GB427260A - Means for testing lubricating oils - Google Patents

Abstract

427,260. Testing efficiency of lubricants. HELMORE, W., and GRIFFITH, A. A., Royal Aircraft Establishment, Farnborough, Hampshire. Oct. 19, 1933, No. 28895. [Class 106 (ii)] Comprises a method of testing lubricating oil by continuously shearing the oil by means of a free piston in a heated sealed cylinder containing a measured quantity of oxygen or other gas and reciprocated relative to the piston, and measuring the friction between cylinder and piston. The cylinder 1 containing a free piston 2 in the form of a ball is attached by pins 3 to the upper ends of levers 4 which are pivoted at their mid length to a reciprocating shaft 6. This cylinder is balanced by a similar cylinder 7, but not fitted with a ball, attached by pins 8 to the lower ends of the levers 4. The shaft 6 is supported in bearings 9 and reciprocated by a crank and link 13, 12. The cylinder may be filled with gas through a needle valve 15, a channel 16 permitting free movement of gas from one end of the cylinder to the other, and the ball and cylinder are lubricated with a small quantity of oil to be tested. Heating chambers 17 surround the cylinders the temperature being indicated by thermometers 18. The rocking of the levers is limited by electrical contacts 19 and a stop 20. One contact 19 is on the lever and the other and the stop 20 are on a yoke 21 fast on the shaft 6. The lever system is slightly overbalanced on the side of the test cylinder. As the reciprocating shaft moves to the right, the contacts 19 are closed, until a point is reached where the reaction of the pivoted system changes sign, when the contacts open and the reaction is transferred to the stop 20. The position of this change depends on the friction acting between the ball 2 and cylinder 1. Connected in series with the contact 19 is a contact breaker 22 operated by rotation of the crank. The contact breaker 22 is arranged to make contact over about quarter of a revolution starting from a point slightly in advance of the earliest point of the right-hand movement of the shaft 6 at which the contacts 19 can break. The time during each revolution in which both sets of contacts 19, 22 are closed depends upon the friction between the ball 2 and cylinder 1, and the onset of gumming is marked by a rapid change in this quantity. The contacts 19, 22 are in series with a source of current 23 a switch 25 and a galvanometer 24. An earth 26 may also be provided. The galvanometer reading indicates the average current and is a measure of the fraction of each revolution during which contacts 19, 22 are closed. Gumming is indicated by a rapid change in reading. In a modification contacts 19, 20 and contact breaker 22 are omitted and electromagnets are attached by a frame to the shaft 6, the polepieces being attached to a spring- restrained lever connected to the lever system. The varying of the air gaps varies an electric circuit.