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Books by
Horstmann & Tousley
Motion Picture Operation, Stage Electrics and Illusions. $2.00
(Ready July 1, 1914.)
Alternating Current Theory, Practice and Diagrams. $2.00
Modern Electric Illumination. $2.00
Practical Armature and Magnet Winding. $1.50
Modern Electrical Construction. $1.50
Electrical Wiring and Construction Tables. $1.50
Dynamo Tending for Engineers. $1.50
Modern Wiring Diagrams and Descriptions. $1.50
Electricians’ Operating and Testing Manual. $1.50
Motion Picture Operation
STAGE ELECTRICS
AND ILLUSIONS
A Practical Hand-book and Guide for Theater
Electricians, Motion Picture Operators and
Managers of Theaters and
Productions
By
Henry C. Horstmann
and
Victor H. Tousley
Authors of
“Alternating Current,” “Modern Wiring Diagrams,” “Modern
Electrical Construction,” “Electrical Wiring and Construction
Tables,” “Practical Armature and Magnet
Winding,” “Electricians’ Operating and Testing
Manual,” “Modern Illumination.”
ILLUSTRATED
[Illustration]
Chicago
FREDERICK J. DRAKE & CO.
Publishers
Copyright 1914, by
HENRY C. HORSTMANN
and
VICTOR H. TOUSLEY
PREFACE
In this volume the authors have attempted to lay before the
Motion-Picture Operators and Theatrical Employes generally, a reference
and handbook making a specialty of electrical requirements about
theaters.
A working knowledge of electricity in general is assumed, and therefore
elementary ideas have been treated sparingly. A specialty, however, has
been made of all matters peculiar to theaters, and it is thought that
theater electricians will find in this volume everything that they need
whether they be operating motion-picture machines or switchboards in
first-class houses.
The two special chapters “Portable Stage Equipment” and “Theater Wiring”
have been arranged so that they are particularly valuable for reference.
They should be consulted before undertaking any electrical construction
work, either for the stage or for the auditorium. These chapters embody
all of the practical knowledge that has come to the notice of the
authors in many years of actual experience with theatrical construction.
The aim of this volume has been to present in a simple and practical way
the essential principles of Motion-Picture Work.
THE AUTHORS.
Table of Contents
PAGE
CHAPTER I
The Electrical Circuit and Electrical Hazards 9
CHAPTER II
The Arc Lamp 19
CHAPTER III
Projection 31
CHAPTER IV
Motion Pictures 55
CHAPTER V
The Motion-Picture Machine 62
CHAPTER VI
The Film 89
CHAPTER VII
General Hints on Installation, Operation and Care of Machines 96
CHAPTER VIII
Light 113
CHAPTER IX
Principles of Vision 122
CHAPTER X
Reflection 126
CHAPTER XI
Refraction 137
CHAPTER XII
Optical Instruments 147
CHAPTER XIII
Optical Illusions 155
CHAPTER XIV
Theater Buildings 163
CHAPTER XV
Operating Room Equipment 176
CHAPTER XVI
Current Control for Arc Lamps 190
CHAPTER XVII
Management of Generators and Motors 213
CHAPTER XVIII
Theater Wiring 218
CHAPTER XIX
Portable Stage Equipment 311
CHAPTER XX
Useful Facts and Formulas 353
CHAPTER XXI
Glossary of Electrical, Mechanical and Optical Words, Terms and
Phrases 358
Index 385
MOTION PICTURE OPERATION
STAGE ELECTRICS AND
ILLUSIONS
CHAPTER I.
THE ELECTRICAL CIRCUIT AND ELECTRICAL HAZARDS.
_Two and Three-Wire Systems._--If the theater electrician will take the
trouble to trace the circuits in the building to their supply, he will
find them entering the building either as two-wire or three-wire
circuits.
[Illustration: FIGURE 1.]
A two-wire circuit is diagrammatically shown in Figure 1. The circuit,
coming from _1_, enters the building, passes through the fuses _2_, and
through switch 3 to the lights. A two-wire system will ordinarily be
found operating at 110 volts, the current varying according to the
number of lights turned on. In the drawing, for instance, only one light
is shown with the switch closed, the other three switches being open.
The current in the circuit is equal to that which passes through the
single lamp. If another switch be closed, another light will burn and
the current will be increased, so that the more lights be turned on, the
greater will be the current.
[Illustration: FIGURE 2.]
The three-wire system, Figure 2, is almost universally used where the
supply is from the outside and where any considerable number of lights
are connected. The chief advantage of the three-wire system lies in its
economy of copper. The middle or neutral wire ordinarily does not carry
current, but it is a necessity whenever the number of lights burning on
the two sides of the system are not equal.
With the neutral wire omitted, we have a straight two-wire system using
double the voltage of the ordinary two-wire system and always operating
two 110-volt lamps in series. Two lamps would always have to be turned
on at the same time and if one of them should burn out, the other would
be extinguished also.
