. The Locomotive. vent turningbetween the wheeland the shaft, end-wise motion or slid-ing usually beingprevented by setscrews or by thecompressing of asplit hub on theshaft. For this rea-son the key should be a close fit on the sides but should have a clear-ance at the top. If this clearance is not provided, the load, whenthe hub bolts are tightened up, will be concentrated over the key,and the stresses tending to break the hub will be very much greater than if the load wereequally distributed overthe shaft. The illustra-tion herewith shows aflywheel hub that wasbroken in this key h
. The Locomotive. vent turningbetween the wheeland the shaft, end-wise motion or slid-ing usually beingprevented by setscrews or by thecompressing of asplit hub on theshaft. For this rea-son the key should be a close fit on the sides but should have a clear-ance at the top. If this clearance is not provided, the load, whenthe hub bolts are tightened up, will be concentrated over the key,and the stresses tending to break the hub will be very much greater than if the load wereequally distributed overthe shaft. The illustra-tion herewith shows aflywheel hub that wasbroken in this key had first beendriven into place with-o u t allowing for theproper clearance and thehub bolts were thenheated, put into placeand pulled up the bolts cooledthey of course exertedan intense clamping effect on the hub. The load was localized, how-ever, over the key and, although failure did not take place immediately,the hub, no longer able to withstand the severe stress, broke, as shown,about a month Flywheel Broken by Key. 1922. THE LOCOMOTI v !•: 41 The Significance of Draftwith Some Notes on the Construction of Steel Smokestacks. CHIMNEYS or smokestacks arc built to serve two the first consideration is the draft required, but somethought must almost always be given the question of deliveringthe products of combustion at a sufficiently high point so that theywill not be obnoxious to the community. This latter consideration isoften governed by local ordinances. Draft, or the ability of a chimney to draw air through the fuelbed, depends upon the fact that the weight of a given volume of airor gas decreases when it is heated. To fully explain the principle ofchimney draft, resource must be had to the atmospheric air or atmosphere in which we live envelops the earth like agreat hollow sphere or shell which physicists have estimated is aboutsixty miles in thickness. Because of the pull of gravity on this en-velope of air a pressureis
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Keywords: ., bookauthorhartfordsteamboilerin, bookcentury1800, bookdecade1860
