Psion Teklogix Vehicle-Mount Computer 8590 - Manual (Page 176)

Appendix D: Mechanical Dynamic Loading
Further Possible Steps For Optimization
D-6 8580/8590 Vehicle-Mount Computer User Manual
The next step is to look through the manufacturer's datasheets (such as those from
gmt-gmbh.de or simrit.de) to find the right types of elastomer springs and rubber
buffers.
Here we have decided to use springs with an M8 thread and cylindrical body made
of natural rubber (NR). Based on the datasheet for a diameter of 30 mm and a height
of 20 mm, for example, we arrived at the pressure load:
Compressive force 539 N / Displacement 1 mm = 539 N/mm for a Shore hardness A
70.
This value lies below the default value. What is the natural frequency?
The following formula can be used to calculate the natural frequency:
This theoretical value of 19.1 Hz lies in the range of 20 Hz to 5 Hz as measured in
practice.
The calculations depicted above are only approximations, which is why we
recommend a final field test with the selected elastomer springs.
D.4.2 Further Possible Steps For Optimization
• If it turns out that the 8580/8590 resonance deflections could be greater, the
natural frequency can be reduced.
Where:
f
e
= natural frequency in Hz
c = total spring constant = 539 N/mm (calculated from datasheet
values)
* 3 (springs) / 22.5 (factor) = 71.9 N/mm
m = oscillatory mass = 5 kg
Hz
m
c
f
e
1 . 19 03 , 5 = ⋅ ≈