A system using double voltage requires only half the current and
consequently but half the copper. In order to obviate the necessity of
always using two lamps together and at the same time economizing in
copper, the neutral wire is provided. As long as the same number of
lamps are burning on each side of the neutral wire, the same current
always passes through two lamps in series and there is no current in
the neutral. Should, however, the group on one side be turned out, the
other would still continue to burn; but the path of the current to the
dynamo, or bank of transformers, would be through the neutral wire.
The system is thus seen to possess all the advantages of the ordinary
two-wire system since each lamp can be operated by itself and at the low
voltage, while the actual supply voltage for the whole system is double
that which is actually used at any lamp. We have thus two voltages at
our command; 110 and 220 being the voltages in common use.
_Electrical Hazards._--Since this work is not intended for mere
beginners, we shall not enter into elementary considerations, but shall
take up the matter of fire and life hazard, both of which are important
items to which attention cannot be too often called.
The electrical current may cause fire by overheating the wires. This
overheating may be due to the willful overloading of circuits; and to
prevent this, no wire should ever be used to carry more current than is
allowed by the table of carrying capacities given on page 238.
The overheating may also be due to an unknown load which is caused by a
“ground” or a partial short circuit. “Ground” is the technical term used
to designate the connection of a wire to any substance over which
electricity may be carried to the wire of opposite polarity. A ground
may be caused by a bare wire coming in contact with the iron framework
of a building, wet wood, or moist substances of any kind. One such
ground on a circuit can do no harm; but, if one ground exists, in the
course of time another one may come on and, when the second one
appears, if it is on the side of the circuit opposite to the first,
there will be trouble at once.
If the two grounds are both “good”--that is, if they are of low
resistance--we shall have a short circuit and probably blow a fuse; but
if they are not “good,” we may have but a small current which may
continue unnoticed for months. Such a current may eat away the copper of
the positive pole and in time cause the wire to break, creating an
electric arc and perhaps causing a fire. It may also cause wet wood
through which it flows to become charred and finally ignited.
The ground is the bane of the electrical worker. If a system can be kept
free of grounds, the chances of trouble are vastly reduced. The cause of
most grounds is moisture. Nearly all substances except metals are fairly
good insulators if dry; and nearly all of them are fairly good
conductors if sufficiently wet.
Another very prolific source of fires is the electrical spark, large and
small. The spark, due to the breaking of an incandescent lamp, often
causes fires when it comes in contact with inflammable material or
gases. The ordinary lamp cord also causes many fires because it is
easily damaged and liable to short circuits which often result in
arcing. Short circuiting two wires or breaking a wire carrying current
may easily ignite inflammable material in the vicinity.
The best way to reduce the fire hazard to a minimum, is to install all
electrical work carefully according to the rules laid down in the
“National Electrical Code”.
The life hazard is one which concerns the operator personally and is
especially great to those traveling with shows. Traveling men are often
obliged to get along with all sorts of make shifts, especially in the
smaller towns where one-night stands are the rule. Here it is often
necessary to connect to trolley circuits or power lines of different
voltages, frequencies, etc.
A person may suffer injury directly from a current of electricity by
making himself part of the circuit. If the system on which he is working
is alive and grounded, he may easily cause injury to himself by touching
a live wire with his hands while standing upon anything that is
grounded. By so doing he completes a path for the current through his
body.
He may also become part of a circuit by holding a wire with both hands
while someone is cutting it between his two hands. As long as a wire so
held is intact, no shock can be received except to ground, but when the
wire is cut or breaks, a very high voltage may be produced for an
instant which will cause a current through the body of the man holding
the wire. The extra high voltage is produced only if the wire is
carrying current at the time it is being cut. Under these circumstances
there will often be a strong flash, due to the momentary increase in
voltage, produced by the breaking of the circuit, which may be
excessive, especially if there is considerable inductance in the
circuit.
The most frequent cause of injury is due to making contact with the two
opposite polarities of a system. As a rule circuits, with which
operators ordinarily have to work, are low voltage, i.e., not over 220
volts. But many deaths have been caused by this voltage, sometimes
directly and at other times indirectly as, for instance, by causing a
fall. People whose hearts are in any way defective should be careful
about exposing themselves to shocks even at 110 volts.
It is true that many wiremen are in the habit of testing 220-volt
circuits by allowing the current to pass through their bodies, but it
will be noticed that they are very careful not to make a good contact.
The current which passes through the body, when one touches two wires of
opposite polarity very lightly with the finger tips, is but a fraction
of what one would receive if he were unwittingly to grab two wires of
opposite polarities with the hands, especially if the hands were moist.
Numerous cases are on record of persons having been killed by 110 volts
under favorable circumstances; as, for instance, while in the bath
receiving a shock from a so-called vibrator. The body partly immersed in
water and perhaps a foot resting against a water pipe forms a conductor
of very low resistance, and a comparatively strong current may pass
through the body.
