 Hello, friends. This is Mr. Nagesh R. Thambake, Assistant Professor of Mechanical Engineering, Walsh and Instruct Technology, Sholapur. Today, we are discussing the topic that is automobile steering system. In this particular session, we are discussing introductory things regarding automobile steering system. Learning outcome. At the end of this session, students will be able to understand the basics of automobile steering system. In this particular session, we are going to discuss following details. Definition of steering system. Requirements of steering system. Functions of steering system. Types of steering system. Difference between Ackerman and Davis steering mechanism. Fundamental condition for true rolling and correct steering angle. Definition. It is the system which provides directional change in the performance of an automobile. This system converts rotary movement of the steering wheel into angular movement of the front wheels. It multiplies driver's effort by mechanical advantage, enabling him to turn the wheels easily. Now, some of the requirements of steering systems are there. It should multiply the turning effort. Whenever a driver is going to rotate a steering wheel, that time he should not feel the steering wheel is more heavy. Therefore, this particular steering system should multiply the turning effort and the result of this will get us the wheels are turning at the required direction. It should be to a certain extent irreversible. So, what will happen? Whenever a vehicle is travelling on a road surface and on the road surface, if holes and bumps are there, that time if the wheels are coming over the holes and bumps, that time the wheels are turning automatically. So, whenever the wheels are turning automatically, that time the steering wheel should not turn to the left or right. So, that becomes irreversible. So, at certain extent that must be irreversible. Otherwise, what will happen? The direction of vehicle will change automatically and that we don't want. Otherwise, it may lead to accident. Therefore, it should be to a certain extent irreversible. The mechanism should have self-righting effect. What is the self-righting effect? When a vehicle, when you are giving a turn to the vehicle, that time you are rotating a steering effect. It should regain its original position of the steering wheel that is called as self-righting effect. So, these are the requirements, functions of the steering system. It provides directional stability. Whenever a vehicle is running on the road surface, that time at the required direction we can have the vehicle wheels. It helps in swinging the wheels to the left or right. It helps in turning the vehicle at the wheel of the driver. It helps in controlling wear and tear of the tires. It helps in achieving the self-righting effect. So, this will fulfill the requirements whatever we have discussed earlier. Also, it converts the rotary movement of the steering wheel into an angular turn of the front wheels. It multiplies the effort of the driver. Also, it absorbs a major part of the road shocks. Now, we are having two types of steering systems. Number one, fifth wheel steering system. Second one is side pivot steering system. Inside pivot steering system, further we are having again two types. That is, Davis steering gear mechanism and a Kerman steering gear mechanism. Now, we will see one by one. Now, in this particular figure, it is shown fifth wheel steering system. In this particular figure, this is the axle and this is the wheel. This wheel is called as a fifth wheel. This particular wheel is connected between the chassis and the axle of the front wheel. So, whenever a steering wheel is rotated, that time this particular fifth wheel is rotating along with the axle and both the wheels are going to turn. So, here the axle is not rigidly fixed over here. So, whatever the turn table is there, that is, pivoted with the help of pivot pin and with the bearing. And this particular whatever the fifth wheel is there, that is having a ring here. With the help of this ring here, the wheel can be rotated to the right or left side. And whenever this wheel is rotating to right and left, that time entire axle together is swinging around this particular pivot. Therefore, it is called as a fifth wheel steering system. Nowadays, this particular fifth wheel steering system is used for trolleys and this is behind the engine. So, what will happen with this? You can see in commercial vehicle, this particular fifth wheel is used for the trolleys. Now next one is side pivot steering system. In that first one is Davis steering mechanism. Davis steering mechanism. What is the difference between Davis and Ackerman steering mechanism? There is some difference. In Davis steering gear mechanism, we are having two sliding joints and in the case of Ackerman that is absent. Therefore, what will happen? Due to this sliding pair, the steering whatever this particular rod is there, the tie rod is there, that is, we are fast and the steering system becomes inaccurate after some interlock time. So, in Ackerman steering gear mechanism, only four turning pairs are there. And due to that, what will happen? Turning pairs are more efficient than the sliding pair. Therefore, Ackerman steering gear mechanism is having more life and more life than that of Davis steering gear mechanism. But geometrically, Davis steering gear mechanism is more accurate than Ackerman steering gear mechanism. Due to faster wear of Davis steering gear mechanism and after some interlock period of time, this becomes inaccurate. Therefore, Ackerman steering gear mechanism is preferred over a Davis steering gear mechanism. Now, we will see how the Davis steering gear mechanism is constructed. In this particular steering gear mechanism, this is a torre that is GH. This is sliding over the sliding pair parallel to this AC that is the axle. And here BA and CD both are the stub axles. Here EAB is one of the bell clamp lever and HCD is another bell clamp lever. This is the alpha that is angle given to the vertical of this vehicle. So, this alpha is ranging from 11.3 degree to 14.1. And also here, whatever the ratio of B by L, B is nothing but the length of the axle and L is nothing but the distance between the two wheels. So, this particular B by L ratio is ranges between 0.4 to 0.5. And after this, this particular steering mechanism is locked and after this, more turn you will not get. So, maximum angle that you are getting from this particular Davis steering gear mechanism that is 14.1. And this is having this particular steering gear mechanism is used rarely in the vehicles. Next one, side pure steering system that is Ackerman steering gear mechanism. This is another type of side pure steering system. Here in this figure, the Ackerman steering mechanism is shown. In the previous case, we have shown for this tie rod, there are two sliding pairs. But here, we don't have any sliding pairs. Whenever a steering wheel rotates, that time this particular tie rod is oscillating with the help of these short arms. Therefore, what will happen? Whenever this particular, whenever the vehicle is going to turn, that time this tie rod is oscillating and the vehicle is getting turned to the right or left. Here in this figure, right side figure, it is shown whenever a vehicle is going to turn, that time there is a principle of Ackerman steering gear mechanism. What the principle says? Whenever a vehicle is going to take a turn, that time access of front wheels should meet at one point where the access of rear wheels are meeting. And this becomes the instantaneous center of the vehicle. And this particular, at this particular condition, the vehicle all wheels are perfectly rolling. Therefore, the vehicle wheels will not wear and tear. Therefore, the life of the tire will increase automatically. Now, we will see fundamental condition for true rolling and correct steering angle. This is the Ackerman steering gear mechanism. Whenever a vehicle is going to, going to have a turn, that time access of all wheels should meet at a one point and that becomes a instantaneous center of a vehicle. During this, the vehicle all wheels of the vehicles are rolling perfectly. Therefore, it is called as true rolling. And we can calculate the correct steering angle with the help of this particular geometry. Now here, cot of theta becomes y by b. Here, this is the theta is the bigger angle and phi is the smaller angle. Smaller angle becomes the outer wheel angle and bigger angle becomes the inner wheel angle. So cot theta is equal to y by b and cot phi is nothing but y by b plus c by b. Therefore, if we combine these two particular equations, y by b is nothing but cot of theta. Therefore, cot of phi minus cot of theta is equal to c by b. If our vehicle is satisfying this particular equation, then definitely our vehicle is having a true rolling as well as it is having a correct steering angle. These are the references. Thank you. Thank you.