[SBE] Rack standards

[Adrienne Abbott]

And don't forget that it was the railroads-or the managers-who developed the
system of time zones.

Adrienne

 

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Edwin
Bukont
Sent: Thursday, October 27, 2011 6:32 PM
To: sbe
Subject: Re: [SBE] Rack standards

 

Well, railroads widths are derived from an english 'coach' standard, that is
based on the width of chariot wheels, or more correctly the width of the
ruts left by such wheels, which are spaced upon the width that a horse's
behind occupies between the wheels. the chariot was imported to england from
rome.
 
don't forget we have not only differing widths of 23" and 19" but also
differing screws, that being 12-24 (telecom) and 10-32 (eia)
 
the 12-24 is thicker, but with fewer TPI, it actually has less strength than
the 'smaller' 10-32 that has a higher TPI.  This is the same dynamic as
pertains to speaker hanging, where 'fine' threaded rod is used, rather than
coarse, as it withstands vibration better.


Edwin Bukont CSRE, DRB, CBNT 
Nashville, Baltimore, Wherever
V- 240.417.2475; F- 240.368.1265
ebukont at msn.com

 








 

  _____  

From: wgbw at lsol.net
To: sbe at sbe.org
Date: Thu, 27 Oct 2011 20:53:14 -0400
Subject: Re: [SBE] Rack standards

this stuff goes back to the age of the Trains, and Western Union / Western
Electric, and patents.

long, long, long, before broadcast was catching on....

24" was one standard,   19" allowed for 18" of clearance for equipment.

back then, they actually enforced patents....  you had to change enough of
the original invention
to make is something different....thus the two sizes.

there was a time, in the United States, that railroad tracks had different
spacing, too... it changed
in 1865 or thereabouts.




 

  _____  

From: "Dan Rapak" <DanRapak at verizon.net>
Sent: Thursday, October 27, 2011 7:07 PM
To: "sbe member discussion mail list" <sbe at sbe.org>
Subject: Re: [SBE] Rack standards

? 

The article explains the origin, but I still have no idea why 19", etc. were
chosen as the numbers. Anyone have any knowledge of that part of the
equation?

 

Dan

----- Original Message ----- 

From: Jonstv <mailto:jonstv at gmail.com>  

To: sbe member discussion mail list <mailto:sbe at sbe.org>  

Sent: Thursday, October 27, 2011 7:50 PM

Subject: Re: [SBE] Rack standards

 

At first I was going to comment "wikipedia.... Must be true ;)". But that is
actually a good article!

Sent from my iPad


On Oct 25, 2011, at 3:05 PM, "Smith, Jeff" <JEFFSMITH at clearchannel.com>
wrote:

Right from Wikipedia.

 

 

http://en.wikipedia.org/wiki/19-inch_rack

 

 


Overview and history


Equipment designed to be placed in a rack is typically described as
rack-mount, rack-mount instrument, a rack mounted system, a rack mount
chassis, subrack, rack mountable, or occasionally simply shelf. The height
of the electronic modules is also standardized as multiples of 1.75 inches
(44.5 mm) or one rack unit <http://en.wikipedia.org/wiki/Rack_unit>  or U
(less commonly RU).

Because of their origin as mounting systems for railroad signaling
<http://en.wikipedia.org/wiki/Railroad_signaling>  relays
<http://en.wikipedia.org/wiki/Relay> , they are still sometimes called relay
racks, but the 19-inch rack format has remained a constant while the
technology that is mounted within it has changed to completely different
fields. The 19-inch (482.6 mm) standard rack arrangement is widely used
throughout the telecommunication
<http://en.wikipedia.org/wiki/Telecommunication> , computing
<http://en.wikipedia.org/wiki/Computer> , audio
<http://en.wikipedia.org/wiki/Sound_recording_and_reproduction> ,
entertainment <http://en.wikipedia.org/wiki/Entertainment>  and other
industries, though the Western Electric
<http://en.wikipedia.org/wiki/Western_Electric>  23-inch standard
<http://en.wikipedia.org/wiki/23-inch_rack> , with holes on 1-inch (25.4 mm)
centers, prevails in telecommunications.

19-inch racks are often used to house professional audio and video
equipment, including amplifiers <http://en.wikipedia.org/wiki/Amplifier> ,
effects units <http://en.wikipedia.org/wiki/Effects_unit> , interfaces,
headphone <http://en.wikipedia.org/wiki/Headphone>  amplifiers, and even
small scale audio mixers. They are also widely used for computer server
<http://en.wikipedia.org/wiki/Computer_server>  equipment, allowing for
dense hardware configurations without occupying excessive floorspace or
requiring shelving. A third common use for rack-mounted equipment is
industrial power, control, and automation hardware.

Typically, a piece of equipment being installed has a front panel height
1/32-inch (0.031 inches (0.787 mm)) less than the allotted number of Us.
Thus, a 1U rackmount computer is not 1.75 inches (44.5 mm) tall but is 1.719
inches (43.7 mm) tall. 2U would be 3.469 inches (88.1 mm) instead of 3.5
inches (88.9 mm). This gap allows a bit of room above and below an installed
piece of equipment so it may be removed without binding on the adjacent
equipment.

In 1965 a durable fiber reinforced plastic
<http://en.wikipedia.org/wiki/Fiber_reinforced_plastic>  19-inch rackmount
case was patented by ECS Composites and became widely used in military and
commercial applications for electronic deployment and operation.
State-of-the-art rackmount cases are now also constructed of thermo stamped
composite, carbon fiber <http://en.wikipedia.org/wiki/Carbon_fiber>  and
DuPont <http://en.wikipedia.org/wiki/DuPont> 's Kevlar
<http://en.wikipedia.org/wiki/Kevlar>  for demanding military and commercial
uses

 

 

Jeff Smith CSRE CBNT

 

Supervisor Broadcast Systems

 

Clear Channel Radio NYC

 

Power 105.1, 103.5 WKTU, Z100, 106.7 Lite FM, Q 104.3

 

 

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Dan
Rapak
Sent: Tuesday, October 25, 2011 1:53 PM
To: SBE Broadcast Group
Subject: [SBE] Rack standards

 

 

 

I just received a question from a colleague that made me scratch my head.
Where did the standards for equipment racks (rack units, 19" width, hole
spacing) come from and why were they set at these values?

 

 

 

Dan Rapak

 

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