1554
THEORY AND PRACTICE OF ENGINEERING.
Book II.
16 inches broad at the ends, and 18 in the middle; their cross ends are 18 inches in heightand 2 in thickness, with inch screw-bolts to each, which pass through the heel and mitreposts, The clap sill was cast in two pieces for each leaf; it is 8 inches in depth and 1-t inchthick ; the height of the sill above the platform is 15 inches. The bottom bar is of oak12 inches thick, 17 inches broad at the ends, and 19 in the middle; this is bedded on feltto the lowermost cast-iron bar, and securely fixed by 1^-inch bolts. The boiler plateswhich line both sides of the gates are so arranged that they break joint; for 6 feet inheight their thickness is§ of an inch, above only T ® g , they overlap each other about inches,and were riveted on while hot, that the rivets might completely fill up the holes. Thecollars of the heel-posts are of wrought-iron, 4 inches by 2 inches, keyed through the anchors,which are of cast-iron, 3| inches square; they are dovetailed into the quoins, and run with lead.The roller segments or railways are 10 inches in breadth by 1^ inch, 4 inches in thickness ;they are sunk into the stone, and securely bolted, and bedded with felt and white lead.
The rollers are of cast-iron and conical, 18 inches in diameter, and 5 inches in thickness,with turned steel axles; the roller boxes are of cast-iron, 1^ inch thick, moulded to thebevel of the gates, and fastened by screw-bolts through the flanks of the horizontal bars :cast-iron covers confine the roller blocks, which slide up and down withinside the boxes bythe action of the top screws ; the roller bars are of wrought-iron, 3 inches in diameter,keyed into the blocks at the bottom, each being steadied by three plummer blocks; eachbar near the top has a coupling, with a square threaded screw, and a brass nut at the top,working in a cast-iron bracket, which bears the whole weight of the outer end of the gate,and is fastened by three screw-bolts through the flanges of the horizontal bars. Eachleaf has a sluice, 3 feet by 2, the frames of which are 7 inches broad and 1| inch thick ;the sluice valves are also 1 \ inch thick ; all the screwed bolts have zinc nuts, to preventthe iron from rusting: the sluice-rods are 2 inches in diameter, and have a squarethreaded screw,' and a brass nut at the top; these are worked by a wheel and pinion,and bevelled gear, with a crank handle, nearly level with the hand-rail.
The gangway is 42 inches in width, and is supported on cast-iron brackets for each leaf ;cast-iron ballusters and a wrought rail is attached to the convex side of the gates, withmovable iron stanchions and chains on the other: in each heel-post is a pump with abrass chamber and boxes, inches in diameter, with a lead pipe down to the bottom.
The gates are worked by four double-purchase capstans, and gearing with seven 8-inchchains.
Their weight is as follows, —
Cast-iron work in the gatesWrought-iron — -
Brass — -
Zinc — -
Cast-iron in segments and other fittings -
Tons. Cwt.64 14
22
0
0
19
1 H
5
n
0
107 0
These gates were made -j.|p H , L.
by Mr. Stirling of Dun- n , . . ^ s
dee. _LiL 3 r li 1 r jJJ )
At Woolwich the clear 1 ~j| : | |
opening of the dock-_ _ -ip . i TiTT ' I E" '' v '1 —X"
gates is 65 feet, and the I j } j \ \ \ \ \ V«'- : -
weight of each of the two » -J-L_
iron gates is 150 tons. 2393 • prince’s dock, Liverpool. Fig. 28
Inclined Planes and Lifts , mentioned by Mr. Smeaton as early as 1774, are adoptmany of our canals to raise and lower the boats from one level to another, and by