209:. The cataract runs at its own speed, but does not measure the resultant speed of the engine. The cataract has also been described as a 'water clock'. This assumes that the relationship between the cataract's operation and the engine's speed is fixed, which is a valid assumption for a beam engine as the cataract controls the timing of the engine's stroke, rather than a variable power or throttle valve. Where a governor controls such a throttle valve, as for the Watt governor, the speed of the engine depends on a complex and unpredictable relation between the engine load, the valve position and the varying efficiency of the engine. Such governors must use a closed-loop control if they are to maintain an effective and precise regulation.
63:
79:
105:, these valves are the upper steam inlet to the top of the cylinder, the equilibrium valve that links upper and lower portions of the cylinder, and the lower exhaust and condensing water injection valves, which share an arbor. Unlike most other steam engines, these engines could be run intermittently: making a single stroke before stopping and waiting for the valves to be restarted again. The speed of each power stroke or 'coming indoors' was a feature of the engine and was not easily varied, but there was no need for the engines to run continuously, stroke after stroke. This was a direct contrast to the
120:. It was an iron box in a cistern filled with water, with a plunger or piston set in the top and pressed downwards by a weight. The water within the pump could only escape through a small tap or valve. As the plunger gradually fell, its motion was passed upwards by a rocking lever and a rod to the valvegear in the middle chamber. Once the rod had risen sufficiently, this opened the first valve to admit steam into the upper part of the cylinder, beginning a new stroke.
323:
17:
156:
encountered these on his trip to
Cornwall in 1777. They were of a simpler type, these early cataracts or 'jack in the box' were a simple tumbling box: a wooden box on a pivot was filled with water through an adjustable cock. When the box was filled sufficiently to overbalance, the engine's injection
123:
Once the stroke had begun, the cataract's rocking lever was pushed downwards by the engine. This lifted the plunger, which acted as a suction pump within the cataract to refill the plunger box, through a flap valve from its surrounding cistern. The cistern was kept filled with water by the pump that
130:
The cataract's actuating rod also had a screw adjuster, which acted to vary the water injection time (Newcomen) or the phasing between the inlet and exhaust valves (Cornish). This could be used to give a longer and more effective condensation time, if the condensing water supply was warm, as in the
188:
Cataracts were also used as an over-speed safety device for direct-acting water pumps. A seesaw or 'differential' lever was placed between the pump's piston rod and a cataract adjusted for the pump's normal working speed. If the pump suddenly accelerated, owing to the pump bursting or similar, the
168:
used the simple tumbling box design of cataract for some years afterwards, to around 1779. After this other designs were used, including a water cataract where the same water was used and recycled continuously and also an air cataract using a circular bellows. An air cataract of this type was
74:
beam engine spanned four floors. The cylinder and the engine driver's usual working position were located in the 'bottom chamber', approximately at ground level. Above this were the 'middle chamber', with the cylinder top cover and 'top nozzle' (the upper valve chest), and above that the 'top
112:
Use of a cataract could allow an engine to be operated at only a third of its ungoverned speed. When pumping load was variable, cataracts could also be connected and disconnected as required, allowing the engine to work at full speed for a period and then stopped in between.
260:
and similar uses could vary, closed-loop control such as the engine speed-based centrifugal governor was also needed. The cataract was thus not used on rotative engines, not even where single-acting
Cornish winding engines were still used in Cornwall.
109:, and the rotary nature of almost all other steam engines. With the original Newcomen cycle, the speed of the return stroke varied according to the boiler pressure, although this still did not affect the strength or speed of the power stroke.
75:
chamber' or beam chamber. The cataracts were located in the lowest part of the engine house, in a chamber below the bottom chamber, along with the exhaust pipe. This space was awkward to access and not visited in normal operation.
293:
This was the initiation of a stroke with the
Cornish cycle. For a Newcomen engine, the cataract triggered the water injection valve that caused condensation in the cylinder, and thus the beginning of the power
101:
are attached to this rod. These tappets strike long curved iron levers or 'horns' that are carried on three horizontal shafts or 'arbors'. Each arbor works one of the engine's valves. For the
252:
With a rotative engine, it was necessary to control the rate at which an engine moved throughout its stroke, not merely to vary the timing between strokes. This required the use of a
127:
The water outlet valve was controlled by a rod from the bottom chamber. This was used by the engine's driver to control the working speed, according to the work required.
