Electric Trams. TO THE EDITOR.

Otago Witness, Issue 2104, 21 June 1894, Page 29

Electric Trams. TO THE EDITOR.

Sib, — HaviDg seen in one of your late issues that the subject of electric tramways for Dunedin is attracting some attention, it has occurred to me that a description of the tramways of this city may be of interest to some of your readers, among whom I have many friends. The tramway system of Denver is acknowledged by all who have examined into its working to be the most perfect and complete in the United States. This arises from the fact that Denver is the- newest large city in the States, hence the latest improvements have been availed of with a readiness that would not occur where the vested interests were more established. * The population of Denver and its suburbs is aboub 150,000, and two-thirds of it has been added in the last 15 years. The city covers an area of about six miles in diameter, while the suburbs extend on all sides about four miles more, making the greatest distance apart between any two' tramway terminals about 12 miles'. .• » The following is approximately the mileage of the various lines now in operation, in or about the city : — Miles. Double track electric tramways ... 49 Doable track cable „ ... 15 • Single track suburban, electric ... 33 Single track horse tramways ... .... 3 Total tramways, about 100 Of the above about 50 miles are operated or controlled by the Denver Tramway Company. The Denver City Railway Company operate the above 15 miles of cable road, but owing to the great expense of, working aud maintenance the company is not, financially, in a prosperous condition. This is easily accounted for by the fact that it requires 80 per cent, of the motive power to move the cable without any c^ra on the road, or of the total power required to work the road oniy 20 per cent, is absorbed ii moving the cars. This enormous frio'ional bss aud the heavy wear and tear of the rope and carrier pulleys condemn the cable system, except for exceptionally heavy grades. In all systems of electric tramways the cars are propelled by electric motors, which actuate the flanged wheels carrying the cars, but the difference in systems consists in the manner in which the motors are sqpplied with current. The ••trolly" system is the one in most general use in the United States. It consists of the usual car, having electric motors placed under the floor of the cars for driving one or more pairs of the car wheels. The electric current is supplied from an overhead naked copper wire, which runs the whole length of the road. The wire is suspended from poles placed on each side by crosß wires placed about 14ft above the ground and directly over the centre of the track. Tho naked wire is in direct electrical communication with a dynamo at the central station. Thy tram rails are also in electrical communication with the same dynamo, but of coarse with the opposite pole, hence if a conductor ba placed between the naked wire and the rails a current will flow through the conductor. Such a conductor is furnished by each passiDg car, which has a " trolly " wheel carried on the upper end cf a rod that projects from the car top. The trolly wheel presses against the lower side of the naked wire, from which it takes the current, aud it is led to the motor by insulated wires. From the motor it returns to the central station through the car wheels and rails of the track.

Another system is the "storage battery " or ••accumulator" system. In this the current is supplied to the motor from storage batteries placed below the seats. These batteries have to be periodically charged

at the central station. The advantages are : The avoidance of poles and naked wires in the street?, and the consequent greater safety to life, while the streets present a more sightly appearance.

The disadvantages are : It is moro expsnsive to operate on account of the loss of power in the accumulators, from the loss of time in charging the accumulators, the difficulty in keeping the batteries in working order, and the extra wtight of the batteries to be carried on each car, amounting to over one ton, and in some cases to one ton and a-half

This system is now in operation at Mount Vernon, near Now York, where it is said to give satisfaction. The cars there in use have to be run into the charging house after a run of six miles, when it takes from 10 to 15 minutes to recharge the accumulators in order to continue work.

The •• underground conductor " or " conduit " system has been tried in a small and imperfect way in this country, but I am not awaro of any line using it being in successful operation. This is due to the first cost being compartively high, and to the fact that there is no legislation against overhead naked wires in the country. The system is very similar to the cable tramway, but the moving rope is replaced by a stationary electrical conductor, against which a trolly wheel presses and takes off the current as in the overhead trolly system. The points to recommend this system are its absolute safety to the public bo far as any danger to life from contact with the conductors, there are no unsightly poles in the streets, and the cost of operating is not in excess of the overhead trolly system.

The only objection is the first cost of laying the road with the continuous Blot, but when once well laid down it is permanent, and not subject to the accidents common to the overhead wires from wind and lightning.

