Roslyn's New Installation of Electric Street Lighting.

Progress, Volume I, Issue 7, 1 May 1906, Page 171

Roslyn's New Installation of Electric Street Lighting.

The Council of the Borough of Roslyn recently invited schemes and tenders thereon from several electrical engineering firms for an installation of electric street lighting in the borough. Up to the time of doing this the borough streets had been lighted with gas ; but a very favourable offer to supply electricity having been made to the Council by the Roslyn and Dunedin Tramway Co., Ltd., it was evident that a system of street lighting by incandescent electric lamps could be substituted for the existing gas lighting, with advantage both in point of cost and illuminating power. Power is supplied by the Roslyn and Dunedin Tramway Co. from the 550-volt directcurrent generator, which also supplies power for the operation of the electric-car line operated by the company within the borough.

The street lighting incandescent lamps are arranged in groups of five ioo-volt lamps in simple series, there being 13 of these groups, making 65 lamps m all. Each lamp is a carbon-filament lamp of I*4o candle power. The conductors are insulated in general with double braid and weatherproof compounding, vulcanised rubber insulation being substituted in positions where telephone or telegraph lines are crossed, conductors throughout being of No. 12 hard-drawn copper wire. Each distribution circuit of five lamps is connected to the feeder or trolley wire of the electric-car line through a spring clip fuse, and a suitable resistance is also provided and inserted in all distribution circuits (except the two most remote from the generator) to absorb the small excess of voltage, the amount of this excess on any distribution circuit depending on the length of conductor in that circuit and the distance from the generator at which the circuit is connected to the supply feeder or trolley wire. A common return conductor fitted with switch gear and ammeter at the power house controls the supply to all the distribution circuits. All conductors are carried overhead on Australian ironbark poles, the average size of poles being 25 ft. long over-all by 8 in. square at base. Wood cross-arms and white porctlam double shed insulators are used lor supporting the conductors. The lamp fittings have been designed and manufactured by Messrs. A. & T. Burt, Ltd., and appear very suitable, the lower shade shown in the accompanying illustration is made of opal glass, and the efficiency of the arrangement is very good. No outer globe is used to enclose the lamp, the maximum light being therefore available for illuminating purposes. The whole system has now been in operation for over two months and is giving complete satisfaction, the chief difficulty that the Council now find is to meet the remonstrances of ratepayers resident in such parts of the borough as are yet unlighted, and there is every probability that the Council will shortly have to extend the system to complete the lighting of the borough,

Compound Gas Engine. — According to the Iron Age, a compound gas engine has been built with two high-pressure cylinders and a single lowpressure cylinder between them. The high-pressure cylinders work on the Otto cycle, the engine receiving one impulse from them each revolution. The exhaust from the two explosions is expanded in the low-pressure cylinder, the crank of which is 1 80° behind the high-pressure cranks. Thus, at every forward stroke the low-pressure cylinder takes the exhaust gases from one of the high-pressure cylinders. The total effect is thus to produce an impulse every half revolution. With a 12-h.p. engine 13 b.h.p. were obtained with the low-pressure cylinder in use, and only 8.9 h.p. without it, 46.2 per cent, being thus added to the power by the use of the low-pressure cylinder and without the expenditure of any additional fuel. — Iron and Ore Supplies.