Jan. 28, 1881. THE ENGINEER. 61 oiled. Having screwed a fine-pointed hard lead-pencil communication with the open air ; the spring, having THE INDICATOR. into the loop of the lever p, and fixed the paper, the atmospheric pressure on the top and bottom, is then neither No. II. regulation of the paper-drum is the only point left. Sup­ compressed nor extended. This position of the piston is Indicators for High Pressures.—If diagrams for very pose that the spring of the paper drum is in its unstrained fixed by the pencil’s drawing a straight line, called the high pressures are required—for instance, with engines position, it has to be bent in order to give the drum a atmospheric line, which forms the base for all the calcula ­ worked explosively—the strongest spring graduated to correct and quick return after having been turned by the tions made by the diagram. The cock is then turned to fifteen atmospheres is too weak. In order to make experi­ string. This operation is performed by lifting oft' the connect the open air with the steam cylinder, in order to ments at a pressure of forty atmospheres with the barrel, loosening the nut x, and turning the cover w until let the steam blow out through the tubes. Afterwards the usual springs, Messrs. Kraft and Sohn supply the tapered the pull of the string has reached the desired tension. In connection between the steam cylinder and the indicator piece d, Fig. 2—see vol. xl., page 415 —with a bore this position the nut is firmly screwed against the cover, piston is effected by turning the plug into the position having a diameter of 12’66 mm., = 0'5in., in which a by which means the latter is secured to the spindle. Before shown in Fig. 2. The diagram is then immediately taken corresponding piston travels. At pressures of about 100 the barrel is replaced on the pulley, its interior, as well as by simply pressing the pencil slightly against the paper. itmospheres, the indicator is supplied with a separate the exterior of the cap, must be oiled, in order to facilitate If the diagram is only taken to ascertain what power the cylinder, of which the diameter is 817 mm., r= 0’32in. the lifting up of the barrel during the motion. After the engine is exerting, it is sufficient to take a double stroke n ( o o iiiiinitT (in Ip %} | C_ V FIC 9 I A FIC -5 D b cl FIC. / wm r| s IP A' JJ< | c I ,C \ T> n jpMfli M fa H i ,N I Wrn wm B m ■ FIC. 8 A! ffllllllllllll ■ •-i K 1 A i nil; lliil D gar ill! tllllllliilli Sr H ■ : | i i j» k i M. Hi! 0*1 IB ! ! F 1C .6 , u I = I I DARKE’S INDICATOR The indicators of these three sizes are sold with springs of termination of the experiment, the spring must be restored and to repeat this several times in order to obtain a good various limits of load, as given in the following table to the unbent state. mean value. If it is important to know the effect of Taking of the Diagram. —We will now suppose the indi­ changes which take place in the engine during the motion, Indicator Area of the pis- Limits of load in atmo- cator-paper —3fin. by 7in.—to be placed on the cylinder, the diagrams are best taken on the same paper, in order Diameter. piston. ton in proportion spheres for the four springs and the important matter of transferring and reducing the to make a comparison. It will be easy for an experienced to that of No. I. of each instrument. experimenter to change the paper without stopping the FIC, IE r+ o + 20 mm. 41^5 c+- o + I-* No. I. <r+ o + 0'79in. FJC 13 c+ o + i nr 12'66 mm. 0 to + 5 Igll 1 0 to + 11'5 M No. II. £3) 0-5in. 2-5 0 to + 20 ill 0 to + 37-5 ill ii i liiiiiniiniMiiiil 817 mm. 0 to + 12 No. III. 1 0 to + 30 0-32in. 6~ 0 to + 48 m 0 to +90 fimiiiniir Fixing and Management of the Indicator. —Notwithstand­ I HA HUHjmOgjJ \ ing that every steam or hydraulic cylinder ought to have a 11 proper entrance for screwing in the indicator, it is very «U| 1 seldom that this is found, even in new engines. The if indicator is therefore always provided with a steel tap (■ IW corresponding to the pitch of the piece i. B p The proper place to put the piece i on the cylinder will i r \T77 Hnm be determined by its giving the most convenient arrange ­ I ment of the indicator, and the most perfect communication r between the cylinder and the indicator-piston. Hence it 7 must not be at a place within the stroke of the piston. T u The