265:
189:
piston would overtake the cataract and the action of the differential lever would then close the pump's steam inlet valve and stop the pump, limiting possible damage.
185:, at least where this was associated with steam engines and their governors. They were used as a damping device to avoid over-sensitivity with centrifugal governors.
264:
Cornish engines were not amenable to control by a throttle valve, as their operating cycle depended on the condensation time more than a throttled steam supply.
731:
170:
217:
One advantage of the independent and open loop nature of the cataract's control was that two engines could be adjusted to run in synchronisation, but in
268:
also had no easy means to drive a centrifugal governor. For these reasons the cataract remained in service for as long as the
Cornish engine did.
1446:
644:
284:
Some
Cornish winding engines had their valves arranged across different number of arbors, although their basic operation remains the same.
724:
1606:
432:
405:
1479:
1616:
874:
1512:
1285:
717:
1181:
1176:
592:
521:
1324:
1640:
1552:
1681:
1506:
62:
1611:
1255:
496:
131:
Summer. This adjustment appears to have been poorly understood though, and little used by the engine drivers.
1500:
899:
1487:
1275:
1625:
1343:
1315:
1199:
811:
754:
1214:
152:'s time, and they may be another of the developments to Newcomen's engine for which he was responsible.
1093:
54:, in that it does not control the speed of the engine's stroke, but rather the timing between strokes.
173:. The plunger pump design of cataract had appeared in Cornwall by 1785, but was not Watt's invention.
78:
1645:
1634:
1492:
1191:
804:
1686:
1419:
1351:
1655:
1650:
1571:
1440:
1295:
1240:
962:
918:
648:
83:
1458:
1219:
1660:
1558:
1432:
1399:
1280:
982:
869:
246:
97:. This is a vertical rod, hung from the beam, and moving in parallel to the piston. Adjustable
652:
1691:
1525:
1250:
1171:
1144:
941:
859:
769:
304:
241:, it was not until 1788 when Watt was the first to apply it to a steam engine. This was the '
1585:
1270:
1209:
1070:
936:
884:
821:
774:
401:
230:
106:
51:
8:
1579:
1113:
987:
904:
894:
206:
1075:
71:
36:
671:
669:
1376:
1224:
1163:
1118:
1098:
1085:
1065:
1047:
992:
946:
816:
759:
588:
517:
492:
202:
1452:
1413:
1139:
1057:
1027:
879:
666:
165:
512:
Kelly, Maurice (2002). "Appendix A: Crofton Nº 1 Boulton & Watt Engine".
1358:
1300:
1108:
1103:
1017:
972:
428:
328:
145:
1544:
1393:
1365:
1042:
864:
854:
764:
253:
198:
40:
21:
1675:
1332:
1305:
1204:
1123:
959:
102:
1533:
1290:
1037:
1022:
977:
831:
826:
740:
149:
117:
16:
1385:
956:
926:
799:
578:
576:
574:
257:
44:
32:
201:. However unlike the better-known Watt centrifugal governor, this is an
1464:
1407:
1032:
967:
951:
889:
846:
836:
242:
221:. With pumping engines, this gave a more even output to their pumping.
153:
90:
571:
434:
A treatise on the steam engine: historical, practical, and descriptive
1260:
1245:
234:
218:
148:
in
Cornwall, although their inventor is unknown. They were known in
93:(or 'working gear') of a Newcomen or Cornish engine is based on the
1149:
238:
303:
These were the type of small reciprocating pump commonly used as
182:
709:
256:
in the steam supply, controlled by the governor. As the load on
1265:
1002:
98:
559:
784:
383:
381:
31:
was a speed governing device used for early single-acting
613:
378:
366:
197:
The cataract, like most regulators, is an example of a
549:
547:
545:
682:
700:'Victoria' Pumping Engine, East London Waterworks, (
625:
601:
530:
482:
480:
465:
412:. Vol. II. Blackie & Son. pp. 275–276.
