DOCK GATES. 



239 



are opened and closed. The amount of sliding on the top of 

 the pivot is controlled by relieving-gear, consisting of a bell 

 crank, carrying weights, that rise and fall and permit of so 

 much movement only on the top of the pivot as will ensure 

 a close contact between the gate and the hollow quoin vertically 

 through the whole surface. 1 



For lubricating the pivots and relieving-gear, oil-pipes are 



FIG. 228. 



Fia. 227. 



SECTION AT B B 



4S'. 



LONGITUDINAL SECTION. 



SCALE 

 'P, ...?.... 9 !P 



20 FEET 



SECTIONAL PLAN 

 FIG 229. 



brought up to the top of the masonry of the gate recess, and 

 a force-pump attached for the purpose of supplying the oil. 



The top anchorage consists of a circular collar, with a bush 

 round an octagonal pin fixed to the top of the heel-posts, 

 sufficient play being allowed to admit of the free adjustment 

 of the gates against the hollow quoins. The strain on the top 

 is taken up by two strong wrought-iron ties anchored to 

 wrought- iron girders built into the masonry at the back. 



1 M.P.I.C.E., vol. ci. p. 165. 