indicator must accurately report the general pressure in the cylinder, and therefore must not be placed near the m a. B= =a ! iiiiiiiiiilin ports, where the steam is rushing out or in, or at any part W t where condensed water may be found. The system of ■if F 1C <11 coupling the top and bottom ends of the cylinder together k by pipes leading to the indicator, in order to avoid the mu little difficulty of having to remove the indicator from top to bottom, and bottom to top again, is a very great evil, especially at high speeds, as the steam pressure will be seriously diminished by passing through these long and mm ■ narrow tubes. To put another spring into an indicator- it cylinder, the cover is to be unscrewed, and the parallel m CASARTELLI’S AND POTTER’S INDICATOR. motion, the pencil, and the piston to be lifted off. The connection between the piston-rod and the pencil-lever is KENYON’S INDICATOR. motion of the indicator, even at high speeds. But it is then to be loosened, the piston and the spring unscrewed, much more convenient to make use of the detent motion and the latter replaced by the new spring. Great attention motion of the steam piston to be completed. We have with which most indicators are supplied, and by which must be given to insure catching the nut and not the coils, then to describe briefly how, when the indicator has the motion of the paper drum is completely stopped with­ and to see that the new spring is completely screwed up. reached the normal temperature, a diagram may be taken. out breaking the connection between the indicator and the Before replacing the piston in the cylinder, it ought to be The plug of the cock is so turned that the indicator is in engine. Such detent motions will be described later. It 62 THE ENGINEER. Jan. 28, 1881. is well worth while to take a great number of diagrams in gun. In order, therefore, to meet with every possible There were elected within the year 80 members of all order to have ample material for subsequent study. The requirement, a shell should be the front projectile in future classes ; there were lost by deceases 8 members of all diagram must contain on its face the most important facts, double-loading experiments. The gas check is attached to classes, and by resignation or removal from the register which are necessary for its calculation. These are (1) the the shell by means of a large hollow central plug; into 40 members of all classes. This effective increase of 32 gross and effective boiler pressures; (2) the point of cut-off; this plug is screwed the pressure gauge, which is thus pro­ is highly satisfactory, considering the position in which (3) the number of revolutions; (4) the vacuum ; (5) the dimen­ tected by the hollow ring of the plug. The rear projectile engineers in general have been placed during the past sions and position of the examined engine ; (6) the scale of is made flat-headed in order that when it eventually year, being fully equal to the average annual increase in the indicator spring ; (7) the areas of the steam and exhaust impinges on the front projectile in the earth butt it shall the Institution. The following deceases of members of ports, and of the inlet and outlet passages ; (8) the cubical not injure the pressure gauge. It is hoped that the pres­ the Institution have occurred during the past year :—Sir contents of the clearance spaces. We will now go on to sure exerted by the front charge on the base of the shell Thomas Bouch, Edinburgh ; William Clark, London ; describe some other types of improved indicators, each will be ascertained. The first charge with which the gun Thomas Elwell, sen., Paris ; Thomas Hawthorn, Gates ­ having special merits of its own. will be tired will be a 22 lb. charge in the rear and a 14 lb. head ; William Ebenezer Marshall, Leeds ; General Richards Indicator , with Darlcds Parallel Motion.—-This charge in the front, both of pebble powder ; the rear shot Arthur Morin, Paris ; Lewis Olrick, London. will weigh 1001b., and the front shell 85 lb.; both pro­ indicator was illustrated in our impression for March 5th, Of these General Morin, director of the Conservatoire jectiles will be fitted with gas checks and studs. Should 1880, but we reproduce the block on the preceding page to des Arts et Metiers, was an honorary life member of the make this series of papers complete.