Besides the obvious: 2ea 3.5" HDDs suspended in my Evercase ECE3505 uATX case, the objectives are A) excellent
point cooling of both HDDs, independent of any case openings, and B) sound blocked except towards the rear of the case.
The removable steel HDD cage is cut away except for the top and 0.4" of the sides to provide a secure removable support for the large structure.
A 5-sided rubber box with at least 3/16" walls holds the fan and HDDs, and is open to the rear of the case. I used buna (neoprene) sheet rubber from McMasters, page 3328, assembled with superglue. The total suspended weight is just under 4lb. Here's the basic idea:
The suspension details (and some construction details if you look closely). I used two (not four) 1.5mm Stretch Magic 5.9" bands (which stretch ~20%); the 1/8" aluminum rods are also from McMaster, page 3427:
The completed model in an empty case except for a dummy motherboard, with old HDDs (note truncated top of the steel HDD cage):
Ready to run with real HDDs and an airflow divider, mounted in my #2 computer:
The fan and airflow divider mounting brackets (friction fit) in white-sidewall rubber:
Rubber-washer production. Note the bottom of the truncated steel HDD cage and the support rods. The center rod was discarded in the final version:
A Scythe 1000RPM 100mm fan cools the two HDDs (Samsung SP0822N, 7.4W idle and "Hitachi" 7K160, 4.9W idle) to 10C over room ambient. If the top HDD is also an SP80, its temp goes up another 1.5C.
By mounting the HDDs and their cooling fan in this enclosure, I can assemble a computer whose only other rotating part is a 220mm fan, replacing the exhaust and PSU 120mm fans (the floppy and optical drives are used every week or two for backup only). Thus, the 220mm fan's noise and vibration can be evaluated without contamination. But that's for another forum.
edit: substituted png for jpg, pic #2
edit2: substituted png for jpg, pic #1