Vehicle Ride 2
Q1.
Ans: total weight = 1900kg
total mass front = 0.55 * 1900 = 1045 kg
unsprung mass front = 90 kg
sprung mass front = 955 kg
total rear mass = 855 kg
unsprung mass rear = 60 kg
sprung mass rear = 795 kg
sprung mass critical damping
Front
c = 2* sqrt (Kr*Ms)
Kr = Ks * Kt/(Ks + Kt)
= 20 * 250 / (20+250)
= 18.51 N/mm
c = 2*sqrt(18.51*955)
= 265.91 N-s/m
Rear
c = 2*sqrt(Kr*Ms)
Kr = Ks*Kt/(Ks+Kt)
= 30*250/(30+250)
= 26.79 N/mm
c = 2*sqrt(26.79*795)
= 291.87 N-s/m
unsprung mass critical damping
Front
c = 2*sqrt(Ke*mus)
ke = ks +Kt
= 20 + 250
= 270 N/mm
c = 2*sqrt(270*90)
= 311.76 N-s/m
Rear
c = 2*sqrt(Ke*mus)
ke = ks + Kt
= 30 +250
= 280 N/mm
c = 2*sqrt(280*60)
= 295.23 N-s/m
sprung mass initial damping coeficient
Front
Damping ratio = 0.7
= 0.7*291.87
= 186.14 N-s/m
Rear
Damping Ratio = 0.7
= 0.7*291.87
= 204.31 N-s/m
unsprung mass initial damping coeficient
Front
Damping Ratio = 0.2
= 0.2*311.76
= 62.352 N-s/m
Rear
Damping ratio = 0.2
= 0.2*259.23
= 51.85 N-s/m
compression damping coeficient
Front
sprung mass = 265.91/2 = 132.96 N-s/m
unsprung mass = 311.76/2 = 155.88 N-s/m
Rear
sprung mass = 291.87/2 = 145.94 N-s/m
unsprung mass = 295.23/2 = 129.62 N-s/m
rebound damping coefficient
Front
sprung mass = 3*132.96 = 398.88 N-s/m
unsprung mass = 3*155.88 = 467.64 N-s/m
Rear
sprung mass = 3*145.94 = 437.82 N-s/m
unsprung mass = 3*129.62 = 388.86 N-s/m
LOw speed compression damping rate
Front
DR = 265.9*0.7
= 186.137 N-s/m
low speed compression damping force
CF = DR*Knee speed
= 186.137*50
= 9,306.85 N
Rear
DR = 291.87*0.7
= 204.31*50
= 10,215.5 N
High speed compression damping rate
Front
DR = 311.76*0.2
= 62.352 N-s/m
CF = DR* max speed
= 62.352*500
=31,176 N
Rear
DR = 259.23 *02
= 51.85 N-s/m
CF = 51.85*500
=25,925 N
Low speed rebound damping rate
Front
DR = 3*186.137
= 558.4 N-s/m
RF = 3*9,306.85
= 27,920.55 N
Rear
DR = 3*204.31
= 612.93 N-s/m
RF = 3*10,215.5
= 30,646.5 N
High speed rebound damping rate
Front
DR = 3*62.352
187.056 N-s/m
RF = 3*31,176
= 93528 N
Rear
DR = 3*51.85
= 155.55 N-s/m
RF = 3*25925
= 77775 N