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Shelf rack

Problem

There was a 19-inch rack gigabit switch, spending its days laying behind a table, resting against a wall. It needed to be attached to a wall in a more permanent way, to keep it accessible but out of the way.

There are off the shelf rack kits for wall mounting. They are however big and expensive. A lightweight solution was desired.

Solution

It was decided to make a pair of shelf brackets, with front side matching the 19" rack mount slots.

Two shelf brackets were bought off-the-shelf (heh). Two pieces of 20mm wide and 4mm thick, 120mm long L-brackets were also bought.


Raw parts, as bought

L-brackets, marked

Raw parts

The L-brackets were large enough for two and half rack units. As the topmost device can rest on the underlying one, up to 3 units can be attached. More can potentially sit on top of these, without fastening to the side mounts.

The hole positions according to the MIL-STD-189 standard were marked on the L-brackets, drilled and tapped with M6 thread. The M6 size was chosen on the basis of being used in the cage nuts for heavier equipment.


L-bracket, drawing

L-bracket, drillled, threaded

L-bracket, drillled, threaded

L-bracket, drillled, threaded

The L-brackets came with existing holes. These were chamfered to take a sink-head M6 screw. Additional hole was drilled in the shelf brackets, and the one existing at the end was enlarged. A pair of M6 screws with nylon-insert self-locking nuts was used to join the shelf brackets with the L-brackets. The switch was mounted with a pair of flat-head M6 screws on each side.


Angle irons mounted on shelf holders

Angle irons mounted on shelf holders

Switch attached

To hang the assembly on the wall, six holes had to be drilled in somewhat accurate locations.

To transfer the hole positions to the wall, the assembly was positioned on a sheet of paper (assembled from three taped-together A4 sheets) and the position of the holes was marked. The distance from the sheet edges was checked to be consistent to make sure the assembly was kept parallel. The sheet was then held against the wall, adjusted to position and made horizontal, and the hole positions were transferred through the paper to the wall by a tip of a screwdriver.

The holes were predrilled with a 6mm drill, then enlarged with 10mm one. Each hole was equipped with a wall plug. Fairly large plugs, requiring 10mm holes, were chosen to have a large surplus of mechanical strength. There is never enough surplus of strength.


Mockup drawing

Mockup drawing

Mockup drawing

Holes in the wall

The rack was attached to the wall plugs using appropriate wood screws.


Mounted rack

Mounted rack

Mounted rack

Mounted rack

It turned out that the distance between the back of the rack and the wall is fairly large; the size of the bracket was chosen conservatively, to facilitate large equipment later. A cable guard to hold the cables closer to the wall was therefore made.

A length of a 10mm wide cover rail was cut to size. Holes were drilled to match the top side holes on the wall brackets. The holes closest to the wall were tapped with M5 thread. The rail was attached to the holes using M5 screws. Cables were led over and behind the resulting cable guard.

The switch itself now can double as a shelf, for storage of various networking equipment.


Shelf top detail

Shelf top detail

Cable guard threaded hole

Cable guard

Cable guard

Cable guard

Cable guard

Final assembly

Final assembly

Results

The system hangs on the wall fairly well. The attachment is surprisingly rigid, seems able to withstand many many times the existing load and won't fall off even if a cable is yanked hard.

Todo

See also


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