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136 Relative Weight and Space. In the early days of the turbine a great deal was said and written about the saving in weight and space consequent on its adoption. Actual- ly there is a valuable saving in weight in the case of high-speed cross-Chan- nel steamers, and generaily also with naval vessels, though not to the same extent. In torpedo craft there is lit- tle to choose betwen the systems in this respect. The weight of the turbine machinery of the Mauritania and Lusitania is practically the same as that of corresponding piston en- gines, and this has generally been -the case whenever turbines have been applied to the heavier classes of vessels in the merchant service, The reason of this is that in such vessels, .in order to keep the number of revo- lutions per minute low and so assist the propeller efficiency, it is neces- sary to make the turbines as large as circumstances will permit. Thus it may be said that, in all cases except high-speed cross-channel steamers and. naval vessels, the weight is gen- erally about the same; but on the other hand the space required is gen- erally greater when turbines are adopt- ed. This increase in space may amount to as much as 25 per cent. - The Question of Vibration. As far as absence of vibration is concerned, there is not a great deal to choose between the systems when applied to merchant vessels, as a well balanced four-cranx engine will run with very little vibration. Al- though, generally, turbine-driven ves- sels are slightly superior in this re- spect, there are a fair number in service in which vibration is rather severe. Thus in the express Cunard- ers there is or was considerable vi- bration in the vicinity of the wing pro- pellers, and there are several cross- channel steamers in which in certain parts of the ship it is distinctly un- pleasant. This vibration in turbine vessels is almost entirely due to the propellers. Even the most careful balancing can- not remove it, because, when the pro- pellers are arranged to run close up to the ship's side, as each 'blade pass- es through the faster moving wake close to the ship's skin the center of effort of the propeller is moved. Thus a succession of shocks is produced. The use of. specially shaped propel- ler blades may reduce the evil, but the most effectual way is to arrange the propellers at a good distance from the skin of the ship.' This in- volves a loss of efficiency, as, by plac- 'surprise the THe Marine REVIEW ing the propellers in the fast-running wake against the ship's sidé some of the work which has been expended in putting the wake into motion 1s regained in the form of additional thrust. Freedom from breakdown 1s another point with regard to which the two systems may be compared. The reciprocating engines fitted to mail and intermediate liners are very free from breakdown, and one would suppose that the same might be said of a well designed and constructed turbine. However, quite a large num- ber of turbine vessels have suffered from blading strips or had their dum- mies carried away. Of course, such happenings are not advertised, but a complete list of such mishaps would outsider. Thus faulty brazing was the cause of an extensive strip in one notable case, whilst an un-mechanical method of rotor con- struction produced the same result in another; a too flexible design of rotor wheel caused the dummies to be car- ried away in other cases; and in another an almost complete strip was caused by opening the regulator too suddenly. The list could be 'extended' to a greater length, but it must be admit- ted that the majority of these mis- haps occurred from inexperience both in design and operation. On the other hand, it,is somewhat discouraging to hear that the turbines of one of our recent second-class cruisers stripped their blading when being tried under -steam in the works, in spite of the fact that the latest type of segmental blading was adopted. However, there can be little doubt that in time, as more experience is gained, such tur- bine troubles will become very rare. Overhauls and Renewals. It is difficult to conceive of any breakdown to a reciprocating engine which cannot be overcome at_ sea. But a serious strip in a turbine would take a very long time tro repair, and it is very doubtful if re-blading could be carried out at sea at all.. On. the other hand, it is scarcely likely that all the shafts. would be put out of 'action at the same time. Again, it is possible to subject a piston engine to a comprete examin- ation at the terminal ports, and such an examination must do much to se- cure immunity from accident. With the heavier class of turbine machinery this is not possible, as the opening out necessary for a complete exam- ination would entail a great deal of time and labor. It must be admitted, however, that in the reciprocating en- gine there is a vast number of bear- 'breakdown. "June, 1909 ings and wearing parts which are constantly requiring adjustment or renewal. The wear and tear with the turbine is practically nil, and the work of the shore gang must be greatly reduced by its adoption. Again, if we could rely on the blading and dummies remaining intact it would only be necessary to open up the turbines at long intervals. On the other hand, it ought not to be for- gotten that very expensive overhauls and renewals have been necessary with several turbine vessels, To sum up our comparisons, it is evident that the turbine system is decidedly superior for all classes of naval vessels, and also for high-speed cross-channel steamers, With regard to high-speed ocean liners, the increase in steam con- sumption per effective horsepower is about 9 per cent with turbines. On the other hand the turbine is much simpler to operate and adjust, and when well designed and constructed should run with very little fear of A considerable saving in oil and attendance results from its use, and in all probability it will last much longer. These advantages must be set against the increase in the coal bill, Now, such an increase on the coal bill of a racing liner is naturally a very serious matter, and it is very doubtful whether any of the above advantages can compensate for it. Balance in Favor of Reciprocating Engines. It would seem, then, that, on the whole, the balance is in favor of the reciprocating engine even for mail steamers of the highest speeds. How- ever, a slight increase in tte efficiency of the turbine-driven propeller might suffice to turn the scale in favor of the turbine system. It must be re- membered that improvements in re- liability and efficiency are in the fu- ture, and it is the present we are con- cerned with. When we consider the case of ocean liners of rather slower speed, it is very evident that the turbine cannot be expected success- fully to compete with the highly effi- cient combination of reciprocating en- gine and propeller fitted to this type of vessel. So that it seems probable that the piston engine will continue to hold its own for some time to come, as far as this class of work is concerned, although something may be done with the combination of the two systems. A good deal has been written lately regarding the application of the tur- bine to slow-speed cargo tramps. A little reflection will show that it is