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1901.] MARINE REVIEW. om it is in a boiler shop. The amount of time lost by men cautiously feeling their way about in semi-darkness, coupled with the time lost by skulkers and loafers dawdling away their time in dark corners, is very considerable; besides which, men very naturally dislike having to work in a dark shop, and their unwillingness affects their attendance and they lose time. "Owing to certain circumstances, the new boiler shop electric light installation was not in working order until the winter season was _ half through, yet from the day the current was switched on the boilermakers' . attendance improved; and while the average time lost before the introduc- tion of electric lighting was 14.72 per cent., after the light was introduced the time lost averaged 13.2 per cent.; a distinct saving of over 1.5 per cent., or three-quarters of an hour per week per man. This is attributed solely to the lighting of the shop. The difference in other directions is most marked. The men can move about with freedom and decision, there are no dark corners, the time-workers have not the same temptation to waste their time, and managers and foremen can see what is going on from end to end of the shop with the utmost distinctness. Table III. (subjoined) gives a comparative statement of the various shop lighting, "With regard to the warming, this a problem which has given the firm much thought for some time back, but as yet no definite decision has been come to in the matter. The range of temperature is not nearly so great in this country as in the United States and Germany, and the want of proper heating facilities.does not become one of daily experience; hence probably the reason why so little has been done in this direction. Never- theless, there cannot be any doubt that as a rule engineering workshops in this country fall very short in this direction. The idea which used to be very prevalent, especially in boilermaking lines, that a cold snap made men work all the harder in order to keep themselves warm, is happily ex- ploded, and a more rational view is now being taken of this hitherto much- neglected subject. How is it to be expected that work, and especially good work, is to be got from men whose hands are chilled to the bone, and while the main energies are naturally taken up with means of keeping up their circulation. TABLE III. Ae . of floor Shop. Area. Lights. space per ampere. Sq yds Amperes Sq. yds : per pair. 5 BoUersshOpr. caus eee Meta s Lae ewes 3700 H 2 ae ne { 13.2 Heavy machine shop C. I. bay.......... 880 12 at 10 7.3 Light machine shop C. I. bay Be 83.5 11 at 10 1.6 ; Hnectine, shopo- :venc ak ies oo Soe 1040 11 at 10 9.4 Heavy machine shop M. I. bay......... 1430 12 at 10 11.9 Heavy machine shop M. I. bay gallery (SCTEWIDS SAllery) sc (ae ee 479 4 at 10 11.9 HMinishing shop: 3: 3.3 Savers nc re 574 12 at 10 4.8 Cinverted) Smithy oe ree a ee Bll 4 at 10 2. : (inverted) Voltage 110. Brokie-Pell lamps. "The premium system, with its attendant-records, very soon showed up the benefits of having duplicate work, as the saving of time was quite considerable where a run of duplicate or nearly similar pieces was given to a machinist. This was so marked that the question of standardizing, not only the details, but the whole engine, was gone into in order to get the full benefit of this; and as patterns began to require renewal the engine was re-designed with this end in view. In carrying out this idea in a new design it was found necessary, not only to consider the engine and its details in relation to themselves alone, but also with special regard to their position in the range of sizes which it was decided to make with a view of keeping down the number of different sizes of details. The question instantly became one not only affecting the whole range of engines made by the firm, but also their practice in connection therewith. This prac- tically meant re-designing simultaneously all the sizes of engines made; but a careful analysis and consideration of the requirements to be met enabled the whole range to be suitably broken up into well-defined groups, each group representing a certain size of main centers, and permitting certain variations of cylinder diameter and stroke within well-defined limits, and suitable for the usual steam pressures. The details--which in each group are never altered, although the cylinders may vary within the group limits--are in very many cases common to several groups, and a large number common to the whole range. This object is always kept in view, in order to provide as much duplicate work as possible. Espe- cially is this so in the case of the very small and numerous details, because in these the governing factor in the cost is the wages, not the material; a slight and unimportant variation in size causing a relatively large variation in wages cost; while in the larger details the conditions are reversed, and the material becomes the important cost factor, a relatively small variation in wages covering a very large variation in size. The location of the dividing line between these two conflicting sets of conditions thus becomes a matter of considerable importance, but the accurate data from the time office enables its position to be fixed with great exactness, so as to allow of as much duplication of parts as will pay. "When, however, duplication of pieces can no longer be carried out on account of the cost of material prohibiting it, much can be done in the way of duplicating similar machined, faced, etc., parts in different groups. This enables and encourages the use of jigs, which, under other conditions, would not have been warranted by the saving in wages. When even this cannot be done, standardization by a graded series of similar pieces does much to make the progress of the work through the drawing office and the shops easy and free from the friction and delay incidental to sudden and abrupt changes in design. In the drawing office it has the effect of crystallizing that vague thing known as 'our practice,' and compels it to carry out its work on well-defined lines, thus avoiding expensive and irritating changes and mistakes or oversight. It has also the effect of economizing draughtsmen's time, as a standard series of drawings once properly arranged do not require to be re-drawn for every new job. In the shops, standardization by its consistency in design famil- iarizes the staff and men with the practice and enables them to go about each new job with confidence and expedition; knowing that each job as it comes forward, if not a duplicate, will at least be similar; all of which go far to speed up the progress of work through the shop and thus in- crease the output. And, above all, by the very fact that the means to effect this calls for the best facilities and most exact workmanship, the result is that the character of the workmanship is raised besides being cheapened, with satisfactory results to both consumer and manufacturer." GRAPHIC ANALYSES OF PROPELLER REACTIONS.