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December, 1909 with steam at the end throttle valves, at 260 pounds, with 50 degrees super- heat. In the Parsons turbine ship the boiler pressure is. about 210 pounds, and the pressure at the en- gine stop valve is a minimum of 175 pounds, with no superheat. This con- 'dition is very much in favor really of the Parsons turbine ship, as every- thing is not worked up to the high pressure that it is in the other case. Mr. Emmet makes the statement that the four propellers of the Par- sons turbine ship interfere with each other. We know from. experience, from the results of all ships that have been tried and are inservice, that one propeller does not interfere with the other, and they are so arranged that each propeller has solid water fed to it. Comparative Weights. With regard to the comparative weights, I see that the weights are given in the electric drive for two turbines without bearings. JI think there should ibe a weight given for the bearings. If not, it will also be seen further that no allowance has been given forthe thrust 'block weight. That is an essential in the engines, and in a ship of this type will amount to a good deal. Now, the last point is this--I think a better comparison could have been made by taking a proposition fitted with Curtis turbines working under the same conditions as the revolu- tions of the two propositions, that is the Curtis turbine and the electric drive, and the conditions would have been practically the same, whereas with the schemes under discussion, the conditions are entirely different. One other point, and that is that the total cost has not been given in this case, but in the bids for the com- bined scheme that was submitted to the government at the time of open- ing the battleship bids, the difference in cost between the lowest Parsons bid that was submitted, and the bid for this combined drive, was about $645,000, which is pretty considerable. Alternative Method of Electric Drive. John Reid: This is a paper which interests me rather closely, in connec- tion with some of my own work, and I only rise to discuss it because I can show the members an alternative method of electrical drive, which has been introduced on the other side, and which is attaining considerable importance. I am satisfied that Mr. Emmet has brought up a subject here which will introduce an entirely new epoch in "TAE Marine REVIEW \ marine engineering, and: that it will go on the records of this society as introducing such a new era, which will bring in tremendous changes in all parts of marine engineering. One noticeable point in the paper as pre- sented, is that Mr. Emmet has as- sumed that no one else has done work on these lines, but that his com- pany has been able to bring forward a proposition which will bring about successful results. I, do not think you will find in this world, in a great movement like this, that but one man or one firm is on the ground. alone, and I will show you in as few words as I can, and at as small an expense of time as possible, a Mavor spinning motor, which... think, ts..as far ad- vanced as Mr. Emmet's motor or the General. Electric Co7s motor... 1 aim not an electrical engineer, and I will ask Mr. Emmet and the electrical en- gineerts present to <orrect: me «1.1 make mistakes. The Mavor. System. This is an "alternating current motor. (illustrating on the black- board), of which I will only draw a part, you have the rotors here. You have the stator surrounding it. Now, in the Mavor system we introduce what is called a spinner which goes around the rotor, that is a floating spinner or fing, and I can best describe the thing by reading to you a few lines from a paper which Mr. Mavor read on the subject about two years ago. This is the rotor, R, and this is the spinner or regulating motor, and this is the stator. He says in his paper: "The machine is thus two motors concentrically arranged round the "common axis. The three speeds which may be described as prime, secondary and tertiary, are attained without loss of efficiency, but if intermediate speeds are desired they are obtained by a slipping 'brake or external re- sistance in each case equally with a constant loss of efficiency. This loss of efficiency is very small, and is less than the loss involved where series wound continuous current motors ate used for speed variations; or intermediate speeds may be ob- tained by providing a separate supply of current to the external motor and changing its speed by change of peri- odicity of the supply. "The electric current is delivered from an outside source to the prim- ary windings of the stator and spin- ner respectively, passing in each case through a simple reversing switch which determines the direction of ro- tation, The stator circuit also sup- . 493 plies a magnet, which, when no cur- rent is passing, releases a brake which brings and keeps the spinner at rest. When current is passing, the magnet lifts the brake and leaves the spinner free to revolve. All the Speed Variations. "The three-speed motor provides a means of obtaining all the speed variations which are required on a ship. The intermediate speeds be- tween the three normal speeds of the. motor are obtained by variations in the speed of the generating plant, which are within the limits of prac- ticability and economy. Each _ pro- peller shaft:is provided with a direct- ly connected motor on which there is co-dxially superimposed .a second motor for speed regulation. The reg- ulating motor is mechanically con- nected and magnetically entrained with the first in such a manner that the speed variation may bbe effected as follows: e "For slow speed, by running the regulating motor in the reverse direc- tion to the direct connected motor; for intermediate speed, by running the direct connected motor alone, the regulating motor being stopped; for full speed, by running the regulating motor in the same direction as the direct connected motor. "This arrangement requires no spur wheels or friction gearing. Each motor is controlled by a simple re- versing switch without any other mech- anism, and there are no power wast- ing devices." That is to say, you will get all the changes of speed necessary in all classes of engines and _ propulsion without resistance or speed reduction devices. You can get the reverse al- most instantaneously, with a_ big range of speed changes. While some may imagine that the introduction of the spinner is an added complication, in practice it works out pretty easily. Now, this scheme has been before practical engineers for some time, and is going to be tested on a large scale. Too Big a Jump. I think that one of the most seri- ous difficulties which Mr. Emmet is undertaking to overcome, is to jump -- from a Chicago fire boat, of a few hundred horsepower, to a battleship at one leap. I-do not believe that can be done. I do not believe it can be done, no matter how you figure or how you plan, or what you calculate --and I do not believe without a proper test, up to a few thousand