As mentioned above, the internal-gear drive axle is really a double reduction, in which two sets of gears are used. It is also similar to the chain drive in that a jack shaft and dead rear axle are used. However, the two units are bolted together and the sprockets and chains are replaced by internal gears in the brake drums and spur pinions on the drive shafts. Among the users of this type of axle may be mentioned the General Vehicle Company, Fremont Mais, Mais, Denby, Republic, Stewart and numerous others.
Fig. 123 serves to illustrate the Fremont-Mais one-and-a-half-ton axle, showing a dead rear axle of I-beam section with integral spring seats and spindles carrying a bronze sleeve and a double row ball bearing upon which the wheel is mounted. The jack-shaft unit, carrying the differential, drive shafts and bevel driving gears, is mounted to the rear of the I-beam axle. The housing of this unit is riveted to the axle and supports tubes which enclose the drive shafts and extend into the brake spider to support the wheel brakes. The drive shafts float in the differential and are supported inside the brake spider by a double row ball bearing next to the spur driving pinion. The hub flange is made large enough so that the brake drum can be riveted to it, while inside the brake drum and bolted to the hub is the internal gear. The driving gear, with its bearing, is enclosed in a separate compartment formed by the brake drum, spider and hub and works in a bath of oil. One set of brakes is located in the wheel drums while the other is mounted on the bevel pinion shaft and supported from the rear axle. This brake acts on both wheels through the driving unit.
Fig. 124 depicts the massive construction of the Studebaker internal gear drive rear axle which possesses several unique features, having a dead rear axle on which are mounted the bevel gear differential and drive shafts which comprise the jack shaft, while the wheels are driven through spur pinions meshing with internal spur gears. The whole mechanism is enclosed and felt packings are provided to keep out dust and retain grease and oil in the various compartments.
The principal difference between this axle and that above is the scheme of the brakes. In front of the bevel gears housing is a very wide brake drum on the bevel pinion shaft. On this drum are the two brake bauds for foot and ratches hand brakes, but an additional hand emergency brake is provided not ratchet retained. It consists of shoes acting upon V-shaped ribs running around on the outside of the internal gears on the rear wheels close to the spokes. It is claimed that this construction relieves all brakes from any danger of slipping due to leakage of grease around the rear wheels and yet provides a brake acting upon the which permits a light structure for the driving unit. The next reduction, of course, is near the wheels and supported directly by them. The reduction in the wheels is such as to provide a high torque direct to the wheels. By making the jack shaft a highspeed unit, considerable weight can be saved. However, it has a greater unsprung weight than the chain drive.
Fig. 123. Fremont Mais Internal Gear Axle.
Fig. 124. Studebuker Internal Gear Drive Axle.
Fig. 125. Russell Internal Gear Axle.
The Torbensen axle shown in Fig. 126 is also of the internal gear type. The dead axle is a one-piece drop forging of I-beam section, with chrome vanadium spindles and fixed spring seats. The cylindrical end of the dead axle is of large diameter, and extends nearly to the center line of the spokes, so that the bending moment of the spindle is reduced to a minimum. All members of the jack shaft are enclosed, affording cleanliness, efficient lubrication and quiet working.
Fig. 127. Clark Internal Gear Driven Rear Axle.
The Clark axle (Fig. 127) is another type of internal gear-drive axle, with a load carrying member of round section. A feature of this axle is that all parts are identical, there being no rights and lefts. The driving unit is located in front of the load carrying member and instead of supporting at the center, the driving unit is supported at each end from the integral spring seats and brake spider. The differential and drive shafts are supported on Hyatt roller bearings and ball thrust learings, while the wheels ore supported on double row ball bearings.
The White 3- and 5-ton trucks arc equipped with a combination double reduction and internal gear-drive axle. This axle (Fig. 128), called a double-reduction drive, but in reality an internal gear drive, has a floating rear axle concentric with the axle housing. The power from the propeller .shaft is transmitted to the usual bevel gear set and differential which in turn drive the axle shafts. These shafts have spur pinions mounted inside the huh ease which mesh with another spur pinion which in turn meshes with the internal gear hotted to the huh of the wheel. By this method of applying the power to the wheel, a second reduction is obtained between the three gears in the hub case very much like the reduction which takes place between the sprocket wheels of a chain drive.
Fig. 128. New Type of Double Reduction and Internal Gear Drive Axle used on White 3 and 4 Ton Trucks.
Fig. 129. Pierce-Arrow Worm Drive Axle.