Hi T-Nagers,

I know that this is a largely Mechanical question, but I need your
recommendations for light-weight materials that I could use in place of
aluminium to make a vibration test jig. I have been landed with designing
an ESS jig to take a 14.5kg (32.5lbs) box that will be attached in three
places - by a wedge-shaped tongue into a groove arrangement along the rear
bottom edge, and by two ARINC fasters at the bottom of the front panel
below all the interface connectors.

The ESS Vibration test is 10 minutes Random vibration in one axis.
Frequencies range between 20Hz and 2000Hz, with the vibration profile
ramping up between 20Hz and 80 Hz at 3dB/octave to an acceleration spectral
density of 0.04g^2/Hz, then ramping down again between 350Hz and 2000Hz at
-3dB/octave. The vibration table we have will take a maximum theoretical
weight of 82 lbs at a spectral density of 0.04g^2/Hz before it self-aborts,
so allowing for some oscillation around the max s.d. figure of the profile
and a margin of safety for the weight of the Unit to be tested, I reckon I
have a maximum weight allowance for the vibration test jig of 37.5 lbs.

The jig we have, designed by someone else without a lot of science or math
involved, weighs in at around 26kg (58lbs), so it has to lose a lot of
weight before we can use our own vibration table.

If I can't put the jig on an effective diet, I'm faced with relying on
renting expensive time at an outside facility that's already pretty
popular, so my windows of opportunity are unlikely to match the times when
I need to use the vibrator without a lot of dead waiting time.

Hope someone out here knows what I'm talking about and can help. I've never
known this forum to be be completely stumped for an answer to anything yet.

Peter

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