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70 THE LOCOMOTIVE. [May, by tirlce the thickness of the head, and divide tlie product by the pressure that is to be carried. The (juotient is the greatest allowable radius of the head. If it is bumped to a longer radius than this, it is not safe : but there is no objection to the use of a shorter one. The foregoing rule, wlien cf)inpiued with the rule for cylinders, shows that if a cylinder and a sphere aie to be made of the same material, and to have the same burst- ino- point, the radius of the S2)here must be equal to the dinmetei' of tlie cylinder. Heuce it is important to bump the head of the dome to a radius equal to the diameter of the dome; for this makes the head and the sides equal in strength. Fig. 5 represents a dome-head bumped in this manner. We do not recommend the use of bumped heads for higli pressures. If it is possible to avoid them; the braced head, presently to be considered, njipears to us to be far better. Leaving the bumped head, therefore, we pass to the consideration of (3) the braced head. This form of head is shown in Fig. 1, and is the one most commonly met with in practice. The riveted joint, by which the head is attached to the shell of the dome, is strong enough to stand the entire pressure on the liead, provided the head is kept flat, so that the strain on the rivets is a simple shear. The object of bracing is to stiffen the head so that it will not bulge out and produce radial strains that would tear it out around tlie flanges. In the head of a 30 inch dome, allowing 3 inches all around as sufficiently stiffened by the flange, there are 707 square inches to be braced. Under a pressure of 90 pounds to the square inch this would correspond to a total pressure on the head of G3,630 lbs. ; and this, allowing 7,000 lbs. to each brace, would call for nine braces. In practice only eight are used, as the nozzle for the steam-pipe contributes materially toward the stiftening of the head. In general, si.x braces are used on a 24- inch dome, eight braces on a 30-inch dome, and ten braces on a 36-inch dome; though this cannot be considered an absolute rule, for with high pressures the number of braces may have to be increased. Crow-foot braces should be used, as shown in the cut, and the rivets by which tlicy are held must not be less than f of an inch in diameter. The braces should run to the sides of the dome, as shown in the cut. It might seem unnec- essary to say this, but we have occasionally seen the braces in domes secured to the shell of the loiler, close to the steam ojiening; and of course they are of practically no use in such cases. The fourth method of stiffening the heads of domes, is to rivet tee-irons or angle- irons across them. This method is sometimes used, but we believe it to be inferior to the bracing, because defects are more readily detected by the inspector where braces are used than where the stiffening is obtained by angle-irons only; and also because the strength of Itraced heads can be calculated more readily, and with greater accuracy. In conclusion, let us say (1) that we believe that if a boiler is properly designed and properly set, it does not need a dome; but if a dome is to be used, we believe (2) that the shell should not be cut away to the full diameter of the dome, but that an elliptical hole, say 11" X 15", is much better, and that a man-hole frame should be securely riveted to this opening; (3) that the dome should be secured to the shell by a double-riveted joint, at least; (4) that the head should be of wrought-iron or steel and that it should be braced to the sides of the shell with a sufficient number of crow-foot braces, secured with rivets at least f of an inch in diameter; (5) that braced heads are superior to cast- iron heads, bumped heads, or heads stiffened only by tee-iron; (6) that if the circum- stances are such that bumped heads become necessary, or highly desira1)le, they should be biunped to a radius not greater than the diameter of the dome; (7) that the curve of the flansre of the dome should fit the curve of the boiler-shell exactly, so that the boiler
imi] THE LOCOMOTIVE, 71 will not l)t' (li'roiiiicd Diit of its proper cylindrical shape in riveting the dome on; (8) that tlie nian-liole slioiild not l)o ])ut on the liead of the dome, but on some other part of tlie boiler. DOMKS KOIl LOCOMOTIVK HoiLEUS. In oases where the pressures carried are very hi
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^ rtE.'pTWE © (§) THE LOCOMOTIVE.
