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Tide-Predicting Machine No. 2

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1040: 1039: 250: 72: 1053: 1028: 816:" approach for mechanically computing cosines as Thomson used, shown in the schematic (right). A rotating drive-wheel ("crank") is fitted with an off-center peg. A shaft with a horizontally-slotted section is free to move vertically up and down. The wheel's off-center peg is located in the slot. As a result, when the peg moves around with the wheel, it makes the shaft move up and down within limits. As a result of this arrangement when the drive-wheel rotates uniformly, say clockwise, the shaft moves sinusoidally up and down. The vertical position of the center of the slot, at any time 1016: 221: 1046:
traces a sinusoid. Each slotted yoke crank is connected by a shaft to a pulley, which causes the pulley to follow the sinusoidal motion. A chain going over and under pulleys sums each of their deflections to compute the tide. Along the top of the photo, connecting shafts drive slotted yoke cranks on both sides of the machine. One side of the machine computes the height of tides while the other determines the times of high and low tides.
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for the 1912 and 1913 tide tables. Then the machine was disassembled, polished, plated, lacquered, and reassembled in time to provide predictions for the 1914 tide tables. Comparisons of the accuracy of the mechanical predictions of tides compared to hand calculations for two challenging locations demonstrated errors in heights of 0.72 inches (1.83 cm) or less.
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Assuming the factors for a location are known, configuring the machine to compute tides for the location requires 2.5–4 hours. Predictions for a year’s tides at that location can then be produced in 8–15 hours. The calculations Tide-Predicting Machine No. 2 can perform in 1 day would require a person
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A tide formula component crank on Tide-Predicting Machine No. 2. The mechanical arrangement (a slotted crank yoke) converts circular motion to a vertical motion that traces a sinusoid. The operator adjusts the position of the pin on the crank to represent a component of the tide formula at a specific
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Tide-Predicting Machine No. 2 was the first tide-predicting machine to incorporate both a paper graph of the tides–the approach used by earlier British machines–and dials and scales that showed the tide height and corresponding date and time–used by Tide-Predicting Machine No. 1. The dials and scales
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The slotted yoke cranks at the top and bottom (with the triangular pieces) move vertically in a sinusoidal pattern. The locations of their pins determine their amplitudes and phases, representing factors in the tide equation. The pulleys across the center move with the attached cranks. The summation
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Other work in the Coast and Geodetic Survey took precedence over construction of the new machine, and a reduction in staff levels precluded all work on the new machine for three years. As a result, Tide-Predicting Machine No. 2 was not functional until 1910. It was first applied to predicting values
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Much consideration was given to the mechanical characteristics of the components to ensure reliability and accuracy. For instance, some components that were hard to replace were designed with a 50-year lifetime. Also, the summation chains were moved across gears under tension for a year of work days
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One side of Old Brass Brains is used to compute the height of the tide. A similar arrangement of components on the other side, but with cranks 90 degrees out of phase, represents the derivative with respect to time of the tide height formula. When the derivative is zero the time of high or low tide
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is the starting phase angle of the peg, measured in radians from the 12 o'clock position to the angular position where the peg was at time zero. An operator adjusted the location of each pin based on the empirically computed parameters for a port’s tides. This arrangement makes a physical analog of
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In 1895 the Coast and Geodetic Survey grew concerned because Tide-Predicting Machine No. 1 had developed considerable wear from almost constant use over 12 years. The office decided to construct a new machine that was faster, more accurate, and more reliable. This became Tide-Predicting Machine No.
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started printing annual tide tables to support safe and effective maritime, coastal, and defense activities. Before long, these tables showed the times and heights of high and low tides to the nearest minute and tenth of a foot, respectively. Tables were printed for a year at a time and distributed
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This photo shows both the top and one side of Tide Predicting Machine No. 2. The tide prediction formula implemented by the machine includes the addition of a series of cosine terms. The triangular metal pieces are part of slotted yoke cranks which convert circular motion to a vertical motion that
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The Coast and Geodetic Survey designers also adopted from the earlier British machines the approach of summing terms by passing a chain over and under pulleys attached to the vertically oscillating yokes. The amount of chain remaining after passing over and under pulleys indicated the sum of the
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To compute tides for a coastal location, the operator has to configure the machine for that location. This is done by adjusting physical settings on the machine based on up to 37 factors. Those factors are determined empirically by harmonic analysis of a time series of tides at the location, and
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Around 1960 Old Brass Brains was modified to replace the hand crank with an electric motor and to add an automatic readout of heights and times. In 1965, the Coast and Geodetic Survey retired the Tide-Predicting Machine No. 2, 55 years after it entered service, and started performing its tide
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and incorporated their best attributes in the design of the new machine. The machine, also known as “Old Brass Brains”, used an intricate arrangement of gears, pulleys, slides, and other components. The design of the new machine was approved in 1895, and construction began in 1896.
