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492 peller shaft; and an electric drive wholly by electric motors. Discussion of Mr. Emmet's Paper. W. Irving Babcock: The very in- teresting and carefully worked out paper to which we have just listened is one of the most important and valuable which has been presented to the society in a long time. It is hardly too much to say that it is epoch making and certainly it will furnish food for the most careful thought to every member of this so-- ciety who is interested in the pro- pulsion of ships--and not naval ships alone. Mr. Emmet's position and rep- utation, as well as that of the great electric company with which he is associated, lend especial force to his statement that that company stands ready today to make contracts along the lines here described and to fully guarantee the results indicated. Between the two methods of pro- pulsion described in the paper, there will doubtless be little difference of opinion as to which is. preferable. The advantages of the electric drive, in simplicity and lightness, are mani- fest. Probably the saving in weight over the straight turbine equipment is the feature that will surprise the naval architect the most, but we can only assume that Mr. Emmet knows what he is talking about. In the case of the Chicago fireboats referred to in the paper, which were built from my design and described in Mr. West's paper last year, the question of weights was not important, but in_ a general way I might say that there was very little difference between the weight of the electric drive equip- ment and what would have been re- quired for the simple double cyclinder steam engines that would otherwise have been used. Great Ease in Handling. Mr. Emmet is quite correct in stat- ing that the performance of the elec- trical part of the installation on those boats has been simple and efficient in every way and probably there are no other boats in the world which can approach them in ease of hand- ling and maneuvering in crowded guartets. This brings up a point which is not referred to in the paper but which, especially for naval ves- sels, is most important, and that is the possibility and practicability of handling the screws directly from the bridge, pilot house or conning tower without the necessity of bells or sig- nals to the engine room or any occa- sion for the intervention of the engi- neer in any way. Misunderstanding < wrecking of a gate ibridge to engine is saved also in operating the crews. TAE MARINE REVIEW © of signals between the captain and engineer has been a fruitful cause of accidents in the past and doubtless will always be so. At this very mo- ment the great traffic between Lake Superior and the lower lakes is al- most at a standstill because of the in one of the canal locks from this cause, and this is the second time this season that that has happened, the Canadian lock having been similarly put out of com- mission for some days a few months ago. One hundred and fifty steel ships of the largest class are anchor- ed above the canal now, waiting to get through, with over a million tons of cargo on board. With this elec- trical drive, operated by controllers immediately under the hand of the captain, all danger of this kind is ab- solutely avoided, for the engineer can- not misunderstand a signal that is not given at all. By this elimination of signals from room, much time and this must be a valuable feature in naval vessels, either during the exigencies of battle or during fleet evolutions, especially in case of the sudden descent of fog or thick weather. . I fear, Mr. 'Chairman, that my _ re- marks are becoming extended, and I will close by again expressing my appreciation of the great value of 4 paper which the society should be proud to have on its records. Greater Cost an Objection. Ernest H. B. Anderson: This pa- per is of special interest to me, be- cause I am one of the men who look- ed into this proposed electric propul- sion about three years ago, with the Parsons Steam Turbine Co., and the final conclusion that Mr. Parsons and the leading officials of the company came to, after making a great many designs and preparing estimates, was as follows: The first disadvantage of the scheme was that the total weight of the turbo-generators and the motors became prohibitive; sec- ondly, there was great difficulty in finding a suitable motor that had a large variation in speed, to meet the conditions of marine service, and the third objection was that the cost of the completed installation was very mich <preater. than that 6f a twin screw reciprocating set, or even an all-turbine arrangement of machinery. With regard to the paper itself, and the combined drive in particular I would like to discuss the following points: I see that at speeds from ~ December, 1909 12 to 15 knots only one generator is in use and the steam from that generator is passed directly into the -condenser, and the low pressure tur- ibines are not used at all. Now, that means that you have two large pipes for exhaust of somewhere around 48 or 50 in. diameter, and it will be necessary to fix valves upon these pipes, so that at full power the steam can be passed from the generator into the low pressure turbine. Well, a battleship does most of her work at cruising speed, around 12, 13 or 14 knots, and the ship is not used at full power a great deal. _ Therefore, when cruising, both these low pres- sure turbines are going to get quite cold, as they are directly connected to the condenser. So that if an order 'came to reverse the engine suddenly, I think they would have great diffi- culty in starting the turbines, for the reason that the engines would quite cold and cause trouble to the blading. Regarding Electric Drive. Another thing, I think thrust blocks of the usual marine type, will need to be fitted, as there will ibe no bal- ance between the steam going to the turbine and the propeller as the tur- bines are shut off. Then, if the tur- bines are to be kept in working or- der, in the other room, it- will be necessary to keep a vacuum on the condenser and the circulating pumps running, so that the thing can be started right away and not have a shut down. Now, regarding the electric drive, I am not in a position to discuss the design of the motors, but I think Mr. Emmet is much too optimistic in his estimated water consumptions, chiefly for this reason, that one of the latest battleships, that has just completed trials, at full power for a speed of about 21 knots, required around 30,- 000 shaft horsepower, and the ship's displacement was 20,000 tons. Now, we have a very similar proposition before us here, and the displacement of the ship is 26,000 tons, but the shaft horsepower is 'based on 26,000. 'I think it 'should be nearer 36,000, to give somewhere near the same re- sults. as the ship that has actually been tried. This, of course, will bring down the cruising rate a great deal. I think the curves made, comparing the electric propulsion with the Par- sons turbine, are hardly quite fair to the Parsons turbine, since the condi- tions are so entirely. different... 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