of D, at position e, is jointed for the horizontal movement of the trolly, and the pipe leading to the riveter is coiled to allow springing during vertical movement. L represents a travelling riveter crane with portable riveter, K. K is an example of the "lever" form of portable riveter, having long arms. M is a forging press suitable for stamping purposes. N shows the flanging press. The table b, on which is fixed the lower die c, is raised by the central ram on the admission of water pressure to the hydraulic cylinder a. The upper die d is carried by the girder or block e. The guides ƒ are provided with nuts, by means of which the position of e can be adjusted. There are four cylinders, g, containing the rams h, which are used for holding up the plate, which has previously been made red hot, against the upper die, while the bottom die is slowly raised by the central ram. The valve box v has two levers, one for controlling the "vice" rams, and the other for the central or flanging ram, the vice rams being first operated until the plate is held against the upper die. After flanging a plate the levers are reversed, thus exhausting the cylinders and lowering the rams, and the plate may be withdrawn. A cubic inch of water A cylindrical foot of water A cylindrical inch of water A column of water 12 in. long I in. square The capacity of a 12-in. cube = 64'00 lbs. = 0037037 lb. = 48.96 lbs. = 0'0284 lb. 0'434 lb. 6.232 gallons. The capacity of a 1-in. square 1 ft. long = == 0'0434 gallon. o' diameter squared. 12 United States gallon. 2310 cubic inches. 0.83 imperial gallon. = 0.22 imperial gallon. = 0'264 United States gallons. = 610 cubic inches. = 0.0353 cubic foot. CHAPTER XVIII. TRANSMISSION OF power. Ir is a common practice to transmit motion by the aid of pulleys and belts, or bands. The general forms are flat or slightly curved pulleys of wrought or cast iron, and leather belting (oak-tanned, raw hide, or link). The cast-iron pulleys are made in various diameters and widths of face, and may be one single casting or built up of halves. Pulleys of the former class are used in machine building and all purposes where it is not difficult to get the pulleys in place. Those of the latter class are called "split" pulleys, and are portable; they can be located anywhere as required (see Fig 410). A familiar instance is given in the machine shop of a general engineer. When a new machine is introduced, a driving pulley is required on the main shaft. Now, a pulley cast all of a piece would necessitate a portion of the shafting to be released from its coupling, and probably several pulleys removed to get the new one in position, causing much trouble and delay. On the other hand, a split pulley can be secured in a few minutes (generally). A great stress is found to exist between the pulley rim and hub or boss, viz. in the arms, rendering them weak when subjected to shock. This tension is caused by unequal cooling after the operation of casting the pulley in the mould. It is not uncommon to see pulleys fractured before any "tooling" operations are commenced, and frequently during the machining stage arm fractures have been discovered. Large pulleys with wrought-iron arms have been designed to overcome the above defect; the arms are placed in the mould, and the rim and hub formed respectively by the molten metal. An example of this type of pulley is seen in the large driving wheels or rope pulleys used at collieries, i.e. the pit-head gear. FIG. 410.-Split pulley. Wrought-iron Pulleys.—A further development is the wrought-iron pulley (Fig. 411). In this case the pulley is constructed or built up by hand. There is much to be said in favour of this class of pulley for high-speed work and heavy drives. Being of wrought iron, it is stronger to resist tensional strain than cast iron, and may therefore be run at higher speeds without risk of breaking, while the weight is from 30 to 50 per cent. less. The rim being of a uniform thickness, the pulley is practically evenly balanced. This feature is a very important one in high-speed running, and gives wrought-iron pulleys a preference to those of cast iron, which have to be balanced after turning, which is a costly item. There are many ways of fixing a pulley to a shaft. The simplest way is to use a split pulley and bore it to be a tight fit on the shaft; then, when the bolts are screwed up, the pulley will grip the shaft tight enough for any ordinary driving for small powers. This plan has also the advantage that a pulley may be located at any point on the shaft without special preparation, and it does not damage the shaft's surface. Another plan is to use set-screws. Saddle or hollow keys are useful for small pulleys, as they do not damage the shaft, but they have no great holding power, and throw a great strain on the pulley boss. If a pulley has to transmit any considerable power, and especially if it be of large diameter, the only really satisfactory way to fix them is by means of sunk keys; gib-headed keys are dangerous, and taper keys have a tendency to burst the boss; they are also expensive to fit and troublesome to remove. Besides this, the key bed is necessarily twice the length of the key, while with a sunk or feather key one length is enough. Plain and Screwed Cone Bushes.-There are several plans whereby one pulley can be made to fit any size of shaft within certain limits. This result has been obtained by the use of loose bushes. The bosses |