336:
318:
542:
453:
441:
477:
423:
421:
419:
353:
351:
245:', an early rotative engine now preserved in the
1673:
676:
582:
565:
516:. Camden Miniature Steam Services. p. 21.
505:
416:
348:
50:The cataract is distinctly different from the
725:
362:. Glasgow: Williams Collins. pp. 60–61.
360:Steam and the Steam Engine: Land and Marine
732:
718:
587:. Moorland Publishing. pp. 183–184.
181:The term 'cataract' became a synonym for
77:
61:
15:
1607:Glossary of steam locomotive components
688:
486:
388:
372:
342:
307:and often described as the 'Weir' type.
224:
1674:
583:Dickinson, H.W.; Jenkins, R. (1981) .
406:"3: A Treatise on Engines and Boilers"
116:The cataract itself resembled a small
713:
701:
631:
619:
607:
553:
536:
511:
471:
459:
447:
427:
400:
357:
645:"The Grand Junction 100 inch Engine"
192:
233:was already known from its use for
82:Valvegear, horns and arbors of the
13:
1459:National Museum of Scotland engine
212:
176:
139:
14:
1703:
739:
1641:List of steam technology patents
437:. Vol. 1. pp. 188–189.
321:
694:
637:
585:James Watt and the Steam Engine
297:
287:
144:The cataract first appeared on
124:the engine itself was working.
1626:Murdoch's model steam carriage
1612:History of steam road vehicles
566:Dickinson & Jenkins (1927)
394:
278:
134:
70:The typical installation of a
1:
1553:Murray's Hypocycloidal Engine
489:Steam Engines and Waterwheels
314:
1276:Return connecting rod engine
677:Dickinson & Jenkins 1927
514:The Non-Rotative Beam Engine
491:. Moorland. pp. 33–34.
57:
7:
1200:Condensing steam locomotive
10:
1708:
1507:"Coalbrookdale Locomotive"
487:Woodall, Frank D. (1975).
157:valve would be triggered.
1599:
1570:
1543:
1524:
1513:"Pen-y-Darren" locomotive
1478:
1431:
1384:
1375:
1342:
1323:
1314:
1233:
1190:
1182:Single- and double-acting
1162:
1132:
1084:
1056:
1010:
1001:
917:
845:
792:
783:
747:
266:Non-rotative beam engines
1352:Newcomen Memorial Engine
271:
1656:Timeline of steam power
1651:Stationary steam engine
1534:Woolf's compound engine
1441:Soho Manufactory engine
1296:Steeple compound engine
963:straight line mechanism
649:Kew Bridge Steam Museum
160:
84:Crofton Pumping Station
1682:Steam engine governors
1661:Water-returning engine
1635:Lean's Engine Reporter
1408:Chacewater Mine engine
1281:Six-column beam engine
305:boiler feedwater pumps
247:Science Museum, London
86:
67:
66:Cataract, c. 1875
24:
20:Bottom chamber of the
1501:London Steam Carriage
402:Clark, Daniel Kinnear
358:Evers, Henry (1875).
81:
65:
19:
1447:Bradley Works engine
1271:Reciprocating engine
1094:Babcock & Wilcox
937:Centrifugal governor
231:centrifugal governor
225:Centrifugal governor
107:rotative beam engine
52:centrifugal governor
43:. It was a kind of
988:Sun and planet gear
704:, pp. 275–276)
679:, pp. 220–223)
622:, pp. 67, 182.
207:closed-loop control
37:atmospheric engines
1488:Richard Trevithick
1086:Water-tube boilers
900:Gresley conjugated
171:Ale and Cakes Mine
87:
68:
25:
1669:
1668:
1595:
1594:
1474:
1473:
1158:
1157:
1058:Fire-tube boilers
913:
912:
391:, pp. 31–33)
375:, pp. 29–30.
