178 RECENT DEVELOPMENTS IN SHIPYARD PLANTS. 



CRANE SERVICE FOR BUILDING SLIPS. 



There is perhaps more room for individual preference in the selection of the 

 type of cranes to be used for handling material at the building slips than in any 

 other feature of shipbuilding yards. This freedom of choice has been fully exer- 

 cised in the extension of the older yards and the construction of the newer ones. 

 With the exception of a limited number of special installations, such as the cable- 

 ways used in some of the western yards, the available types fall into three general 

 classes: — 



1. Traveling, traversing cranes. Those which have both a longitudinal travel 

 and a cross travel. 



2. Traveling, rotating cranes. Those which have a longitudinal travel and a 

 rotating motion. 



3. Fixed, rotating cranes. Those which have no longitudinal travel, and de- 

 liver their material at the desired point by rotating, and either by troUeying or 

 luffing. 



In the first class is included the cantilever type, which was in favor in the early 

 days of large shipbuilding, but which has now generally been abandoned, at least as 

 far as new installations are concerned ; and the bridge type, which probably gives the 

 most effective service, though generally at the highest cost. Cantilever cranes are 

 not a desirable type on account of the great inertia of the moving part, and on ac- 

 count of the limited number of hooks that can be made available, the combination 

 tending to limit the speed of erection. Bridge cranes permit the handling of the 

 heaviest weights and provide an installation that most nearly approximates shop con- 

 ditions, so far as concerns ability to deliver material at all points. The principal 

 argument against this type is its initial cost. It has been generally adopted for the 

 larger and more expensive slips, and some one of the rotating types has found most 

 favor for the slips intended for smaller vessels, or where it is not feasible to finance 

 the higher original cost. 



The traveling rotating types include the hammerhead and luffing types of 

 cranes operating on wide-gauge tracks on the ground, and also electric and steam 

 locomotive cranes operating on runways of the general type used with cantilever 

 cranes. The cost of these types is apt to be less than bridge cranes and also less 

 than the fixed, rotating cranes, if a limited service only is to be provided. With an 

 equivalent service as compared with the fixed, rotating cranes, the cost should not 

 be radically different. Some very rapid construction in the last few years has been 

 done, utilizing electric locomotive cranes on elevated runways, and where the weights 

 to be handled are not high or the length of the ships under construction great, this 

 gives an effective service. The cranes that travel on the ground are more expensive 

 than is at first apparent, on account of the cost of the track installation. Their 

 longitudinal travel is relatively slow, owing to the inertia of the moving parts. In 

 general, this class of crane appears to the best advantage in building vessels of 

 moderate size, where the individual weights to be handled are not large. 



