A NOVEL PISTON RING
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WE have recently received from Messrs. Henderson Bros., 77, Windsor House, Victoria Street, London, S.W.1, details of a new type of piston ring, sold under the name of Perfect Seal, which is claimed to possess certain advantages over the standard type. The chief feature of the new ring is the use of an inner steel ring in what. is really the piston ring proper, a state of continuous circumferential expansion being maintained by a coil spring which exerts a Constant pressore on its ends. The resultant effect is that the outer ring receives and transmits to the cylinder walls a radial pressure, which experience has shown is equal at all points on its circumference. An important noint is that a piston ring of
this type can assume the shape of a worn cylinder bore and thus the necessity for re-boring and fitting oyersize pistons is postponed considerably.
Some doubt might exist as to the ability of the spring to retain its properties of expansion under the influence of high temperatures and to give durable Service. It should be mentioned, however, that it is not a loose component and (-anent fall out of position, for it is retained in place by undercutting the groove in which it lies. We are told that tests have proved that the spring retains its strength under much greater . temperatures than those. Met With in an internal-combustion engine:
Messrs. Henderson Bros., who are the distributing agents for Perfect Sehl
piston rings, inferm us that during the past two years this form of ring has been tested under severe working conditions, and it has been found that increased efficiency per piston can be obtained with one ring only. If this be the case, it is certainly a step in the right directhin, since the use of one instead of several rings must reduce friction on the 'cylinder walls, and thereby enable an increase of power to be obtained. It gives a gas and oil-tight seal between piston and cylinder wall.
The price of the pistoii rings up to 3 ins, in diameter is 2s. 6d. each, those above 41,ins, and up to 5 ins, diameter selling at 4s. each, whilst intermediate sizes are listed at proportionate figures between these prices.