193:Open loop control
169:supplied for the
1699:
1619:fardier à vapeur
1453:Whitbread Engine
1414:Smethwick Engine
1382:
1381:
1321:
1320:
1140:Feedwater heater
1008:
1007:
790:
789:
734:
727:
720:
711:
710:
705:
698:
692:
686:
680:
673:
664:
663:
661:
660:
651:. Archived from
641:
635:
629:
623:
617:
611:
605:
599:
598:
580:
569:
563:
557:
551:
540:
534:
528:
527:
509:
503:
502:
484:
475:
469:
463:
457:
451:
445:
439:
438:
425:
414:
413:
410:The Steam Engine
398:
392:
385:
376:
370:
364:
363:
355:
346:
340:
331:
326:
325:
324:
308:
301:
295:
291:
285:
282:
166:Boulton and Watt
146:Newcomen engines
1707:
1706:
1702:
1701:
1700:
1698:
1697:
1696:
1687:Cornish engines
1672:
1671:
1670:
1665:
1591:
1566:
1539:
1520:
1470:
1427:
1371:
1359:Fairbottom Bobs
1344:Newcomen engine
1338:
1310:
1256:Expansion valve
1229:
1215:Watt's separate
1186:
1154:
1128:
1080:
1052:
997:
973:Parallel motion
909:
860:Stephenson link
841:
779:
748:Operating cycle
743:
738:
708:
699:
695:
687:
683:
674:
667:
658:
656:
643:
642:
638:
630:
626:
618:
614:
606:
602:
595:
581:
572:
564:
560:
552:
543:
535:
531:
524:
510:
506:
499:
485:
478:
470:
466:
458:
454:
446:
442:
426:
417:
399:
395:
386:
379:
371:
367:
356:
349:
341:
337:
329:Cornwall portal
327:
322:
320:
317:
312:
311:
302:
298:
292:
288:
283:
279:
274:
227:
215:
213:Synchronisation
195:
179:
177:Later cataracts
163:
142:
140:Early cataracts
137:
60:
41:Cornish engines
35:, particularly
12:
11:
5:
1705:
1695:
1694:
1689:
1684:
1667:
1666:
1664:
1663:
1658:
1653:
1648:
1643:
1638:
1631:
1630:
1629:
1623:
1609:
1603:
1601:
1597:
1596:
1593:
1592:
1590:
1589:
1583:
1576:
1574:
1568:
1567:
1565:
1564:
1556:
1549:
1547:
1541:
1540:
1538:
1537:
1530:
1528:
1522:
1521:
1519:
1518:
1517:
1516:
1510:
1504:
1498:
1484:
1482:
1476:
1475:
1472:
1471:
1469:
1468:
1462:
1456:
1450:
1444:
1437:
1435:
1429:
1428:
1426:
1425:
1417:
1411:
1405:
1397:
1394:Kinneil Engine
1390:
1388:
1379:
1373:
1372:
1370:
1369:
1366:Elsecar Engine
1363:
1355:
1348:
1346:
1340:
1339:
1337:
1336:
1329:
1327:
1318:
1312:
1311:
1309:
1308:
1303:
1298:
1293:
1288:
1286:Steeple engine
1283:
1278:
1273:
1268:
1263:
1258:
1253:
1248:
1243:
1237:
1235:
1231:
1230:
1228:
1227:
1222:
1217:
1212:
1207:
1202:
1196:
1194:
1188:
1187:
1185:
1184:
1179:
1174:
1168:
1166:
1160:
1159:
1156:
1155:
1153:
1152:
1147:
1145:Feedwater pump
1142:
1136:
1134:
1130:
1129:
1127:
1126:
1121:
1116:
1111:
1106:
1101:
1096:
1090:
1088:
1082:
1081:
1079:
1078:
1073:
1068:
1062:
1060:
1054:
1053:
1051:
1050:
1045:
1040:
1035:
1030:
1025:
1020:
1014:
1012:
1011:Simple boilers
1005:
999:
998:
996:
995:
993:Watt's linkage
990:
985:
980:
975:
970:
965:
954:
949:
944:
942:Connecting rod
939:
934:
929:
923:
921:
915:
914:
911:
910:
908:
907:
902:
897:
892:
887:
882:
877:
872:
867:
862:
857:
851:
849:
843:
842:
840:
839:
834:
829:
824:
819:
814:
809:
808:
807:
796:
794:
787:
781:
780:
778:
777:
772:
767:
762:
757:
751:
749:
745:
744:
737:
736:
729:
722:
714:
707:
706:
693:
689:Woodall (1975)
681:
665:
636:
634:, p. 281.