* BY MR. J. MELLEN ADAM. PART I. An endeavor is made in this paper to concentrate attention on the pro- peller and the fluid which passes through it as a conservative system. Although apparently an elementary inquiry, it may be useful to examine, and, if possible, to define the reactions produced in a fluid by a rotating screw. The difference between the screw pitch and the resultant ship speed provides the angle of incidence without which no energy would be usefully expended. This angle of incidence is immediately taken by the leading edge of the blade with a certain shock, and a reduced pressure of the reverse, which at high speeds results in tip cavitation, a phenomenon apparently similar to vena contracta. Attempts to adopt gaining pitches have not been successful, probably because the radial component is increased thereby, and also because an acceleration uniform from tip to boss is not possible in a helical vane in which, by construction, the tip subtends a much smaller angle of rotation than the root. A feature of the helical screw, therefore, is its essentially non-gaining pitch, and this latter element is necessary for high efficiency. When waves roll on shelving rocks at low angles, they immediately break in impotent foam; but in several places on our coasts, owing to a different formation of rock, the water under similar impulse is deflected upwards in an un- broken column 30 ft. or 40 ft. high, and a little consideration will lead us to deduce the form of surface most favorable to the latter result. A particle escaping from the impact of a narrow inclined plane--mov- ing uniformly in a straight line at right angles to its length--will move according to Newton's second law in a straight line, and the direction will be determined by the angle of incidence at first contact, and will indicate the resultant direction of the oblique force. This resultant may, firstly, be resolved into two component forces: A, at right angles to the path of the vane representing the deflection of the particle, or work done; and B, parallel to the path, representing the inertia of the mass, or what has been erroneously called useless resistance. If, now, we take account of the length of the plane, we form a conception of two sheets. of force, A and B, characterized as above. Let the inclined plane be pivoted at one end and the free end moved through an arc, then the component sheets become A, parallel with the axis, or for our present purpose, effective; and B, at right angles thereto, tangential to the arc--but in this case tangential only for an infinitesimal instant of time, and with varying magnitude falling to nil at the axis, and each particle in reaction still retains its direction in a straight line. Let the plane or vane be twisted to co-relate the angle of incidence to the radius,then the force becomes extra tangential, because every arc is bound- ed on its outer edge by an arc whose angle of incidence is somewhat less steep. Remembering that to compel a mass to describe a curved path, it must be acted on by a force directed towards the center of curvature, the helical screw possesses no restraining element opposing tangential ae therefore centrifugal escape of energy, but adds a material inducement thereto. Let us consider a rotating disc to consist of a sheet of radii, and a uniform system of tangents to be superposed on the same plane and ex- tended to infinity. Then, as a component, B may be characterized as a plane of forces perpendicular: to A, but with a definite direction equiva- lent to the converse of a couple. B may now be compared to the case of uniform motion in a circle. For this purpose let two components of resistance to the force B be c circumferential, and d at right angles thereto cr diametrical. If d, acting along the radius, be directed outwards from the center, the stress would fall within the circumference of the disc and correspond to a moving force directed toward the center of the circle, altering the direction but not the magnitude of the velocity, and therefore absorbing no power. But we have seen that the resultant direction of displacement by the angle of incidence of the helical screw is extra tangential; d, therefore, as a component resistance acting along the radius, is directed inwards toward the center, and the reaction falling without the circle is occluded from.c. The value of c, therefore, asa resistance appears to be diminished by the recession of the tangent through each quadrant of rotation with a definite loss of pressure. PART Il. Let an immersed hollow cone be rotated in its axis; it is obvious no energy will be expended beyond overcoming skin friction. Let the cone be divided and its axis inclined on the plane of division to the axis of rotation (these axes intersecting at the apex); let the apogee be the lead- ing edge, and a reactive surface will emerge having several peculiar features. Obviously also the greater the inclination, as the perigee approaches the "shaft axis'? the more pronounced will be the reactive surface; or, in other words, the greater will be the potential pitch ratio, yet the apogee edge will continue nil pitch through every phase, having a tangent which is common to an arc of gyration. The pitch lines of a rotating half-cone correspond to the figure of cylinders concentric to its shaft axis intersecting the conic surface, and on development are seen to be symmetrical curves of increasing pitch from zero to apogee, with equal acceleration, and therefore equal pressure over the whole surface. Every pitch line so defined is identical in form, differ- ing only in scale of magnitude, and perfectly co-related to the radius, and all contiguous lines produced by a rotary movement are therefore iden- tical in direction, so that the resulting current is homogeneous over the whole surface. A remarkable feature of these lines--distinguishing them from those of a helical screw--is that every arc is bounded by an arc whose angle of incidence is much more steep; so that the theoretical or cylindrical stream line is also the path of least resistance to a fluid escaping from the impact of this surface. The required vane will be found on this surface, and its position will be rigidly determined by the respective pitches required for the leading and following edges. *Abstract of paper read before International Engineering Congress, Glasgow.