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4 MARINE REVIEW. Report of Experimental Trip, MADE UPON SCREW STEAMER HE. P. WILBUR TO THE BUILDERS, THE GLOBE IRON WORKS COMPANY, CLEVELAND, O., [BY GEO. C. SHEPARD.| Curves From Extract of Loc Mean Damer ote Mea Oaarr ei" ¢ sa ” Os Mies Pee Hove At such times as when we were making a coal and water test or when the engine was in a different condition, took indica- tor diagrams. Diagrams were taken with three, sometimes four indicators and all within one minute. Revolutions were counted at the same time for two or three minutes. At every second set of diagrams, indicator pistons were taken out and oiled and pen- cils sharpened, while at the end of the test the indicators were removed and carefully cleaned. . Cards No.1 were taken with engine in third notch and throttle two-thirds open ; other diagrams were taken with throttle wide open. Up to No. 9 high pressure diagrams were taken with two indicators at the ends of the cylinder, after that from juncture of two ends, except in case of cards Nos. 16 and 17 which were taken with three indicators on high pressure cylin- der—one at each end and one at juncture—to get the error of tak- ing cards at juncture. _ Table 2is a statement of data and results obtained from the diagram. In computations, allowances were made for areas of piston rods and low pressure tail rod and each end was computed separately for indicated horse power. So far as the adjustment of the valves, as shown by the diagrams is concerned the lead of the high pressure valves might be increased a little with advan- tage and all the valves evenedup. It will be observed, however, that the indicated horse power of the several cylinders vary con- siderably; that of the medium pressure is always in excess of that of the high pressure, sometimes to the amount of 17 per cent. and in excess of that of the low pressure 23 percent., while that of the high pressure is sometimes greater and sometimes less than that of the low pressure, according to speed and vacuum. This uneven distribution of power is against best economy but in this construction cannot be avoided, since points of cut off in separate engines are all fixed together, allowing no adjustment to correct above error. On Plate 2 can be seen points whose position with reference to certain axial lines represent the value of the ratio of indicated horse power and revolutions as found in the columns on Table 2 or more primarialy in indicator diagrams taken. Here also does the difference in draft of vessels make it necessary to draw points with different origins. The reason of digression of points from curve can be explained in several ways, viz: ‘The trim of vessel was changeable, altering at least the surface friction of wheel. Again the amount of injection water by air pump and the effect of the vacuum upon low pressure piston are indepen- dent elements in the working of the machine, and do not vary either with steam pressure or rate of rotation. Also evena slight SRE Vy nen IE Age: Ee Sarr Sa PARTICULARS OF INDICATOR DIAGRAMS. TABLE 2. | Gauge || Mean Effective | Indicated Horse Power. J | No. |tngine| Rey-| Readings. || Pressure. || Nol Tin, |e ey epe s | Log. | Noteh-| win, | | | Boiler | Vac. ||H.P. | M.P.|L. P. || H. P.| M.P.| L.P. || Total. pkvaet WONT Reeeeetatiry framereinel Pevahle aca | (esidsndieicnes Foncasstoncad —— | . | | Rh x ~ 1 | 3d 80.5 | 154 922.3 || 62. | 25.3 | 8.13 || 468.2 | 485.7 | 403.5 1,357.4 2] tk | sd | 85 | 145 | 227 || 622 | ase |o6 || 4882 | 5735 | 404s || 1561. 3/ 13 | 24° | 78. | 142 | 23. |) 588 | 23.7 | 7.8 || 393.7 | 440.9 | 875.1 |) 1,209.7 4| 14 74s ea a (Ag 130 | 238. 50.2 | 22.3 | 7.32 || 361.6 407.9 346.4 1,115.7 5 | 14 2d | 77, | 133 | 23.2 || 50.4 | 22.9 | 7.44 || 364.3 420.5 353.1 1,137.9 To Oe 82.5 135 | 22.5 || 58.4 | 25.7 | 7.86 || 452.5 | 505.7 400.8 1,359, 8| 19 | 3d 82.5 140 23. || 59. 