Theatre Design & Technology - Summer 1992 - 49

What's

Wrong
With
Welding

Cable?

f rhe message has nor reached
you as a rouring road elecrrician,
marion picrure gaffer, roadie,
lighring direcror, carnival
elecrrician, or producrion
manager, rhen rhere has been a serious
breakdown in your "grapevine." Some of
you no doubr have heard rumors rhar
welding cable is "no good," "outlawed,"
or "illegal." Ir is rhe intention of rhis
arricle ro ler vou know exactly whar has
happened, why, and whar you should be
prepared ro do abour ir.

BACKGROUND

Since rhe dawn of elecrrical lighring in
rhe rhearre and marion picrures, some
form of heavy dury, high currenr-rared
cable has been used for feeder
applicarions in supplying rhe elecrric
RICHARD D
THOMPSON power ro porrable dimmer boards. Prior
ro World War II, rhe principal use of high
currenr feeder cables was limired ro rhe
rhearre and rhe Hollywood srudios. Early
forms of cable included rope-srranded
copper cable pulled rhrough rubber sream
hose, or rhe same copper cable wirh an
asbesros c10rh srirched around
if. Larer forms included
NEW
corron braid and various rypes
REQUIREMENTS of rubber as insularion.
The srandard size of cable
FOR
was 4/0 as rhe early rhearrical
road boards or piano boards
POWER
were designed around a rwopole, single-phase, rhree-wire
DISTRIBUTION
(110/220 voir), 200 ampCABLE
fused swirch. Ir so happened
rhar rhar was rhe largesr
available fuse and swirch in
rhe early 1920s when rhese
sysrems were firsr designed. The ampaciry
raring of rhe early cable design was a
maximum of 400 amps. Ar rhe rime rhis
was based on rhe use of~vpe AA (Marion
Picrure Machine \Vire) which was
asbesros covered. From rhe rhearre's
company swirch (Bull Swirch) ro rhe road
boards was an average cable run of 25 ro
50 feer.

For all rhose .\'ears rhar svsrem
worked
.
and lirrle was rhoughr abour if. In
Hollywood, rhe marion picrure srudios
used similar 4/0 feeders. As rhey were
small ciries wirhin a ciry, rhey were
considered by rhe aurhoriries as selfpolicing.
As relevision developed in rhe Unired
Srares following World War II, rhe use of
large mobile air condirioned relevision
rrucks, wirh energy-consuming, vacuum
rube powered video equipmenr and high
warrage lighring began. There was a need
for a durable e1ecrrical cable wirh a high
current-carrying capacity ro power rhese
vehicles. Many TV elecrricians came from
a rhearre or marion picrure background
and rhey remembered rhe 4/0 feeders.
Television pracrice was ro park rhe
video rrailer ar some place as close ro rhe
shoo ring locarion as possible, bur as rhis
was a 45' rracror rrailer rig, ir usually did
nor find irself anywhere near [he elecrrical
power source. This meant rhar several
hundred feer of cable had ro be run from
rhe elecrrical service ro rhe rrailer. By now
rhe 4/0 cable had a name, "welding
cable." Neoprene insularion was one of
rhe spinoff rechnologies of rhe war and
neoprene insularion on a finely srranded
copper cable was very flexible; a 100-foor
coil could easily be carried on a man's
shoulder. An ex post facto indusrry
srandard was found.
Ar rhe rime, you could buy welding
cable wirh eirher a 300 voir or a 600 voir
raring. The i ndusrry assumed rhar rhis
raring was rhe insularion's dielecrric
srrengrh similar ro rhe wording on mulriconducror cable Type SO. Some cable
also had an Underwrirer's Laborarory, Inc.
( L) label, bur in rhose days,
L was
somerhing rhar wenr on elecrric irons and
roasrers for rhe home, nor "professional
equipmenr." The 300 voir cable wirhour
rhe U L sym bol was cheaper; rherefore,
large quanriries were purchased by rhe
relevision networks and renral houses.
During this period, lirtle change was
raking place wirh rhe Natiol/al Electrical
Code as far as rhearre, marion picrure, and
TD&T

1992 SUMMER

47
Table of Contents for the Digital Edition of Theatre Design & Technology - Summer 1992
