Tracta Constant Velocity Joint
The tracta constant velocity joints was invented by Fennille in France and was later manufactured by Bendix Limited in England. In some respect these joints are similar in action to a double Hooke's type constant velocity joint. This type of joint incorporates two outer yoke
jaws members and two intermediate semi spherical members (Fig. 26.15A). Each yoke jaw engages a circular groove formed on the intermediate members. Both intermediate members are coupled together in turn by a swivel tongue and grooved joint
Fig. 26.15. Bendix tracta joint. A. Pictorial view. B. Exploded view.
C. Front wheel drive hub swivel pins and axle incorporating a tracta joint.
D. Plan view.
Relative motion between the outer jaw yokes and the intermediate spherical members is provided by the yoke jaw, which is fitted into circular grooves formed in each intermediate member. Relative movement between adjacent intermediate members takes place due to a double tongue formed on one member slotting into a second circular groove, which is cut at right angles to the jaw grooves (Fig. 26.15B). In normal position, both the outer yoke jaws are in alignment, but the central tongue and groove part of the joint remains at right angles to them. When the input and output shafts are inclined at some working angle to each other, the driving intermediate member accelerates and decelerates during each revolution. Since the central tongue and groove joint are a quarter of a revolution out of phase with the yoke jaws, the corresponding speed fluctuation of the driven intermediate and output jaw members exactly counteract and neutralize the speed variation of input half member. Thus the output speed change is identical to that of the input drive, providing constant velocity rotation.
Since roiling motion takes place between members of this type of joint, friction losses are slightly higher than for couplings. But, due to the large flat rubbing surfaces in contect the joint has large torque transmitting capability. Although the size of these joints are fairly large compared to other types of constant velocity joint arrangements, but these joints provide constant velocity rotation at angles up to 50 degrees. A tracta joint incorporated in a rigid front wheel drive axle is shown in (Fig. 26.15C and D).
26.2.5.
C. Front wheel drive hub swivel pins and axle incorporating a tracta joint.
D. Plan view.
Relative motion between the outer jaw yokes and the intermediate spherical members is provided by the yoke jaw, which is fitted into circular grooves formed in each intermediate member. Relative movement between adjacent intermediate members takes place due to a double tongue formed on one member slotting into a second circular groove, which is cut at right angles to the jaw grooves (Fig. 26.15B). In normal position, both the outer yoke jaws are in alignment, but the central tongue and groove part of the joint remains at right angles to them. When the input and output shafts are inclined at some working angle to each other, the driving intermediate member accelerates and decelerates during each revolution. Since the central tongue and groove joint are a quarter of a revolution out of phase with the yoke jaws, the corresponding speed fluctuation of the driven intermediate and output jaw members exactly counteract and neutralize the speed variation of input half member. Thus the output speed change is identical to that of the input drive, providing constant velocity rotation.
Since roiling motion takes place between members of this type of joint, friction losses are slightly higher than for couplings. But, due to the large flat rubbing surfaces in contect the joint has large torque transmitting capability. Although the size of these joints are fairly large compared to other types of constant velocity joint arrangements, but these joints provide constant velocity rotation at angles up to 50 degrees. A tracta joint incorporated in a rigid front wheel drive axle is shown in (Fig. 26.15C and D).
26.2.5.
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