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LECTURE BY MR E. E. STARK. The monthly lecture under the auspices . the technological branch off the Otago Institute was delivered last night by Mr K E. Stark, electrical engineer, who chose for ilia subject I' fiction and Lub,’-i-ation.’ Professor Park presided. The* lecturer explained that the object of lubrication was to ameliorate friction, hut in some cases frictional resistance between opposing surfaces was utilised as a means of transmitting motion from one part of a machine to another, or from one machine to anothei. Friction clutches, belts, and rope drive were instances Ot tins. In these cases it was the object to make the frictional resistance as great as possible, so that the opposing forces will not slip. These, generally sneaking, were not lubricated, except possibly to prevent seizing. Lubrication was effected by the interposition of a liquid or solid substance between the friction surfaces to decrease friction, and such substances are called lubricants. Frictional resistance varied gveatlv between different surfaces and materials, being least between hard and nolished; and greatest between solt ami rough, surfaces. Cohesion is a- cause ot diction to be considered which aggravates friction rather than diminishes it, because the more perfectly two surfaces were m contact the move the area of contact, amt it

the surfaces are perfectly clean and smooth they will adhere together. In fact, two such surfaces may be welded. # For example, two, lead blocks, if cleaned and pressed together, will seize or weld together. Dissimilar metals always 'work better and with greater ease upon each other than do similar ones. The entire office of a lubricating oil was to prevent solid friction by effectively separating the rubbing surfaces with the lubricant. In a perfectly lubricated journal the oil film is actiiallv a perfect electrical insulator between the shaft and the bearing. Another property of the oil was its ability ' 1 cover a surface. This property was called capillarity, and was due to surface ten* sion. In conclusion, the lecturer said he was constructing a machine which ho hoped would fulfil the conditions of testing to some of the requirements of lubricants, and at a later-date hoped to be able to give the institute the benefits of the results obtained.

Professor Waters and Mr J. C. Scott entered into the discussion of the various features brought out by the lecturer. A hearty vote of thanks was accorded the lecturer, on the motion of Professor Waters.

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Bibliographic details

OTAGO INSTITUTE, Issue 15629, 21 October 1914

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OTAGO INSTITUTE Issue 15629, 21 October 1914

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