DOCK GATES. 



223 



versed line of the arc being one-sixth the span from centre to 

 centre of the heel-posts. The back of the gate is the arc of a 

 circle of such a radius that at the middle of the gate it coincides 

 with the arc A B. The 

 front of the gate is a straight 

 line from heel to mitre-post. 

 With this form, the recess 

 in the side walls would not 

 be inconveniently large. 

 The face of the gates, when 

 open, would with the ordi- 

 nary fenders be in line 

 with the side walls of the 

 entrance, and the gangway 

 at the top would also form 

 a straight line with the side 

 walls. This form would allow 

 of access to the interior for 

 repairs, etc. ; whilst the 

 width would give consider- 

 able flotation power; more- 

 over, the straight face would 

 permit of the gate being braced diagonally from the heel-post 

 to the foot of the mitre-post, and thus enable the greater part of 

 the weight being sustained by the anchor-straps, to the relief 

 of the roller. 



In practice, the rise will be found to vary from one-sixth 

 to one-fourth the span of the entrance, the latter predominating. 



FIG. 209. 



Name. 



Span. 

 Ft. in. 



rase. 



Authority. 



Victoria Dock Extension, London 80 



Dunkirk ............ 69 



Whitehaven ......... 50 



Avonmouth ......... 70 



Limerick ... . ........ 70 



Barry ...... ...... 80 



Victoria Docks, Hull ...... 80 



Bo'nesa 50 



4 M.P.I.C.E., vol. lix. p. 30. 



I Ibid., p. 29. 



Ibid, vol. ly. p. 42, 44. 



\ Ibid., vol. lv., plans. 



~ Ibid., vol. xcvii. p. 336. 



1 Ibid., vol. ci. p. 139. 



5 ^ Ibid., vol.xcii. p. 153, and plans. 



\ Ibid., vol. Ixx., plans. 



Nipping. This consists in the line of pressure being thrown 

 to the extreme inner or outer edge of the meeting faces l 

 of the mitre-posts. The condition may be due to faulty work- 

 manship in fitting the gate-leaves ; they may be made a little 

 1 M.P.I.C.E., vol. Iviii. p. IC5. 



