(See pp. 739, May, 1920; 1171, August, and 1776, December, 1933; 651, May, 1934, Proceedings)
Harry Leypoldt.—In view of the several articles dealing with Martelli's method, all of which failed to properly analyze the intricacies deliberately introduced into the method, undoubtedly to increase sales of the publication, the following terse descriptions of the tables are given, as well as his variation of the fundamental formula:
Table I is a juggled log cosine table with 9.5000 subtracted from the usual log cosines. Since two entries into the table are required, no change in the mantissa occurs.
Table II is a natural cosine table, with each value increased by 0.2000. However, in order to increase the deception, the resulting numbers are converted into degrees, minutes, and seconds.
Table III is a natural versine table where the argument is the co-altitude. Again circular measure instead of numbers is used.
Table IV is a common co-logarithm table. It has been altered by the addition of 0.3344 to each value (upon conversion of the circular measure into numbers). First, however, 20' 00'' (or 1.2000) must be subtracted from the tabulated values.
Table V is a colog versine table, also altered by the addition of 0.3344. This alteration balances the same value introduced on other side of the equality sign.
As to published articles showing what type of problems can be solved with Martelli’s Tables, simple observation of the formula shows that it contains four variables; with any three known, the fourth can be found by proper substitution.
Diesel-Driven Surface Craft
(See page 1564, November, 1934, Proceedings)
Captain A. M. Procter, U. S. Navy (Retired).—The present conflict in opinion as to the relative availability, and the relative desirability, of the Diesel engine and the steam turbine is a repetition of a condition which has always arisen when, in the process of evolution, it has become necessary to replace old forms by new ones. A situation which was almost an exact parallel to that existing at present was that which existed at the time when the great engineering question of the day was the battle between the water-tube and the cylindrical boiler. In writing on this subject in Brassey’s Naval Annual, 1896, Mr. G. R. Dunell gave an analysis of the situation which subsequent events proved to be strikingly accurate.
Mr. Dunell, in words which can be used verbatim to describe the present situation, stated:
The great engineering question of the day is the battle between the shell and the pipe boiler. The Admiralty authorities have not been backward in recognizing this, and the boldness with which they are grappling with the problem must have astonished those persons, if any still exist, who take the once conventional view that the Admiralty is the stronghold of obstruction and meaningless conservatism. Whatever may prove to be the best form of water-tube boiler—most probably it has yet to be designed—marine engineers will do well in the future to remember that it is the engineering department of the Royal Navy to whom the credit is due of successfully introducing water-tube boilers on a large scale. ... A new system, whatever may be its potential advantages, never works smoothly at first. It is human nature, and especially seagoing human nature, to suffer patiently accustomed evils, but to be very intolerant of new difficulties.
For this reason what might prove a trifling and remediable defect in a water-tube boiler may be considered to outweigh all the long-standing troubles experienced with the older type. Again in making a change of this wholesale nature most powerful vested interests have to be attacked. If water-tube boilers supersede the present flame-tube shell boilers, many hundreds of thousands of pounds worth of boiler plant will become obsolete, and that is not a prospect contractors are likely to view with equanimity, or suffer in silence.
In a consideration of the situation which confronted the British Admiralty in 1896, and that which exists today in regard to the use of Diesel engines for naval surface ships, there is one important point of difference.
In 1896 the water-tube boiler was a new device which had not been tested in service over a period of years. The Diesel engine, on the other hand, has been in use in the merchant service for more than twenty years, and for a number of years past the power of the Diesels installed each year has been materially greater than that of steam plants installed. During this time there has been a material decrease in the total tonnage of steamers in service, and a very large increase in that of motor ships. Taking at random one of the summaries, published from time to time by the British Motor Ship, the horsepower of the motor ships ordered between January, 1934, and April, 1934, was four times that of steamers.
Outside of Great Britain, where the conservatism of the private shipowner has been much greater than that found in the rest of the world (except in the U.S. where there has in the past few years been little or no shipbuilding), the ratio of motor horsepower to steam horsepower was 1.2 to 1.0.
In this list there was but one steamer of over 1,000 tons ordered outside of Great Britain.
Lieutenant Commander J. O. Huse has given an analysis of the situation which brings out the overwhelming advantages of the Diesel engine for naval use.
This analysis cannot but impress that branch of the Navy which is responsible for fleet operations; and which must, in the final analysis, have the deciding voice as to whether a change from the old order to the new is desirable.
