Chapter V (2)

[S] 76. "Such an instrument, suitable for detecting the currents in an electric bell circuit, may be made up at the cost of a few shillings for material, and by the exercise of a little constructive ability. We shall need, first of all, a magnetised needle; this can be made out of a piece of watch spring. Procure a piece of watch spring two inches long, soften it by heating it to redness, and allowing it to cool gradually in a bed of hot ashes; then file it up to the form of a long lozenge, drill a small hole in the centre to receive the spindle or pivot, see that the needle is quite straight, then harden it by heating it again to a bright red and plunging it at once into cold water. It now has to be magnetised. To do this, rub it on a permanent horse-shoe, or other magnet, until it will attract an ordinary sewing needle strongly, or wrap it up in several turns of insulated line wire, and send many jerky charges of electricity from a strong battery through the wire. When it has been well magnetised, mount it on a spindle of fine hard wire, and secure it by a drop of solder. We will next turn our attention to the case, bobbin, or chamber in which the needle has to work. This may be made out of cardboard entirely, or the end pieces may be made of ivory or ebonite, or it may be made out of thin sheet brass; for our purpose we will choose cardboard. Procure a piece of stout cardboard 4-3/4 inches long by 2 inches wide, double it to the form of a T[:a]ndstickor match-box, and pierce it in exactly opposite sides, and in the centre of those sides with holes for the needle spindle. Now cut another piece of stout, stiff cardboard 2-3/4 inches long by 3/4 inch wide, and cut a slit with a sharp knife to exactly fit the ends of the case or body already prepared. The spindle holes must now be bushed with short lengths of hard brass or glass bugles, or tubing, made to allow the spindle free movement, and these secured in position by a little melted shellac, sealing-wax, or glue. The needle must now be placed in the case, the long end of the spindle first, then the short end in its bearing; then, whilst the case with the needle enclosed is held between the finger and thumb of the left hand, we secure the joint with a little glue or with melted sealing-wax. The end-pieces are now to be put on, glued, or sealed in position, and set aside to get firm, whilst we turn our attention to other parts. The case, 5 inches by 4 inches by 2 inches in depth, may be improvised out of an old cigar-box, but is best made of thin mahogany or teak, nicely polished on the outside, and fitted with a cover sliding in a groove, or hinged to form the back of the instrument. The binding screws should be of the pattern known as the telegraph pattern, fitted with nuts, shown at Fig. 27. A small brass handle to be fitted to the top of the instrument, will also be handy. A circular piece of smooth cardboard 3-1/4 inches in diameter, with a graduated arc, marked as shown in Fig. 95, will serve the purpose of a dial, and a piece of thin brass, bent to the form of [box open down], will be required as a needle guard. The face of the dial may be a circular piece of glass, held in a brass ogee, or a hole the size of the dial may be cut in a piece of thin wood; this, glazed on the inside with a square of glass, may be made to form the front of the instrument over the dial. An indicating needle will also be required for an outside needle; this is usually made of watch spring, and nicely blued; but it may be made of brass or any other metal, one made of aluminium being probably the best on account of its lightness. It must be pierced with a hole exactly in the centre, so as to balance it as the beam of scales should be balanced, and should one end be heavier than the other it must be filed until they are equal.

We will now turn our attention to the coil.

Procure sixpennyworth of No. 36 silk-covered copper wire and wind three layers of it very evenly on the coil case or bobbin, being careful in passing the needle spindle not to pinch it or throw it out of truth. When this has been wound on, it will be found that one end of the wire points to the left and the other end to the right. These are destined to be connected to the under side of the binding screws shown on the top of Fig. 95. We therefore secure them to their respective sides with a touch of sealing wax, and leave enough wire free at the ends to reach the binding screws--say, about 6 inches. It is handy to have an additional coil for testing strong currents, and as this may be combined in one instrument at a trifle additional cost, we will get some line wire (No. 22) and wind six or eight turns of it around the coil outside the other wire; one end of this wire will be attached to an additional binding screw placed between the others, and the other end to left binding screw shown. The coil thus prepared may now be mounted in position. Pierce the board dial and the wood at its back with a hole large enough for the needle spindle to pass through from the back to the centre of the dial. See that the thick end of the inside needle hangs downwards, then place the coil in the position it is intended to occupy, and note how far the needle spindle protrudes on the face of the dial. If this is too long, nip off the end and file it up taper and smooth until it will work freely in a hole in the needle guard, with all parts in their proper places. This being satisfactory, secure the coil in its place by sealing wax, or, better still, by two thin straps of brass, held by screws at each end, placed across the coil. Now clean the free ends of the coil wires, insert them under the nuts of the binding screws, fix the indicating needle on the end of the spindle outside, and see that it hangs in a vertical position with the inside needle when the instrument is standing on a level surface. Secure it in this position, screw on the needle guard, fasten on the glass face, and the instrument will be complete.

