AN HOUR AT ALL SAINTS' WORKS DERBY
(JOHN DAVIS & SON).
the suggestion of the Local Committee of the Federated Institution of Mining Engineers, which was appointed to arrange the business for the Annual Meeting to be held at Derby in February, 1893, the proprietors of All Saints' Works were invited to throw them open for inspection. It was with some diffidence that the firm consented, for although they fully appreciated the compliment paid, they felt that while the mere exhibition of plant and apparatus used in mines might savour of a trade advertisement, such portions of the manufactures as could be witnessed in the short space of time available might leave the members very little wiser; the production of such apparatus being slow, and not resembling the Hindoo conjuring trick where spectators at one sitting can witness the growth of an adult tree from the seed.
At the request of the Local Committee, the following notes have been compiled, showing what the visitors may expect to see should they find themselves at Derby with an hour or so hanging on their hands.
The firm, which, perhaps, is best known as manufacterers of mining and surveying instruments, has, during the last few years, so developed its operations in electricity that it has been found necessary to divide the management into two distinct branches, under the departments classed A and B; the former (A) being the production on the old lines, and the latter (B) being the installation of electric light and power plants with their collateral electrical accessories, and of telephones and electric signals.
Taking the points of interest in the various rooms, which, for the convenience of the visitors have been numbered:‑
Room 1 contains lathes which have mostly been specially constructed for the production of miners' safety lamps. Here may be noted the ease and precision with which the various screw threads of a safety lamp may be cut. Standards in steel being worked to in all cases, uniformity of size, and the interchangeability of parts are ensured throughout. This improved screw‑cutting tackle is employed for all apparatus manufactured at All Saints' Works, and for some few years the various parts, especially those of miners' dials and levels (which instruments will be more fully demonstrated in Room 2), have been made to standard sizes, and are, therefore, interchangeable.
In this room has recently been constructed some improved apparatus for naval signalling, invented by Lieut. INGLEFIELD, R.N. An order has been executed this year for the German Navy, and Messrs. JOHN DAVIS & SON have received the gratifying intelligence that it is the intention of Prince HENRY of PRUSSIA to adopt the same throughout the whole German Navy; and this same apparatus is to be used throughout the British Navy.
Mercier's Mining Bell.
A new form of ringing key is now being manufactured, designed by Mr. M. Mercier, and also an electric signal bell. The special feature in both bell and key is protection against damp and dust of pits and all exposed situations; the contacts are enclosed in gas‑tight chambers, so that any fear of igniting gas in a fiery mine is eliminated.
An improved form of insulator is also exhibited which is designed by Messrs. MORGAN and JAMES chiefly for colliery planes where it is desired to carry the wires side by side so that a signal may be transmitted from any point in the plane. The insulator has two transverse grooves which keep the wires at a proper distance apart. It is intended to run the upper wire taut, and the lower loose, to avoid contact between the insulators.
While on the subject of electric signalling it will not be out of place to call attention to a demonstration of the manner of connecting up signal wires so that they can be used for speaking by telephone. In the engine room is fixed a telephone and automatic switch, which cuts out the bell and battery when the telephone is in use; at the distant end of the plane, or any desired point, the second instrument is fixed, and in addition to this, or in place of it, portable telephones can be carried in the pockets of the Deputies and hooked on to the wires at any point. A special signal must of course be arranged when the telephone is to be used. Though the above system works well, it is best to run one separate wire for the telephones, the earth wire being common to both signals and telephones.
Room 2 is chiefly devoted to the manufacture of scientific instruments other than electric, but here electricity plays an important part in the production of finely divided and figured faces or dials for such articles as Anemometers. The process of reproduction by electrotyping of the faces for these instruments may be witnessed throughout. First, the plate engraved by the machine to be seen in Room 3. This forms‑the inverted copy or matrix‑then upon this is deposited the patrix, from which further copies of the matrix are produced. Next comes the process of waxing the lines and figures, and then the silvering process.
In this room are constructed Magneto machines for shot firing and blasting on the " High Tension " and Low Tension " principles, and also batteries for the latter method, the battery being much lighter and cheaper than a Magneto exploder of the same power.
As most of the members are probably aware, the high tension fuse (which has been in general use until recently), is fired by a spark jumping across two points in the fuse. The low tension, which is the more reliable of the two, has only recently come into use. It consists of a bridge of fine platinum wire between the two leading wires; this bridge is heated by the current from the battery and thus fires the fuse. One of the chief advantages of the low tension fuse is, that it can be tested before use and a defective fuse detected. Mining bells and signalling apparatus of various forms are also constructed in this room.
