Amal Accessories to Promote Efficiency
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CIF all the safety devices available for the vehicle of tu-day, probably none has received less discussion than the flame trap. Nevertheless, it has filled a want in the safety campaign for road, sea and air, and has a most promising future in the motor industry.
The flame trap was developed at The Royal Aircraft Establishment, Farnborough, to prevent fire in the event of a blow-back. It has since been produced and marketed ty Anial, Ltd., Birmingham, and is a standard fitting on many engines.
The flame trap is an ingenious contrivance. Altnough it may never be called upon to do its job it is always on duty, working with remarkable efficiency. To appreciate this it must be realized that it consists of many yards of metal—covering the entire air intake, and yet giving no appreciable hindrance to the air flow. Actually 80 per cent. of its surface is free to air, and, as will be seen from the illustration, the increased size of the external surface more than compensates the hindrance offered.
Its action is to divide the flame and cool it through thousands of channels, so that it is extinguished before it can pass through to the air. The total cooling surface of the trap represents 125 sq. ins, for every square inch of its external surface.
This enormous area is obtained by winding two strips of metal simultaneously around a spindle. The width and thickness of this copper-nickel alloy have been determined from practical experiments and are .75 in. and .001 in. respectively. As one strip is flat and the other corrugated. the result is myriads of minute triangular tunnels.
The flame trap is compulsory on all gas-driven vehicles. Its action is so positive that a petrol-soaked rag may be held against it without danger, even when flames from the most violent blow-backs can be seen on the Other side. It has tremendous possibilities on account of the negligible resistance offered, and for some time has been used as a safety device in the filler pipes of petrol tanks. Although this point is of more importance in tropical countries, the fact cannot be overlooked that disastrous fires have occurred through carelessness on the part of those " used to handling petrol."
The flame trap is made in all sizes up to six inches dia meter, and can be obtained in square types if specially ordered. Another popular Amal product is the series 120 fuel pump, equally suitable for petrol or oil fuel. It is of the diaphragm type, driven from a camshaft eccentric. It can be band-primed, irrespective of the position of the rocker arm, but in practice the first revolutions of the engine are sufficient to draw fuel from a tank some 'distance from the carburetter.
The fuel flow is regulated automatically by the fluid pressing against the carburetter needle valve, a calibrated spring allowing the diaphragm to oscillate only when the supply in the float chamber is reduced.