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made it much easier for an operator to precisely determine the height and time of high and low tides. The paper graph, referred to as a tide curve, was very useful as a record of the computation that could be checked later to confirm the calculations were performed correctly.
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the Coast and Geodetic Survey produced annual tide tables for major ports four years in advance in case Old Brass Brains broke down or was sabotaged. The Coast and Geodetic Survey also provided tide predictions for a number of additional locations in the
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This photo shows the largest of the three sections of Tide-Predicting Machine No. 2. The gears on the left transmit power from the hand crank. The components on the right contribute to the computation of the time of high and low
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of tide heights. This analysis can be performed with a record as short as two weeks but a 369-day sample is standard. The longer sample minimizes the errors introduced by wind storms, freshets, and other non-regular influences.
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represent the influence of the moon, sun, depth of bay, offshore islands, etc. Once computed the factors for a location can be applied to past and future years. and are shared widely so anyone can perform tide calculations.
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of the Coast and Geodetic Survey designed a tide-predicting machine. Fauth & Co. Instrument Makers built Tide-Predicting Machine No. 1 and delivered it in 1882. The Survey started using the machine routinely in 1883.
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attempt to account for these factors but lead to complex calculations. Originally, calculations were performed by hand, which was very labor-intensive and error-prone. The burden became even larger when the
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considerations, which were determined by Thomson and Darwin and have been almost universally used. For instance one speed represents the speed of a theoretical moon with a uniform speed in a circular
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terms. For example, a large value for a term would move its pulley further from a neutral position, deflecting the chain, and reducing the amount of excess chain remaining in system.
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The pulleys move up and down in a sinusoidal motion, representing components of the tide equation. The summation chain that passes above and below the pulleys sums their influences.
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are used to mark the start of hours and days on the paper graph and to stop the machine when high and low tides were reached so the operator can note the height and time.
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The prediction of tides is very challenging as it depends on multiple factors–including the alignment of the Sun and Moon, the shape of the coastline, and near-shore
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Old Brass Brains is 10.8 feet (3.3 m) long, 6.2 feet (1.9 m) high, 2 feet (0.6 m) wide and weighs approximately 2,500 pounds (1,134 kg).
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is the relative phase of the term. This is the equation computed by most tide-predicting machines, including Old Brass Brains which handles 37 such terms.
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Internals: the machine uses an intricate arrangement of gears, pulleys, chains, slides, and other mechanical components to perform the computations.
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has been reached. An electrical circuit detects this condition and stops the machine so the operator can record the date, time, and tide height.
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Tide Predicting Machine No. 2 is based on the first accurate mathematical approach for predicting tides, which was developed around 1867 by
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Rolin Harris and E. G. Fischer of the Coast and Geodetic Survey led the effort. The design team studied previous British and U.S.
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for specific locations. The machine can perform tide calculations much faster than a person could do with pencil and paper. The
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before being installed in the machine to ensure they were sufficiently flexible and their length would remain constant.
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Tides are the rise and fall of sea levels caused by the combined effects of gravitational forces exerted by the
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coastal port before starting computations. The pin position affects the amplitude and phase of the sinusoid.
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The Power of the Sea: Tsunamis, Storm Surges, Rogue Waves, and Our Quest to Predict Disasters
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put the machine into operation in 1910. It was used until 1965, when it was replaced by an
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The operator reads the height and time of high and low tides from these dials and scales.
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To compute those terms the Coast and Geodetic Survey designers incorporated the same "
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turned by the operator provides the power for the machine’s mechanical calculations.
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Description of the U.S. Coast and geodetic survey tide-predicting machine, Issue 2
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10.8 feet (3.3 m) long, 6.2 feet (1.9 m) high, 2 feet (0.6 m) wide
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just one term in the tide equation. Old Brass Brains computes 37 such terms.
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Around 1915, the machine was used to produce annual tide tables for 70 major
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To significantly reduce the work required to predict tides, in 1881
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of the term’s contribution to tide height above mean sea level,
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is the radial distance from the wheel's center to the peg,
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chain above and below the pulleys sums their influences.
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worldwide. Additional ports were added in later years.