The Hedley Dial will be familiar to most of the members, the firm having been actively engaged in their manufacture for over half a century; but as finality or perfection is never arrived at, and as it is always endeavoured to produce the batch in hand something better than the last, some points of novelty and improvement may be observed. As the boundaries of a coal mine are more nearly approached the demand for more accurate instruments increases, and year by year the Hedley Dial claims closer relationship to the Theodolite. Thus, in the latest improved form, the Hoffman Patent joint has a centering movement, self contained, and clamped by the same set of screws. The limbs of this dial have been recently remodelled to give greater rigidity, and at the same time weigh less than the pattern of its predecessor.
Aluminium is now extensively employed in the construction of surveying instruments, particularly for large foreign properties.
This wonderful metal combines strength with extreme lightness. The transit Theodolite, now nearing completion, is constructed wholly of aluminium, contains many points of novelty, and weighs only 15lb. 2 oz. complete with its legs, against 29½lb. for the same instrument in brass.
Dumpy Levels with an improved beam, Clinometers in aluminium, and Biram's Anemometer, so well known, may be seen in course of construction, but the Self‑timing Anemometer, although it has found its, way to most parts of the mining world, may not be so familiar.
Briefly describing its action and construction, it will be seen that the fan, after revolving freely and taking up a velocity due to the current of air, is engaged in winding up a spring similar to the mainspring of a watch.
This spring carries a hand over a graduated dial, which shows the current of air in feet per second. To calibrate this anemometer, a special form of testing apparatus has been constructed, and to ensure accuracy each instrument is separately calibrated throughout the whole of its range.
In ROOM 4 may be seen the machine for testing anemometers on the Biram principle, illustrated above. The modus operandi consists in the passing of the instrument through still air at various velocities, while the machine for calibrating the Self‑timing Anemometer, by placing it in the same current of air as a Biram Anemometer, may be seen in action; the various velocities being obtained by a partial vacuum caused by a steam jet.
In Room 3, the manufacture of safety lamp‑ gauzes is extensively carried on with a small staff of workpeople by the aid of machine tools. Here may be seen the various processes from cutting the blanks from the roll to a finished and well‑knit gauze, passing through the hands of the operatives sixteen times before completion. A most useful and ingenious machine is at work engraving and dividing the faces of dials, which work was hitherto executed by hand. A specially interesting feature of this machine is that it is driven by an electric motor
which takes its current from the Electric Station (to be shortly noticed more
fully and the required variation in speed is obtained by switching in more or less resistance, readily adjusted by turning the small handle as exhibited.
In Room 4 are stored the various parts of bonneted miners' safety lamps, and, in passing, the practical value of reducing the manufacture to standard sizes may be remarked, the shells of the lamps being interchangeable and all internal parts being constructed to fit these shells. Lamps of all types, whether Marsauts, bonneted Mueselers, bonneted Clannys, or any other of their modifications, can be rapidly put together and consigned to their destination.
Here may be mentioned the safety lamp cleaning machine shown in Room 5. This is the invention of Mr. WOLSTENHOLM, of the Bestwood Coal and Iron Company. It has several advantages over other machines of‑the‑kind. Arrangements are made‑for unscrewing the ring holding the glass and gauze, for cleaning and polishing all parts of the lamp, and for screwing the ring up again into position. An eccentric imparts an oscillating movement to a brush which rapidly cleans the gauze.
Wolstenholme's Lamp Cleaning Machine.
Special fittings for the protection of incandescent electric lamps in dusty, damp. and all exposed positions, are manufactured, and a large stock kept in readiness, these being in considerable demand by various electrical engineering firms, especially for lighting up the surface and underground of collieries, in which the firm of JOHN DAVIS & SON have been of late years actively engaged.
A fitting specially for lighting a sinking pit has been designed and is now in use at several collieries. It is exhibited with its lamps alight, and consists of a cast‑iron dish‑strong glass protector containing three incandescent lamps of 25 candle power each. A strong flexible cable of twin conductors is told out from a drum at the top of the pit shaft.
