Experience with, and problems relating to, bottom bearings of electricity meters

The paper first outlines the results obtained over a period of 10 years with oiled sapphire-steel bearings on a single type of meter used by a large supply undertaking, and describes tests carried out on new and worn pivots and jewels with various lubricants and abrasives. The results indicate that oil greately increases the life of a bearing, but that, even when oiled or greasy jewels are used, the presence of rust or debris is the major cause of wear and consequent errors in the reading of the meter. A series of wear tests on various pivot materials, both oiled and dry, is next described. The results show that materials of all hardnesses give comparatively good results when oiled. No conclusive evidence is obtained of the validity of Stott´s theory that oxygen is set free from sapphire under the influence of the large cohesive forces which operate in meter bearings. The cause of surface cracking in sapphire jewels is then investigated, by means of a device which initiates impacts at the rate of 18 per minute between the pivot and the jewel of a meter bearing. Finally, an account is given of apparatus designed for the rotational testing of meter bearings in air and inert atmospheres, providing special facilities for the microscopical examination of jewels. The results of tests in nitrogen, argon, neon, hydrogen, and a vacuum, are discussed, and it is concluded that further experimental work is necessary in order to confirm or disprove the sapphire-oxygen theory.