Possibilities of the Diesel-Engined 10,000-Ton Cruiser
(See page 505, June, 1930, Proceedings)
Captain H. C. Dinger, U. S. Navy (Retired).—The article is an endeavor to indicate the effect of putting Diesel drive on a 10,000-ton cruiser to show how it can be done and the advantages to be secured. The data presented, however, are in a considerable measure, hypothetical and academic, and some of the information is not the kind upon which actual vessels are designed. Hence the picture of the possibilities of Diesel drive for cruisers calls for some comment. In actual design, it is necessary to deal with actual weights and actual space and volume. The author deals somewhat with assumed characteristics.
The law of similitude used is interesting, but it is doubtful whether it could be used as a basis for actual design. There are too many ifs and ands about it. The ratios used, while they<may be to some extent indicative and informative, would be too uncertain upon which to base actual construction. There is no fixed ratio between weight of gun and rapidity of fire, between horsepower and weight, or between volume of cylinder and weight of engine. There would be if a thousand and one other things remained the same, which they do not. Therefore, curves drawn on the basis of such deductions are not of very much practical significance and are vitiated by any material departure from the assumed conditions. The use of light alloys in lieu of iron or steel parts throws the ratio out of joint. It also will cause a material change in pressure, an improvement in economy, etc.
The author attempts to make weight comparisons in a way that leaves the reader in doubt as to what it is all about. Such terms as fixed engineering weights and weight per cubic inch of cylinder volume are of no particular meaning; nor is it easy to distinguish between propulsive machinery, auxiliary machinery, and ship service machinery, because no definite line exists as to where one begins and the other leaves off. If we have a total weight of machinery that is something more definite—with this figure some comparisons can be made.
After considerable discussion, the paper arrives at a figure 1,079 tons engineering weight and 47.9 pounds weight per shaft horsepower. This is a rational figure for the type of machinery proposed. This figure might have been assumed in the beginning. It is substantially the total machinery weight of the Ersatz Preussen and about 60 per cent below weights on our submarines. No other installation on board ship has ever approached this figure. It can, however, be done, if some one wishes to spend the money to accomplish it. The decrease in weight of the Ersatz Preussen is largely due to the use of light alloys and special refinement in design. This costs money and also may take considerable toll on reliability.
The upshot then is that if we use the machinery suggested, which has not been fully tried out, we can get an 80,000-horsepower Diesel machinery installation on about fifty pounds per shaft horsepower. If we use the best possibilities of the steam turbo-reduction gear, we can do it on just about one- half of this weight. Modern destroyer installations, which do not make full use of high-pressure steam nor of welding and use of light alloys, have already secured the figure of thirty pounds.
Direct or geared drive.—There is likely to be but little difference in weight here, as the author has indicated. The decision to use the geared type will be based on other matters. In the case of the cruisers, there is insufficient headroom properly to accommodate direct-connected engines for the power required, namely 20,000 shaft horsepower per shaft. It is hardly practicable to place the engines as they are located by the author. The shaft line is shown too low to make proper connection to propellers. There is insufficient headroom over tops of cylinders and the space at sides is extremely cramped. As it is, the cylinders project well above the water line. Therefore, if we must have Diesels for the cruiser, we will have to use a shorter engine of higher revolutions, say 450, and connect to propeller by means of gears, or use electric drive. This will require more space and perhaps more weight and will make such a complicated installation that it cannot be considered very desirable.
Now, what fuel consumption will such an installation give us? We may perhaps secure 0.5 pound of oil per horsepower for all purposes at near full power. The author’s curve on page 510 is, in my opinion, about 10 per cent optimistic. At cruising speed the fuel consumption will go down to 0.75 pound per shaft horsepower at fourteen knots. With a steam turbo-reduction gear of up-to-date design, we can secure 0.55 to 0.6 pound at full power; with Diesel cruising equipment we can get about 0.7 pound at twelve knots. The weight of this machinery will be approximately 60 per cent of the Diesel equipment proposed by the author and its cost will be only about two- thirds of the Diesel. We will have gained a greater radius for the vessel at twelve knots and lessened the radius somewhat at the higher power. But if the weight saved by the steam plant is put into fuel, we can regain this lost radius and more.
Having this picture in mind, and the uncertainty in regard to the reliability of any light-weight Diesel, there is no notable advantage in putting the Diesel in for the main drive. We merely secure the prospect of uncertain reliability and greater expense for a talking point.
The cost of operation of the Diesel, when all things are considered—(1) extra cost of fuel or of cleaning bunker oil, (2) extra lubricating oil, (3) extra repairs and renewals—will probably be greater than with the turbo-reduction gear installation, and materially more if the steam plant is fitted with Diesel electric cruising equipment.
