698 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



power developed be obtained, but it is possible, by overspeeding the 

 turbines at full power, to maintain the economy over a larger range 

 of the ship's speed than could be done with a direct-coupled turbine. 

 With the gear-wheel method of speed reduction a considerable amount 

 of experience has now been obtained, and up to the present time two 

 small cargo vessels and seven cross-channel steamers have been put on 

 service, while four sets each of about 12,000 horsepower are under 

 construction, two for ocean liners and two for swift coasters. 



In 1911 the channel steamers Nonnannia and Hantonia were each 

 fitted with four turbines, two running at 2,000 and two at 1,400 revo- 

 lutions, and connected by means of toothed-wheel gearing to two pro- 

 peller shafts running at 310 revolutions per minute. The experi- 

 ment was a notable success, the coal consumed per trip being only 43 

 tons as compared with the 70 tons used by the immediately preceding 

 vessels, which were of the same capacity but propelled by direct- 

 driven three-screw turbines. 



Last summer the channel steamer Paris^ 293^ feet in length and 

 having geared turbine propulsion, attained the remarkable speed of 

 25.07 knots on a run from Newhaven to Dieppe, the speed-length ratio 

 workiiig out at 1.47 — a result which has only been surpassed by tor- 

 pedo craft. 



The introduction of toothed gearing for the main drive has been 

 looked upon by many as a retrograde step. The conditions are, how- 

 ever, in no way similar to those in which formerly gearing up was 

 necessary, and where a very variable turning moment in the recipro- 

 cating engine had to be contended with. The loss in transmission is 

 small, being probably not more than 2 per cent of the power trans- 

 mitted, and the wear on the teeth is inappreciable. Some objection 

 has been raised to the noise caused by the gearing, but, although 

 doubtless not so silent as the direct-driven turbine, the geared-turbine 

 installation can compare favorably with the reciprocating engine in 

 this respect. The actual vibration transmitted through the struc- 

 ture of the ship is inappreciable; the eifect of the gearing being felt 

 altogether in an air vibration in the engine room itself, and this will 

 be reduced to a minimum with the more accurate methods of gear 

 cutting recentlj^ introduced. 



The large speed reduction which can be effected makes the system 

 suitable for ships of low speed and moderate power, and it is almost 

 certain that this method will greath^ extend the usefulness of the 

 steam turbine for marine propulsion. 



In Germany the hydraulic transmitter invented by Dr. Fottinger 

 has lately been developed. The principle of the transmitter is that 

 of combining a high-speed turbo-centrifugal pump with a water 

 turbine designed for a lower speed of revolution. The former 



