RINGLESS PISTON

Waipa Post, Volume 48, Issue 3480, 16 June 1934, Page 6

RINGLESS PISTON

EXPERIMENT IN ENGLAND MANY ADVANTAGES CLAIMED Unusual claims are made about the advantages of a new make of piston, which can be used in internal combustion engines without the need for fitting piston rings. The invention is at present the subject of experiment in England, and is being tested in a fleet of heavy commercial vehicles. It is said that a great benefit procured is that a deeper oil film can be maintained on the cylinder walls and that as the new piston also accommodates itself to all distortion of the cylinder, wear is greatly reduced. But it is thought that for various technical reasons it will most probably be suitable only for large engines of wide cylinder bore and having a fairly slow working speed. This ringless piston takes th e form o 5: a thin cast iron shell, which is bolted to light alloy blocks, which provide a mounting for the gudgeon pin. It has a microscopically fine taper, the wider clearance at the head when installed in an engine being .01 inch, but reducing to the normal clearance employed with a ringed piston. The gudgeon pin being separately mounted and inside th 6 piston walls cannot possibly cause scoring, and it is maintained that the tapered shape ensures an excellent oil film and so retards wear and tear,to prevent crankcase dilution. A large engine in a heavy truck was equipped with these pistons, and run for 9000 miles, after which the engine was stripped and a close examination made. It was then obsei-ved that th e thin carbon deposit on the cylinder walls ended abruptly at the point where the tappering of the piston skirt ceased, and th e overall wear of the piston and the bore was negligible.