This article, from The Engineer, October 23, 1896, describes the recently opened Upper Douglas Cable Tramway.
DOUGLAS CABLE TRAMWAY
The Douglas cable tramway, of which we give some illustrations, has recently been completed by Messrs. Dick, Kerr, and Co., of London, who have previously constructed cable lines between Brixton and Streatham, at Matlock Bridge, Derbyshire, and two cable routes at Edinburgh, under the engineers of those lines.
The cable line at Douglas has been constructed for the Isle of Man Tramway and Electric Power Company, and connects the higher districts of Douglas with the Bay tramway route previously existing. The construction of this Upper Town tramway was made a condition by the Douglas Town Commissioners in connection with the renewal of the lease to the tramway company of their horse tram route along the promenade. The new Upper Town route presented, however, physical difficulties, owing to several very severe gradients that not only put horse traction entirely out of question, but rendered it impossible to use any power dependent upon adhesion to the rails, and after an inspection of the two cable lines put down in Edinburgh with similar gradients, the company decided upon a cable line for their Upper Town route in Douglas, and the construction of this line was placed in the hands of Messrs. Dick, Kerr, and Co. In its main details the Upper Town cable route at Douglas is very similar to those put down by the same firm at Edinburgh, and recently between Brixton and Streatham, and the series of drawings and illustrations we give render it unnecessary to enter into any very detailed description, beyond reference to one or two special features which have been introduced where the construction of the line presented some exceptional difficulty. The route of the Douglas cable line is 1 5/8 mile in length, extending from the Peveril Hotel, close to the landing pier, passing up Victoria street, Prospect-hill, Bucks-road, into Ballaquayle-road, and down Broadway to join the Bay or Promenade horse tramway line. and throughout its entire length is a double line, except at one or two points presenting some exceptional difficulties, such as an exceedingly sharp curve or an exceptionally steep gradient. The gauge is 3ft., and the track rails are 75lb. per linear yard. The conduit -- in which the cable is laid, and which runs over vertical and horizontal pulleys -- is constructed of concrete, 5 to 1 . The track rails are laid on 6in. of similar concrete ; the slot rails, which are of special section, weighing 37 lb. per linear yard, are carried on cast iron yokes imbedded in the concrete, and the conduit is drained at each point where there is a vertical pulley pit, these pits, on an average, being placed 49ft. spart. The horizontal pulleys are set according to the radius of the curve in different parts of the line. and are only 3ft.-6ft. apart at one point,where there is a eurve of 40ft. radius. All the pulleys both vertical and horizonta|, are 12in. diameter in the tread. The vertieal pulleys are run in lignum vitae bushes, the horizontal pulleys running loose on steel pins, and bushed with white metal. Both are lubricated with petroleum grease, the vertical pulleys having a grease box, and the horizontal pulleys fitted with Stauffer's lubricators, this method having given the greatest satisfaction on other lines constructed by Messrs. Dick, Kerr, and Co., the verlical pulleys requiring very little attention. in some cases not necessitating examination for three months. At the engine house the grip pulley is 10ft. in diameter, and the jaws are lined with white metal. This pulley is made to grip the cable almost three quarters of the circumference, by the use of an idle pulley close up, also lOft. in diameter, under which the cable passes after leaving tho grip pulley. The idle or tension, terminal and diversion pulleys are all cast in ha]ves, having loose rims or treads which can be readily removed, and so constructced to minimise, as far as possiible, wear and tear upon the rope. From the engine-house the rope passes into the main diverting pit, where it is run round 8ft. pulleys placed at an angle, and over a 5ft. pulley, after which it is delivered into the conduit ready for gripping, the course being along the conduit to tbe terminal pit at the bottom of Broadway, round two 8ft. pulleys in this pit and up Broadway again, past the engine-house in the up line, along the whole route to the terminal pit at the Peveril Hotel, round to the pulleys there, and back, along the down Iine, round to the large diverting pulley in the main pit at the power station, and into the subway and tension race of the engine-house. The cable, which is 3 1/2in. circumference, is made of the very finest steel wire laid on a hemp core with six strands of thirteen wires each, seven round six, on the "Lang" lay principle, and was manufactured by Messrs. Craddock and Co., of Wakefield. The cable complete weighs 20 tons, and was manufactured entirely in one length, but had to be shipped on two service reels, so that it might be lifted in two lifts by the crane in Douglas harbour, which is only capable of raising 15 tons.
