ALQUIST GEARING FOR SHIP PROPULSION. 191 
discontinued according to need. Connections are changed only on dead circuit, even in the 
ordinary operations of stopping, starting, and reversing, and automatic means are provided 
by which any diversion of current from any cause produces an unbalancing which instantly 
breaks the field circuit and de-energizes the system. 
The aggregate weight of this equipment, with cables, switches, instruments, and con- 
trolling apparatus, is 1,865 tons. 
Equipment if Gear-Driven.—lf such a vessel were gear-driven, a plurality of ahead tur- 
bines would be connected through helical gearing to each propeller shaft, one or more back- 
ing turbines would also be connected through the same gearing, and if good cruising economy 
were sought, it would be necessary to provide also cruising turbines connected through sep- 
arate systems of gearing and arranged with couplings so that they could be detached during 
high-speed operation. 
A just comparison of this method with the electric equipment proposed would require a 
complete design and analytical study of the geared equipment and its performances. The 
writer has not made such a study in the case of these vessels, therefore no exact figures 
can be given. The space and number of turbine elements connected to each shaft will de- 
termine the space required for turbines, and this spacing will govern the length and weight 
of the shafts, piping, valves, and supporting structures. 
In some of the installations which have been proposed abroad for vessels of much less 
power than these, the multiplication of parts has been very great and the size and extent of 
turbines and supporting structures such that the adoption of similar methods in these ships 
would certainly give weights nearly as great, if not greater, than those proposed for the elec- 
tric drive. Some of our shipbuilders, in bidding to the government on these vessels, have 
stated that by using geared equipment they could save about 1,000 tons in weight and about 
$1,000,000 in cost, but whether these statements will bear analysis or not cannot be said 
without study of their detailed designs, if any have been made. 
Detachment.—Without further description or discussion of either type of apparatus, we 
are in a position to make a comparison which constitutes one of the most important ad- 
vantages of electric drive. In the geared equipment, each shaft has a system of turbines, 
gears, bearings, thrust balancing devices, and lubricating systems, all mechanically locked 
together. With high-speed machinery any kind of trouble with any of these parts will 
almost certainly necessitate the immediate stoppage of the whole system. To keep a high- 
speed turbine running out of balance or with bearing trouble is impossible, and the gearing 
part would present almost equal difficulty. In the event of mechanical trouble of such char- 
acter, a ship would have to be stopped until the wreck could be cleared. The work neces- 
sary to uncouple and disconnect any part of such very heavy apparatus would be a seri- 
ous matter, involving much time, including that required to stop the ship. After the discon- 
nection was made the idle propeller would act as a very serious drag on a fast vessel. 
In the electrically driven ship there is no mechanical connection of the shaft to any- 
thing but the rotors of motors. These are self-contained, iron-clad structures and cannot by 
any possibility be subject to mechanical interference. The shafts are subject to the same 
possibilities of bearing or thrust trouble as shafts in other ships, but the presence of the 
motors does not increase this danger, and the speed being low it is remote in any case. 
With this equipment any motor, generator, or turbine, if in any kind of trouble, can be in- 
stantly disconnected without stopping the ship and with only a small loss from the highest 
speed capacity. 
