706 



STEAM-ENGINE 



STEAM-IIAMMKK 



of work done, and not of the rate at which it is 

 done. It is the numlter <>f foot-pounds of nett 

 work resulting from the consumption of a given 

 quantity of coal, usually either a bushel of 94 IK. 

 or a r\\ i. At the beginning of the I'.it h century the 

 maximum duty that had peen attained hy any 

 Cornish engine was 20 millions of foot-pounds i>er 

 cwt. <>f mill, Kut six timea that duty has since 

 lieen occasionally obtained. In these engines it is 

 the actual nett work done which is taken into 

 account ; the duty would be 20 or -'."> per cent. 

 go-ater if the total load on the steam-piston had 

 been considered instead. 



For engines whose power can only be measured 

 by the indicator the standard of economy is the 

 number of pounds of steam used per hour per indi- 

 cated horse-power. A first-class mm condensing 

 engine, working with steam of about 100 Ib. pressure, 

 uses about 22 IK. of steam per i.b.p. per hour, which 

 i- reduced to 17 or 18 IK. by the employment of con- 

 densation. Occasionally better results than these 

 are obtained, but in ordinary good work the figures 

 are at least 25 per cent, greater, and they are often 

 more than double as great. In any case economy 

 is only to l>e obtained if the engines are worked at 

 or near their full power, and with the full steam- 

 pressure for which they are intended. It, is very 

 common to speak of the amount of coal burned per 

 i.h.p. per hour, and this is a very important quan- 

 tity. It is, however, a measure of the combined 

 economy of a boiler and engine, and not of the 

 economy of an engine alone. A pound of Welsh 

 coal can be mode to evaporate 10 to 11 Ib. of water 

 under special conditions. In ordinary circumstance* 

 and over long periods the evaporation is more like 

 7J to 9 Ib. of water per Ib. coal. Inferior fuels, or 

 even good fuel badly burned, give, of course, very 

 much lower results. 



For other points, see articles STEAM. ENERGY, THKHMO- 

 DTNAMICS, GAH, FUEL, SAFETY-VALVE, HORSE- POWER, 

 INDICATOR-DIAGRAM, INJKCTOB, AIR-ENGINE, GAS- 

 K.W.IXE, RAILWAYS, SHIPBUILDING, kc. See also for 

 theory, Cotterall's Steam Emiitte <u a Heat Engine, 

 Rankine's Steam Engine, and Northcott's Strum Eivjint ; 

 Beaton'* Marine Enijine : Galloway's The Steam Eniine 

 anditt Inventnrt ( 1881 ) ; Thurrton'a Hittory of the Kti nut 

 Eru.iine ( N. Y. 1878 ) ; Hughes's Modern Loromotive ( 1894 ) ; 

 Kwing's Steam Eiujiiu and other Heat Enginet ( 1894 ). 



Steam-hammer, a contrivance which has 

 done more perhaps than any other mechanical 



invention of modern times to develop the wonder- 

 ful resources of the iron trade. The first idea of a 

 steam hammer appears to have been due to James 

 Watt, the great father of engineers, and w a- 

 patented by him in 1784. In 1808 William Deverell, 

 'an engineer of Surrey,' also took out a patent for 

 one ; but in neither case does it appear that steam- 

 hammers were actually const ructed, though in both 

 specifications a direct-acting steam hammer is, so 

 to speak, sketched in words, From this time till 

 1839 the idea seems to have been entirely lost sight 

 of. It was then again taken up by Mr James 

 Nasmyth, of the liridgewater Foundry near Man- 

 chester. Mr Humphries, engineer to the Great 

 Western Steamship Co., who had Keen unable to 

 induce any torge master to undertake the heavy 

 forging* required for the intermediate paddle- 

 shaft* of the Grent Britain steamship, then in 

 course of construction, applied to his friend 

 Nasmyth for suggestions as to how this diflieulty 

 might lie overcome. Nasmyth made a sketch of 

 a hammer o|>erated by steam power, and sent 

 his sketch to Humphries, who, along with Brunei 

 and others, heartily approved of tin* scheme; but 

 in consequence of a change of design, and the 

 substitution of a screw for paddles, the proposed 

 tieavy shafts were not required, and the hammer 

 was not then constructed. The scheme was then 



offered to many forge-masters and engineers ; hut 

 they failed to duly appreciate its value and im; 

