GENERAL IDEA ABOUT STEERING FEEDBACK

REPORT –   Q.1.What is self-aligning torque? A – When a side or lateral force is applied to the rolling tyre, the centre of the contact patch is no longer at the centre and has shifted towards the trailing edge of the tyre. Since the side force acts through this centre, the trail distance between the original point and the displaced point acts as a moment arm and hence, a torque is created. This torque tries to return the tyre back to the direction of rolling motion and this torque is called the self-aligning torque.   Q.2.How do we increase the pneumatic trail? A – Pneumatic trail is the elastic deformation in the rubber, caused by the action of the side or lateral force acting on the tyre. It can also be referred to as the distance between the original position of the centre of the contact patch and the shifted position of the centre. Pneumatic trail can be increased by increasing the vertical load on the wheel. Q.3.What is the effect of caster on the weight of the car? A – Caster is necessary because the load of the car is carried through the steering axis. When a large amount of caster is present, the wheels are moved up and down as the steering wheel is turned. Because of this, camber changes occur.  Because of this change in camber the tires show wear and tear. In high speed cornering, the vehicle tends to continue straight ahead when the steering is initially turned. Due to this, and the amount of camber change that takes place, the tires of the vehicle may scrub and wear. When a left turn is made at a high speed with a vehicle which has positive caster, the caster of the left front wheel changes toward positive but the car is moving straight ahead. This causes the inside of the left front tire to scrub as it is turned. Q.4.What has self-aligning torque got to do with response and     feedback of the car? A – As the slip angle increases, the self-aligning torque increases along with the coefficient of friction. Therefore, there is a great resistance to the turning of the car. But, the torque decreases drastically with increase in slip angle after a certain maximum is attained, but there is still an increase in coefficient of friction. There is also a continuous decrease in pneumatic trail. From this moment onwards the tyres do not have any force to counteract their movement and hence there is a tendency for the car to understeer due to loss of grip on the road surface. This is felt on the steering by the driver who realises that he is losing control over the car.