Railway Master Mechanic, Volume 4

Front Cover

From inside the book

What people are saying - Write a review

User Review - Flag as inappropriate

this is my grand mother laura r brown 512-289-5035 contact date 11-08-2015

Other editions - View all

Common terms and phrases

Popular passages

Page 9 - Coefficient of friction. .3818 .2C86 .2171 .1849 .1743 The ratio of the changing coefficient varies with the temperature at which the range of results is taken. Friction varies with the area, because the adhesiveness of the lubricant is proportional to the area, and the resistance due to this cause is a larger fraction of the total mechanical effect with light, than it is with heavy pressures. The limit of pressure permitting free lubrication varies with the conditions ; for constant pressures and...
Page 8 - The operation of these machines, by their failure to obtain correct data, adduced certain negative evidence which established positive conditions as indispensable in the construction of a machine capable of measuring the friction of oils. The following circumstances must be known or preserved constant, — temperature, velocity, pressure, area of the frictional surfaces, thickness of the film of oil between the surfaces, and the mechanical effect of the friction. In addition to the foregoing conditions,...
Page 29 - The lubricant used is one of the most important factors in the cost of power. In the present condition of engineering science, it is impossible to state what exact proportion of the power used by a mill is lost in sliding friction, but in a...
Page 30 - ... bearings, kerosene oil is the only lubricant which can be used. I think it extremely probable, that at these low temperatures, the viscosity of kerosene oil is equal to that of lubricating oils at the average temperature of bearings in general use. On the other hand, only the most viscous oils can be used in such extremely high temperatures as the cylinder and steam chest of steam engines. According to the results which I have obtained, the coefficient of friction at 50 is about 75 per cent,...
Page 31 - ... but the results of the two are so nearly uniform as to be practically identical. The result of bleaching does not affect the anti-frictional properties of the oil, although it undoubtedly reduces its gumming qualities. The friction of sperm oil is subject to sudden variations which occur at certain temperatures for the same sample of oil. The explanation of this lies in the fact that sperm oil consists of a large number of varieties of spermaceti, each of which is liquefied at certain temperatures,...
Page 30 - Association, measurements showing the effects of humidity on textile bands, and I am also of the opinion that there is a difference of friction in machinery due to atmospheric influences upon the lubricant. Possibly the moisture condensed upon the cold metal from the atmosphere becomes commingled with the oil and thereby reduces its viscosity, diminishing the friction. The question of endurance of oils has not been given in these experiments, because the consumption of oil varies with the temperature,...
Page 30 - ... where the temperature was controlled and kept constant by circulation from a reservoir kept at the desired temperature. The capacity of the bulb is 28 cubic centimetres and the orifice measures three and a half inches long and .039 of an inch in diameter. The oil was drawn into the bulb of the pipette, and after the •whole was brought to the desired temperature, the time required for its discharge accurately noted by a stop watch. These observations were made on each of the oils for a series...
Page 8 - ... interval. A thin copper tube closed at the lower end, reaching through the cover, extends to the bottom of the disk ; the bulb of a thermometer is inserted in this tube and measures the temperature of the disks, an oil tube runs to the centre of the disk, and a glass tube at the upper end indicates the supply and its rate of consumption and also serves to maintain a uniform head of oil fed to the bearing surfaces.
Page 10 - When the disks are ready to test the oil, the apparatus is cooled by the circulation of water ; the flow of which is stopped when the machine is started. At every degree of temperature, the corresponding resistance is read on the dynamometer. When the thermometer indicates a temperature of sixty degrees, the counter is thrown in gear, and the time noted. When one hundred and thirty degrees is reached, the counter is thrown out of gear, and the time noted. This not only gives the velocity of the rubbing...
Page 8 - Industrielle de Mulhouse, June 28, 1854. M. Hirn, however, confined his attention chiefly to the determination of the mechanical equivalent of heat, as measured by the amount of heat imparted to the circulating water, expressed in the work of friction. His investigations of lubrication with this apparatus were confined to the friction of lard and olive oils, at the light pressure of about one and four-tenths pounds to the square inch. Mr. Chas. N.

Bibliographic information