MILLWORK. In the machinery of transmission as great improvements have been made as in any other department of practical science, and I have to attribute my own success in life to the changes which it has been my privilege to introduce into this class of machinery. When I first entered Manchester the mills were driven by large square cast-iron shafts (fig. 38), on which huge wooden drums revolved at the rate of about forty revolutions per minute; and the couplings were so badly fitted that you might hear them croaking at some distance from the mills. Now, the wheels and shafts (fig. 39) are Fig. 38. ᄆᄆᄆ Fig. 39. executed with an almost mathematical precision, and instead of huge drums four or five feet in diameter, revolving thirty or forty times a minute, we have small light turned pulleys, keyed upon polished iron shafts, revolving at 120 to 200 times per minute. In figs. 38 and 39 the change is apparent, as both shafts are calculated to perform the same amount of work, notwithstanding their apparent difference in size and strength. The introduction of lighter shafting led also to the simplification of the hangers and fixings by which it is supported, and to the introduction of the half-lap coupling, so well known to millwrights and engineers. The fly-wheel of the engine was also converted into a first motion by the formation of teeth on the periphery (w, figs. 36 and 37), which resulted in a considerable saving of cost and power. This system was at first condemned by some of our leading engineers, and it was with difficulty that I overcame the opposition they created; indeed it was not until a wheel of thirty tons weight for a pair of engines of 100-horse power each was erected, that the prognostications of failure entirely ceased. The principle has now become general wherever steam is employed as a motive power in mills. Fig. 40. |