Calculation of Time lag using frequency

1. Wheel rate differs from spring rate because of motion ratio. motion ration generates because of suspension geometry like arm length and suspension attachment point etc. And Wheel rate = Spring rate * (MR)`square`.

2. Wheel rate measures by wheel center line considering stiffness of spring and motion ratio. And Ride rate measures by ground level considering stiiffness of spring and tyre as well. So their value are differ by considering equivalent stiffness.

3. No.

At Low speed frequncy high damping is required and at high speed frequncy low damping is required.

At Compression low damping is required because spring absorbs the energy and at rebound high damping is required.

4. If both front and rear ride frequency are same then pitching of vehicle occurs due to incresed time lag after hitting a bump. If we keep rear frequency higher than front, then time lag reduces and we can match cycle earlier for flat ride.

5. For improved vibration isolation, 

Lower unsprung mass and lower damping is necessary.


6. The ride height can be optimised based on the speed, type of surface and whether the truck is laden or empty. Usually an unladen truck will be taller than a laden truck because the suspension isn’t compressed, but with air suspension, the ride height can be lowered. Travelling with a lower ride height means better handling and ride characteristics and cornering performance.


7. K(eqv) for sprung mass frequency= 22.727 N/mm, Corner weight is 500 Kg

Sprung mass Frequency is 1.073 Hz

K(eqv) for unsprung mass frequency= 275 N/mm, Unsprung mass is 50 Kg

Unsprung mass frequency is 11.80 Hz


8.  Time lag for  case 1 is 0.0055 sec

Time lag for case 2 is 0.00101 sec

Difference in time period for case 1 is 0.4166 sec

Difference in time period for case 2 is 0.1436 sec


Time lag due to wheel base and speed is 0.15 sec.

Based on above result case 2 setup is suitable for flat ride.

Relevant calculations are attached.

Projects by Kartik Suthar

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Frequency calculation
Kartik Suthar · 2019-09-17 13:07:13

1) I) Rear sprung mass frequency based on wheel base and speed will be 1.358 Hz, time lag because of wheel base and speed is 0.10 sec. II) Front sprung mass frequency at design condition 1.131 Hz III) Front Spring rate 23.853 N/mm IV) Rear Spring rate 27.711 N/mm V) Read more

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The End