CHAPTER IVTHE STEERING GEAR AND BRAKES
The Steering Column.—This is a very important mechanical element of the car. Its direct useful functions are to carry or hold the mechanism for steering the machine, and for the motor control, controlling the air supply for the fuel, as well as for regulating the sparking mechanism.
Motor Control.—Some machines are provided with a foot lever mechanism (accelerator) as well as the throttle lever on the steering wheel. This is advantageous, because in moving through crowded streets, where frequent and quick changes are necessary, the foot is the most convenient for controlling purposes.
Throttle Movement.—A downward pressure of the foot opens the throttle, and a spring returns it to its normal position. The foot throttle is also convenient when shifting the transmission gear, as both hands are otherwise engaged, one to operate the gear-shifting levers, and the other for steering.
The hand throttle on the steering wheel, however,is most convenient for long runs, when little change is required, and it can then be set so as to avoid the use of the foot lever.
The levers are so arranged that they do not entirely close the throttle, but, when fully thrown to a closed position, will still provide a sufficient opening to keep the engine running light.
Fig. 20. Steering Wheel.
Fig. 20. Steering Wheel.
Steering Wheel Type.—The drawing, Fig. 20, shows a type of steering wheel, which has a segment A. The long lever B is for throttling purposes, as above described, and the short lever C for operating the sparking device.
These levers are differently disposed and arranged on the wheel, or on the column supporting the wheel shaft, but the illustration is sufficient to show the principle of construction, and we are interested only in the types and not in the modifications which are available, and are constantly being made to meet certain conditions.
Fig. 21. Steering Gear.
Fig. 21. Steering Gear.
Steering Gear.—Fig. 21 shows an approved form of construction for the gear, which converts the rotating motion to a direct line movement. Inthis the hollow supporting column A, is firmly fixed to a base B.
The shaft C which passes through the column, has a worm D at its lower end, and is journaled in a base E, which carries a cross shaft F, in which is mounted the worm wheel G. One end of the shaft F has an arm H for moving the arms of the wheel knuckles.
Within the tubular shaft C, is a tubular shaft I, for the throttle lever to operate, the lower end of which has an arm J, and within the shaft I, is a shaft K for the sparking lever, the lower end having an arm L.
In the best cars all these parts are made adjustable, so as to provide for wear. In examining or selecting a car, this is one of the points to note.
Fig. 22. Type of Front Axle.
Fig. 22. Type of Front Axle.
Front Axle.—Fig. 22 shows a common form of front axle, with knuckles and cross connecting rod A, the latter providing means, by the nuts B C, for alineing the wheels.
The Brakes.—These are made in two types, onewhich is usually in the form of a contracting band, and the other which expands.
All cars are now equipped with two braking systems, one being the service, or running brake, and the other the emergency brake. These brakes are all of the drum type, and are either expanding, or contracting bands tightening against the drums.
Fig. 23. Contracting Brake.Fig. 24. Expanding Brake.
Fig. 23. Contracting Brake.
Fig. 23. Contracting Brake.
Fig. 24. Expanding Brake.
Fig. 24. Expanding Brake.
Running Brake.—The running brake is operated by the foot pedal, whereas the emergency brake is generally connected up with the lever at the side of the seat.
The foot pedal is on some cars connected with the clutch in such a way that when pedal is pressed to set the brake, the clutch is released. This prevents an inexperienced or confused driver fromapplying the brake when he forgets to release the clutch.
Double-Acting Contracting Brake.—Fig. 23 shows the manner in which a double-acting contracting brake operates. As the band A, has a tension on each end, when the rod B, is drawn forwardly, it is immaterial which way the brake drum C travels.
In Fig. 24 the drum C has a pair of oppositely-disposed shoes D, which are held in such a position that they are not revoluble, and may be moved outwardly by the lever E and links F.
These figures, of course, show merely the simple forms of the two types, and do not go into the refinements of construction which make them so effective in service.
It is obvious, however, that the power exerted through either type of brake, depends on the leverage afforded by the relative lengths of the limbs of the bell-crank lever E, to each other.
Contracting Brake.—Fig. 25 shows a well-known type of contraction brake, in which the cylinder A, has thereon two brake bands B C, hinged together at their rear ends. At their front ends they are connected with a bell-crank lever D, the forward movement of the upper end of the lever being such as to cause the bands to pinch the drum A.
A contractile spring E draws back the lever when the foot releases the pedal, and the link F, between the bell-crank lever and the upper band C, has a turnbuckle arrangement to provide for taking up in case of wear.
The brake bands have means for automatically holding them clear of the wheels when not in use.
Fig. 25. Contract Mechanism.
Fig. 25. Contract Mechanism.
Equalizers.—Sometimes the brake is placed on the propeller shaft; but when one of the brakes is placed on each wheel, an equalizing bar, or other means, must be used. One form of this is shown in Fig.26, in which A is the bar, B the rod which goes to the brake lever, and C C, the rods that run back to the brakes on the wheels.
Naturally, the equalizer will not act with thesame effect on both wheels, unless they are in the same condition. Frequently one of the brake cylinders will be dry and the other coated with grease, or accumulate moisture from some source. It is, therefore, a necessary part of inspection and care to keep them in serviceable condition.
Fig. 26. Equalizer Bar.
Fig. 26. Equalizer Bar.
The Emergency Brake.—The emergency brake has a pawl which acts in the teeth of a segment alongside of the lever, so it may be held in any position to which the lever may be thrown. This lever has no provision whereby the clutch is disengaged when the brake is applied, for the reason that should it become necessary to stop a car going up hill, and when the emergency brake is required, the brakes would have to be released before the clutch could be thrown in, so that the car would be likely to start down hill before this could be done. On this account the emergency brake has no connection with the clutch.
Fig. 27. Rear axle. Service and Emergency Brake.
Fig. 27. Rear axle. Service and Emergency Brake.
Combined Service and Emergency Brake.—Fig. 27represents a standard type of service and emergency brake, each of the internal expanding type. As both are inclosed in a drum they are absolutely free from dirt and dust, and the construction shown eliminates rattling of the parts.
The wheel bearing is also represented by the annular ball-bearing type of construction, in which the balls are unusually large, and therefore, capable of taking great weight and high speed without undue wear.