624:
612:
610:, p. 365.
600:
593:
570:
558:
541:
539:, p. 169.
529:
522:
504:
497:
476:
474:, p. 203.
464:
462:, p. 339.
452:
450:, p. 187.
440:
415:
393:
377:
373:Woodall (1975)
365:
347:
343:Woodall (1975)
334:
333:
332:
316:
313:
310:
309:
296:
286:
276:
275:
273:
270:
254:throttle valve
226:
223:
214:
211:
205:, rather than
199:servomechanism
194:
191:
178:
175:
162:
159:
141:
138:
136:
133:
103:Cornish cycles
59:
56:
22:Elsecar Engine
9:
6:
4:
3:
2:
1704:
1693:
1690:
1688:
1685:
1683:
1680:
1679:
1677:
1662:
1659:
1657:
1654:
1652:
1649:
1647:
1644:
1642:
1639:
1637:
1636:
1632:
1627:
1624:
1621:
1620:
1615:
1614:
1613:
1610:
1608:
1605:
1604:
1602:
1598:
1587:
1584:
1581:
1578:
1577:
1575:
1573:
1569:
1562:
1561:
1557:
1554:
1551:
1550:
1548:
1546:
1542:
1535:
1532:
1531:
1529:
1527:
1523:
1514:
1511:
1508:
1505:
1502:
1499:
1496:
1495:
1494:Puffing Devil
1491:
1490:
1489:
1486:
1485:
1483:
1481:
1480:High-pressure
1477:
1466:
1463:
1460:
1457:
1454:
1451:
1448:
1445:
1442:
1439:
1438:
1436:
1434:
1433:Rotative beam
1430:
1423:
1422:
1418:
1415:
1412:
1409:
1406:
1403:
1402:
1398:
1395:
1392:
1391:
1389:
1387:
1383:
1380:
1378:
1374:
1367:
1364:
1361:
1360:
1356:
1353:
1350:
1349:
1347:
1345:
1341:
1334:
1333:Savery Engine
1331:
1330:
1328:
1326:
1322:
1319:
1317:
1313:
1307:
1306:Working fluid
1304:
1302:
1299:
1297:
1294:
1292:
1289:
1287:
1284:
1282:
1279:
1277:
1274:
1272:
1269:
1267:
1264:
1262:
1259:
1257:
1254:
1252:
1249:
1247:
1244:
1242:
1239:
1238:
1236:
1232:
1226:
1223:
1221:
1218:
1216:
1213:
1211:
1208:
1206:
1203:
1201:
1198:
1197:
1195:
1193:
1189:
1183:
1180:
1178:
1175:
1173:
1170:
1169:
1167:
1165:
1161:
1151:
1148:
1146:
1143:
1141:
1138:
1137:
1135:
1131:
1125:
1122:
1120:
1117:
1115:
1112:
1110:
1107:
1105:
1102:
1100:
1097:
1095:
1092:
1091:
1089:
1087:
1083:
1077:
1074:
1072:
1069:
1067:
1064:
1063:
1061:
1059:
1055:
1049:
1046:
1044:
1041:
1039:
1036:
1034:
1031:
1029:
1026:
1024:
1021:
1019:
1016:
1015:
1013:
1009:
1006:
1004:
1000:
994:
991:
989:
986:
984:
983:Rotative beam
981:
979:
976:
974:
971:
969:
966:
964:
961:
960:hypocycloidal
958:
955:
953:
950:
948:
945:
943:
940:
938:
935:
933:
930:
928:
925:
924:
922:
920:
916:
906:
903:
901:
898:
896:
893:
891:
888:
886:
883:
881:
878:
876:
873:
871:
868:
866:
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746:
742:
741:Steam engines
735:
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728:
723:
721:
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712:
703:
697:
691:, p. 49.
