APPLIED MECHANICS. 



[LOCOMOTIVE BOILERS. 



paw, and without excmaire weight of material. 



: .-presents the arrangement of tube* in a locom 

 boiler. 



The body of the boiler A U cylindrical : at one end B 

 ii the fire-box, surrounded by water space ; at the other 

 11* 1M. 



according to the magnitude of the work, and the 

 . pressure which they are intruded to sustain. 

 These plates are made to overlap each other at the 

 edges, and are fastened together l>y rivets or round ] 

 iron, passed red-hot through holes provided in t 

 and riveted over so as to form a head. A hea\ 

 iron is held against the under side of the i and 



the other end of the rivet is struck repeatedly !>v heavy 

 hammers, and frequently finished by applying a tool 

 hollowed to the shape of the intended head, and striking 

 the tool by the hammers. The rivet, when the operation 

 is complete, is of the form A (Fig. 155) when tin 

 by smart hammering, called ftnjf-rit<t <; ; and like B 

 when finished V>y the tool, being then said to be Inittmi- 

 headed. As the operation of riveting is performed hen 

 the rivet is red-hot, not only is the quality of the rivet 

 not impaired by the hammering, as it would be if ham- 

 mered when cold, but also the contraction or shrinking 

 of the rivet in its length when it cools draws the edges 

 of the two plates together with great force, and renders 

 the joint impervious to fluid. When it is found l>v trial 

 that the joints of the plates, or the edges of the i 

 heads, are not quite tight, as manifested by the leakage 



Hg. we. 



end C is the smoke-box, surmounted by the chimney. 

 In the body are arranged numerous small tubes com- 

 pletely surrounded by water, through which the products 

 of combustion pass in their progress from the fire to the 

 chimney, delivering the greater portion of their heat to 

 the surrounding water. The evaporating power of a 

 boiler of this kind is very great, as we may readily 

 believe on calculating the amount of 

 heating-surface in a boiler of the fol- 

 lowing dimensions : 



Fire-box inside, 3 feet 6 inches x 3 

 feet 6 inches X 3 feet G inches, has 60 

 square feet actually exposed to the 

 fire, and there-fore most valuable as 

 heating-surface. 120 tubes 2J inches 

 diameter and 10 feet long, give 800 

 square feet of effective flue surface ; 

 the whole, including smoke-box, being 

 contained in a space about 13 feet 

 long, 4 feet 6 inches wide, and 4 feet 

 n* high, and yet being equiva- 

 lent to 80 or 90 horses' power. 



STRUCTION OF HOILERS. 



have now described, generally, 

 the different kinds of boilers used 

 fnr generating steam. They are, of 

 course, subject to numerous modifica- 

 tions in their details and proportions, 

 according to local circumstances and 

 peculiarities of use and situation. 

 They are generally made of wrought- 



Flf . 1U. 



of water or steam through any of them, a blunt steel 

 chisel or caulking tool is applied to the leaking edge, and 

 struck smartly by a hammer, so as to caulk the joints, or 

 force part of the iron into the crevice. 



If we suppose, for instance, that an opening exists 

 between the plates at B, and round the rivet-head at A 

 (shown greatly exaggerated in . the cuui 



tool applied at the points marked C, forces the iron of 

 the plate edges and of the rivet-heads into the inter- 

 stices, and thus renders the jointing tight. For jointing 

 the plates at the angles, a peculiar kind of iron, called 

 aiiyle-iron, indicated in section at A, Fig. 157, is eni- 



Fig. 157. 



U 



^^^^^M 



Iron plate*, from Jth Inch to Jths inch in thickn 



ployed ; and where there are considerable 

 flat surfaces of plate exposed to bursting, 

 pressure stays, B, are introduced at 

 proper intervals to prevent the plates 

 from being forced asunder. 



For fixing the tubes of tubular boilers 

 in the plates through which they pass, 

 holes are first bored in the plates 



proper size to fit the tubes tightly ; and the 



