Here is what a U is:
Main article: Rack unit <https://en.wikipedia.org/wiki/Rack_unit>
Racks are divided into regions, 44.50 millimeters (1.752??in) in height,
within which there are three complete hole pairs in a vertically
symmetric pattern, the holes being centered 6.35 millimeters (0.25??in),
22.25 millimeters (0.88??in), and 38.15 millimeters (1.50??in) from the
top or bottom of the region. Such a region is commonly known as a *U*,
for /unit/, or, in German, *HE*, for /H??heneinheit
<https://de.wikipedia.org/wiki/H%C3%B6heneinheit>/, and heights within
racks are measured by this unit. Rack-mountable equipment is usually
designed to occupy some integer number of U. For example, an
oscilloscope <https://en.wikipedia.org/wiki/Oscilloscope> might be 4U
high, and rack-mountable computers are mostly between 1U and 4U high. A
blade server <https://en.wikipedia.org/wiki/Blade_server> enclosure
might require 10U.
Occasionally, one may see fractional U devices such as a 1.5U server,
but these are much less common.
The height of a rack can vary from a few inches, such as in a broadcast
console, to a floor mounted rack whose interior is 45 rack units (200.2
centimeters or 78.82 inches) high, with 42U being a common
configuration. Many wall-mounted industrial equipment enclosures have
19-inch rack rails to support mounting of equipment.
A R-390 is 10.5 inches tall so it is 6U.
Your rack could be drilled for using mounting screws of: 10-32, 12-24,
M6 or require a nut plate for equipment mounting.
73
Glenn
On 6/11/2019 2:02 AM, Perry Sandeen via time-nuts wrote:
Yo Bubba Dudes!,
Needing to go vertical with my test equipment I went bottom feeding for an
equipment cabinet on ebay.
To make a long search story short: they were way too expensive, too heavy to
ship and too far away for pickup.
So I kept searching and finally came across what was listed as *42U Four Post
Open Frame Server Data Rack 19 inches.?? Adjustable depth 23 to 32 inches.ebay
number 152319524877.Sold by Raising Electronics for US $188 and free shipping.
I was unsure what a *U* height meant put it seemed tall enough so I bought one.
I was a little apprehensive about this being a Chinese metal product.?? I was
very pleasantly proven very wrong.
Although it only comes with a picture of an assembled unit it has been engine
ed so there is no way you can assemble improperly. The four posts are all equal
and can be installed with any end up or down and the top and bottom brackets
will fit.?? It comes with the exact 50 M6-20 head bolts and nuts needed for
assembly.?? The nearest SAE equivalent bolt size is 1/4 20 x 1/2L which I
purchased to hold L shelf brackets to the frame.
I set the depth of mine to 26 inches so my 5370's fit well and I had space for
both power and BNC cables to be inside the frame.
This rack is designed to be bolted to the floor.?? Wanting to be able to move
it, I cut a piece of 3/4 inch plywood a little longer and wider then the base
footprint and installed 4 inch tall Harbor Freight swivel casters on the four
corners for ease of movement in any direction, even on floor carpeting.?? After
assembly it was 6 ft 9 inches tall.
Now this being a bolted together *skeleton frame* it is prone to twisting and
or becoming a parallelogram sideways.?? To prevent twisting, I fitted a plywood
board on the top bolted to the top front and rear angle pieces.?? To prevent a
side-to-side movement required an 8 inch wide piece of scrap aluminum plate
bolted to the rear vertical posts.?? This is easy to do as there are a plethora
of precision spaced holes available.
There was some very serious thought given to the vertical post design.?? It has
six 90 degree folds done in such a way that the inner edge on each outer side
gives a 19 inch opening.
??However behind it is as inner fold where one can install recessed L shaped
brackets. Now the inner fold is about and inch narrower than the outside
edge.This allows making a wider shelf that can *float* on top the brackets but
can't slide out either end.
This was very useful when configuring the instrument arrangement.
I also found that with the bottom shelf being just 6 inches above the floor I
was able to install more equipment in the same vertical space than in my
previous normal sized equipment cabinet.
Another bonus with this type of configuration is that it's easier to keep the
equipment cool and it's much lighter.
Regards,
Perrier
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4...@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.