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. MARINE REVIEW. [December 5, CALCULATIONS FOR BALANCES. (a) Cornecting rod****: : "(b) Counterbalancing the parts revolving with the crank: % au . mn Sng 4.7% od be GS $2 995 80 oH] B38 On m& = < a Part of connecting rod to he taken as revolving eo ank pin--from . és ee Ay tese snes 2,580-X 24 = 61,920 as BOLO 2 he... 1,158 X 24 = 27,792 Crank webs~ on : crank pin side of CRANK FIN shaft center ..... 2,930 X 14.1 = 41,313 131,025 sp " perank radius... 579 X 24 = 13,896 ' Total amount.. 117,129 Two counterbal- ances and parts of crank webs on same side of 'shaft center*****, 5,250 < 22.3 =117,075 "The counterbalances thus ex- actly balance the other parts re- volying with the crank, as the inertia forces are equal and op- positely directed in the same plane, '(c) Reduced mass to be taken for levers. "As all parts of the main levers } have not the full 48-in. travel, they | must be taken at a reduced weight, the moment of each end being reckoned from the rocking center and the arm being measured parallel to the center line of the lever, similarly to the calculation for the counter- balances in (b), above. | COUNTED RALRNGE Crank end Outer end : of lever. of lever. Length between rocking center and end centers..... in. 39 in. IAB See ee ares ene eae ee aoe owas eae siecs sins 2,482 lbs. 2,123 Ibs. Moment ..... Beare cs ae be ee he SS 54,604 in.-lbs. 44,160 in.-lbs. Arm: = moment ---- mass oy5sici sii. Sess elcat 0. hie ols eie 22, in. 20.8 in. ; 2,482 X 22 2,123 X 20.8 RIGGUCEG IMASS fos ca eis esses as og ehiw we gesvae oo' we TO Ee 394 39 = 1,400 Ibs. = 1,182 lbs. "(d) The parts moving with the crosshead of the high-pressure cylin- der must now balance those of the second intermediate pressure; similarly, the corresponding parts of the first intermediate pressure and low pressure must balance, as in the following table: Second First inter- inter- High mediate mediate Low pressure. presstre. pressure. pressure. Lbs. Lbs. Lbs. bs. PISTON oe ae i is gene e ee brewer es tad 662 2,329 1,416 3,083 IPABLONGT OG eee aan aioe 6 neces ieee tien 1,180 1,428 1,180 1,428 Guidet block 45 ae oe Sotho ee ae 15425 689 1,425 689 Part of connecting rod. See (a)... te 2,068 Fares 1,068 ae' Links: to evers: 665.0% es oie. a 1,067 . 1,224 1,067 1,224 Reduced mass of levers ........... 1,400 1,182 1,400 1,132 MOA er eset cao. sane ene ses 4s 6,802 6,802 7,556 7,556 "The vertical forces fronr these parts are now exactly balanced, and are zero. (Approximately for design Figs. 7 to 18; exactly for the other designs.) The piston rods and crossheads of the high pressure and first intermediate pressure are shown bored out, merely to call atfention to the fact that the balance may be obtained by deducting weight as well as by the less costly way of adding weight, say to the pistons, where necessary. In the design shown, it has not been necessary to depart from the usual pro- portions of the parts to effect a balance. "(e) The parts of the main levers, and links at their ends, have a small transverse movement, principally of second period; but the forces from this are also balanced thus: ; Crank end. Outer end. Masseot Uniks: isc gigee pot cer res reas sds ciclavee oh aes neds 6 1,067 lbs. 1,224 lbs. Beneth Of imksick ck eos eas cos ang Seine coe cs 55 in 55 in. Distance of center of gravity of links from upper ends... 27.5 in. 35 in. 1,067 X 27.5 1,224 < 35 Reduced mass of links for estimating horizontal forces... ~~ 55 ees = 633.5 lbs, = (19: lbs, Reduced mass of levers from (¢).......... acne nce ciety = 1,400 lbs. =<1,132 Ibs. Teak i. Ce 1,933.5 Ibs, --«+1, 911 Ibs. "To produce this balance, the extremity of the outer end of the lever has been thickened to 5/ in., whereas 4 in. is ample for strength. By a very small further addition, the totals 1,933.5 and 1,911 could be made to agree exactly; but they are left, in order to indicate that an infinitesimal residuum need not be taken account of. "(f) Mode of proceedure. "Tf the following sequence be observed in making drawings and calcu- MV **Mor the reason of this calculation, see 'Analysis of the: Inertia Forces) of the Moving Parts of an Engine,' by the present writer; Engineering, Vol. 'LXIV, p. 513, remarks after equations (15) and (17); or, Journal of the American. Society of Naval Engineers, Vol. IX, p. 518, remarks after equations (83) and (85). ; One OonnectingtTOd a iiiiei csc teed ous sve Poh ihe eta q i gegt \ Lepsih Pak nite ot egea p The gecs sack ee ix ma oe ane Center of, gravity, of rod from crosshead ................5.. cnr se 16.8840. Part bt "connecting Ott TB88 in, ce par '76.88 71RD _tod to be taken as revolving with é, ge: OES rv C : VEL Ety. eit ,crank DAD, fyegeegytecse eres teste nee eeeeeee tee eeete ee ens sion 87048 x T08 = 2,580 Ibs. Part of connecting 'rod to be taken as reciprocating with GYOSBDOBG iii. cgilcnns ccc recess ccs eMeeaiies essere erik ote: 3,648 -- 2,580 = 1,068 lbs, *x***Obviously, in counting the moment for the counterbalances, the sum to be taken is Mx, where M is any small portion of the mass and x its. distance from the shaft center, measured parallel to the crank radius. See sketch, lations, no further delay need be incurred in the design than the time required to make a few simple. calculations. "(1) After the crank shaft and connecting rod are drawn, calculate and draw the counterbalance of the requisite size. : "(2) After the main levers and their links are drawn, make any slight addition required to one or other end of the levers to produce horizontal balance, as in .