The moderately powered merchant ship of 3,000 to 10,000 horsepower presents a somewhat different picture, so does the yacht and fishing boat, car ferry, etc. There are marine installations where the Diesel is unquestionably the thing. However, it is at a disadvantage in a high-powered cruiser for the U. S. Navy.
The turbo-reduction gear has the following advantages:
- Definite reliability—can be operated even with major derangements.
- Essentials can all be placed below the water line, except uptakes.
- Can be made more compact.
- At least 50 per cent advantage in weight.
- Better maneuvering qualities.
- Operation is well understood by operators likely to be available.
- Requires no specially clean fuel and can use any available fuel oil.
- Uses much less lubricating oil.
Against these advantages, we have a slightly greater fuel consumption at some speeds. This one point is not enough to balance all the other advantages. Furthermore, no actual builder of Diesel engines in this country is now prepared to build the engines that the author presents for our consideration. There would have to be considerable experimentation and development before the engines could be produced successfully. The Navy is now proceeding to determine what Diesel engines may be used for Navy motor boats. Here is where the Diesel has special possibilities, yet there appear to be relatively few Diesel engines of American manufacture adaptable to this class of service. After a period of development and considerable experimental work, Diesel engines satisfactory for such service will be produced. But even here, in this relatively simple application, the problem is actually much more than taking some one’s idea of an engine and placing it in a boat.
Punishments Humanized
(See page 582, July, 1930, Proceedings)
Lieutenant H. J. Wright, U. S. Navy— Lieutenant Minckler’s article on the theory and practice of punishments as exemplified in the Navy touches upon a subject not only timely and of vital interest to the Navy but also to the nation itself. It is, as he has stated, a highly controversial topic. He discusses the mission of punishment, hindrances in our present naval system of justice to the realization of the mission, and makes a decision to insure the fulfillment of the mission.
The writer takes issue with Lieutenant Minckler on the theory of punishment. He states that the mission of punishment is “to punish in such a way as to obviate the necessity for future punishment.” To use an expression of the author, this is but “the elucidation of the obvious.” The question to be decided is threefold—shall we punish in order to satisfy a desire for revenge, to deter would-be offenders, or to correct the individual. The author discusses these phases of the question and arrives at the conclusion that the correction of the individual is paramount.
The writer believes that the theory of deterrence is the most effective and practical for the service as well as for the state at large. If we examine the subject in the modern scientific method which is a posteriori synthetic—a method which investigates and tabulates a vast number of effects and from these induces a cause—we find that in communities and nations where sharp, summary, and almost Levitical punishment follows swiftly the commission of a crime, the incidence of crime is very much less than where a so-called system of humanitarian penology is in vogue. The incidence of murder in the United States and in England need only be mentioned in passing as an illustration.
From personal experience the writer has seen the salutary effect of a captain’s practice at the mast of “soaking” them. The ship was. a cruiser with five hundred men aboard. The “Old Man” was a salty, upstanding gentleman of the “old school” and when a liberty jumper or shirker appeared at his mast, he was “soaked”—make no mistake about it. That ship, during the two years of the captain’s tour of duty, not only stood one in gunnery and engineering and won the “meat ball” but also stood one in the conduct tabulation for ships of her class, having fewer breaches of discipline and fewer summaries than any other cruiser. And it was because a report meant inevitable punishment. That ship was, in addition, what is known in the service as a “happy” one. The captain’s attitude was based on sound philosophy—he believed that to mollycoddle the offender was to be very unfair to the men who were manly and played the game. Every division officer conducted his own men to mast and he had to know his men properly to answer the skipper’s questions. The deterrent theory was a grand success in that ship. The writer believes that the mission of punishment is to punish in order to deter others and the offender from further breaches of the law.
The author criticizes rather severely the summary court-martial. He says:
Our legal machinery is complicated and cumbersome; our procedure follows closely that of a criminal court under the civil law. Officers acting as prosecutor and defense counsel are expected to display almost the same learning in legal matters as is expected of a trained criminal lawyer. The members of the court combine the functions of judge and jury.
The writer holds that the naval court is the fairest court in the world. The interests of the accused are safeguarded as in no other tribunal. Why should our procedure not follow that of the civil courts? It is in the main a procedure based on the old common law. It is neither complicated nor cumbersome—there are no continuances, injunctions, and appeals to clutter up the procedure as in civil courts. The main object of the proceedings is to get the facts, and “learning in legal matters” is a drug on the market in a naval court. Spellbinders, “sob sisters,” and sea lawyers are soon squelched by a good “senior member.”