[S] 77. Provided thus with an efficient detector, the fitter may proceed to test his work. In cases of _new installations_, take the wire off the carbon binding screw of the battery and attach it to one screw of the galvanometer (on the intensity coil side), next attach a piece of wire from the other binding screw of the galvanometer (the central one) so as to place the galvanometer in circuit. _There should be no movement of the needle_, and in proportion to the deflection of the needle, so will the loss or waste be. If loss is going on, every means must be used to remedy it. It is of the utmost importance to the effective working of the battery and bells that not the _slightest leakage_ or _local action_ should be allowed to remain. However slight such loss may be, it will eventually ruin the battery. Let damp places be sought out, and the wires removed from near them. Bad or injured coverings must also be looked for, such as may have been caused by roughly drawing the wires across angular walls, treading on them, or driving staples too tightly over them. Two or more staples may be touching, or two or more wires carelessly allowed to lie under one staple. The wire may have been bared in some places in passing over the sharp edges of the zinc tube. The backs of the pushes should be examined to see if too much wire has been bared, and is touching another wire at the back of the push-case itself. Or the same thing may be taking place at the junction with the relays or at the indicator cases. Should the defect not be at any of these places, the indicator should next be examined, and wire by wire detached (not cut) until the particular wire in which the loss is going on has been found. This wire should then be traced until the defect has been discovered. In testing underground wires for a loss or break, it will be necessary first to uncouple the _distant_ end, then to disconnect the other end from the instruments, and attach the wire going underground to the screw of the galvanometer. A piece of wire must then be taken from the other screw of the detector to the carbon end of the battery, and a second wire from the zinc end of the battery to the earth plate or other connection. Proceeding to that part of the wire where the injury is suspected, the wire is taken up, and a temporary earth connection having been made (water main, gas pipe, etc.), and by means of a sharp knife connected with this latter, the covering of the suspected wire penetrated through to the wire, so as to make a good connection between this suspected wire and the temporary earth plates. If, when this is done, the needle is deflected fully, the injury is farther away from the testing end, and other trials must be made farther on, until the spot is discovered. Wherever the covering of the wire has been pierced for testing, it must be carefully recovered, finished off with Prout's elastic glue, or gutta-percha, and made quite sound. The connections with the earth plates very frequently give trouble, the wires corrode or become detached from the iron pipes etc., and then the circuit is broken.