(e). : ~ "(3) After all the other moving parts are drawn, add to one or other of the balancing pistons sufficient to make exact balance, as in (d). "This also suggests the proper mode of procedure in building the engine. A little metal should be left on each piston till all the other moving parts are finished and weighed, after which the requisite amounts of metal should be taken off to produce the exact required balance. "(g) The balance of the valve gears is obtained in precisely the same way as in the foregoing. But it would be ample to make-- Reduced mass of ahead eccentric - Bol gO Reduced mass of outer end of levers 1 AVAe=FOd nic nce eee ee aes = + crosshead ue Great oe ee es + valve spindles + reduced mass of crank end of levers.. + 2d intermediate pressure valves. -Migh=Dressure Valves. sc ays secs use « "And, similarly, for the first intermediate pressure and low-pressure gear.' : Obtaining an exact vertical and horizontal balance for all periods will prevent those short vibrations or tremors which are not only annoying, but must make the correct aiming of a gun much more difficult. The alternative and modified designs, Figs. 16 to 21, show the clearances of the steam passages in the cylinders over the-cranks reduced to a minimum; the engine will thus be brought up to the highest efficiency of any modern marine engine. 'The counterbalances marked "G," Fig. 16, are added to bene the inertia of the valves of these cylinders into the plane of the valve evers. vos Mr. MacAlpine discusses the various points of the designs Figs. 7 to 18 and 22 to 27 very fully, but in this we need hardly follow him. A care- ful examination of the design will show that practical questions of con- struction, accessibility and overhaul, have been fully attended to. But as the design, Figs. 19 to 21, is now put forward for the first time, I may give a few notes to show wherein it has even been improved in these respects. The bearing surfaces in this and the merchant engine design have all been increased. Though the surfaces in the earlier design seem:ample, the increase puts the long running of the engine without readjustment beyond question. By bringing the main guides to the outsides, their accessibility - is considerably increased, and it also allows the levers, though raised, to be kept closer together with their center bearings outside them and in easy reach. Making a center front column leaves the engine perfectly open over the main bearings, so that not only these, but also the main cross- heads, front links, and center lever bearings, can be easily got at, even when the engine is running. To make this easier at the after end the after back column of the second I. P. cylinder is moved a few inches aft of the center of the corresponding main bearing. As strength is easily provided, this shift may be made without fear. Also, to give better headroom above the intermediate platform, the H.P. and first I.P. valves are worked from above. This is also improved by dispensing with the jaw guides of these gears, as shown in the view of the valve gear, Fig, 21. The extra length of back piston rod, required by the modification of the design, is 25 in., but this weight is almost entirely saved by the short- ening of the links. In any casé, its inertia at full speed only increases the pressure on the main bearings by 2% lbs. per square inch, so that the addition is unimportant. The travel of the levers above and below the horizontal position is made unequal. This in no way affects the balance, but by preventing the lever and links from drawing so nearly into line when the crank is at the top makes the adjustment of the whole connection less delicate. The links have also been so designed that they can be kept exactly to length. The levers'can readily be withdrawn to the back. The back links and glands of back cylinders are in easy reach. The crossties are attached so that the expansion of the cylinders will have no sensible effect. Some of the weight saved by bringing down the back cylinders is added to the front columns and some to the front of the bed-plate, so that the total is not much altered. 'The front cylinders are held from fore-and- aft movement by a jaw cast on the L. P. cylinder, which holds, by sliding contact only and without bolting, the foot for the center back column of the front cylinders. The front of the» engine may now be toward the center of the ship, as is usually most convenient; and the hatches, instead of coming close together, will leave a wide passage on deck between them, The hatches do not now require to come much beyond the center of the back cylinders, which will leave these openings of about the ordinary width, and give broad side passages on deck. The H.P. and first I.P. valves draw up, those of the second I.P. and L.P. draw down. This not only suits the design, but also the narrower hatches. Is it admissible to introduce the lever into high-speed engines? So far as the valve gear is concerned there are ample precedents, and consequently there can be no question. Not only has the Stephenson link been used with an almost identical arrangement of lever, but we have in the Marshall gear quite as indirect a connection, and in. the Heusinger-von-Waldegge gear one much more indirect. But these are good gears, and only require to be well and carefully designed to give great satisfaction. In regard to the levers connecting the back cylinders, Mr. MacAlpine gives an elaborate defence of their introduction. In Britain, the beam engine is rarely or never seen on board ships, but we cannot cross our ferries or sail up our broad rivers, or take a summer trip up Long Island time to become acquainted with their good qualities. The piston speed-- and it is principally piston speed that counts--runs sometimes as high as 1,000 ft. per/minute, and the beam works-aften to a great angle. There is no smoother: |working, engine made, and it is the most economical in the sound without being for the time shipmates with one, thus -having- ample aise of lubricants of any engine known;.and the chief engineer may often >be seen sitting in his easy ¢hair, the; picture of unconcern. Mr. MacAlpine quotes our experience, andyhaving livedifor six years with us--having had the misfortune to just miss being turnedcintoraigood citizen of our Republic--ought.to know. The beama engine forming part of our earliest recollections and of our maturest experience, we hardly need the arguments: he adduces to convince us. He speaks of the number of joints between the piston and crank, He has precisely the same number