« ÎnapoiContinuați »
The latest achievement in this line was the trial trip of the E. S. Electricity (to coin an abbreviation for “electric ship”) from the works of the “Electrical Power Storage Company” of Millwall to London Bridge and back on September 28, 1882. This electric launch is 25 feet long by 5 feet across the beam, and draws about 2 feet of water. She was propelled by a 22 inch screw driven by a Siemens dynamo, which was actuated by the current from 45 accumulators of the SellonVolckmar type. These reservoirs of electricity were stored in different parts of the vessel and served as ballast. They were charged with electricity before starting and were capable of furnishing 4 horse-power of energy during a period of six hours. Two Siemens dynamos were taken, and either or both could be driven by the current at will. The rotation of the Siemens bobbin was communicated by proper gearing to the shaft of the propeller.
With four persons on board the Electricity made the course from Millwall to London Bridge and back, in spite of wind and tide, in 24 minutes; calculation shows that this effort corresponded to an expenditure of over 3 horse-power during the time; but it would have been more satisfactory had the voyage lasted longer, in order to test the staying powers of the accumulators. The singular appearance of the craft shooting along as if self-impelled and emitting neither smoke nor noise, attracted much attention. On pleasaunce waters, such as the upper reaches of the Thames, a quiet vessel of this kind would be preferable to the fussy little launches which infest them.
The electric plough promises well as an application of the transmission of power by electricity. It has an
advantage over the steam-plough in that no fuel has to be transported at great expense in horses from the farm-yard to the field where the steam-engine is stationed; for the engine can work at the yard itself, or it may be at the coal-pit mouth, and its power can be transmitted by wire to the distant field where the plough is working. The plough itself need not differ from the ordinary steam-plough with one or more shares, which is pulled by ropes from one end of the furrow to the other; and the only change necessary is in the stationary winches or drums which wind and unwind the ropes pulling the plough. These winches are fitted, as in the ploughs of M. Felix, with dynamo-electric motors, through the bobbins of which the current is passed. The rotation thus produced is communicated to the drums by proper gearing
There are many other uses for electric power, some of which have been already tried, others only thought about. The Siemens electric lift, for example, was operating day after day in the Paris Electrical Exhibition: so also was the electric hoist of Dr. J. Hopkinson.
In the electric lift, the cage, supported by two ropes, is raised or lowered by means of a toothed pinion working into a kind of rack or ladder. The pinion is turned by a Siemens dynamo, carried in a box beneath the cage, and deriving its current by wires from a stationary generator.
In the electric hoist, the chains carrying the weight to be lifted are wound and unwound on a drum or pulley by a dynamo attached to the latter, and the reversal of the current reverses the motion of the pulley and chain. Here again the power is drawn from a generating dynamo.
The electric hammer of M. Marcel Deprez consists of a hollow column or solenoid, built up of coils of wire placed one above another. This solenoid is supported on a table, and contains within it a stem or core of soft iron which has a hammer head fixed to its lower end. The separate coils forming the solenoid are connected to the contact pieces of a circular commutator in such a manner that though they are all joined together end to end, a wire runs from each junction of a pair of coils to one of the commutator contacts. Two metal brushes can be made to sweep one of these contacts by turning a handle, and as the current enters and leaves the coils by the two brushes, the number of coils and their position in the column will be determined by the angle between the two brushes and the position of the handles. Thus if there are ten coils included between the two brushes the current will traverse these ten coils, and if the handles be made to sway round the commutator with a see-saw motion the current will travel up and down the solenoid, exciting ten coils at a time. The soft iron core will be attracted by the excited coils, and hence will rise and fall in the hollow solenoid following the march of the excited coils. In this way an up and down motion will be given to the hammer head.
In passing from out-of-door operations to the duties of the household, we come to the small electric motors which have been devised for driving sewing-machines, lathes, punkahs, coffee-mills, and such-like appliances. Motors of this kind have been constructed by M. Trouvé, M. Marcel Deprez, Jablochkoff, and others; but perhaps the most efficient of these for its size and cost is a pigmy motor, invented by Mr. W. W. Griscom, of Philadelphia.
This apparatus is illustrated in Fig. 77 in the act of
driving a sewing-machine. It consists of an electromagnet in the form of a flat ring of soft iron wound on its opposite sides with insulated wire. Two bare zones of the ring above and below, act as "north” and “south " poles. Between these poles is placed a movable bobbin, with poles like an electro-magnet, to which
the current is led by terminals and commutator brushes. The current traverses alike the coils of the ring electro-magnet, and the bobbin thereby rotates the latter, and drives a pulley which communicates its motion by a strap to the pulleys of the sewing machine.
This motor is peculiarly powerful, owing to the fact that the currents induced in the coils of the magnet by the rotation of the bobbin with its magnet poles inside it, are caused to assist the magnetising current supplied to the ring coils by the commutator, and thus heighten the magnetism of the ring poles.
In form it is only two inches and a half long by two inches in diameter, and weighs two pounds and a half. Nevertheless, with the current from a battery of six bichromate of potash cells running throughout the bobbin, it attains a speed of 5,000 revolutions per minute, and yields sufficient power to drive a sewingmachine or a small lathe at a rapid rate. As exhibited at the Crystal Palace, the bichromate of potash battery for working the machine is contained in a box, and the power of the battery, and thus the speed of the machine, can be regulated at the will of the seamstress, by working a pedal with her feet, and raising or lowering the battery-plates in the solution which surrounds them. The greater the extent of plate-surface immersed in the liquid the greater the current obtained from the battery, and the more energetic the action of the motor and machine. According to the vendors the estimated cost of working this little motor is about 1d. per hour per horse-power of energy obtained.
When the electric light and power corporations have been fairly launched, and central stations for