[S] 78. When the fitter is called to localise defects which may have occurred in an installation which has been put up some time, before proceeding to work let him ask questions as to what kind of defect there is, and when and where it evinces itself. If all the bells have broken down, and will not ring, either the battery or the main go and return wires are at fault. Let him proceed to the battery, examine the binding screws and connected wires for corrosion. If they are all right, let the batteries themselves be tested to see if they are giving the right amount of current. This should be done with the quantity coil of the detector. Should the battery be faulty, it will be well to renew the zincs and recharge the battery, if the porous cell be still in good condition; if not, new cells should be substituted for the old ones. Should the battery be all right, and still none of the bells ring, a break or bad contact, or short circuit in the main wires near the battery may be the cause of the mischief. If some bell rings continuously, there must be a short circuit in the push or pushes somewhere; the upper spring of one of the pushes may have got bent, or have otherwise caught in the lower spring. _Pulls_ are very subject to this defect. By violent manipulations on the part of mischievous butcher or baker boys, the return spring may be broken, or so far weakened as not to return the pull into the "off" position. If, the batteries being in good order, any bell rings feebly, there is either leakage along its line, or else bad contact in the push or in the connections of the wires to and from the push. There should be platinum contacts at the ends of the push springs; if there are not, the springs may have worked dirty at the points of contact, hence the poor current and poor ringing. It is seldom that the bells themselves, unless, indeed, of the lowest quality, give any serious trouble. Still the set screw may have shaken loose (which must then be adjusted and tightened up), or the platinum speck has got solder on its face and therefore got oxidised. This may be scraped carefully with a penknife until bright. Or, purposely or inadvertently, no platinum is on the speck at all, only the solder. A piece of platinum foil should be soldered on the spot, if this is so. Or again (and this only in very bad bells), the electro-magnets being of hard iron, may have retained a certain amount of _permanent magnetism_, and pull the armature into permanent contact with itself. This can be remedied by sticking a thin piece of paper (stamp paper will do) over the poles of the magnet, between them and the armature. In no case should the fitter _cut_ or _draw up_ out of tubes, etc., any wire or wires, without having first ascertained that the fault is in that wire; for, however carefully joints are made, it is rare that the jointed places are so thoroughly insulated as they were before the cutting and subsequent joining were undertaken. To avoid as much as possible cutting uselessly, let every binding screw be examined and tightened up, and every length of wire, which it is possible to get at, be tested for continuity before any "slashing" at the wires, or furious onslaughts on the indicator be consummated.

In conclusion, I beg to record my thanks for the very generous assistance which I have received in the compilation of the foregoing pages from the electrical firms of Messrs. Blakey Emmot, Binswanger, Gent, Judson, Jensen, and Thorpe.

ADDENDUM.

THE GASSNER BATTERY.

Since the compilation of the foregoing pages, a _dry battery_, known by the above name, has found great favour with electric-bell fitters. Its peculiarity consists in the zinc element forming the outside cell. In this is placed the carbon, which is separated from the zinc by a thick paste or jelly made of gypsum and oxide of zinc. The cell can be placed in any position, works as well on its side as upright, is not subject to creeping, has an E.M.F. of about 1.5 volt, with an internal resistance of only 0.25 ohm in the round form, and 0.6 in the flat form. The Gassner dry battery polarizes much less quickly than the ordinary Leclanch['e]. The only defects at present noticeable, are the flimsy connections, and the fact that the outer cases being _metal_ must be carefully guarded from touching one another. This can be effected by enclosing in a partitioned _wooden box_.

INDEX.

A.

Acid, Chromic, 33, 46

---- Hydrobromic, 20

---- Hydrochloric, 20

---- Hydriodic, 20

---- Nitric, 20

---- Sulphuric, 20

Action in Bichromate, 47

---- Dotting, 116

---- of electric bell, 81

---- Leclanch['e], 35

---- Relay, 134

---- Rubbing, 116

---- of zinc on acids, 21

Agglomerate block, 38

---- Cell, 38

---- Compo, 38

Alarms, Burglar, 113

---- Fire, 123

---- Frost, 121

---- Thermometer, 122

---- Thief, 113

---- Watch, 124

Amber, 1

Amp[e']re, 55

Amp[e']re's law, 11

Annealing iron, 13

Arrangement of bells for lifts, 171

---- Ships, 170

Attraction, 3

B.

Batteries, 18

Battery agglomerate, 39

Battery, Bichromate, 48

---- Bunsen, 33

---- Chromic acid, 46

---- Daniell's, 29

---- Gassner (addendum), 186

---- Gent's, 44

---- Gravity, 31

---- Modified, 120

---- Grenet, 46

---- Grove, 33

---- Judson's, 41

---- Leclanch['e], 33

---- Reversed, 46

---- Minotto, 31

---- Smee's, 27

---- Walker's, 27

Bell action, case for, 88

Blocks, wooden, 150

Bobbins, electric bell, 67

Box for batteries, 43

Brushes, dynamo, 17

C.

