OTIRA TUNNEL

Hokitika Guardian, 17 September 1920, Page 4

OTIRA TUNNEL

THE ELECTRICAL EQUIPMENT. SOME INTERESING DEAILS. Tho electrical equipment of the Arthur’s Pass tunnpl section of the Midland Railway has now reached the {joint of the ttL'ceptaiidb of tho contract of the English Electric Company for £313,000. Avoiding the use of technical expressions as much as possible, the tlectric equipment is described as follows, states the Wellfigton “Post.” It will consist of two main generators of 1600 kilowatts capacity, geared to turbines with- a speed of 450 revolutions per minute. These generators will generate district current at 1650 volts for working the electric trains. They will bo reuqired to cany an overload of .100 per cent, for short periods. In addition to thOse main generators of 100 kilowatt capacity (in duplicate) forsupplying light required-in the tunnel, the stations at either end* the yards and shops, and for other .general purposes. The tunnel will be. lit at intervals of 75 feet with 60 watt lamps. It will bo fairly, light all the way through. Provision will he made in the tunnel for auxiliary fighting for use at any point fab era men may be required to work. That light will be equal to double the above; the tunnel light will be capable of being switched on and off as necessary.

The locomotives will number five for the trains service, and there will also be a battery locomotive for inspection and light shunting purposes. The locomotives will he of 680 hotse-power and weigh 48 tons. They will take current at 1500 volts. They will be specially built for the job. Each will be capable of operating a double-header train with one engine crew. Those to he used for the trains, goods and passengers will have the appearance of a closed-in tram car. They will simply replace the steam locomotives at the respective ends of the tunnel, taking Itlie train over from one steam locomotive and delivering it to another at the other end of the tunnel. There will be no necessity for passengers to leave their seats when the electric locomotive replaces that driven by steam. The system adopted is similar to that in use in Christchurch, viz. an overhead contact wire with rail return, but the voltage on the tunnel line will be 1500 volts. '

There will be no trolley-poles used in the tunnel. Instead, there will ho a pantograph current-collector, comparable to a bicycle frame in appearance, expanding or contracting according to the changes in height of the tiolley Wire. The collector is used.in preference to a trolley wheel ,as being less liable to leave the wire, especially at high speed, on its own accord. The speed at which .the electric trains will run will he eighteen miles per hour on the up grade and a few miles faster on the down grade. The time in the tunnel of an electric train will not exceed twenty to twenty-five minutes; less, of course, when coming down. r l he actual tunnel is 5 miles 25.18 chains in length ; but the whole section to he electrified is 8 miles 54 chains, single track, and, of course, of 3ft 6in. gauge. There are to be sidings at Otira and Arthur’s Pass stations. The minimum traffic to be provided is one passenger train and 1000 tons of- freight per day from west to cast, and one passenger train and 700 tons of freight pel daj from east to west. There will only he one train at a- time on tlie 'line, at any rate for some time after the line is in running order. Tho power station will be at Otira, and wjll be erected by the PublicWorks Department, which will also furnish the boilers, designed for 180 gauge pressure. Rails for the electrified sec tion will be provided, laid and ballasted by the Public Works Department. The time for completion of the electrification contract is eighteen months from the date of acceptance of the tender, and the contractors must maintain the. whole plant for at least twelve months from the time of completion of the installation. ■ In the specifications interesting- derails of the climate and topographical features of the tunnel are furnished. It is shewn that the rainfall—at Otirar—is heavy, being an average over thirteen years of 195.17 in. per annum. The heaviest fall in any one month occurs in- October, 23.04 in. and the lightest in February, 10.01 in. over a period of thirteen years. Considerable snowfalls are experienced during some winters, as much as sft having been recorded at Otira; but the fall seldom exceeds one foot, and the average of tlie biggest falls of snow for each of tlie past ten years would be six inches. The temperature recorded ranges from lldeg" to 82deg Fahr., but it is never likely to fall below zero. High wind pressures and gaTes of great violence have had to bo .allowed for by tlie en-

gineers. The section to be electrified is on a grade’of lin 33 for a considerable portion of the tunnel. The summit of the line is 1177 feet' above Otira, itself 1260 feet above sea level, so that a point 2437 feet above sea-level is reached. Men already in the locomotive branch of the New Zealand Government railways will be selected for training todrive the electric locomotives. They will be instructed by the contractor for the electrical equipment during, the progress of tho' contract, and only such as receive certificates of competency from the contractor will be employed on-tho locomotive anffi generating plant.