The last electric line set to work in Denver is the East Colfax avenue line, which until last year was a cable line. It may, therefore, be taken as the best example of the latest practice in this country.

It has a double track, three and one-quarter miles in length from terminal to terminal. It is 42i0 gauge, with curves of 37ft radius, and a maximum grade of one in 10. The interval in time between the cars is 6min, and eight cars are required on the road at one time to maintain the service.

This line has the heaviest- traffic in the city, and a speed of from 12 to 15 miles per hour is easily obtained between stops, the round trip being made in 45min. The cars are very substantially built, measuring 33ft over all in length, by Bft wide inside Seats are provided for 48 passengers, arranged athwart ship, as in a railway car, with a central pasiage, and doors at the ends. At night the cars are lighted with ten 16-candle power incandescent lamps, which allow of reading ordinary print with comfort. The cars are carried on two " bogie tracks " each of which is provided with a 15-horse power motor. The "motorneer" (a new American word) stands on the front platform, and works the brake with his right hand, the regulator with his left, while with his foot he sounds a gong by means of a button on the platform. The conductor collects the fares, and at the same time pulls a cord that runs the length of the car. This sounds a bell, and at the same time records the fare and shows the number of fares paid duriDg the trip on a large dial placed at the end of the car.

A uniform fare of 5 cents is charged all over the city, and this entitles each passenger to a transfer ticket on to any line operated by the same company. The tickets have the date, hoar, and street punched when issued. They | are not transferable, and are only good at the place and time of issue. There are two central power stations, one at the north side of the city and one at the south. The plant in the former consists of three 300-horse power dynamos, each capable of giving off 550 amperes of current of 550 volts. They are driven by three horizontal steam engines of about 500 indicated horse power each. Any- two of the engines - are capable of supplying sufficient power to run all the lines connected with the station, so that there is always a spare eDgine and dynamo available in case of accident. . As to the cost of working electric tr an ways when compared with horse traction. The electric car travels twice aB fast as the horse car, hence one-third less cars will maintain the same service, and allow of the same time interval between the cars ; and the cars can be built to have much larger carrying capacity. Thus a large saving is effected in the wages account. Again, the dynamos only generate current ss it is required ; hence, if all the cars on the road are standing at any one moment, no power is generated except to overcome the friction of the machinery in motion ; while, on the other hand, if all the cars be in motion at any one moment, the dynamo gives off the full power required, so that the coal consumption is in exact proportion to the number of cars at work and the load on them. If we assume, for example, a line of seven miles in length operated in one case by horse power and in the other case by electric power, the account would stand as follows :—: — Running expenses of a horse tramway, seven miles in length, with a time interval of 6min between the cars : 28 drivers (two eight- hour shifts) at 7s , per day .£9 16 0 28 conductors (two eight-hour shifts) at 7aperday 9 16 0 3 maintenance men at 8s per day ... 14 0 Horse feed for 80 horses at la tid per day 6 0 0 10 stable hands at 6s per day 3 0 0 Depreciation of horses, say ... ... 2 0 0 Total running expenses „£3116 0 Expenses of an electric tramway to maintain the same service": — 3 tons coal at £1 103 per ton £4 10 0 18 drivers at 7s 6 6 0 IS conductors at 7s 6 6 0 4 maintenance men at 8s 1 12 0 2 engine drivers at 10s 10 0 ; 2 stokers at 63 0 12 0 j Total running expenses £20 6 0 ! In both these cases management, repairs, and depreciation may be taken at about the same, and no account is taken of the larger number of passengers that would travel on account of the greater facilities offered, for the present horse car is only tolerated as a small saving in time and boot leather, that is hardly balanced by the discomfort, while a well constructed electric car has all the comfort of a first-class railway carriage. In the above estimates, if the actual wages and cost of fuel in Dunedin be substituted for the figures given, the total results will be practically correct. — I am, &c, Thos. J. Watebs. Denver % Colorado, April 24. In the report of the Land Board, which appears in another column, the words " block IX" in the paragraph referring to the subdivision of a run in the Maniototo district should read "block XI"; and tha resolution with regard to section 17 in that block should read : •' Mr J. Baxter to be allowed to acquire as a small grazing run at a rental of 9d per acre, capital value 18s 9d per acre, valuation for improvements £15 45."