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American Mathematical Society/Bill Casselman (2009),
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Feature Column: Monthly Essays on Mathematical Topics
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mechanism for generating sinusoidal motion component
314:(who later became Lord Kelvin) and later refined by 121: 113: 105: 97: 89: 81: 978: 959:per unit of time) and is determined by gears, and 947: 920: 893: 828: 784: 757: 714: 684: 657: 637: 606: 579: 541: 507: 894:{\displaystyle A_{1}\cos(\omega _{1}t+\phi _{1})} 1490:National Oceanic and Atmospheric Administration 1113:National Oceanic and Atmospheric Administration 549:is the height of mean sea level. For each term 296:National Oceanic and Atmospheric Administration 1416:American Mathematical Society/Tony Phillips, 8: 64: 1431:Operator with Tide-Predicting Machine No. 2 286:calculations with an electronic computer. 70: 1462: 970: 964: 955:is the rate at which the wheel turns (in 939: 933: 912: 906: 882: 866: 847: 841: 821: 776: 770: 749: 743: 706: 700: 676: 670: 650: 629: 623: 598: 592: 554: 533: 527: 490: 474: 455: 439: 423: 404: 388: 372: 353: 340: 334: 19:For broader coverage of this topic, see 1241:. U.S. Coast and Geodetic Survey. 1915. 1069: 1011: 167:United States Coast and Geodetic Survey 93:United States Coast and Geodetic Survey 55:United States Coast and Geodetic Survey 1203:10.1038/scientificamerican03071914-197 645:determines the frequency of the term, 63: 1270: 1268: 7: 1385:"Fourier Analysis of Ocean Tides II" 1266: 1264: 1262: 1260: 1258: 1256: 1254: 1252: 1250: 1248: 1231: 1229: 1227: 1225: 1223: 1221: 1219: 1180: 1178: 1176: 1174: 1172: 1140: 1138: 1136: 1134: 1132: 1130: 1100: 1098: 1096: 1094: 1092: 278:, including potential locations for 1425:Fourier Analysis of Ocean Tides III 1077:"The fall of 'Old Brass Brains'". 173:for predictions of tides in 1884. 132:Early U.S. tide-prediction efforts 14: 1418:Fourier Analysis of Ocean Tides I 1151:International Hydrographic Review 326:for sea height is represented as 1439:"The tide predictions for D-Day" 1051: 1038: 1026: 1014: 153:prior to the start of the year. 1185:Claudy, C. H. (March 7, 1914). 518:containing 10, 20 or even more 888: 859: 496: 467: 445: 416: 394: 365: 1: 1500:Silver Spring, Maryland (CDP) 1393:American Mathematical Society 580:{\displaystyle i=1,\ldots ,n} 259:125 days to perform by hand. 76:Tide Predicting Machine No. 2 65:Tide-Predicting Machine No. 2 27:Tide-Predicting Machine No. 2 117:2,500 pounds (1,134 kg) 1275:Fischer, E. G. (May 1912). 948:{\displaystyle \omega _{1}} 836:, can then be expressed as 715:{\displaystyle \omega _{i}} 638:{\displaystyle \omega _{i}} 1536: 150:United States Coast Survey 18: 16:Mechanical analog computer 1341:. Macmillan. p. 39. 979:{\displaystyle \phi _{1}} 785:{\displaystyle \phi _{i}} 685:{\displaystyle \phi _{i}} 69: 195:tide-predicting machines 33:, was a special-purpose 1318:www.co-ops.nos.noaa.gov 300:Silver Spring, Maryland 21:Tide-predicting machine 1515:Mechanical calculators 1437:Parker, Bruce (2011). 1337:Parker, Bruce (2012). 1145:Hicks, Steacy (1967). 