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THE LOCOMOTIVE. [January, a o o M -
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6 THE LOCOMOTIVE. [January. In both
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3 THE LOCOMOTIVE. [Januahy, been em
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^Q THE LOCOMOTIVE. [January, ])rove
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42 THE LOCOMOTIVE. [January, Sit «
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14 THE LOCOMOTIVE. [January. After
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16 TlIK hOCOMO'J'i Vi.. Incorporate
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18 THE LOCOMOTIVE, [Februaky, stren
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Page 34 and 35: 26 THE LOCOMOTIVE. [February, injur
Page 36 and 37: 28 THE LOCOMOTIVE. Pit *0tiim$tlt
Page 38 and 39: 30 THE LOCOMOTIVE. [February, jured
Page 40 and 41: 32 Incorporated 1866. THE LOCOMOTIV
Page 42 and 43: 34 THE LOCOMOTIVE, [March, pressure
Page 44 and 45: 36 T II E L () C O yi O T l\E. [Mar
Page 46 and 47: 38 'i^il^ LOCOMOTl V i:. [Makcu, (1
Page 48 and 49: 40 THE LOCOMOTIVE. [March, art & Co
Page 50 and 51: 42 THE LOCOMOTIVE. [March, Ml ^^^'3
Page 52 and 53: 44 THE LOCOMOTIVE. [Makch, should h
Page 54 and 55: ^(3 THE LOCOMOTIVE. [March, power o
Page 56 and 57: 48 Incorporated 1866. THE LOC (J MO
Page 58 and 59: 50 THE L O C O 31 U T I ^' E , [Apr
Page 60 and 61: 52 THE LOCOMOTIVE. [April, (This is
Page 62 and 63: 54 THE LOCOMOTIVE. [April, Castle,
Page 64 and 65: 56 THE LOCOMOTIVE. [April, sious ar
Page 66 and 67: 58 ' THE LOCOMOTIVE. [April, Hit St
Page 68 and 69: ,60 THE LOCOMOTIVE. L-^p«il, nortl
Page 70 and 71: 62 THE LOCOMOTIVE. [Aprfl, these pi
Page 72 and 73: 64t Incorporated 1866. THE LOCOMOTI
Page 74 and 75: 66 THE LOCOMOTIVE. [May, much as we
Page 76 and 77: 68 THE LOCOMOTIVE. [May, diameter o
Page 80 and 81: 72 THE LOCOMOTIVE. [May, Boiler Exp
Page 82 and 83: 74 THE LOCOMOTIVE. [May, HARTFORD,
Page 84 and 85: 76 THE LOCOMOTIVE. [Mat, weeks amou
Page 86 and 87: '^8 THE LOCOMOTIVE. [Ma\% coat-tail
Page 90 and 91: 82 THE LOCOMOTIVE, [June,
Page 92 and 93: 84 THE LOCOMOTIVE. [June, Boiler Ex
Page 94 and 95: 86 THE LOCOMOTIVE. [June, (105.)
Page 96 and 97: 88 THE LOCOMOTIVE. [June, The Heliu
Page 98 and 99: go THE LOCOMOTIVE. [JrxE, Mkt Elttt
Page 100 and 101: 92 THE LOCOMOTIVE. [June, ills lett
Page 102 and 103: •94 THE LOCOMOTIVE [June, .21 ia
Page 106 and 107: 98 THE LOCOMOTIVE. [July, worked ov
Page 108 and 109: : ^QO THE LOCOMOTIVE. [July, Inspec
Page 110 and 111: 102 THE LOCOMOTIVE. [July, (132).
Page 112 and 113: 104 THE LOCOMOTIVE. [July, " The am
Page 114 and 115: 106 THE LOCOMOTIVE. [July, tttSttlt
Page 116 and 117: -iQQ THE LOCOMOTIVE. [July, and als
Page 118 and 119: 110 THE LOCOMOTIVE. [July without t
Page 120 and 121: 112 THE LOCOMOTIVE. [July. Incorpor
Page 122 and 123: 114 THE LOCOMOTIVE. [August, to whi
Page 124 and 125: 116 THE LOCOMOTIVE. [August, tion.
Page 126 and 127: 118 THE LOCOMOTIVE. [August, (147.)
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-120 THE LOCOMOTIVE. [August, A lar
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•J22 THE LOCOMOTIVE. [August, git
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124 THE LOCOMOTIVE [August, hard en
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126 THE LOCOMOTIVE. [August, The Bu
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128 THE LOCOMOTIVE. [August. Incorp
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^30 THE LOCOMOTIVE. [September, pau
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132 THE LOCOMOTIVE. [September,. iu
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-[34 THE LOCOMOTIVE. [September, Fi
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136 THE LOCOMOTIVE, [September, .35
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138 THE LOCOMOTIVE, [September, add
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140 THE LOCOMOTIVE lSeptember, On a
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d42 THE LOCOMOTIVE. [September, cas
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144 Incorporated 1866. THE LOCOMOTI
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146 THE LOCOMOTIVE. [Octobek, in pl
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i48 THE LOCOMOTIVE. [October, Natur
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[50 THE LOCOMOTIVE. [October, Curti
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•152 THE LOCOMOTIVE. [Octobeb, an
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^54 THE LOCOMOTIVE. [Octobeb, Mkt e
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-[56 THE LOCOMOTIVE. [October, Tlie
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158 THE LOCOMOTIVE. [October, Of co
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162 THE LOCOMOTIVE. [November, that
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: 16^4 THE LOCOMOTIVE. [XOVEMLER, I
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166 THE LOCOMOTIVE. [November, boil
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168 THE LOCOMOTIVE. Sit Ktttmttit c
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170 THE LOCOMOTIVE. [November, KILL
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172 THE LOCOMOTIVE [November, Boile
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174 THE LOCOMOTIVE. [:November, sel
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178 THE LOCOMOTIVE. [December, grap
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: 180 THE LOCOMOTIVE. [December, In
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^82 THE LOCOMOTIVE. [December, that
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184 THE LOCOMOTIVE. [December, HART
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186 THE LOCOMOTIVE. [December, The
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188 THE LOCOMOTIVE [Decembeb, angle
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190 THE LOCOMOTIVE. [December, Such
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i92 Incorporated 1866. THE LOCOMOTI
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INDEX, Equivalent of heat, redeterm
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