All About Engines

122 All About Engines £ Fig. 73.—Hartnell governor The simple form illustrated in Fig. 8 and Watt’s governor were all right in their way, but they were not very powerful. They do not respond very quickly to change of speed, and have defects which it would require a good deal of mathematics to explain. A common modification is the Porter governor, which is like that shown in Fig. 8, but has a pear-shaped iron weight on the spindle which helps to keep the balls down. This enables a higher speed to be attained, and consequently makes the governor more powerful. The Pickering governor, which was also described in Chapter I., and will be seen on the engine on Plate i, has the balls mounted on flat steel springs which offer some resist- ance to bending. These serve the same purpose as the weight on the spindle. One of the best governors obtainable is that invented by Mr. Wilson Hartnell, of Leeds, over thirty years ago, and shown in Fig. 73. The balls are mounted on the ends of small “ bell-crank ” levers, the other ends being kept down by means of a spiral spring. The levers are mounted at the base of a bell-shaped cover which is