 ance, and the hammer remained a mere sketch in 

 Na-m\ih's ' scheme liook ' till 1842. In thcspiing 

 of that year Nasmyth, much to his surprise, s., 

 Creiisot in !' ranee a steam hammer at work, which 

 had IM-CII built ill accordance with a copy of his 

 own rough ' MhaOM-book ' sketch, Hindi* by two 

 French engineers dining a business visit to the, 

 Hridgewater works. Nat-myth had Ix-en previously 

 urged by his friends to protect his invention by 

 a patent, and immediately on his return to F.ngland 

 secured one in June 1842. It is interesting to noie 

 that this patent mentions the u-e of steam ali\e 

 the piston to increase the intensity of the blow, 

 and also a self-acting arrangement. The first 

 English steam-hammer under this patent was made 

 at the Hridgewater Foundry early in 1S43; but, 

 although considered an improvement upon the old 

 'helves' hitherto used for forging purposes ( see 

 HAMMKR), it was far from living a perfect tool. 

 The principle on which the hammer worked was 

 as follows: two vertical columns or flames sup- 

 ported an inverted vertical steam -c\ linder : the 

 hammerhead or tup was attached to the m.l of the 

 pi-ton working in this, while vertically beneath, 

 supported on the floor, was the anvil ; steam 

 admitted beneath the piston raised it, and with it 

 the hammerhead, at some chosen point the supply 

 was en t oil' and the steam beneath the pi- ton allowed 

 to escape into the atmosphere, the piston and tup 

 at once fell and gave a blow to anything placed on 

 the anvil ; the force of this blow simply depended 

 on the weight of the tup and the height to which 

 it was raised In-fore being allowed to fall. The 

 admission and exhaust of the steam \\as controlled 

 by means of an ordinary slide valve worked by 

 a long lever, requiring great labour and constant 

 attention in order to give the blow required ; some 

 automatic contrivance was considered necessary to 

 secure complete command over the power of the 

 blow, and to insure that the instant the blow was 

 struck the block should immediately rise again, 

 thus preventing the heat in the ma of iron on 

 the anvil lieing reduced by the cold face of the 

 block. The peculiar difliculty of securing a true 

 automatic arrangement will M seen, when it is 

 considered that the time of descent of the hammer 

 iiiust vary with almost every blow that is struck ; 

 for the piece on the anvil becomes thinner and 

 thinner by each succeeding blow, and with flat liars 

 a blow is first given on the flat side and then on 

 the edge, the difference in the fall of the hammer 

 in I he two rases being often many inches; further- 

 more the hammer must be under perfect control at 

 all times. 



It is stated that Nasmyth failed to devise a 

 satisfactory automatic arrangement, but Mr Koliert 



Wilson, then ongin -ing manager of the works, 



afterwards managing director and successor to 

 Nasmyth on his retirement, who was assisting to 

 work out the details, lifter a week's .scheming 

 solved the difficult problem. His automatic de\ ice 

 was first tried on a small ."> c\\ t. hammer, the second 

 one made, and as it at once proved successful was 

 immediately fitted to several fi ton hammers then 

 under order; tin- first one actually made for sale 

 was delivered to the Low Moor lionworks on 

 August 18, 1843, and answered even expectation. 

 This improvement was covered by a patent taken 

 put by Nasmyth in July 1843. The time of releas- 

 ing steam from under the platan, and therefore the 

 height of fall, was regulated by a tappet-lever 

 carried by two vertical screws. The tup in ite 

 upward movement struck this lever, I hereby mov- 

 ing the valve, cutting off the steam, and also 

 releasing it so as to allow the hammerhead to fall. 

 The attendant turning these screws by a small 



