=0.2

Rear unsprung mass initial damping coefficient=damping ratio*rear unsprung mass critical damping

=0.2*259.23

=51.85N-s/m

v and vii) Low speed compression and rebound damping co-efficent

wkt R=3C, R+C/2=I

So, C=I/2 and R=3*I/2

Front Intial damping I = 2*C = 2*.7*sqrt(1900*20*.55)=202.39 Ns/m
a) Compresion damping = 202.39/2=101.19 Ns/m
b) Rebound damping = 3*C = 3*101.19=303.6 Ns/m

Rear Initial damping I=2*C = 2*.7*sqrt(1900*30*.45)=125.06 Ns/m

a) Compresion damping = 125.06/2=62.53 Ns/m

b) Rebound damping = 3*C = 3*62.53=187.59 Ns/m

vi and viii) High speed compression and rebound damping co-efficent