Efficient Air Compressors
Page 54
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AN efficiency as' high as 80 per cent. is claimed for the wide range of air compressors manufactured by Bristol Pneumatic Tools, Ltd. These include, on the one hand, a large twin-cylindered, water-jacketed machine with a capacity of 300 cubic ft. per min, and, at the other extreme, a model with a displacement of 24 cubic ft. per min. In order to prevent the possibility of oil passing into the air line this small compressor is lubricated with grease, its main and big-end bearings being ball races. For the lubrication of the cast-iron cylinders and piston a felt pad is arranged at the, base of the former, and is kept saturated by the grease in the crankcase.
This compressor is marketed in several different forms. In the simplest it is attached to a base plate carrying a fast-and-loose pulley for flat-belt ave. Probably more convenient for many garages is the model which includes a h.p. electric motor of the repulsion-induction type, which provides an exceptionally high starting torque so that the conapresSor can be used quite safely to top up a tyre which is already at a high pressure. This unit can be obtained either with a carrying handle or mounted on a small three-wheeled truck. In both eases the equipment includes a heavy-duty switch, 20 ft. of electric flex and flexible metallic air hose; the latter is connected to a rubber hose provided with a heavy-type, instantaneous valve connector.
In various other forms this unit is combined with a 21 cubic ft, air receiver and is provided with • an automatic switch operated by the pressure in the receiver.'
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