The cars used, which are of the bogie type. and very neat in design , are built to carrry thirty-five passengers. and were supplied by Messrs. Geo. F. Milnes and Co., Birkenhead . ln order that the drivers may have complete control over the cars, on the very steep gradients which they have to mount and descend at the several points of the line, the heaviest of these being 1 in 10.4, exceptional brake power has, of course, been requisite. In the first place, the cars are controlled by a wheel brake, actuated by a screw, which operates a brake block on each of the eight wheels, and a sand-box is provided at both ends of the car. In attition to these brakes, there is also provided an emergency slot brake, originally designed by Mr. James More, jun., the engineer for Messrs. Dick, Kerr, and Co., to meet the exceptional requirements of the Matlock Bridge cable tramway, where there is a gradient of 1 in 4 1/2. This brake, the details of which will he fully shown in illustrations, which we shaIl publish in another impression; is of sufficient power to bring the car to rest at any part of the route in half its own Iength. The main features of this emergency brake are two blocks, one comng in contact with the top of the slot rail, and the other with a lower shoulderˇof the rail, and when it is required to operate the brake those blocks are brought in contact with the rail by means of a chain and spindle, and act as a powerful vice in gripping the rail. As this emergency brake is fitted on both of the bogies, it can be actuated from either end of the car, and it may be added that, with the exception of the Matlock Bridge route, the Douglas Upper Town cable line is better provided with brake power than any other similar line in the country.
With regard to the drivig plant, it may be stated that the engines and boilers are in duplicate. The engines are of the horizontal high pressure non.condensing type, and are fitted with Proell's automatic expansion gear and governor; this gear, which is most sensitive, and accommodates itself instantly to the greatest variations of Ioad, effecting a great gain in economy of fuel and steady running. One engine is sufficient to drive the line, the other being a stand-by, and they can be coupled and uncoupled in a few minutes by means of flange couplings on the crank shafts. The shafts are geared to a counter-shaft by means of a double helical spur and pinion gear, and the counter-shaft carries a Weston's friction clutch, which operates the driving or grip pulley. The boiler-house is 8ft. below the level of the engine-house, with which it communicates by a flight of stairs, and under the firing floor of this house there is an underground storage tank of 6000 gallons capacity, into which a spring runs, a settling tank being used before running the water into it. There is also a blow-off tank, with separate blow-off pipes for each boiler. The steam power is supplied by two of Messrs. Galloways' Lancashire boilers, with their Galloway tubes, the water being passed through a Green's economiser, where, from 60 deg. Fah., it is raised to about 250 deg. Fah. before entering the boilers. The reel-house, where there are two permanent storage drums for storing cable, lies behind the boiler-house, and is connected to the car-shed by a flight of stairs, whilst adjoining it, and under the car-shed, is a smithy and workshop for repairing grippers, brakes &c. An overhead storage feed-water tank, of 6000 gallons capacity , is also provided in this house. The carshed, which is 236ft. Iong, and will accommodate twenty-one cars, has four Iines of rails, with repairing pits extending the whole length. The cars are got on to these by the use of a traverser, which is so constructed that the cars can be run in without lifting the grippers. There are also small board-room. office, store, lamp-room, and lavatories. The cars gravitate into and out of the shed by two curves, which form a triangle with the main line. With the exceptions mentioned, all the engines, driving gear, terminal and conduit pulleys, and depot buildings, have been eonstructed by Messrs. Dick, Kerr, and Co., London, and designed and carried out by their engineer, Mr. James More, jun., A.M.l.C.E., who was assisted by Mr. E. Rotter, A.M.I.C.E., and Mr. A. Windsor.
It may be added that, in conjunction with the cable and horse tramways, which now provide a very complete service for the town of Douglas, there is also an electric line, under the control of the same company, which in two sections extends first, to Laxey, and then, by a mountain railway, to the top of Snaefell, the highest point in the island, with a circuitous ascent of 1 in 20. This line, wlth a continuous Iength of 10 1/2 miles of direct armoured cable, is now one of the mo)st important electric railway undertakings in the kingdom. For driving the cars, plant is provided for developing 1100-horse power in three generator stations along the route, and, in addition, there are two accumulator stations, in which 200 additional horse-power can be stored. A description of the line has already appeared in THE ENGINEER; but it may be interesting to mention a simpIe and ingenious device, designed during the past season by Mr. J. Aldworlh, the general manager of the company, with the object of preventing the loss and inconvenience not unfrequently arising from oecasional breakages of th main overhead conductor wires, a defect in the overhead transmission of power which is a matter of more or less general complaint on simiIa r electric tramway systems in other parts of the country. Mr. Aldworth has not aimed at preventing the liability to breakage but in the event of the conductor wire snapping , to prevent any serious inconvenience being experienced: and he has suceeded in this by simply providing at each of the supporting arms over which the main conductor wire passes, an auxiliary insulated attachment for clipping the wires, in addition to the ordinary insulated clip. This clip consists of a half circle branch wire insulated, and fastened to the conductor wire above and on each side of the supporting arm. As the breakages invariably occur at this particular point, in the event of the conductor wire being snapped, the connection is kept up by the auxiliary attachment, which then rests upon the supporting arm, and there is no interference with the current. Some half-dozen breakages of the main conductor wire have ocurred during the past season, which under ordinary circumstances, would have resulted in a temporary stoppage of traffic and a considerable loss to the company; but in no instance was the regular working of the electric railway interrupted, the auxiliary clips maintaining the connection until the requisite repairs could be effected at night, when traffic was stopped.
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