Cable, many stranded, 174

Case for bell action, 88

Cells in parallel, 57

---- series, 53

Charging fluid, recipes, 48

---- Fuller, 49

Circuits, closed, 52, 118

---- Of bells complete in house, 168

---- For signalling, 167

---- In both directions, 168

Circuits of bells with Morse key, 165
In parallel, 161
Series, 162
With relay, 164
Single bell and wire, 159
Earth, 160
Two pushes, 161
Push and pull, 161
Open, 52

Closed circuit system, 118

Code for signalling, 130

Coil spring, 108

Conductors, 3

Connecting up, 144, 159

Contacts, burglar alarm, 113
Door, 116
Drawer, 121
Floor, 113
For closed circuits, 121
Mackenzie's humming, 113
Shop door, 116
Till, 121
Watch alarm, 124
Window sash, 116

Corrugated carbons, 41

Creeping in cells, 43
To remedy, 44

Callow's attachment, 99

Current, 54
To ring bell, 145

D.

Daniell's cell, 29
Action in, 29

Deflection of needle, 9, 11

Detector or galvanometer, to make, 178

Detent lever, 94

Door contact, 116

Dotting action, 116

Drawing out plans, 169

Dynamo, 15
Armature, 16
Brushes, 17
Commutator, 17

Dynamo, Cumulative effects, 17
Field magnets, 16

E.

Earth, 52
Plate, 53
Return, 153

Electric bell, action of, 81
Armature, 74
Base, 61
Bobbins, 67
Contact screw, 75
Continuous, 92
Circular bell, 106
Gong, 77
How to make, 60
In lifts, 171
Ships, 170
Jensen's, 101
Joining E. M. wire, 73
Magnets, 63
Magneto, 174
Mining, 106
Paraffining, 69
Platinum tip, 76
Putting together, 78
Single stroke, 91
Spring, 74
Thorpe's, 100
Trembling, 81, 90
Winding wire on, 71
Wire for, 69
Trumpet, 107

Electricity, sources of, 2

Electrodes, 26

Electro-motive force, 51

Electron, 1

E.M.F., 51

Excitation, 6

F.

Faults to detect, 182

Fire alarms, 123

Floor contacts, 113

Frost alarms, 121

Fuller charging, 49

G.

Galvanometer, 176

Gas evolved, 18

Gassner battery (addendum), 186

Generator (magneto), 174

Gent's battery, 44

Glue, Prout's elastic, 148

Graphite, 27

Gravity battery, 31
Daniell battery, 31
Modified, 120

Grenet battery, 46

Grove battery, 33

Gutta-percha, 148

I.

Indicator, 135
Automatic, 138
Drop, 136
Electric replacement, 136
Gent's, 140
Tripolar, 143
Mechanical replacement, 136
Mode of coupling up, 142
Pendulum, 139
Polarised, 139
Self replacing, 136
Semaphore, 136

Inductor, 174

Insulation, 68

Insulators, 4

Internal resistance, 56

Interior of push, 151

Iron, importance of soft, 65
Yoke, 66

J.

Jensen's bell, 101

Joining wires to push, 151

Judson's cell, 41

K.

Key, Morse, 129

L.

Leakage, 52

Leclanch['e] cell, 33
reversed, 46

Legge's contact, 115

Lever switches, 128

Lifts, bells for, 171

Localising faults, 144, 175

Lodge bell, 169

M.

Magnetic field, 14

Magneto bells, 175
Electric machines, 14, 15

Magnets, 13

Magnets producing electricity, 14

Magnetisation of iron, 12
Steel, 13

Manganese oxide, 33

Minotto cell, 31

Modified gravity battery, 120

Morse key, 129

Musical instrument, novel, 108

N.

Negative electricity, 7

Non-conductors, 3

Novel musical instrument, 108

O.

Ohm, 55

Ohm's law, 55

Open circuit, 52

Overhead lines, 152

P.

