AN ELECTRIC LAUNCH.

Timaru Herald, Volume XL, Issue 3019, 28 May 1884, Page 3

AN ELECTRIC LAUNCH.

A late number of the Engineer contains, m a report of the annual meeting of the Institution of Naval Architects, held m London on April 2nd, an abstract of a paper read by Mr Yarrow, a member, of the noted firm of steam yacht and launch builders. The subject of the paper was an electric launch built by Yarrow and Co., m conjunction with Siemens Brothers, the famous electricians, and the Electric Storage Company. The launch was 40ft long, with a beam of Gft, and weighed under the trials from 4£ to 5 tons. It was driven by a screw propeller, actuated by an electric engine, the motive current for which was supplied by storage cells or accumulators. Each of these cells measured 9£ inches m length, 9 inches m depth, and 7h inches m width. Each cell weighed 561 b, or forty weighed a ton, and a few over a hundred measured a ship's ton of 40 cubic feet. Each cell contained 18 pairs of lead plates, one of each pair, the " positive," being pasted with rod lead, and the other, the '* negative," with litharge. Electricity is " stored "m these plates by passing a current through them, when the red lead of the positive plate is converted into peroxide of lead, a substance of a chocolate color, and the litharge of the negative plate is " reduced " and becomes spongy lead. The plates are emerged while being charged, m a solution of sulphuric acid, m the proportion of one of acid to four of water. The effect of charging is a chemical action, the positive plates taking up oxygen and the negative ones hydrogen. In applying the plates to use, the reverse action is brought about, the positive plates give up oxygen and the negative ones hydrogen, leaving the pistes m the exact state they were prior to the charging process. The reversal of tho process develops an electric currrent, such as disappeared m the charging process. The chemical change m the one case io the result of the power expended ; m tho other case the power generated is the result of the chemical change. The losses of_ power incurred m the process of changing tho plates and recovering tho electricy are variously estimated ; an average of a number of estimates gives — loss between engine and dynamo, converting mechanical into electrical energy, 15 per cent ; loss of olectrical energy m charging the accumulators, converting olectrical into chemical energy, 10 per cent ; loss iv the reverse action, converting chemical energy into electrical energy and this into mechanical energy, 25 percent j leaving an estimated residue of useful effect of 67$ per cent. W. Yarrow was certain from his own experience that from 45 to 50 per cent of useful effect may be relied on. The motor used m the launch was tested up to 8 h.p. by the brake, but it is not stated how many storage cells were used to obtain this effect. Tho best result obtained m the trials wsb 0.9 knots Bn hour, with a displacement of fivo tons. For this speed, it is stated, 71 cells were m circuit, but wo are not informed for how long that number maintained the stated efficiency. Each half-hundred weight cell, whon fully charged, is considered to be equal to one net horsepower for one hour developed on the Bhaft, but m aotual praotice a considerable deduction from this estimate must be made. The advantages of stored eleotricity as compared with steam, as a motive power for launches, are mentioned by Mr Yarrow, as follow* :— (1) Entire absence of noise, (2) great cleanliness, (3) the whole of the boat is available for passengers (the cells being stowed under the Beats), (4) when once oharged it is ready at a moment's notice. Tho points against it are — (1) the difficulty and dolay of frequent charging, (2) the greater first cost, (3) the still greater first oost if an engine has to be specially laid down for tho purpose of charging. In a discussion which followed the reading of the paper, the suitability of stored electricity to the propulsion of lifeboats was pointed out, as a capsize would not at all affect the cells, whilo no stoam boiler could be tnado to stand a capsize. Admiral Selwyn

said he had lately been shown n, storage battery weighing only 561 b which would give out one indicated horsepower for ten hoars, which cost only £3, and would last for ten years. Others questioned the Bcouraoy of tho Admiral's information. That there is a possibility of great improvement m the batteries, however, admits of no doubt, for theoretically a pound of lead is capable of storing 300,000 foot-pounds, equal to a horse-power for ten hours from a 561 b coll, but m practice only some 33,000 foot-pounds could be stored m a pound of lead, equal to rather less than n horsa-power for one hour from a 561 b cell. If it were possible to make an iron battory, the theoreticnl powor of it would be 1,500,000 foot-pounda per pound, which would open up a vast future for the storage battery.

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