It is true, as the author says, that there are lists of punishments issued to cover certain offenses—they are but a guide to the court. The writer has “respectfully adhered” to sentences adjudged by his court, which did not follow the schedule but were in accordance with the A. G. N. and the Navy Regulations—and the sentences have stood. There is no court worth the paper in its precept that does not try to get behind the obvious facts and delve into the motives of the accused and, learning these, take them into its deliberations.
In his “decision” the author recommends that we do away with schedules of punishment and “let the officer on the spot determine what is best.” He suggests delegation to the division officer the power to punish minor offenses; and in serious cases meriting court-martial, a preliminary investigation by the division officer before going to mast.
There is not a division officer afloat worth his salt who does not do just these things. The division officer, in submitting his liberty list to the executive, may omit from it certain names for cause. There are jobs to be done outside of extra duty in the regular course of routine that may be saddled on the shirker to his great disgust; there are baseball teams on which to play; smokers on other ships—many little things that if denied soon wake up a man if he is worth waking. In serious matters at mast the writer’s skippers have always demanded an account of the accused and the particular circumstances surrounding the alleged offense, from the division officer, before taking action. The boatswain’s mate can get plenty of action from a good division officer in the case of Jones, second-class seaman, who will not turn out at reveille, without punching said Jones in the nose. As a matter of fact the writer believes that the punching petty officer has almost completely disappeared. In fact the main trouble with the modern boatswain’s mate is that he is too chummy with the cubs under him.
There are many points made by the author in his article that are valuable and to the point and the subject is, to the writer’s mind, quite the most important before the naval service. He believes, however, that the answer to the problem, if there be an answer, lies in the recrudescence of an old specialty that has gone to pot, that of being a real division officer. The graduate engineer, the ordnance shark, the radio wizard, all have their importance aboard ship; but the boy who pounds the tar and the tin receives little help or encouragement. He as a junior division officer gets mighty little in the way of precept and example from his immediate senior in the troubled job of being a good division officer, because his immediate senior does not know how either. And soon the junior becomes the senior— and division leadership remains submerged. The real reason that small ships, such as destroyers, seem to have a higher state of morale than the larger ones is, to the writer’s mind, because there is really only one division officer, the executive officer, who is an experiencer, capable officer usually—he has to be to get by in that particular billet.
A Method of Calibrating Range Finders at Sea
(See Proceedings for February, 1930, p. 137; May, 1930, p. 440.)
Lieutenant Commander Alfred Tawresey, U. S. Navy.—The method of checking range finders, ably set forth by Commander Parker, and commented upon by Commander Lee, may be further simplified. Commander Parker’s equation R"/S = (B + b)/b may be written R" = S(B/b + 1), or R" = S X N. If we let r' equal the error in R’, and r" equal the error in R", and d the difference, we can write: d = R' — R" = r' — r". The error is demonstrably inversely proportional to the base. From Fig. 1 we can then write r'/r" = (B + b)/b. Substituting the value of r', thus obtained, in the equation d = r' — r", will give r" = d/(B/b).
The computation is then simple, and the solution is rigorous, except for observational errors. Commander Parker’s examples, worked thus are as follows:
If the first formula is written log R" = log S + log (B/b + I), it is apparent that a slide rule can be constructed to solve for R". A logarithmic scale of ranges S sliding against a logarithmic scale of ranges R", positioned by an index located for b and sliding against a logarithmic scale of B + b will give R" direct from S. With such a rule, the parts of the solution above marked * can be omitted.
Furthermore, when a range can be taken on an object with a known base line, the slide rule makes it practicable to employ this stadimeter method for obtaining a range of greater accuracy than can be obtained using the range finder in the ordinary manner. It is important to note, however, that in any use of the method, an error in reading 5 is multiplied by (B/b + 1) in R", and affects the result in that proportion.
Ballistic Engineering Problems: Empirical Summaries
(See page 411, May, 1930, Proceedings)
C. G. Williams, Chief Engineer, Green Bay Barker Machine & Tool Works.— I wish to take exception to some of the statements made in that part of the article “Ballistic Engineering Problems,” dealing with erosion rates and life of guns.
My remarks will apply principally to the following clause: “Immediately subsequent to the full engraving of the band, a displacement of a few inches at most, the gun tube begins to expand appreciably from the position of close contact with the engraving surface.” In actual practice this cannot be true. The intense heat developed by the powder attains its maximum when the shell is less than one-half caliber past the ramp. The engraving on the band has been completed but the effect of inertia has caused the engraved slots to be prolonged somewhat, giving a slight stripping effect. This will leave an opening at the side of the rifling away from the contact pressure.
