STEAM-HAMMER 



STEATITE 



707 



hand-wheel was able to rapidly alter the vertical 

 height of the tappet-lever, and therefore the length 

 of fall. The second point i.e. the instant rise of 

 the tup after the blow was obtained in a very 

 ingenious fashion by taking advantage of the 

 inertia of a rocking lever carried on the tup. When 

 the hammerhead struck the metal on the anvil, 

 this lever, by virtue of its momentum, continued 

 to move down against the resistance of a light 

 spring, and in doing so set in motion a system of 

 levers which at once opened the valve, admitted 

 steam under the piston, and again raised the tup. 

 The system of levers could also be operated by 

 hand ; thus steam could be admitted under the 

 piston, and the hammer checked and stopped at 

 any point of its descent. This gearing reduced 

 enormously the labour of operating the hammer, 

 increased greatly the number of blows which could 

 be given in any time, and brought it so completely 

 under control that while at one instant the tup 

 could be brought down so gently that it failed to 

 crack an egg on the anvil, the next blow could be 

 made to snake the very ground on which the 

 hammer stood with the violence of the shock. 

 Snch satisfaction was given by this remarkable 

 tool that orders began at once to flow in from all 

 parts of the country. The hammer remained in 

 this condition, with slight improvements in details, 

 till 1853, when Wilson devised and applied to 

 steam-hammers what is known as the ' circular 

 balanced valve,' in substitution for the flat slide- 

 valve hitherto used. The steam-pressure on the 

 back of the old flat valve was so great that the 

 friction during any movement of the valve was 

 excessive. This made the expenditure of power in 

 opening and closing the valve very heavy and 

 wasteful, and was one of the chief reasons for 

 introducing the automatic device. By the use of 

 the balanced circular valve the movements of open- 

 ing and closing became so easy that they could be 

 readily and rapidly made by hand-power, and as a 

 result the somewhat complex automatic gear was 

 abandoned, the mechanism being entirely operated 

 by hand-gearing only. A patent was taken out for 

 this in 1856. 



The next improvement, made with the object 

 of greatly increasing the power of the hammer 

 without increasing the weight of the tup, was 

 introduced in 1861 by Wilson. It is known as the 

 double-acting hand-year motion. In this arrange- 

 ment steam is admitted under the piston as before 

 to raise it ; then just at the instant when the fall 

 is about to take place, by slightly increasing the 

 travel of the hand-lever, steam is admitted into the 

 cylinder above the piston. The effect of this steam- 

 pressure on the top of the piston is to enormously 

 increase the intensity of the blow, and hence the 

 capacity of the hammer, since the hammerhead 

 will descend with much greater velocity, and there- 

 fore possess much more energy when it strikes. 

 For example, a double-acting 5-ton hammer may 

 become equal in power to a single-acting 10- or 15- 

 ton one. It should be stated that steam-hammers 

 are commercially rated by the weight of the falling 

 tup, piston, and rod, even when they are fitted to 

 be used as double-acting ; so that the power of the 

 blow is not known unless the range of fall is also 

 stated, and whether it is single or double acting. 



The figure shows the form of the modern simpli- 

 fied steam-hammer. They are often of great size ; 

 80-ton ones have been made, double-acting, possess- 

 ing therefore enormous power, as at Essen in Ger- 

 many and Creusot in France, as well as in the 

 United Kingdom ; one in Pennsylvania, the largest 

 made up till 1891, of 125 tons. Of recent years 

 powerful hydraulic presses have been substituted 

 for these big hammers for heavy forging work, but 

 many engineers still prefer the hammering action. 



In Condie's hammers, a patent for which was 

 taken out in 1846, the piston is stationary, while 

 the cylinder with the tup attached to it is the 

 moving piece. Since the expiration of Nasmyth's 

 patent great numbers of different types of hammers 

 have been put on the market, but they differ 

 from one another principally only in details, the 

 general arrangement being the same. The modern 



Steam-hammer, with Wrought-iron Framing. 



double-acting hammer can usually be worked in 

 four ways : (a) as a single-acting one, no steam 

 being admitted above the piston-, the falling weight 

 therefore alone acting, and again the blow may be 

 made a dead one or a cushioned and elastic one, 

 the latter effect being obtained by admitting steam 

 under the piston before the blow is finished to 

 cushion the piston and cause the tup to rebound 

 the instant it has struck; (6) as a double-acting 

 hammer, by using steam-pressure above the piston 

 during the fall, giving also either dead or elastic 

 blows. 



Steam-navigation. See SHIPBUILDING. 



Steam-navvy. See EXCAVATORS. 



Steam-plough. See PLOUGH. 



Stearin, C 3 H 5 (O-C 18 H 35 O) 3 , is one of the fats 

 occurring in animals and plants. Like the other 

 fats it may be regarded as an ether of the triatomic 

 alcohol glycerine, all three hydroxyl molecules 

 being replaced by radicles of the fatty acid stearic 

 acid, CVSjsO-OH. 



OH 



OH = Glycerine. 

 OH 



C 3 H S 



It is the chief constituent of the more solid fats, 

 such as mutton suet, and is characterised by its 

 high melting-point from 53 to 66 C. by its 

 slight solubility in alcohol as compared with 

 palmitin and olein, and by its crystallising from 

 its alcoholic solution in the form of brilliant 

 quadrangular plates. Like the other fats it may 

 be readily split into glycerine and a fatty acid, and 

 if an alkali be present the acid combines with this 

 to form a soap. Stearoptene is the crystalline solid 

 substance which separates from volatile Oils (q.v.) 

 on long standing or at low temperatures. For 

 Physiology of Fats, see FATS. See also CANDLES. 

 Steatite, or SOAPSTONE, a compact or massive 

 variety of Talc (q.v.), is a hydrous silicate of mag- 

 lesia. It is found massive, or sometimes assuming 

 ;he forms of the crystals of other minerals which it 

 'ias replaced. It is plentiful in many parts of the 



