and makers of timekeepers who had produced 

 astonishingly accurate work, but such work comprised 

 relatively small items, all being within the scope of 

 a bench lathe, hand tools, and superb handwork. 

 The rapid advancement of machine tools, which 

 greatly expanded the scope of the machine-building 

 art, began during the Boulton and Watt partnership 

 (1775-1800). 



In April 1775 the skirmish at Concord between 

 American colonists and British redcoats marked the 

 beginning of a war that was to determine for the 

 future the course of political events in the Western 

 Hemisphere. 



Another event of April 1775 occurring in Birming- 

 ham now appears to have been one that marked the 

 beginning of a new era of technological advance. 

 It was near the end of this month that Boulton, at 

 the Soho Works, wrote to his partner and commented 

 upon receiving the cast iron steam engine cylinder 

 that had been finished in John Wilkinson's boring 

 mill: 



... it seems tolerably true, but is an inch thick and weighs 

 about 10 cwt. Its diameter is about as much above i8 

 inches as the tin one was under, and therefore it is become 

 necessary to add a brass hoop to the piston, which is made 

 almost two inches broad.'' 



This cylinder indeed marked the turning point in 

 the discouragingly long development of the Watt 

 steam engine, which for 10 years had occupied nearly 

 all of Watt's thoughts and all the time he could spare 

 from the requirements of earning a living. Although 

 there were many trials ahead for the firm of Boulton 

 and Watt in further developing and perfecting the 

 steam engine, the crucial problem of leakage of 

 steam past the piston in the cylinder had now been 

 solved by Wilkinson's new boring mill, which was 

 the first large machine tool capable of boring a cylin- 

 der both round and straight. 



The boring mill is pertinent to the development 

 of linkages "in great," being the first of a new class 

 of machine tools that over the next 50 or 60 years 

 came to include nearly all of the basic types of heavy 

 chip-removing tools that are in use today. The 

 development of tools was accelerated by the inherent 

 accuracy required of the linkages that were originated 

 by Watt. Once it had been demonstrated that a 

 large and complex machine, such as the steam 

 engine, could be built accuratelv enough so that its 



* Ibid., vol. 2, p. 84. 



operation would be relatively free of trouble, many 

 outstanding minds became engaged in the develop- 

 inent of machines and tools. It is interesting, how- 

 ever, to see how Watt and others grappled with 

 the solutions of problems that resulted from the 

 advance of the steam engine. 



During the 1770's the demand for continuous, 

 dependable power applied to a rotating shaft was 

 becoming insistent, and much of Boulton's and 

 Watt's effort was directed toward meeting this 

 demand. Mills of all kinds used water or horses 

 to turn "wheel-work," but, while these sources of 

 power were adequate for small operations, the 

 quantity of water available was often limited, and 

 the use of enormous horse-whims was frequently 

 impracticable. 



The only type of steam engine then in existence was 

 the Newcomen beam engine, which had been intro- 

 duced in 1712 by Thomas Newcomen, also an 

 Englishman. This type of engine was widely used, 

 mostly for pumping water out of mines but occa- 

 sionally for pumping water into a reservoir to supply 

 a waterwheel. It was arranged with a vertical steam 

 cylinder located beneath one end of a large pivoted 

 working beam and a vertical plunger-type pump 

 beneath the other end. Heavy, flat chains were 

 secured to a sector at each end of the working beam 

 and to the engine and pump piston rods in such a 

 way that the rods were always tangent to a circle 

 whose center was at the beam pivot. The weight of 

 the reciprocating pump parts pulled the pump end 

 of the beam down; the atmosphere, acting on the 

 open top of the piston in the steam cylinder, caused 

 the engine end of the beam to be pulled down when 

 the steam beneath the piston was condensed. The 

 chains would of course transmit force from piston to 

 beam only in tension. 



It is now obvious that a connecting rod, a crank, 

 and a sufficiently heavy flywheel might have been 

 used in a conventional Newcomen engine in order to 

 supply power to a rotating shaft, but contemporary 

 evidence makes it clear that this solution was by no 

 means obvious to Watt nor to his contemporaries. 



At the time of his first engine patent, in 1769, Watt 

 had devised a "steam wheel," or rotary engine, that 

 used liquid mercury in the lower part of a toroidal 

 chamber to provide a boundary for steam spaces 

 successively formed by flap gates within the chamber. 

 The practical difficulties of construction finally ruled 

 out this solution to the problem of a rotating power 



PAPER 27: KINEMATICS FROM THE TIME OF WATT 



191 



