After a long break, I'm finally getting some time to write about my new robot(not named yet).
After making a couple of differential-type bots, I decided to switch over to a car-type bot which would implement A Strearing mechanism similar to the one in real Automobile. Here's the robot I've made.
There are several Streaing mechanisms like Rack and Pinion, Recirculating ball, Worm and Sector out of which I chose the Rack and Pinion. The building materials were:
1. A base
2. A Rack and a suitable Pinion which exactly meshes with the rack.
3. DC motors ( I've used two)
4. Wheels
5. Other building material like metal strips, bolts, nuts, axles etc.
6. Gears (I will deal with them later)
First design: (Without Differentials)
1. My first design was similar to one seen in the above image except for the use of gears. Instead , I used a single axle driven by belt drive and wheels connected to both ends.
(Unfortunately, I don't have an image of my old design)
2. Here's the schematic representation:
3. However, it possesed a serious drowback. Since the rear wheels are connected to the ends of a same axle, they are forced to move at a same speed. But each wheel of a car travels different distances while turning and the inside wheels travel a shorter distance than the outside wheels. Since Speed= Distance / Time, hence the wheels that travel shorter distance should travel with lower speed. Therefore, the inside wheels travel with a lower speed than the outside wheels.
4. Since the front wheels of my car are not driven by the motor, they stand out of this scene and can easily rotate at different speeds.
5. However, the rear wheels are forced to spin at the same speed (since connected to the same axle). This does not allow the rear wheels to travel at different speeds while turning. As a result, the car is not able to turn properly and slips on the floor.
6. If a real Automobile is without differentials then for the car to be able to turn, one tire would have to slip. With modern tires and concrete roads, a great deal of force is required to make the tire slip. This force would have been transmitted through the axle from one wheel to the another, putting heavy strain on axle components.
Second design: (With Differentials)
What is a differential ?
A Differential is a device which allows the two axles connected to it to rotate at different speeds.
As seen there are two axles to which each wheel is connected and these axles are fed to the differential. The key is use of two axles and the beauty is both wheels travel at same speed while moving straight but at different speeds while turning.
Videos below explain working of differentials.
Procedure:
1. In my differential, the driving gear is a spur gear connected to motor shaft.
2. It drives another spur gear which drives the entire differential unit. ( In automobiles, Crown wheel is used)
3. A set of 3 bevel gears perform the functioning.
Rack and Pinion mechanism
----- 
1. Rear wheels of my car are driving wheels, whereas front wheels perform the stearing action.
2. Pinion is connected to the motor which meshes with rack.
3. Ends of the rack are connected to wheels.
Advantages over Differential type bot:
1. This bot can take turns on the curved path.
2. It can take turns while moving forward as well as backwards.
3. Use of 4 wheels increases stability and only 2 motors make it efficient. Whereas differential type bot needs 4 motors for driving 4 wheels.
4. This bot looks nice. :)
Comment any feedback or suggestions. Thanks to all.
