Vehicle Ride 1
The MS Excel file of this work is also attached, find that below.
The Answer to Question 1(i):
First of all, let\'s find the time lag between the front ride and rear ride.
Wheelbase = 2700 mm = 2.7 m
Speed = 60 mph = 26.82 m/s
Time lag, t = Wheelbase / speed
= 0.1 s
Front sprung mass frequency, Ff = 1.15 Hz
Front sprung mass time period, Tf = 1/1.15 = 0.87 s
For a flat ride,
Tr + t = Tf
Tr + 0.1 = 0.87
Tr = 0.77 s
rear sprung mass frequency, Fr = 1/0.77 = 1.3 Hz
The Answer to Question 1(ii):
Front sprung mass frequency, Ff = 1.15 Hz (given)
The Answer to Question 1(iii):
Front spring rate = Ksf
Front wheel rate = Kwf = 245 N/mm
motion ratio = 0.97
We know that,
Kwf = Ksf X (motion ratio)^2
Ksf = ( 245 X 1000) / 0.97^2Ksf
Ksf =260.39 N/mm
The Answer to Question 1(iv):
rear spring rate = Ksr
rear wheel rate = Kwr = 245 N/mm
motion ratio = 0.85
We know that,
Kwr = Ksr X (motion ratio)^2
Ksr = ( 245 X 1000) / 0.85^2Ksf
Ksr =339.1 N/mm
The Answer to Question 1(v):
calculations for Curb:
Curb weight of a vehicle is the weight with all the Types of equipment and fuel but the weight of passengers is excluded.
Total weight = 1500 kg
%F = 60
total front weight = 60% of 1500 = 900 kg
Total front weight in quarter car model = 900/2 = 450 kg
unsprung mass front = 90 kg
front unsprung mass in quarter car model, Mfus = 90/2 = 45 kg
front sprung mass in quarter car model, Mfs = 450 - 45 = 405 kg
Similarly,
total rear weight = 40% of 1500 = 600 kg
Total rear weight in quarter car model = 600/2 = 300 kg
unsprung mass rear = 60 kg
rear unsprung mass in quarter car model, Mrus = 60/2 = 30 kg
rear sprung mass in quarter car model, Mrs = 300 - 30 = 270 kg
calculations for GVW:
Curb weight of a vehicle is the weight with all the Types of equipment and fuel but the weight of passengers is excluded.
Total weight = 2000 kg
%F = 52
total front weight = 52% of 2000 = 1040 kg
Total front weight in quarter car model = 1040/2 = 520 kg
unsprung mass front = 90 kg
front unsprung mass in quarter car model, Mfus = 90/2 = 45 kg
front sprung mass in quarter car model, Mfs = 520 - 45 = 475 kg
Similarly,
total rear weight = 48% of 2000 = 960 kg
Total rear weight in quarter car model = 960/2 = 480 kg
unsprung mass rear = 60 kg
rear unsprung mass in quarter car model, Mrus = 60/2 = 30 kg
rear sprung mass in quarter car model, Mrs = 480 - 30 = 450 kg
calculations for Design:
Curb weight of a vehicle is the weight with all the Types of equipment and fuel but the weight of passengers is excluded.
Total weight = 1825 kg
%F = 55
total front weight = 55% of 1825 = 1003.75 kg
Total front weight in quarter car model = 1003.75/2 = 501.875 kg
unsprung mass front = 90 kg
front unsprung mass in quarter car model, Mfus = 90/2 = 45 kg
front sprung mass in quarter car model, Mfs = 501.875 - 45 = 456.875 kg
Similarly,
total rear weight = 45% of 1825 = 821.25 kg
Total rear weight in quarter car model = 821.25/2 = 410.625 kg
unsprung mass rear = 60 kg
rear unsprung mass in quarter car model, Mrus = 60/2 = 30 kg
rear sprung mass in quarter car model, Mrs = 410.625 - 30 = 380.625 kg
Hence, fsf (curb) = 2.81 Hz
fsf (GVW) = 2.81 Hz
The Answer to Question 1(vi):
rear sprung mass in the Quarter car model, Mrs (curb)= 300 - 30 = 270 kg (calculated in the previous section)
rear sprung mass in the Quarter car model, Mrs (GVW) = 480 - 30 = 450 kg (calculated in the previous section)
Hence, fsr (curb) = 2.81 Hz
fsr (GVW) = 2.81 Hz
The Answer to Question 1(vii):
front unsprung mass in quarter car model, Mfus = 90/2 = 45 kg (calculated in earlier parts)
unsprung mass at all three load condition is equal. so the natural frequency of the front unsprung mass is 16.87 Hz.
The Answer to Question 1(viii):
rear unsprung mass in Quarter car model, Mrus = 60/2 = 30 kg (calculated in earlier parts)
unsprung mass at all three load condition is equal. so the natural frequency of the rear unsprung mass is 22.20 Hz.
The Answer to Question 1(ix):
For curb:
f(rear)/f(front) = 3.65 / 2.81 = 1.30
For GVW:
f(rear)/f(front) = 2.83 / 2.59 = 1.09
for Design:
f(rear)/f(front) = 2.9 / 2.64 = 1.10
For unsprung mass:(same in all loading condition):
f(rear)/f(front) = 22.20 / 16.87 = 1.32
The Answer to Question 2:
For Curb:
For GVW:
For Design: