The Evans joint (Fig. 91) is also of the trunnion type with trunnion blocks located in diametrically opposite slots; however, the outer walls of these slots are curved in the direction of the axis of the shaft, thus distributing the pressure to the three walls of the slots. The pins which carry the trunnion blocks are forged integral with the slip yoke. The joint is enclosed by a pressed steel housing provided with a packing washer and spring to retain lubricant.
In the Detroit universal joint shown in Fig. 92 the trunnion blocks are replaced by steel balls which operated in a pressed steel housing provided with diametrically opposite slots. The construction is similar to Fig. 89.
The joint shown in Fig. 93 is similar to the block and trunnion type, however, the yoke is provided with diametrically opposite slots and the pin is provided with square ends which fit into the slot. This pin is inserted through a bushing in the hub of the joint which is spherical while the housing and yoke are also provided with spherical surfaces.
Perhaps the most popular types of joints in use at present are the Spicer, Arvac, Hartford and Blood shown in Figs. 94 to 97. The Spicer joint is somewhat related to the ring type. It comprises a central ring with pins forged integral, having their axis in the same plane. One forked end is forged integral with a hub which bolts to the hub of the permanent shaft end, while the other fork may have either a short hub for permanent attachment to the propeller shaft or a long hub to provide a slip joint. The bearing ends of the fork have an opening large enough to permit inserting the pins, while they are also bored out large enough to take hardened and ground bushings, which hold the ring and its pins in position. These bushings and fork ends have circular grooves cut in them so that a soft wire can be inserted to hold the bushings in place. The mechanism is enclosed in a pressed steel housing which also serves as a retainer for the lubricant.
Fig. 91. Evans Type of Block and Trunnion Universal Joint.
Fig. 92. Detroit Ball Hearing Universal Joint.
Fig. 93. The Hoosier Universal Joint.
The Arvac joint (Fig. 95) differs from those depicted above, as it con sists of a ball yoke and socket fitted with a cross block and pins enclosed in a forged steel housing. This housing supports two bushings which provide the bearings for the king pin, thus providing a light but strong driving member of tubular section. The bushings which fit into the yoke are provided with shoulders and form the bearings for the yoke pin. Bushings are provided with oil grooves and the oblong space provided by the housing forms grease pockets, this grease being oscillated by centrifugal action and this action forces the lubricant into the oil grooves of the bushings. The pins are a press fit into the cross, practically forming a one-piece driving member. The yoke end is provided with a spherical surface which with a packing contained in a retainer forms a seal to hold the lubricant.
Fig. 94. Spicer Universal Joint and Propeller Shaft Assembly.
Fig. 95. Arvac Universal Joint and Propeller Shaft Assembly.
The Hartford pin joint (Fig. 96) is of the type using one long and two short pins, and is related to the ring type in that a central ring is used which carries the bushings that form the bearings for the pins. One fork end in forged integral with a hub which bolts to the hub of the permanent shaft end. This hub has lugs in the form of a clevis so that the load is placed on both ends of the pin instead of at one point. The long pin passes through both extensions of the yoke end and all pins are held in place by washers and cotter pins. The mechanism is enclosed in a pressed steel housing provided with packing to retain lubricant. The Blood universal joint is depicted in Fig. 97. This is also of the pin type, however, it is of the open construction since no housing is provided. It consists of a central member in the form of a cube, which is provided with a large and small pin, the latter pin passes through this cube and large pin and is locked in position by a locking pin. The two forks are provided with bushings and the outer ends of these are enclosed by caps which contain the lubricant.
The universal joint assembly shown in Fig. 98 represents the type used on the military class A and B trucks. It is essentially a pin joint and follows accepted practice, being provided with a central cross into which the pins are pressed. In order to form a solid unit these parts are locked by a bolt which posses through them. These pins pivot in hardened and ground-steel bushings which are pressed into the fork and flange yoke. The entire assembly is enclosed in a pressed steel housing. A leather boot is attached to the propeller shaft and this with the housing forms the grease retainer.
These universals are suitable for use between the clutch and transmission and the latter and the rear axle. In commercial vehicles two universals are necessary for either location when amid-ship mounting is provided for the transmission. In the rear position one must always be provided with a slip joint or fitting, while when a slip joint is used at the front end it compensates for variations in shaft and frame lengths, clutch movement and is also an advantage in assembling. The slip joint in the rear must be provided to compensate for variations in the distance between the axle and the transmission due to the play of the springs. This joint may either be a square or fluted shaft with a corresponding hub or sleeve.
Fig. 96. Hartford Pin Type Universal Joint.
Fig. 97. Blood Bros. Universal Joint and Divided Propeller Shaft.
Fig. 98. Universal Joint Used on the Class 15 Military Trucks.