Recognizing the fact that the subject is a highly controversial one, upon which differences of informed opinion are inevitable, I find myself in disagreement with the two major conclusions of the writer.
These two conclusions are:
- Diesels for cruising should be installed.
- Adoption of all-Diesel drive not advocated.
Looking back over the history of the past it will be found that a fear of breaking away from the old and familiar types has led, almost invariably, to the design of hybrid installations which have had all of the disadvantages of the old forms without realizing fully the advantages of the new. If the Diesel engine has not been developed to the point where it is dependable for the main drive, it is doubtful if the advantages of the auxiliary drive will be great enough to outweigh the disadvantages of the hybrid plant.
Certainly no commander in chief who had doubts as to the reliability of the auxiliary Diesel plant would be justified embarking on an over-seas campaign with a tanker supply based on the Diesel radius; and one of the great advantages of such a plant would vanish.
Lieutenant Commander Huse states that the adoption of the all-Diesel drive is not advocated because the Diesel engine required for this purpose is in the infancy of its development, and that "to install a 1933 Diesel in the main drive plants of our new ships would inevitably result in vessels which could not take their places on the battle line." This statement suggests that the writer has in mind the use of the only type of engine which has as yet been used for the main drive of surface ships—that used in the German Deutschland. If this is correct I am inclined to agree, for notwithstanding the fact that the Germans have laid down two and possibly three ships with the same engine, which suggests that there has been no disappointment with the first, it must be admitted that it will be several years before the reliability of this engine can be determined in service.
Information released by the Bureau of Engineering, in regard to the plans for reengining some of the old colliers, suggests that the geared drive is contemplated for surface ship propulsion.
With 5,000 s.hp., a 4-shaft drive, and 4 engines geared to each shaft, the s.hp. per engine would be 3,125.
This is an attractive proposition and it is quite possible that this may be the final solution; but at present there is no developed engine which can be installed within the weight limitation except that of the Deutschland.
There is, however, another way in which the result can be accomplished without the use of an undeveloped engine and without introducing any doubtful elements.
Owing to the intensive development which has been carried on during the past few years, there are a number of high-speed supercharged engines, with cylinder diameters near 10 inches, which develop specific powers far greater than those to which the marine engineer has been accustomed. This development brought about by the demand for engines for locomotive drive is proceeding with great rapidity, and before another twelve months have passed engines of still greater specific output will be available.
Information in regard to several of these engines which have been developed abroad is published in the September number of The Oil Engine, which states:
The demand for higher powered Diesel engines, both for fast rail cars and locomotives, has led to the adoption of pressure charging with the object of increasing the output at the expense of a comparatively small addition of weight. The last Maybach engines now building, for instance, will develop 600 b.hp. with Buchi pressure charging, although as unsupercharged engines the output is 410 b.hp.
Similarly, the new M.A.N. high-speed traction Diesel engines will maintain about 700 b.hp. when pressure charged, and their weight is little more than an unsupercharged engine of the same type developing about 400 b.hp. Some tests were recently made with a high-speed S.L.M. traction engine manufactured by the Swiss Locomotive works, Winterthur, provided with Buchi exhaust turbo charging. The engine has 6 cylinders with a diameter of 260 mm., the piston stroke being 320 ram.
Although designed for 450 b. hp., without supercharging, the output with turbo charging is 700 b.hp., at a speed of 800 r.p.m., and this corresponds to a mean effective pressure of 7.75 kg. per sq. centimeter, or 110 lb. per sq. in.
The M.E.P. is that referred to brake horsepower. With a mechanical efficiency of 85 per cent, the mean indicated pressure is about 130 lb. per sq. in. The increases in power of the above engines are: Maybach 46 per cent, M.A.N. 75 per cent, and S.I.M. 55 per cent.
The S.L.M. engine develops 700 b.hp. with 6 cylinders. Built as a V-12, the power would be 1,400 b.hp., which would require 44 engines to develop with D.C. electric drive, which is the only form of transmission that could be used with this number of engines—the shaft horsepower of H.M.S. Nelson and H.M.S. Rodney, which are the only ships which have been built in accordance with the provisions of the Washington treaty.