The most important precautions against injury while working on live
circuits are:
(1) Insulate yourself from the ground.
(2) Handle only one side of a line at a time.
(3) If possible, work with only one hand at a time in contact with the
wires.
(4) Use rubber gloves, or rubber boots where necessary, but bear in mind
that they are of little value unless kept dry. Moisture will allow some
current to pass over the surface of any substance no matter how good an
insulator it may otherwise be.
(5) Always place yourself so that a slight shock which might cause you
to lose your balance will not give you a bad fall.
(6) Remember that if once you make good contact with an
alternating-current circuit, you cannot let go.
(7) Fix firmly in your mind the directions for resuscitation from
electric shock, on pages 15-18.
When energy is obtained through transformers, there is another danger to
be added to the above, viz., the possibility of the breaking down of the
insulation between primary and secondary wires of the transformer. If
this happens, we have suddenly and without warning, instead of the 110
or 220 volts supposed to exist between the wires forming the circuit,
2,000 or 3,000 volts. Such accidents are especially likely during
thunder storms when lightning often breaks down transformers.
In order to reduce this danger to a minimum, the secondaries of
transformers are grounded. It will be well for the electrician to assure
himself that the secondaries of the transformers from which he is
getting his supply are grounded. This can be tested by an incandescent
lamp. Connect the lamp to ground with one wire and, with the other, try
the two sides of the circuit. If the transformer secondaries are
properly grounded, the lamp will burn at full candle power from one of
the wires; this will show that the other wire is grounded.
A person working on such a circuit is of course more likely to receive a
low voltage shock than if the secondaries were not grounded, but he is
fairly well protected against the primary voltage or lightning.
RESUSCITATION FROM ELECTRIC SHOCK.
Rules recommended by commission on resuscitation from electric shock,
representing The American Medical Association, The National Electric
Light Association, The American Institute of Electrical Engineers: Dr.
W. B. Cannon, chairman; professor of physiology, Harvard University. Dr.
Yandell Henderson, professor of physiology, Yale University; Dr. S. J.
Meltzer, head of department of physiology and pharmacology, Rockefeller
Institute for Medical Research; Dr. Edw. Anthony Spitzka, director and
professor of general anatomy, Daniel Baugh Institute of Anatomy,
Jefferson Medical College; Dr. George W. Crile, professor of surgery,
Western Reserve University; W. C. L. Eglin, past-president National
Electric Light Association; Dr. A. E. Kennelly, professor of electrical
engineering, Harvard University; Dr. Elihu Thomson, electrician, General
Electric Company; W. D. Weaver, secretary, editor Electrical World.
Issued and copyrighted by National Electric Light Association. Reprinted
by permission. Follow these instructions even if victim appears dead.
I. IMMEDIATELY BREAK THE CIRCUIT.
With a single quick motion, free the victim from the current. Use any
_dry non-conductor_ (clothing, rope, board) to move either the victim or
the wire. Beware of using metal or any moist material. While freeing the
victim from the live conductor have every effort also made to shut off
the current quickly.
II. INSTANTLY ATTEND TO THE VICTIM’S BREATHING.
1. As soon as the victim is clear of the conductor, rapidly feel with
your finger in his mouth and throat and remove any foreign body
(tobacco, false teeth, etc.) Then _begin artificial respiration at
once_. Do not stop to loosen the victim’s clothing now; _every moment of
delay is serious_. Proceed as follows:
_a._ Lay the subject on his belly, with arms extended as straightforward
as possible and with face to one side, so that nose and mouth are free
for breathing, see Figure on page 17. Let an assistant draw forward the
subject’s tongue.
[Illustration: INSPIRATION--PRESSURE OFF.]
_b._ Kneel straddling the subject’s thighs and facing his head; rest the
palms of your hands on the loins (on the muscles of the small of the
back), with fingers spread over the lowest ribs, as in Figure on page
17.
_c._ With arms held straight, swing forward slowly so that the weight of
your body is gradually, but _not violently_, brought to bear upon the
subject, see Figure on page 18. This act should take from two to three
seconds.
Immediately swing backward so as to remove the pressure, thus returning
to the position shown in the Figure on page 17.
_d._ Repeat deliberately twelve to fifteen times a minute the swinging
forward and back--a complete respiration in four or five seconds.
_e._ As soon as this artificial respiration has been started, and while
it is being continued, an assistant should loosen any tight clothing
about the subject’s neck, chest or waist.
[Illustration: EXPIRATION--PRESSURE ON.]
2. Continue the artificial respiration (if necessary, at least an hour),
_without interruption_, until natural breathing is restored, or until a
physician arrives. If natural breathing stops after being restored, use
artificial respiration again.
3. _Do not give any liquid by mouth until the subject is fully
conscious._
4. Give the subject fresh air, but keep him warm.
III. SEND FOR NEAREST DOCTOR AS SOON AS ACCIDENT IS DISCOVERED.