LEEVENSPARK

Differential Lock In a two-wheel drive vehicle if one driving wheel loses adhesion, the propelling force is considerably reduced. This results in the immobilization of the vehicle so that the differential action becomes undesirable on the vehicles designed to operate over poor surfaces. This action can be prevented by locking together any two individual units of a differential. One such arrangement is illustrated in Fig. 26.45. A sliding dog clutch member is splined to a differential sun wheel, which engages with dog teeth formed on the cage of the differential. The clutch is engaged by means of a fork, which can be moved by a lever fitted on the outside of the axle. When engaged, the sun wheel, and hence the rear wheel connected to this sun gear, is made to turn at the same speed as the cage. Locking one sun gear to the cage in this way ensures that the other sun gear also turns at the same speed. Fig. 26.45. Differential lock

Differential When both rear wheels are connected to a common driving shaft rapid wear of\rear tyre, and difficulty in steering from the straight-ahead position are soon experienced. It can be seen in Fig. 26.43 that the outer wheel must travel a greater distance than the inner wheels during cornering of the vehicle. Hence, if the wheels are interconnected, the tyres have to 'scrub' over the road surface and tend to keep the vehicle moving straight ahead. These problems can be minimized by driving one wheel and allowing the other to run free. But this provides unbalanced driving thrust and unequal cornering speeds due to which the arrangement was not accepted. The problem was solved in 1827 by Pequeur of France who invented the differential. This mechanism rotates the wheels at different speeds, while maintaining a drive to both wheels. Example 26.4. The steering set of a, vehicle provides a turning-circle radius of 6.6 m with a wheel-track width of 1.2 m. The effective road whe