I really liked the idea and design of HDD holder by Johny555, but needed specific spacing for my HDDs. I also wanted to conserve filament and time in printing. So, I poked a few holes in the design, with this re-design using FreeCAD. To make it possibly more useful for others, I also added a couple of "generic" drive spacing versions. The versions here:

1. HDD_Rack - combination:

• 1 slot @ 15mm wide
• 2 slots @ 22mm wide
• 1 slot @ 36mm wide

2. HDD_Rack-17mm - 4 slots @17mm wide each
3. HDD_Rack-22mm - 4 slots @22mm wide each

Update Note: I have added a smaller version of this rack, designed for smaller external, portable SSD (*Solid State Drive) memory devices. See my thing "SSD Storage Holder-Rack" for details.

Customization

I've included the source .FCStd for FreeCAD (free download), in case you want to customize your own spacings for your drives. Just download and install FreeCAD, run it and load the .FCStd file closest to what you need, then edit (double-click) the "Profile Sketch" under "Profile Pad" (on the "Model" tab, "Labels & Attributes" tree). The drive slot spacings are shown as dimensions on the sketch - just position the mouse cursor over the dimension number on the sketch until it turns yellow, then double-click to change the dimension. Try small changes first to see how your changes affect the entire part, as some "radical" changes may "break" the design.