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I'm driving a small, benchtop vibe table (shaker) with two Crown DSI-1000 PA's, and also cleaning my signal with a DBX 231s EQ. Currently running the system at 6.8 GRMS, but I'm looking to increase my overall driving level.

With the test article mass/ test levels I'm shooting for, I'm conflicting with the specified peak capability of my shaker.

To be more precise, I would like to drive a ~5.5 lb object to ~10 grms (random vibe). According to my back-of-the-envelope calcs (Eqn 1), I don't think there is much I can do besides purchasing a larger shaker. This shaker tops out at 200 lbf. However I figured it would be worthwhile to probe the community for ideas in case there is some sort of engineering voodoo I can employ. Will also post in EE stack exchange.

TL:DR, Is there any way for me to increase the peak driving force/ capabiltiy of my shaker table without the risk of damaging it?

My PA's and EQ are also getting close to their maximums, at just 6.8 grms.

Desired profile: NASA GEVs STD-7000a: enter image description here

Eqn 1: GRMS = [PEAK_SHAKER_FORCE / (ARTICLE_MASS + ARMATURE_MASS)] / 2 . --> GRMS = (200 lbs/ 13.5 lbs) / 2 ...................................................................... --> GRMS_MAX = 7.4

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No, there is not really much you can do. If you want to get 10 Grms, you'll need a bigger shaker. The only trick you could play would be to decrease the bandwidth of your test spectrum. i.e. instead of testing 20 - 2000 Hz, just test 20 - 1000 Hz. The g^2/Hz stays the same, but the Hz range is smaller, so now you don't have to drive 10 Grms anymore, but a smaller number. You could perhaps split your testing into multiple segments. Segment 1 test 20 - 1000 Hz, and then segment 2 test 1000 - 2000. Depending on the intent of the test, this may or may not be acceptable.

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  • $\begingroup$ Thanks Daniel, that's a really interesting idea. I'll need to do some more research to determine if this is an acceptable route for my testing campaign. If not, I'll go ahead and look into getting a larger shaker. Cheers! $\endgroup$ – Austin Prater Aug 14 '18 at 16:51

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