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

King pin optimization
Kartik Suthar · 2020-03-30 04:39:28

After hardpoint tuning, less amount of camber gain observed, and less amount of toe-change reduced.   We can\'t control all parameters independently.. caster, caster arm length and steer axis offset(longitudinal) are dependend on each-other. and King pin inclin Read more

post processing
Kartik Suthar · 2019-10-16 16:11:29

All screenshots are attached in ZIP file.... Read more

Damping co-efficient
Kartik Suthar · 2019-09-24 06:43:17

I) Front sprung mass critical damping 5947.299 Kg/sec     Rear sprung mass critical damping 6526.046 Kg/sec II) Front unsprung mass critical damping 6971.37 Kg/sec      Rear unsprung mass critical damping 5796.55 Kg/sec III) Front sprung mas Read more

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

Side View Geometry
Kartik Suthar · 2019-08-13 15:13:37

1. Castor- 6 degree positive     Mechanical trail- 15 mm     KPI- 10 degree      Scrub radius- 30 mm     Spindle Length- 90 mm 2. Restoring Moment- 50 Nm 3. Suggested Change to change sign of scrub radius     Read more

1. Instant Center location Y= 950 mm (negative)                                      Z= 235 mm   2. Roll center Height = 190 mm (below ground)   zip file attach Read more


The End