Room 5. A pioneer station for the distribution of electric current is here installed, and has been at constant work for over four years. This plant consists of an engine, dynamo and battery of sixty accumulators, with its accompanying set of switches to regulate the current in its various distributing cables ; voltmeters to indicate the pressure of the current, ammeters to show the volume of current going out, and electricity meters to ascertain the total amount of current consumed during any period. Regulating switches with resistance coils to adjust the exact pressure to the varying load, and an automatic switch to disconnect the dynamo from the accumulators, should the pressure of the former fall below that of the latter. The whole of the available current is daily in demand supplying neighbouring hotels, shops, offices, and private houses with electric light, and it may be here stated that from the day
that the current was first` laid on" over four years ago, no single hitch or stoppage of supply has occurred.
Electricity for transmission of power is daily becoming recognised by coal‑owners as a reliable agent, and already some hundreds.of horse power is being transmitted electrically in‑mines‑ of this country, It was found impossible to illustrate the application of electrical transmission
3 Brake H.P. Davis and Stokes' Patent Safety Motor
of power to coal‑cutting and holing on the present occasion, but the same power applied to pumping may be novel to some of the members.
Up to the present time a danger has been felt to exist in the use of electric motors in fiery mines, from the fact that bad setting or wearing of the brushes might result in sparking, and the possible ignition of any gas that might be present ; in fact, the use of electric motors in any mine where safety 'lamps are necessary has hitherto‑been considered unsafe, and the progress of ‑electrical transmission of power has thereby been greatly retarded.
Previous attempts at the construction of a safe motor have taken. thel direction of encasing either the whole machine,.the armature, or the
Safety Commutator open for cleaning interior and brushes.
commutator and ‑brushes. These arrangements not only introduced difficulties in the ventilation of the armature, but also necessarily included a considerable air space, so that when this space became filled with gas it would be possible for an explosion to take place inside the case of such violence as to entirely destroy the cover or case, and communicate with the outside atmosphere, thus causing an explosion.
The arrangement illustrated has been designed to overcome these difficulties, and is so arranged that the commutator itself is practically equivalent to a locked safety lamp enclosing the brushes, since it cannot be worked unless closed, and cannot be opened while running; the junction between the fixed and the revolving portions of the machine being made by a flame‑tight joint which requires no packing and causes no friction.
The most marked deviation from the ordinary commutator is, that instead of the brush contact being on the outside of the cylinder formed by the commutator segments, this cylinder is bellow, and the brushes bear on the inside face of the segments. The method of construction is as follows:-
The commutator ‑segments are clamped between a ring and a disc, the latter being keyed on the shaft. This disc foirns a permanently closed end to the commutator cylinder at the side nearest the armature.
The brass bearing of the shaft is extended nearly up to the disc, leaving room for a slight end play (the shaft of course only bearing in the usual portion of the brass), and means are provided to prevent the oil from the bearing working along the extended portion of the brass and entering the commutator.
Half Section of Commutator shewing bearing with elongated brass.
The open end of the commutator cylinder is closed by a disc sliding on the extended brass bearing and carryingthe brush holders and brushes; and a clamping handle (not shown in the illustration) provides for setting the disc and brushes in their proper position. This disc, as stated, closes the end of the hollow cylinder, the latter revolving with a clearance of 1‑32 in. from the disc; and in order to avoid the chance of the disc with its brushes being withdrawn while the machine is running, or started before properly closed, a locking ring is provided, as shown in the illustration.
Small windows are provided in the disc, by which any sparking at the brushes can be seen and corrected, and the brushholders are fitted with springs working on the outside of the disc, for adjusting their pressure while running.
When it is necessary to clean the interior of the commutator and brushes, the locking ring is unscrewed, and the disc, with brushes attached, is slid towards the bearing as far as possible, thus leaving both commutator and brushes clear for cleaning and inspection; means are provided for attaching a small slide rest, so that by the use of a crank handle bolted to the pulley, the commutator can be turned up in position, should this be required.
Carbon brushes of a special type, admitting of very easy renewal, are used, thus obviating any trouble that might occur from accumulation of copper dust within the commutator with the ordinary copper brushes.
One of the chief difficulties experienced by the firm is in making a judicious selection from the various devices which are brought by inventors to be perfected, manufactured, and introduced.
Amongst inventions recently taken up at All Saints' Works may be
An Electric Signalling Apparatus for the Navy;
An Electric Indicator to show high and low water levels in tanks;
A Machine for Closing and Unclosing Lead Locks of Miners' Lamps;
An Electrical Time Checking Apparatus;
A Lamp for Testing Small Percentages of Gas in Mines;
A System of Humidifying the Air in Mines, so that coal dust is effectually damped.
The inventors will, no doubt, in due course give the Members of the Federated Institution of Engineers a more detailed description of their apparatus.