There are many other important points of crane construction too numerous to mention here, but it may be said generally that the advent of electricity has tended to increase speeds, and in consequence great attention is paid to all details that reduce friction and wear, such as roller and ball bearings and improved methods of lubrication; and, as in all other quick-running machinery, great stress has to be laid on accuracy of workmanship. The machinery, thus being of a higher class, requires more protection, and cranes that work in the open are now fitted with elaborate crane-houses or cabins, furnished with weather-tight doors and windows, and more care is taken to provide proper platforms, hand-rails and ladders of access, and also guards for the revolving parts of gearing.
Its viscid character, and its non-liability to dry and harden by exposure to air, also fit it for various other uses, such as lubrication, &c., whilst its peculiar physical characters, enabling it to blend with either aqueous or oily matters under certain circumstances, render it a useful ingredient in a large number of products of varied kinds.
The heating at the surfaces, the variations in their smoothness, and the variations of the lubrication make continuously variable, and necessitate frequent adjustment of W or of the nuts.
The principal uses of rape oil are for lubrication and lighting; but since the introduction of mineral oils for both these purposes the importance of rape has considerably decreased.
For further information on this point and on Osborne Reynoldss theory of lubrication see BEARINGS and LUBRICATION.
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