The objection might be raised that the type of engine proposed is, in a pressure charged state, an undeveloped product. The answer is, not that engines of this type are now built for sale to men whose reputation for conservative action is equal to that of naval officers, and for service more rigorous than that demanded of naval engines, but that, owing to the small size and cost of the units, type engines can be tested to destruction several times, and rebuilt, during the time necessary to build a battleship, and that all development troubles can be eliminated in this time engines of this size can be installed in such a way that the removal and replacement of an engine would be a matter of hours. If 25 per cent of spares are provided, as is now the practice with turret guns, an annual replacement program would provide for the renewal of the entire engine plant, with new or rebuilt engines, once every four years. The problem, at maximum powers, would be one of endurance life, and with a fleet speed 2 knots below the maximum, the demands for full power would probably not exceed 24 hours per year. At cruising speeds, and at fleet battle speeds, the rating would not be higher than that found today in a number of commercial engines rated for continuous operation.
The important question to be decided is not whether a proposed installation is as good as one which can be obtained by future development, or whether the proposed installation is an improvement on the existing practice.
In 1896 the British Admiralty made the bold decision to install Belleville boilers in the Powerful and Terrible. This action was the subject of severe criticism and led to the appointment of the famous Boiler Commission. Subsequent events proved that much better results were obtained with boilers developed a few years later, but since the Powerful remained on the effective list until 1910 and the Terrible until about 1917 with the original Belleville boilers, it cannot be argued that this decision was a mistake; since the alternative in the case of these two ships was the cylindrical boiler.
The two sketches show the minimum installation dimensions of a 10 in. by 10 in., V-12, 4-cycle engine (Fig. 1), and the result obtained by fitting engines of this type in a battleship having the same dimensions and the same general characteristics as H.M.S. Nelson. Figure 2 is one of a number of studies which have been made. These have covered a wide range between maximum concentration—with the engines in three tiers below the armored deck and maximum dispersion—with the engines in one tier below a deck which is 12 ft. below the 34-ft. water line. In all of these studies it has been possible to install the machinery in materially less space than that occupied by the present steam plant.
There are a number of advantages in an installation of this type, in addition to those enumerated by Lieutenant Commander Huse for all-Diesel plants; but there are two outstanding ones, which should make a strong appeal to the operating engineer.
(1) Since the replacement of a group of engines with spares could be made in a few days, all major engine repairs can be transferred from the ship—where they cannot be properly made—to a shop on shore, where the engines can be rebuilt by methods developed in the modem automobile shop. (2) Since only about 15 per cent of the engines will be required at ordinary cruising speeds, the time available for the routine examinations and replacements, which are so necessary to keep a plant in condition, will be very materially increased.
Promotion by Selection
(See page 769, June, 1934, Proceedings)
Commander Ernesto Ciurlo, R.I.N.—I read the proposals of Admiral Sims with great interest. His name and reputation assure consideration for anything he writes, and, besides, the Italian Ministry of Marine is studying the same problem. There is general agreement that selection is advisable, but the question is one regarding method of selection. More specifically, the question is one of providing the selection board with information on which the board can act.
In 1926, a system was introduced in the Italian Navy substantially similar to that advocated by Admiral Sims. Prior to the selections for promotion to the grades of rear admiral, captain and commander votes are secured from officers of the grade above that held by the candidates. The results of these votes are submitted to the selection boards for their information only, and it is not possible to state how much use the members of the boards have made of the information thus obtained.
I am inclined to believe that the collection of this data and its submission to selection boards is desirable, but, in any consideration of selection methods, it must be borne in mind that the ultimate aim of selection is to secure officers who are capable of successful leadership in time of war. As far as I know there is no way of being sure that one’s estimate of the capabilities of an individual is a correct one. Especially it is difficult to foresee how an individual will perform under the stress of war conditions.
Accuracy in Aerial Dead Reckoning
(See page 1561, November, 1934, Proceedings)
Lieutenant W. E. Gist, U.S. Navy.—Mr. Gatty said, “In the practice of dead reckoning, the Army Air Corps has found it entirely impractical to use wind direction and velocity in the determination of drift and ground speed.” I am not familiar with Army practice, but this statement would not be correct if applied also to the Navy.
The aerological service of our Navy is comparatively new, but it is well established and is advancing along progressive lines. Our aircraft carriers and our naval air stations are able to supply our pilots with considerable information upon which they can base their calculations regarding wind direction and velocity. In practice such data are supplied and are used with satisfactory results. The collection and use of such weather information is increasing and the accuracy of estimates is improving. With more experience our weather forecasters are doing better work.
It should be remembered that present- day drift indicators appear to be of no value unless the pilot can see either the ground or the water. The best practice for a pilot today is to use the estimated velocity of the wind, and the estimated direction, and attempt to check the estimated velocity and direction by use of his drift indicator.