CHAPTER XXXII
AXLE TYPES, OPERATION AND CARE
Two types of rear axles are being used by the manufacturers of automobiles—the live axle, and the dead axle. The live axle which carries the weight of the load and transmits the power of rotation to the wheels, is built in two distinct designs called the semi-floating axle, and the full-floating axle. The semi-floating design is used extensively in manufacturing cars of light weight, while the full-floating design is favored more by the manufacturers of cars of medium and heavy weight. Both designs give equally satisfactory results.
The dead axle carries the weight of the car and load in much the same manner as a horse drawn vehicle. The power is conveyed to the loose wheels on the axle, by means of a chain which operates on a sprocket attached to the hub of the wheel, or by an internal gear drive arranged and housed in the brake drums.
The Semi-floating Axle.—In the semi-floating design of axle, the axle shaft carries the weight and transmits the rotation power to the wheel, which is keyed and locked to the outer end. The axle shaft is provided with a bearing at each end which operates on the inside of a closely fitted housing. The inside end of each axle shaft is bolted directly to the differential. The housing is split or divided into two halves, and bolts together in the center over the differential. This design of axle gives excellent service, but has one disadvantage in that it is somewhat difficult to disassemble, as the rear system must be disconnected from the car to take the housing apart. [Fig. 119] shows a part sectional view of a semi-floating axle used by the Detroit Taxicab Co. The wide series of S. K. F. ball bearings used on this axle are self aligning, which prevents any binding action from shaft deflection.
Fig. 119. Semi-Floating Rear Axle
The Full-floating Axle.—The full-floating design of axle serves the same functional purpose as the semi-floating design, but is constructed differently and operates on a widely different plan. In the full-floating design of axle, the axle shaft does not support any of the weight of the car or load, but serves simply as a member to transmit the power rotation to the wheels. The wheels are mounted on separate bearings, which operate on the outside of the outer end of the housing. The inner ends of the axle shafts are squared, or splined and slide into slots or seats in the differential gears. The differential assembly is in a separate unit, and is floated on bearings held by retainers extending from the forward end of the large ball-shaped center of the housing. The outer end of the axle shaft extends through the hub of the wheel, and has an umbrella-shaped plate on the end which bolts to the outside face of the wheel, as shown in [Fig. 120], thus transmitting the power directly to the outside of the wheel, without the axle shaft taking any bearing. The axle shaft may be drawn out through the wheel, by removing the nuts which secure the umbrella plate, without removing the weight of the car from the wheels. The differential unit can also be removed without disassembling the housing, by removing a large cover plate from the center of the housing. [Fig. 121] shows a typical full-floating axle, with a spiral bevel gear drive. The wheels in this case are mounted on a set of double series radial and thrust ball-bearings. The Hotchkiss type of short shaft final drive is carried in the forward extended part of the housing.
Fig. 120. Full-Floating Axle—Wheel-End Arrangement