26.6 | 8.79 457. 523.5 447.2 1,427 i 9} 20 3d 80.6 | 135 22.8 || 57.8 | 25.1 | 7.89 436.9 482.1 391.7 1,310 l 11} 87°}: 2d 73. 120 24. || 46.4 | 21.8 | 6.96 317.9 380.5 313 3 1,011 7 12 |. 37 | 2d 70.5 120 23.8 || 46.2 | 21.2 | 6.78 305.8 | 356.5°| 284.7 947 : 13} 38 | 2d | 78.5) 150 | 23.5 |} 56.6 | 26.6 | 8.52 || 413.8 | 498.8 | 412.4 1,324.2 14 | 38 2d 76.5 142 23.5 || 54.3 | 25.2 |. 8.34 390. 459.8 | 393.5 1,243.3 15 | 48 2d 78. | 155 22.5 || 55.6 | 26.4 | 9.48 407.1 | 491.1 | 465.9 1,354.1 16 | 44 2d Le(OyoctsahOO coldoestenes 55.9 | 28.6 | 9.54 420.6 | 588.9 | 464.8 1,424.3 17 | 44 a 218.72) > 165: 2 | 28 55.7 | 28.6 | 9.66 || 417. 536.1 469.8 1,421.9 18 | 45 3d | 80. 150 21.5 || 61.4 | 28.3 {10.03 461,1 | 539.9 497.2 1,498.2 19 | 47 3d 79.5 140 22. || 56.8 | 26.2 | 9.48 423.8 496.7 464.7 1,385.1 20; 651 2d 81. | 150 | 22. || 60.8 | 27.7 10.44 || 462.4 535.2 523.4 1,521. 21] 762 2d 76. 145 22. || 50.4 | 24.7 | 8.31 359.6 | 447.7 | 389.5 1,196.8 22 | 58 4th 88. 153 | 21. || 67.2 | 28.9 | 9.48 || 523.5 | 572.3 | 504.3 1,600.1 I pitching was sufficient to effect considerably the revolutions of the wheel with the aggregate mean effective pressure constant. Two of the most important factors in the economy of a triple engine are the expansion of the steam and the distribution of this expansion, and to enable us to see this more clearly have expanded five sets of diagrams that presented different conditions, drawing diagrams of different engines all to the same scale of volume and of pressure. Because of slight wire drawing through the passages and of the inertia of moving parts of engine, could not locate the absolute point of cut-off, so have drawn a adiabatic curve of expansion P. V. C. tangential to apparent line of expansion in the high pressnre diagram, computing the vol- ume for every ten pounds absolute pressure. As the indicated work done is represented by the area of the indicator diagrams, so may the theoretical work to be done be represented by an area enclosed by expansion curve from line of initial pressure to line of back pressure in low pressure cylinder, and from line of high pressure clearance to line marking volume of low pressure cylinder measured from line of high pressure clearance. The ratio of this area representing theoretical work to the sum of the areas representing actual work is one measure of effiiciency of engines under that condition. ‘Table 111 shows these areas and their ratios. TABLE 3. COMPARATIVE AREA OF EXPANDED DIAGRAMS. eda oak AREAS OF CARDS. Per Cent No. ead DER Ay ray he EE eR er ae Pe Minn pe | oe PE en | Gunes Eo Cues. So oP pape 80.5 144 1.48 1.32 4.21 6.30 671 2 | 1561: 83.5 1.49 1.67 1.51 4.67 6.65 |: .702 2 947. 70.5 1.08 1.27 110 3.45 4.77 723 20 | 1,521. 81, 1.42 1.65 1.61 4.68 |‘ 6.66 701 25 | 1600.1 83. 154 1:69. | 1.50 4.93 6.27 "705 [TO BE CONTINUED. | Work of the Minnesota Boats. An unofficial report regarding the work of the six steel boats in the Minnesota Steamship Company’s fleet, now in the grain trade, credits them with having carried 290,944 gross tons of ore from ‘Two Harbors to Lake Erie during the season, which closed with last week. Following is the record: eh Trips. Tonnage, Average load. AYIMA..scsecevesedarresecsseccscennas 23 49,7 2,166 Mariska: ccori hee 25 eg 2,120 Maruba..icsecccrcccsae 24 51,889 2,162 Matoas..ciciscns specs ieee eeseteceues 21 45,660 2,174 Mamnola ccsisiis. ssc cckerecreie oe 23 49,527 2,153 Masada sischavrsticcaceeeceuee 19 41,073 2,162 The Masaba was late in leaving the shi i i yard in the sprin and the Matoa took a load of grain deca September. othe. round trip distance between ‘wo Harbors and Cleveland is 1,778 miles but these boats averaged seven days to a trip through- nces it was made in a little over