Paraffin, 69, 170

Percha, gutta, 148

Plans, drawing out, 169

Platinum, riveting, 76

Platinum, use of, 76

Plug switches, 128

Polarisation, 26

Positive electricity, 7

Proportions of bell parts, table of, 89

Pressels, 111

Prout's elastic glue, 148

Pulls, 111

Push, 92, 151, 109
Interior of, 151
Joining wires to, 151

R.

Relay, 96, 133
Action of, 134

Repulsion, 3

Resinous electricity, 7

Resistance of wire, table of, 146

Return current, 153

Riveting platinum, 76

Rubbing action, 116

S.

Ships, bells for, 170

Shop door contact, 116

Signalling by bells, 130
Code, 130

Silver platinised, 27

Single cell, 9

Sizes of Leclanch['e]'s, 42

Smee's cell, 27

Spring coil, 108

Standard size of wires, 146

Switches, lever, 128
Plug, 128

T.

Table of batteries, E.M.F. and R., 58
Conductors and insulators, 4, 68
Metals in acid, 8

Table of Proportions of bell parts, 89
Wire resistance, etc., 146

Testing new work, 182
Old, 183

Thermometer alarms, 122

Thorpe's Ball, 100

U.

Use of platinum, 76

V.

Vitreous electricity, 7

Volt, 53

W.

Walker's cell, 27

Watchman's clock, 124

Water level indicator, 127

Washer, insulating, 77

Window sash contact, 116

Wiping contact, 102

Wire covering, 147
In iron pipes, 152
In wooden boxes, 152
Iron, 152
Joining, 148
To push, 151
Laying in tubes, 149
Leading, 147, 150
Overhead, 152
Resistance, table of, 146
Return, 147, 150
Soldering iron, 148
Tinned, 147
Underground, 152

Wiring, general instructions, 155
Up, 144

Z.

Zinc, amalgamated, 22
Blacking, 45
Consumption, 21
Commercial, 19
Pure, 19

WILLIAM RIDER AND SON, PRINTERS, LONDON.

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Transcriber's Note

Page 12: changed "guage" to "gauge" (... cotton-covered copper wire, say No. 20 gauge ...)

Page 35: changed "change" to "charge" (... losing at the same time its electrical charge ...)

Page 55: changed "guage" to "gauge" (... 1 foot of No. 41 gauge pure copper wire ...)

Page 64: changed "exaet" to "exact" (... of the exact diameter of the turned ends of the cores ...)

Page 73: moved comma "Rivetting, is" to "Rivetting is," (Rivetting, is perhaps, the best mode ...)

Page 81: added hyphen (... along the short length of wire to the right-hand binding-screw ...)

Page 83: changed "head" to "heads" (... the possible defects of electric bells may be classed under four heads: ...)

Page 92: changed "its" to "it" (... until it rests against the stop or studs.)

Page 102: changed "contract-breaker" to "contact-breaker" (When the contact-breaker is used, ...)

Page 103: changed "instead" to "Instead" (Instead of the armature and clapper ...)

Page 132: in the Morse code for "BRING THE", the code for "H" has been corrected from two dots to four dots.

Page 136: changed "eletro-magnet" to "electro-magnet" (... if the electro-magnet were energised ...)

Page 137: changed "idicator" to "indicator" (since the indicator falls forwards)

Page 146: changed "arrangment" to "arrangement" (the size and arrangement of the batteries and wires)

Page 146: added comma "nails," (... chance contact with nails, staples, metal pipes or other wires ...)

Page 179: changed "carboard" to "cardboard" (... for our purpose we will choose cardboard.)

Page 179: changed "Tanstickor" to "T[:a]ndstickor" (... double it to the form of a T[:a]ndstickor match-box, ...)

Page 185: suspected typo (unchanged) "Emmot" should perhaps be "Emmott" (... the electrical firms of Messrs. Blakey Emmot, ...)

Page 186: changed "Leclanch[e']" to "Leclanch['e]" (... polarizes much less quickly than the ordinary Leclanch['e].)

Page 187: changed two instances of "Amp['e]re" to "Amp[e']re" in the index (Amp[e']re, 55 / Amp[e']re's law, 11)

End of Project Gutenberg's Electric Bells and All About Them, by S. R. Bottone