Psion Teklogix Vehicle-Mount Computer 8590 - Manual (Page 173)

8580/8590 Vehicle-Mount Computer User Manual D-3
Appendix D: Mechanical Dynamic Loading
Passive Vibration Insulation (tuned to low frequency)
D.3 Passive Vibration Insulation (tuned to low frequency)
Selection criteria: Mobile use
Note: The system can be tuned to a low frequency by installing a
flexible bearing.
For example, you can attach the mounting bracket to elastomer springs or rubber
buffers.
The ideal total spring constant should be dimensioned in such a way so that the
natural frequency of the system falls below the lowest excitation frequency.
All excitations with a frequency greater than 1.4 times the natural frequency would
then be dampened by a counter-phase effect. This is practically impossible, if you
consider that excitation accelerations within the range of around 10 Hz to 200 Hz or
more may occur. Furthermore, the springs of the 8580/8590 would strongly deflect
while static or visibly swivel while resonating (blurred display).
Based on our experience, we have found that the natural frequencies of unsprung
ground vehicles lie between 15 Hz and 25 Hz. Although the elastic bearing does
create an interfering resonance, it can suppress high excitation frequencies to
various degrees of success.
D.4 Dimensioning Example 8580
Example for dimensioning an elastic bearing with mounting bracket for mobile
application.
The 8580 is screwed into a mobile position with a mounting bracket. Elastomer
springs should be installed between the back of the mounting bracket and the
assembly surface in the vehicle so that the depth can be adjusted.
The point of resonance for the spatial axis with the greatest deflection should be
20Hz.
• Which elastomer springs are suitable?
• Which insulating effects can be expected for different excitation frequen-
cies?