LOCK GATES AND VALV&S. 187 



used on rivers, has been found open to another objection, which is, that the upper or 

 non-w.iter-ti^ht co:npartments fill up with mud. This can only be removed through 

 the manholes, and with much trouble, and if left in, adds considerably to the weight 

 of the gate and causes it to rust. 



It would appear that single- sheathed gates, although less rigid than those with 

 double sheathing, are preferable for all cases which are likely to occur in the 

 ordinary practice of the engineer. For the few cases which may require extraordinary 

 dimensions, a study of the local conditions must of course decide the choice of type. 



It may be added that both for single and for double sheathing the anchorages and 

 maneuvering apparatus should be proportioned to take the heaviest strain that can 

 result from the construction, that is, when the gate is swinging in air. 



Combination Gates. In order to avoid the loss of strength resulting from the 

 rusting of iron and steel under the water, a style of gate has been proposed in 

 which the parts constantly submerged would be of timber, while those above water 

 would be of metal. We are not aware of any case where this idea has been put 

 into practice, but there appears to be no reason why it could not be successfully 

 applied. 



DETAILS OP CONSTRUCTION, ETC. 



Anchor-bars, Pintles, and other Fittings. The simplest style of anchor-bar for 

 locks of all but unusual size consists of an ordinary eye-bar provided with a turnbuckle, 

 one eye being connected with the gudgeon or bonnet pin, and the other being place^ 

 over a large bolt cemented in the masonry, and provided with a collar or casting at the 

 top to distribute the pressure. The bars are placed horizontally in recesses which 

 are covered with cast-iron plates, and are thus accessible at all times for examination 

 or adjustment. They require a minimum of forging, which is a desirable feature, not 

 only because of economy, but also because this class of work is not always reliable. 

 Not more than one bolt should be used to each bar, as where two or more are used it is 

 not possible to set them to an exact enough position to secure an equal strain on each, 

 and as the result only one of them actually bears the load. 



Usually two anchor-bars are used for each gate, one placed in continuation of the 

 line of the gate when closed, the other placed a little back from the same line when the 

 gate is open, so as to avoid bringing the bolts too close to the edge of the masonry. 

 This gives the gate a slight tendency to over-balance when open, which is usually 

 counteracted by the second anchor-bar. Should the motion exist, however, it will 

 be so slight as to be of no practical importance. 



The strain on anchor-bars, except for very large gates, should not exceed 5000 

 Ibs. per square inch, as they occasionally have to withstand the impact of boats, etc. 



Two forms of pintle are in use, one in which a steel pin forming the support is set 

 into a cast bed-plate, the latter being set into and flush with the masonry; the other, 

 in which the support and the bed-plate are cast in one piece and set about an inch 



