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Show LESSON NO. 107. The Steering Mechanise In the last lesson, you were shown how the front wheels of the automobile must each turn on its separate pivot axle is shown. The part, known as the steering knuckle, which comprises the wheel axle, the arm 2, called the tie rod arm, and the hub through which :he- kine pin, marked 1, passes, is shown as A. You will note that the steering explained for the thrust bearing ad- n s i r. c n - You may have noticed in catalogues the exprc.-don: "Irreversible worm and wheel.'' By this is meant that the wiiet'ls can be turned only by turning he hand h e p 1 , they being sort of 'locked" in rhe position set by the hand wheel. This is accomplished by having the pitch of the worm quite small; that is, the teeth come near to taking the shape of rings, or of a spiral of many turns to the foot of length. Obviously, were the teeth to be rings, instead of spiral, pressing the steering arm would dimply press the teMi of the worm wheel against those of the worm, but there could be no movement of cither. By having the teeth of the worm nearly in the form of rings, prac-MriUy prac-MriUy th'"1 same thinr is accomplished-Thus accomplished-Thus the wheels fan be turned ouly by turning the hand wheel, and the mechanism mech-anism is irreversible. As the wheel is constantly striking obstructions in the road, the steering mechanism, and (when reversible) the driver's hand, would be subjected to many severe blows, unless there were niiie ''cushioning" device furnished. -T-i. . J , , nA : , tiow-and correct amount for turning j curve of any radius. f rom the above we sec that the steering steer-ing mechanism, operated by the ban"! wheel, net-d only act on one. of the wheels. Thus, vou will see, that t!K left-haad knuckle has fastened to i an arm (C). Bv moving this arm (C) the wheels will bo made to turn on ticking tic-king pins. The arm (C) is moved by the dr.v: link (E, Fig. 3 which, in turn, i. moved by tho steering arm ( F . t h ; -steering (F) being moved by means oi the mechanism at the bottom of the steering column, as shown ia Figure 3. While the construction of the steering steer-ing knuckle, tie rod, drag link and steering arm is nearly the same for a., cars, there is considerable variation in . the design and construction of the steering mechanism proper. In the majority ma-jority of cars the steering arm is op erated by means of a worm and worm wheeL Figure 4 shows a detail of the worm wheel. M is the worm, N the. worn: wheel and F the s:ecrni'j arm. Th worm is connected to a hallow shaft, to the other end of which thaft is connected con-nected the steering hand wheel. Yo" will be able to see how, when the hand wheel is turned, it turns the worm, which, in turn, will make the worn, wheel revolve, and so swing the steeling steel-ing arm back or forth. Study this worm and worm wheel for a moment. What will harden whn they become w-ornf Why, there will be a back lash ' ' or play in the hand, wheel. How can this play be taken out? you ask. The simplest way would bo to" take off the steering arm, from its square-ended shaft, and then turn the hand wheel until the shaft has made a half of revolution, and put bs''k the arm. This, you will notice, will bring the back portion of the worm wheel, marked 4. into mesh with the worm. As this portion of the worm wheel has not yet been used, doing this will be the same as installing a new worm wheel. Plav in the hand wheel will also result re-sult from the thrust bearings, H and I. becoming worn, so that the worm can move up and down. ' To take out tins plav, the nut (K) is screwed dovn. When this is done, however, both wheels must be jacked up and tests made of the hand wheel so as to be sure that it does not bind. In most cars the nut (K) is 'Mocked" by having hav-ing the top portion of the worm housing hous-ing split and clamped around the nut. To turn the nut, therefore, the upper housing bolts will first have to be loosened loos-ened a little. In some cars the wear of the worm and worm wheel can be taken up besetting be-setting the worm wheel closer to the worm. To accomplish this, the shaft of the worm wheel is set in eccentric bearings, which bearings can be turned and so press the shaft and its worm wheel closer to the worm. JFigure 5 shows one of these bearings. Care must be taken to turn both of the bearings, which will be found on each side of the worm wheel, an equal amount, and also 'o see that there is no ' binding, ' ' as to the stecrine arm and to the steering steer-ing knuckle, by spring-cushioned ball and sockets. These must be kept packed wih grea. The steering mechanism requires little lit-tle care, but it is important to keep the various parrs of it well lubricated. Neglect Ne-glect in this respect will result in 'plav.'' whieh play is not only annoy-hi annoy-hi 2 to the driver, but resuls in the tires wearing out quicker than they otherwise would. Castor Action. Still another seheme used to make the car travel in a straight line, irrespective irre-spective of the road faults, is to set the front axle so that it is forward of the middle of the springs. This will cause the axle and, therefore, king pin, to be at an anele to the vertical, so that a lice drawn through the king pin, as shown in Fig. 3 by dotted line, win strike the ground at a point in front of that at which the wheel touches it. By so setting the axle the wheel will always try to follow this point, the action ac-tion beine'very mueh the snme as that of the castors of tables, pianos, etc. j . I ! llF' ' Fife S when steering, and how this pivot must be brought as near to the wheel as possible. pos-sible. Ve have now to see how the steering of the wheels on their pivots is controlled bj the steering hand-wheel. hand-wheel. Tn Fi?. 1 the construction of a front knuckles of the two weels are connected connect-ed by the rod B, which rod is termed the tie rod and often the reach rod. This tie rod' connects the knuckles in such a way that, because of the angularity angu-larity of the tie row arms 2, when one wheel is turned, the other will also have to turn, and in the proper direc- 1 L KANAB To GRAND CANYON mf1l'les 1 175 ..ferrj I j . J IS) i m W it ri ' v - V , . AJUy I Salt LakfilribuRQ I 1 I GRAND CANYON |