690:
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655:on 2018-09-25
654:
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621:
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594:0-903485-92-3
590:
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579:
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568:, p. 46.
567:
562:
556:, p. 56.
555:
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523:0-9536523-3-5
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229:Although the
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55:
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48:
46:
42:
38:
34:
30:
23:
18:
1692:Beam engines
1646:Modern steam
1633:
1618:
1580:Porter-Allen
1559:
1493:
1420:
1400:
1357:
1291:Safety valve
1220:"Pickle-pot"
1114:Thimble tube
931:
696:
684:
657:. Retrieved
653:the original
639:
632:Clark (1892)
627:
620:Clark (1892)
615:
608:Clark (1892)
603:
584:
561:
554:Kelly (2002)
537:Clark (1892)
532:
513:
507:
488:
472:Clark (1892)
467:
460:Clark (1892)
455:
448:Farey (1827)
443:
433:
409:
396:
389:Woodall 1975
368:
359:
338:
299:
289:
280:
263:
258:mill engines
251:
228:
216:
196:
187:
180:
164:
143:
129:
126:
122:
118:plunger pump
115:
111:
94:
88:
69:
49:
33:beam engines
28:
26:
1377:Watt engine
1177:Oscillating
1133:Boiler feed
978:Plate chain
957:Tusi couple
870:Walschaerts
755:Atmospheric
429:Farey, John
135:Development
72:house-built
45:water clock
1676:Categories
1586:Ljungström
1572:High-speed
1465:Lap Engine
1421:Resolution
1325:Precursors
1210:Kirchweger
1172:Locomotive
1119:Three-drum
1099:Field-tube
1066:Locomotive
1048:Lancashire
968:Link chain
952:Crankshaft
919:Mechanisms
847:Valve gear
702:Clark 1892
659:2017-01-12
498:0903485354
315:References
243:Lap Engine
154:James Watt
91:valve gear
1617:Cugnot's
1560:Salamanca
1261:Hydrolock
1246:Crosshead
1192:Condenser
1028:Egg-ended
239:windmills
219:antiphase
203:open-loop
58:Operation
1600:See also
1526:Compound
1401:Old Bess
1241:Blowback
1164:Cylinder
1150:Injector
1109:Stirling
1104:Sentinel
1018:Haystack
932:Cataract
905:Southern
895:Caprotti
770:Compound
431:(1827).
404:(1892).
95:plug rod
29:cataract
1316:History
1225:Surface
1043:Cornish
1003:Boilers
885:Corliss
822:Corliss
805:D slide
775:Uniflow
765:Cornish
294:stroke.
183:dashpot
150:Smeaton
99:tappets
1628:(1784)
1622:(1769)
1588:(1908)
1582:(1862)
1563:(1812)
1555:(1805)
1545:Murray
1536:(1803)
1515:(1804)
1509:(1803)
1503:(1803)
1497:(1801)
1467:(1788)
1461:(1786)
1455:(1785)
1449:(1783)
1443:(1782)
1424:(1781)
1416:(1779)
1410:(1778)
1404:(1777)
1396:(1768)
1368:(1795)
1362:(1760)
1354:(1725)
1335:(1698)
1301:Stroke
1266:Piston
1251:Cutoff
1124:Yarrow
1076:Launch
1071:Scotch
832:Sleeve
827:Poppet
812:Piston
793:Valves
785:Valves
591:
520:
495:
235:water-
1234:Other
1038:Flued
1023:Wagon
947:Crank
890:Lentz
880:Baker
875:Allan
800:Slide
272:Notes
1386:Beam
927:Beam
837:Bash
817:Drop
760:Watt
589:ISBN
518:ISBN
493:ISBN
237:and
161:Watt
89:The
39:and
1205:Jet
1033:Box
865:Joy
855:Gab
1678::
668:^
647:.
573:^
544:^
479:^
418:^
408:.
380:^
350:^
249:.
47:.
27:A
733:e
726:t
719:v
675:(
662:.
597:.
526:.
501:.
387:(
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