478 TRANSACTIONS OF SECTION G. 



most concisely stated by pointing out the deficiencies of the other two methods 

 as compared with the electrical. In the case of the mechanical transmission by 

 the tooth-gear which has been carried out by the Parsons Marine Steam Turbine 

 Company and by the Westinghouse Company in America the results at sea appear 

 to be quite satisfactory, but we are still left with the necessity of providing a 

 reversing turbine, and while there are means of connecting two separate units to 

 the same shaft frequent and sudden reversal of motion of the propeller by means 

 of the reversing turbines would probably disturb the satisfactory running con- 

 dition of the gear, so that while it has been demonstrated to be suited for long- 

 distance runs it remains to be proved that it will stand the rough-and-tumble 

 service of a vessel where there is much ' backing and filling ' to do. In weight, 

 price, and economy the mechanical transmission-gear appears to show no advan- 

 tage over the electric gear, as the same economy and weight per shaft horse- 

 power can be guaranteed for thp electric transmission as is claimed for the 

 mechanical gear transmission. This arises from the fact that the gear ratio can 

 be made higher. 



The other competitor is the Fottinger hydraulic transmission, an interesting 

 and ingenious proposition. It has one apparent advantage over the mechanical 

 gear, viz., that it is less rigid in its character, but it is not so flexible as the 

 electric transmission, and it also lacks the possibility of convenient application 

 or withdrawal of individual units, although it might be developed in this respect. 

 The efficiency claimed for it is as high as can be attained by electrical means. 

 The costs and weights are not known to the author, but the experience of trans- 

 mission with high-pressure water is not uniformly encouraging, and for an equal 

 range of adaptation it appears certain that the electric transmission will be 

 cheaper and more efficient, and the convenience in manoeuvring is entirely in 

 favour of the electric gear. 



To show that the advantages claimed for the electric gear can be realised in 

 practice a vessel has been built and experimental trials and demonstrations have 

 taken place in the presence of the leading shipowners and shipbuilders on the 

 Clyde. The author believes he is justified in claiming that he has proved that 

 the claims made as to convenience and rapidity of manoeuvring and the prac- 

 ticability of the whole arrangement have been fully demonstrated. The actual 

 economy to be gained is a question of study of individual cases. Many of these 

 have been gone into, and although in some it has been found that there is no room 

 for electric transmission, others seem to offer conditions favourable to the use of 

 the electric arrangement, which has always against it the handicap of additional 

 cost and usually of additional weight. It has therefore to win its way against 

 an initial disadvantage which is rather hard to overcome, but the indications are 

 that the ultimate advantages in many instances are such as to warrant the addi- 

 tional expenditure in view of the economy to be gained. 



Drawings and photographs of the experimental vessel, and also general 

 arrangement of equipments which have been designed and compared with the 

 normal equipments for the same vessels, were shown. 



2. Electrical Steering. By B. P. Haigh, B.Sc, Asscc.M.Inst.C.E. 



Electrical steering offers considerable advantages for steamers as well as for 

 vessels propelled by internal-combustion engines, for the improved economy cor- 

 responds to a saving of weight in boilers and fuel. Difficulty has been expe- 

 rienced in obtaining a reliable system of control, capable of dealing with the power 

 necessary to put the helm hard over in emergency in the shortest possible time, 

 and possessing sufficient sensitiveness to enable an accurate course to be kept by 

 moving the rudder promptly in small angles. Sensitiveness is shown by absence 

 of ' time lag ' between the movement of the hand-wheel and the corresponding 

 movement of the rudder, and in this respect electrical gears promise an improve- 

 ment on steam gears, whose economy is reduced when large control valves are 

 fitted. Sensitiveness also requires an absence of undue ' idle travel ' of the 

 hand-wheel, but a certain small amount is nevertheless desirable. The steering 

 motor may be started and stopped for every motion of the rudder, but it is 

 preferably kept running continuously, mechanical control being introduced either 

 in the form of hydraulic transmission or in the form of magnetic clutches as 



