DOCK GATES. 237 



This small roller was not made adjustable, the chief object being 

 to keep the gates perpendicular while they were being mitred. 

 The plan was successful, and enabled a perfect mitre joint to 

 be made. 



WMtehaven Dock Gates. 1 These gates are constructed of 

 pitch-pine, with the exception of the heel- and mitre-posts, 

 which are of greenheart. 



The height from the roller-path to the gangway is 35 feet, 

 and when closed the ratio of rise to span is 1 to 5. 



The ribs, which are straight next the sill and curved on 

 the pressure side, are formed of two baulks placed side by side, 

 bolted and dowelled together, and tenoned into the heel- and 

 mitre-posts. Their depth is 12 inches, and constant throughout; 

 the thickness at the centre being 2 feet 2 inches, diminished 

 to 1 foot 4J inches at the ends. 



The planking consists of pitch-pine 3 inches thick, feathered, 

 caulked, and secured to the ribs by treenails \\ inch in diameter 

 and 15 inches long. 



A cast-iron cup, fitted with a gun-metal disc, is let into the 

 bottom of each heel-post. The disc bears upon a cast-iron pivot 

 9 inches in diameter let into and bolted down to the granite 

 heel-post stone. The radius of the bearing surface of the pivot 

 is 9 inches, and that of the disc 12 inches. 



The top hollow quoin consists of a cast-iron block formed 

 to clip the heel-post in a similar manner to the granite quoins, 

 and tied into the side wall by wrought-iron anchor-straps. 



The heel-post is hooped, and held in position by a wrought- 

 iron strap screwed at each end, the nuts clamping the inside 

 of the anchor casting. 



Each gate is fitted with a cast-iron roller, bearing upon a 

 cast-iron roller-path of 26 feet radius. The weight upon the 

 roller is adjusted by a screw working in a fixed nut attached 

 to the gate in a casting fixed above high- water mark. 



The gates are surmounted with a gangway 4 feet wide, 

 supported on saddle castings bolted to the top rib, and fitted 

 on each side with movable standards and guard-chains. 



Two sluices are fitted to each gate for adjusting the level 

 of the water in the dock, for scouring the apron, and for keeping 

 the channel clear in the vicinity of the entrance. 



Fig. 226 shows a section through the centre of the leaf. 



1 M.P.I.C.E., vol. lv. p. 44. 



