Vehicle Ride 1
1. i)
Fs=1.15 Hz
Wheelbase=2700 mm= 2.7m
Speed= 60 mph= 26.82 m/sec
Time delay= 2.7/26.82= 0.1 sec
Tf=1/1.15= 0.87 sec
Tf=Tr+Tl
Tr=0.87-0.1= 0.77
Fr=1/0.77=1.30 Hz
Rear sprung mass frequency= 1.30 Hz
ii)-ix)
Front spring rate
Kt=Ks*(MR)^2
Ks=Kt/(MR)^2
=245/(0.97)^2
=260.39 N/mm
Rear spring rate
Kt=Ks*(MR)^2
Ks=Kt/(MR)^2
=245/(0.85)^2
=339.1 N/mm
Front
Kr=Ks*Kt/(Ks+Kt)
=260.4*245/(260.4+245)
=126.23 N/mm
Ke=Ks+Kt
=260.4+245
=505.4 N/mm
Rear
Kr=Ks*Kt/(Ks+Kt)
=339.1*245/(339.1+245)
=142.235 N/mm
Ke=Ks+Kt
=339.1+245
=584.1 N/mm
DESIGN CONDITION
Total weight=1825Kg
% Front=55%
Front
Unsprung mass front=90Kg
Unsprung mass rear=60Kg
Total mass in front=1003.75Kg
Total mass in front quarter=501.875Kg
Sprung mass quarter front=456.875Kg
Unsprung mass quarter front=45Kg
Front sprung mass natural frequency=1/2pi*sqrt(Kr/Sm)
=1/2pi*sqrt(126.232*10^3/456.875)
=2.64 Hz
Front unsprung mass natural frequency=1/2pi*sqrt(Ke/Su)
=1/2pi*sqrt(505.4*10^3/45)
=16.87 Hz
Rear
Total mass in rear=821.25Kg
Total mass in the rear quarter=410.625Kg
Rear unsprung mass quarter=30Kg
Rear sprung mass quarter=380.625Kg
Rear sprung mass natural frequency=1/2pi*sqrt(Kr/Sm)
=1/2pi*sqrt(142.235*10^3/380.625)
=3.08 Hz
Rear unsprung mass natural frequency=1/2pi*sqrt(Ke/Su)
=1/2pi*sqrt(584.1*10^3/30)
=22.21 Hz
Rear/Front sprung mass frequency ratio=1.17
Rear/Front unsprung mass frequency ratio=1.32
CURB CONDITION
Total weight=1500Kg
% Front=60%
Front
Unsprung mass front=90Kg
Unsprung mass rear=60Kg
Total mass in front=900Kg
Total mass in front quarter=450Kg
Sprung mass quarter front=405Kg
Unsprung mass quarter front=45Kg
Front sprung mass natural frequency=1/2pi*sqrt(Kr/Sm)
=1/2pi*sqrt(126.232*10^3/405)
=2.81 Hz
Front unsprung mass natural frequency=1/2pi*sqrt(Ke/Su)
=1/2pi*sqrt(505.4*10^3/45)
=16.87 Hz
Rear
Total mass in rear=600Kg
Total mass in the rear quarter=300Kg
Rear unsprung mass quarter=30Kg
Rear sprung mass quarter=270Kg
Rear sprung mass natural frequency=1/2pi*sqrt(Kr/Sm)
=1/2pi*sqrt(142.235*10^3/270)
=3.65 Hz
Rear unsprung mass natural frequency=1/2pi*sqrt(Ke/Su)
=1/2pi*sqrt(584.1*10^3/30)
=22.21 Hz
Rear/Front sprung mass frequency ratio=1.30
Rear/Front unsprung mass frequency ratio=1.32
GVW CONDITION
Total weight=2000Kg
% Front=52%
Front
Unsprung mass front=90Kg
Unsprung mass rear=60Kg
Total mass in front=1040Kg
Total mass in front quarter=520Kg
Sprung mass quarter front=475Kg
Unsprung mass quarter front=45Kg
Front sprung mass natural frequency=1/2pi*sqrt(Kr/Sm)
=1/2pi*sqrt(126.232*10^3/475)
=2.59 Hz
Front unsprung mass natural frequency=1/2pi*sqrt(Ke/Su)
=1/2pi*sqrt(505.4*10^3/45)
=16.87 Hz
Rear
Total mass in rear=960Kg
Total mass in the rear quarter=480Kg
Rear unsprung mass quarter=30Kg
Rear sprung mass quarter=450Kg
Rear sprung mass natural frequency=1/2pi*sqrt(Kr/Sm)
=1/2pi*sqrt(142.235*10^3/450)
=2.83 Hz
Rear unsprung mass natural frequency=1/2pi*sqrt(Ke/Su)
=1/2pi*sqrt(584.1*10^3/30)
=22.21 Hz
Rear/Front sprung mass frequency ratio=1.09
Rear/Front unsprung mass frequency ratio=1.32
2.
Design condition
Curb condition
GVW condition