The expansion caused by the heat of explosion or combustion of the powder is not accompanied by an enlargement of the bore as Mr. Thompson would have us believe. Because of the restriction of the cold outer bands of metal, the expansion that accompanies the absorption of heat by the inner layers of steel composing the main tube is internal instead of external, from the fact that the outer rings of the metal are always colder than are the innermost rings. This condition is true from the first shot fired to the last one.
It is taken for granted that the condition to begin with is that which is the general condition of the gun before the first shot is fired; that the same practical condition exists between shots as existed prior to the first shot relative to the action of the metal in the gun toward the projectile; that as subsequent shots are fired the expansion is carried still further until such a time as the heat has been transmitted to the outer layer of the outermost band of the gun. From this time on, there is a possibility that the interior of the bore does expand slightly, but this would be a muted question for, as each shot was fired, the innermost rings of metal absorbing heat from the incandescent gases will be actually hotter than will each succeeding ring of metal to and including the outermost ring, each ring in succession being cooler than the next ring nearer the bore of the gun.
One of the attendant phenomena of this state of expansion is the deep cracks that in time invest the inner portion of the bore, especially that portion known as the cone and the ramp which, because of their positions in relation to the bore and their contour, are acted upon more severely by the incandescent powder gases than are the portions of the bore more remote from the powder chamber.
If there is any variation between the bore of the gun and the rotating band, as Mr. Thompson would have us believe, it is I believe fully compensated for by the expansion of the rear of the projectile and of the rotating band, which, being of copper, has a greater affinity for heat and greater conductivity of heat. Consequently the heat absorbed by the band will act upon the copper more severely than it will upon the interior layers of steel surrounding the bore and have a tendency to keep the bore sealed up by the band, excepting that portion opened up by the shear of the metal composing the ring, caused by the inertia of the weight of metal in the projectile resisting the tortional effect of the rifling. It is through these orifices that some of the gases that are always to be found ahead of the projectile escape. However, it is believed that by far the greater amount of the gases found ahead of the projectile come there through other means than through this orifice. This gas ahead of the projectile, added to which will be fresh gas that escapes past the stripped sections of the band, will assist the erosive action at the muzzle by giving up of its heat as it passes along the bore. This gas is not free to move as it has considerable pressure imposed upon it by the action of the air that fills the bore of the gun before the powder is ignited. An attempt could be made to compute this pressure by the formula of moving gases.
In any gun, from the mountain howitzer to the heaviest coast artillery, after several shots have been fired there will be found innumerable small hair-line cracks extending up the surface of the steel parallel to the axis of the bore. These are caused by the internal expansion of the metal surrounding the bore crushing the crystals of the metal into a more dense structure and in a sense giving an effect of cold working on the metal. This expansion causes the metal to be worked past the elastic limit and a permanent set occurs in the innermost layers of the metal. If the metal is now allowed to cool, there is a reaction that is sufficiently intensive to disrupt the metal at many points, because the reaction will not be of such a nature as to be able to work the metal opposite to that work occasioned by it. As the contraction of the metal continues by the absorption of the heat both by the atmosphere within the barrel and by the outer layers of the steel, the metal will be strained past the elastic limit and cracks will appear. As the firing progresses this action is intensified until the hair cracks become deep dangerous fissures in the steel. These fissures gradually open up circumferentially as well as longitudinally, though the longitudinal fissures will always be found to be the more strongly developed. It is through these fissures that we see the greater portion of the gas ahead of and surrounding the projectile as it emerges from the bore.
Much of the wear or erosion to be found at the muzzle of the gun is occasioned by the rush of the heated gases through the orifice that is opened up after the rotating band has passed from the bore and the body of the projectile still extends within the bore.
It is believed that this action will be all the more violent in the modem gun with the modern boat-tailed projectile as a longer period of time will elapse between the clearing of the bore by the rotating band and the final clearing by the base of the projectile because, from the very nature of the contour of the base of the boat-tailed projectile, the rotating band is farther from the base than it was in the old square-base projectile. As this action continues, the point where the opening between the bore and the rotating band occurs will extend farther and farther up the bore from the muzzle with each succeeding shot, and as this point recedes from the muzzle, it is still further accentuated by the stream of gases that pour past the band after the clearance has been effected. Thus the effect is multiplied many fold as is intimated by Mr. Thompson, until all semblance of accuracy has been destroyed.
Many experiments have been carried on in the past to determine the erosive effect of incandescent powder gases passing through a small orifice but at this time no attempt will be made to derive a formula for this action or to give any value to a constant, denoting this effect.