STARTING ENGINES BY COMPRESSED AIR.
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Economy, Simplicity and Ease of Operation, the Keynotes of an Interesting Power Starter which will Deal with Large Power Units,
THE IDEA of utilizing compressed air for starting internal-combustion engines is not absolutely new, but the Ida compressed-air starter strikes a fresh note, in so far as it is a self-contained unit and, may be fitted to almost any existing petrol engine—even to those of comparatively high power.
Invented several years ago, the Ida starter has undergone very severe tests, from which it has emerged with flying colours, mid is said to have proved satisfactory in every way. One of the chief features is that the same size starter is equally effective in starting a 100 h.p. engine or a 20 h.p. unit,. cud both with the same eaee and rapidity.
To describe the actual mechanism the (I-impresser consists of a srnail twincylinder monoblec 'casting, which is finned and air-cooled by the air drawn through the radiator ot the vehicle by the fan. When either piston is at the bottom of its stroke, air is drawn through gauze-covered holes in the cylinder walls by the vacuum created by the descent of the piston, and is pumped out, on the top stroke, through a non-return poppet valve in the cylinder head into the compressed-air container.
On the way to the main air reservoir the air passes through a, filter and fiveway cock. The filter is for the purpose of collecting any water or oil which may be deposited and which otherwise would go straight to the air container.
On the filter is fitted a safety valve, which may be adjusted to blow a warning whistle at any pressure; a nonreturn valve is also fitted to prevent the air blowing back,.
The five-way cock is provided to give a bypass to the pressure-gauge on the dash and also to enable the compressor to be used as a tyre pump (if pneumatics are fitted) or to be connected to air-brakes if desired. Lubrication of the compressor is effected by connecting it up to some convenient place in the oiling circuit of the engine; thus it is entirely automatic. Both the compressor and the actual starter are mounted as a unit on an accessibly situated platform, and are driven at engine speed, either from the main shaft of magneto shaft, by means of a roller or silent chain.
Driven from the main compressor shaft is a small camshaft on which are mounted a number of cams, which number varies with the type of engine; that is to say, four ieirns for a four-cylinder -engine and six for a six-cylinder; this camshaft is timed in conjunction with the engine to which the starter is fitted.
To start the engine, a lever, which is controlled by a Bowden cable from the dash, is moved, bringing into position a movable shaft having reickers, or fingers, mounted on it. As the shaft is rocked Over, a cam, moving with it, opens a main control valve, which allows the compressed air to enter the header of the starter in which are situated the lour other valves (we are assuming this is for a four-cylinder engine), at the seine time the rocker corresponding to the cylinder which happens to be on the correct stroke ithe engine must always stop in such it position that one cylinder is always ready for starting) is brought its contact with its cam and lifts the valve in the header, allowing air to pass into the cylinder of the engine via a non-return valve in the cylinder head. As this initial charge turns the engine over the other cams automatically come into action.
When the engine fires, the lever is dropped, thus cutting off the air. With the engine running the compressor may be engaged at any time irrespective of peed; this is done by a dog clutch which is operated from the driver's cab by a Bowden control, the teeth of this clutch being bevelled to give easy engagement. For both fourand six-cylinder engines there are two types of starters; type A, for mounting on the off side, and 13, for the near sidieof the engine.
It has been found by experiment that for any engine; up to .50 h.p. an air reservoir of 5 cubic at a-pressure of 100 lb. is ample and perfectly satisfate tory for starting up, provided the eugine is in such a condition that it is possible to start at all, but it is sometimes advisable to keep a slightly higler pressure in reserve, especially if an exceptional amount of stepping and starting is to be done.
it should be understood that the chief advantage of the Ida starter is its great efficiency ; namely, its quick recovery of air_ We were given a demonstration of this and found that the speed at which the air was compressed was extraordinary. The lorry to which the starter was fitted was a 4-ton Commer Car, and after getting the air up to a pressure of 165 lb. the engine was stopped.
The pressure lost on restarting was only 5 ft., and by the time top gear had been engaged this loss had been made good—the gauge again registering 165 lb.
We then travelled for half a mile, with the compressor engaged, when 205 lb. pressure was registered, thus showing the rapidity with which the air is compressed.
Starting from dead cold without injecting, the pressure lost was about 25lb. In starting a large 100 h.p. Clerget aeroplane engine from cold with a container of one cubic foot. the loss was 11. lb.
It will be seen from the results of these tests that the Ida starter is admirably suited for lorries and transport vehicles which are called upon to do a large amount of stopping and starting. Its economy is one of the strongest features, owing to the fact that no " doping " or carburetter flooding is necessary for starting, and also because, where, in the ordinary course of events during a short stop, the engine would be left, running, with the Ida starter it may be switched off and started again without effort or leas of time. One large transport concern that has fitted the Ida starters states that the saving in petrol is two gallons per vehicle per day on short delivery work, which is certainly a big item. Before delivery the reservoir is tested to a, pressure of 525 lb., whilst • the capper piping has withstood 800 lb. pressure. The starters are made for Ida Starter, Ltd., of Pilgrim Street, Birkenhead, and (lapel House, 54, New Broad Street, London, B.C. 2; by the Westinghouse Brake and Saxby Signal Co., Ltd., Chippenhana, Wilts.