MOTOR CAR 



5537 



MOTOR CAR 



nliaft to \\ hi.-li is M-i'iirrd |. mi. .11 II 

 ig uith D. The pillion .1 is 



I in tlir .ruin- nf tin- drum 

 K and rir-a-_''S \\itli K. U'lini (lie 



i 1 1' I. in tightened on drum 

 M, tin- planetary system of 

 ivm. i in- lixi'd in space. Pini"u I', 

 thru dmrs ( ', u liirh through I) 



I 1 and shaft O in the same 

 din-it ion as A, but at a slower 

 speed which is determined by the 

 proportion of D to H. The motion 

 ma\ IN- followed by the diagram- 

 mat u view of the gear. To reverse 

 or drive G in opposite direction to 

 A the brake strap N is tightened 

 on the dm in K, which holds J 

 stationary and obliges E to roll 

 round on K and so drive H and the 

 abaft G in the same direction as A. 



transmits power by friction, the 

 gear ran., m. M-asing as B ap- 

 proaches the i-dj-c of A. Reversing 

 nii-n-lv iv(|iiiivs the traverse to be 

 made in the opposite direction be- 

 voinl the centre. No separate 

 clutch is needed. 



The drive from gear box to road 

 wheels is usually effected in two 

 diilrrent ways. Where the chain 

 drive is used, shaft C, projecting 

 from the gear box (Fig. 7), 

 turns, through bevel gear, a trans- 

 verse counter-shaft in two parts, 

 which meet in a central differential 

 gear box. (See below.) Each part 

 is supported by a bracket near the 

 outer end, whereon is a toothed 



Motor Car. 



Fig. 5. Diagram of epicyclic gear. 

 See text 



When the multiple disk-brake 

 is tightened the entire system re- 

 volves as one unit with the shaft 

 A. The engine, clutch, and gear 

 box are in such cases generally com- 

 bined to form a unit. Friction gear 

 ( Kii:. ti) has been applied to small 

 light cars with success. The en- 

 gine turns a large disk, A, mounted 

 en a shaft in line with the crank- 

 shaft. The edge of another disk B, 

 which can be moved sideways on 

 a traverse shaft, presses against 

 the face of A. B is at right angles 

 to A ; and the shaft which it 

 slides on and turns drives the road 

 wheels through chains. When B is 

 opposite the centre of A, it is not 

 affected, but if moved sideways it 



Motor Car. Fig. 6. Friction Gear. 



Diagram showing how such gears 



work. Ntv text 



sprocket wheel. Chains running 

 on the sprockets and larger chain- 

 wheels bolted to the inside of the 

 road wheels transmit the drive of 

 the latter. The wheels are mounted 

 on fixed axles, which are kept 

 parallel to the counter- shaft by 

 radius rods, hinged at the front to 

 the counter-shaft and free to move 

 up and down with the axles. 

 Chain and Shaft Drives 

 Chain-driving is now practically 

 confined to commercial 

 vehicles, and is being gradu- 

 ally ousted by direct axle 

 drive in all vehicles. For 

 pleasure cars and 

 many other 

 motors the shaft 

 drive is preferred. 

 In this case the 

 gear-box shaft C is con- 

 nected by a universal 

 joint with the forward 

 end of a long propelfer 

 shaft, which turns, 

 through a differential gear, 

 the two " live " axles to 

 which driving wheels are 

 keyed. The axles, differen- 

 tial gear, and, in Motor Car 

 some cars, the 



Shaft 



Fig. 7. 

 Differential gear. 



Motor Car. Fig. 8. Expanding 

 brake. See text 



propeller shaft, are enclosed and 

 fully protected from dust and dirt. 

 The differential gear used on the 

 counter-shaft or axles of a motor 

 car is necessary to allow the drive 

 to be transmitted to the wheels in 

 a manner which leaves the wheels 

 free to revolve at different speeds 

 when travelling on a curve. Fig. 7 

 explains the principle of the gear 

 diagrammatically. Bevel B on 

 shaft S (the propeller shaft or the 

 gear-box shaft, as the case may 

 be) meshes with C, which carries 

 round with it bevels D 1 and D' ! , 

 free to revolve on centre pins and 

 in gear respectively with E 1 , keyed 

 to A 1 , and E-', keyed to A'-'. (A 1 and 

 A- are either the halves of a coun- 

 ter-shaft or " live " axles, according 

 to which type of transmission be 

 employed). Assume the driving 

 wheels to be off the ground and C 

 to revolve 20 times per minute, 

 then A 1 and A 2 will both be drawn 

 round by D 1 and D- at that rate. If 

 the right-hand wheel be held, E- 

 becomes a rack on which D 1 and 

 D- run, and, as their axes are half- 

 way between E 1 and E-', E 1 and A 1 

 revolve 40 times a minute. The 

 ai-erage speed of E 1 and E- is 

 still the same as that of C ; and 

 this averaging condition exists 

 when either wheel runs faster 

 than the other. In some types of 

 electrical vehicles two sepa- 

 rate motors are used each 

 drawing one wheel, so mak- 

 ing the above mechanism 

 unnecessary. 



Instead of 

 small bevel B a 

 worm . is often 

 employed, and a 

 worm-wheel 

 takes the place of large bevel 

 ('. The worm gear is quite 

 noiseless and, if well made, 

 very efficient. 



Ball or roller bearings are 

 used for axles and also for 

 the propeller shaft. The axle- 

 casing of a shaft-driven 

 car has a ten- 



Diagram of 



See text dency to twist 



