A New Aluminium - piston Expander.
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The efficiency losses caused, by excessive clearance between pistons and cylinder walls are claimed to be minimized, if not entirely eliminated, by a new device called the Perfect Circle piston expander marketed by R. M. Papelian, Ltd., Edgware Road, Cricklewood, London, N.W.2. It consists of a specially shaped steel spring, which, when inserted into a piston, is held securely in position by the gudgeon pin, and exerts pressure in a radial direction at 10 points, the greater expanding force being at right angles to the axis of the gudgeon pill.
Engines requiring a set of new pistons and reboring, can be rejuvenated, the concessionnaire states, by replacing the old rings with new ones and fitting the pistons—provided that they are of aluminium alloy—with Perfect Circle expanders. An inclusive price quoted for the treatment of a typical four-cylindered engine is £5 5s.