996: 980: 949: 922: 895: 830: 809: 786: 759: 716: 686: 659: 639: 608: 581: 543: 509: 255: 226: 993: 981: 950: 923: 921:{\displaystyle A_{1}} 896: 831: 807: 787: 760: 758:{\displaystyle A_{i}} 717: 687: 660: 640: 609: 607:{\displaystyle A_{i}} 582: 544: 542:{\displaystyle H_{0}} 510: 252: 223: 185:History and mechanism 146:rotation of the Earth 963: 932: 905: 840: 820: 769: 742: 722:are determined from 699: 669: 649: 622: 591: 553: 526: 333: 280:amphibious invasions 1455:2011PhT....64i..35P 1293:1912PA.....20..269F 1191:Scientific American 1079:Product Engineering 738:. The coefficients 312:Sir William Thomson 215:electrical circuits 66: 59:electronic computer 35:mechanical computer 1106:"Old Brass Brains" 997: 976: 945: 918: 891: 826: 814:slotted yoke crank 810: 792:are determined by 782: 755: 712: 682: 655: 635: 604: 577: 539: 505: 306:Mathematical basis 256: 227: 1520:Harmonic analysis 1464:10.1063/PT.3.1257 1363:"NOAA Open House" 1348:978-0-230-12074-7 1281:Popular Astronomy 829:{\displaystyle t} 665:is the time, and 658:{\displaystyle t} 316:Sir George Darwin 129: 128: 1527: 1495:Analog computers 1476: 1466: 1404: 1403: 1401: 1399: 1383:Phillips, Tony. 1380: 1374: 1373: 1371: 1369: 1359: 1353: 1352: 1334: 1328: 1327: 1325: 1324: 1310: 1304: 1303: 1301: 1299: 1272: 1243: 1242: 1233: 1214: 1213: 1211: 1209: 1182: 1167: 1166: 1164: 1162: 1142: 1125: 1124: 1122: 1120: 1110: 1102: 1087: 1086: 1085:(1–6): 98. 1970. 1074: 1055: 1042: 1030: 1018: 985: 983: 982: 977: 975: 974: 954: 952: 951: 946: 944: 943: 927: 925: 924: 919: 917: 916: 900: 898: 897: 892: 887: 886: 871: 870: 852: 851: 835: 833: 832: 827: 794:Fourier analysis 791: 789: 788: 783: 781: 780: 764: 762: 761: 756: 754: 753: 732:equatorial plane 721: 719: 718: 713: 711: 710: 695:The frequencies 691: 689: 688: 683: 681: 680: 664: 662: 661: 656: 644: 642: 641: 636: 634: 633: 613: 611: 610: 605: 603: 602: 586: 584: 583: 578: 548: 546: 545: 540: 538: 537: 514: 512: 511: 506: 495: 494: 479: 478: 460: 459: 444: 443: 428: 427: 409: 408: 393: 392: 377: 376: 358: 357: 345: 344: 74: 67: 31:Old Brass Brains 29:, also known as 1535: 1534: 1530: 1529: 1528: 1526: 1525: 1524: 1480: 1479: 1436: 1413: 1408: 1407: 1397: 1395: 1382: 1381: 1377: 1367: 1365: 1361: 1360: 1356: 1349: 1336: 1335: 1331: 1322: 1320: 1312: 1311: 1307: 1297: 1295: 1274: 1273: 1246: 1235: 1234: 1217: 1207: 1205: 1184: 1183: 1170: 1160: 1158: 1144: 1143: 1128: 1118: 1116: 1115:. 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The 225:tides. 144:, and 114:Weight 47:chains 1505:Tides 1109:(PDF) 796:of a 728:orbit 264:ports 207:crank 51:tides 39:gears 1469:ISSN 1400:2016 1370:2016 1343:ISBN 1300:2016 1210:2016 1163:2016 1155:XLIV 1121:2016 765:and 736:Moon 294:The 138:Moon 109:1965 101:1910 85:1895 1459:doi 1199:doi 1195:110 854:cos 462:cos 411:cos 360:cos 241:Use 190:2. 142:Sun 1486:: 1467:. 1457:. 1447:64 1445:. 1441:. 1391:. 1387:. 1316:. 1285:20 1283:. 1279:. 1247:^ 1218:^ 1193:. 1189:. 1171:^ 1153:. 1149:. 1129:^ 1111:. 1091:^ 1083:41 1081:. 587:, 160:. 140:, 61:. 45:, 41:, 1475:. 1461:: 1453:: 1433:. 1427:. 1420:. 1402:. 1372:. 1351:. 1326:. 1302:. 1291:: 1212:. 1201:: 1165:. 1123:. 972:1 941:1 914:1 910:A 889:) 884:1 876:+ 873:t 868:1 860:( 849:1 845:A 824:t 778:i 751:i 747:A 708:i 678:i 653:t 631:i 600:i 596:A 575:n 572:, 566:, 563:1 560:= 557:i 535:0 531:H 500:+ 497:) 492:3 484:+ 481:t 476:3 468:( 457:3 453:A 449:+ 446:) 441:2 433:+ 430:t 425:2 417:( 406:2 402:A 398:+ 395:) 390:1 382:+ 379:t 374:1 366:( 355:1 351:A 347:+ 342:0 338:H 23:.

Index

Tide-predicting machine
mechanical computer
gears
pulleys
chains
tides
United States Coast and Geodetic Survey
electronic computer

Moon
Sun
rotation of the Earth
United States Coast Survey
bathymetry
Tide theories
United States Coast and Geodetic Survey
harmonic method
William Ferrel
tide-predicting machines
crank
Battery
electrical circuits
Gears, pulleys, and other components

ports
World War II
Pacific
amphibious invasions
National Oceanic and Atmospheric Administration
Silver Spring, Maryland

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