RECENT DEVELOPMENTS IN SHIPYARD PLANTS. 181 



rapidly at the very long lengths, and machine-tool manufacturers are not generally 

 equipped to provide machines of greater capacities, so it is likely that an increase 

 beyond this size will not come for some time. 



FITTING-GUT CRANE. 



The nature of the building slips has been touched on, also the characteristics of 

 the structural shop, and the next item vi^hich plays an important role in the general 

 scheme of construction is the fitting-out crane; for on its size and ability to handle 

 heavy weights is dependent to a considerable extent the point at which it is desirable 

 to launch and the condition of assembly of machinery and other parts that can be 

 taken care of. 



Compared with the large shipbuilding plants abroad, there is poor equipment 

 for handling heavy weights in this country, whether in private yards or in govern- 

 ment establishments. The maximum capacity of any crane in this country at the 

 present time, so far as shipyards are concerned, is 150 tons, and there are few of 

 these, whereas in the big foreign yards there are many cranes of 250 tons capacity. 

 The great cost of this class of equipment has undoubtedly prevented its installa- 

 tion, especially in view of the fact that very large merchant construction has not 

 been undertaken, and it has been possible to get through past naval programs with 

 available facilities. With the possibilities of larger merchant construction and the 

 growth in the size of naval vessels and of their ordnance, 150-ton cranes are no 

 longer of sufficient capacity, and provision for a materially larger lifting capacity 

 must be made if future naval requirements are to be met. 



The heaviest weights required in ship construction are the turrets of battleships. 

 Their weight, stripped of armor and guns, is likely to be in excess of any practicable 

 crane, so that the problem to be faced in determining crane capacity is how great a 

 capacity can be obtained without involving excessive or unreasonable expenditures. 

 All of the Navy's large cranes have so far been of the floating type, the earlier ones 

 of the cantilever construction, and the later of the revolving, luffing type. 



An investigation of the possibilities of building floating cranes of materially 

 greater capacity led to the opinion that the cost of such cranes would become pro- 

 hibitive, and further, that their great size would be such as to make it practically 

 as difficult to move them as to move the ship for which the weights are to be handled. 

 This study further led to the view that it was feasible to obtain fixed shore cranes 

 of the revolving, hammerhead type of 350 tons capacity, but that a capacity ap- 

 proaching this could not well be obtained with a traveling crane of any type, and 

 that no other type appeared to compare favorably with the hammerhead type. As 

 a result of this investigation a crane is now under construction for one of our navy 

 yards having a capacity of main hoist of 350 tons at a radius of 1 15 feet, and of 50 

 tons at a radius of 190 feet. In addition to the main hoist, there is an auxiliary 

 hoist of 50 tons capacity. The height of the main hoist above the yard level is 145 

 feet. The base of the crane is of the portal type, the over-all width being 61 feet. 



