190 ALQUIST GEARING FOR SHIP PROPULSION. 
Chas. G. Curtis, and others who have had important influence in marine engineering. Most 
of this opposition is undoubtedly sincere, but is not altogether disinterested, since ship- 
builders want to use machinery which they know how to build, and since turbine inventors 
have in the past received large royalties from turbine-driven ships which are cut off by the 
advent of electric drive. Although the power still comes from turbines, the electric drive 
is, by license agreements, free from royalty charges. The possibilities of large electrical 
apparatus do not appeal strongly to those who are not thoroughly familiar with its uses. 
Electric propelling machinery will be generally heavier and more expensive than the best 
developments of geared-turbine machinery, and variations of opinion have rested upon the 
relative importance given to advantages and disadvantages. 
The General Electric Company has, under the writer’s direction, also carried on exten- 
sive developments and operations in ship propulsion by turbines connected to ships’ pro- 
pellers by gearing. Machinery of this class for 79 large vessels has been contracted for by 
them, and many of these ships are in service and showing unqualified success. Our view, 
therefore, is not entirely one-sided, and although it may be considered that we are particu- 
larly interested in the development of the uses of electrical machinery, we believe that we 
have judged fairly and that our efforts will lead to important and lasting success. 
In explaining the advantages of electric drive, comparisons will be made only with the 
geared-turbine drive. All other methods for propelling large vessels may be considered 
obsolete although many ships are still being built with engines or with direct-connected 
turbines. 
A wise rule in engineering is to advocate new things only for the purpose in which 
they afford the greatest advantages, and this rule has been closely followed in the promotion 
of electric propulsion, which was originally advocated mainly for large warships. This first 
move was made before the use of mechanical gearing for such a purpose had been suggested, 
but its advantages for this particular use are so striking that it is still believed that the won- 
derful development of gearing possibilities have not changed the original case. 
The subject of electric drive is too large for full discussion in such an article as this. Its 
possibilities and advantages can be best suggested by taking as an example the case of the 
new battle cruisers in which its use has been and still is the subject of much discussion 
and criticism. This may be considered as the extreme case where advantages are most im- 
portant and in which the disadvantage of increased weight is most serious. 
New Battle Cruisers——Four of these vessels are authorized in the navy bill of 1916. 
They are designed to make 35 knots each, requiring 180,000 horse-power delivered to four 
shafts turning at full speed about 250 revolutions per minute. These are the fastest and 
most highly powered vessels ever built. The electrical installation proposed in each of 
them far exceeds in extent any single installation ever made for any purpose. 
Apparatus Proposed.—It is proposed to install in these ships four high-speed turbine- 
driven generating units of the best type, similar in most respects to those used in power sta- 
tions on shore. Upon each of the four propeller shafts will be mounted two independent in- 
duction motors. Cable connections and switching arrangements will be provided by which 
any combination of motors and generators can be immediately provided for and by which 
all the changes of connections for operation, reversal, etc., can be instantly made under all 
running conditions. The details of design and method of operation need not be described 
in this discussion. They are quite simple, in fact much simpler than in most electrical instal- 
lations. The electric supply is produced for the one purpose of propulsion and is varied or 
