2.2 OBJECTIVE OF THE PROJECT
Our objective is to design and simulate a mechanism to implement the conventional four wheel steering and the four wheel crab steering in the same vehicle thereby reducing the turning radius of vehicle using four wheel conventional steering and easy manoeuvring of vehicle at high speeds using crab steering. The control for shifting from one type of steering to another is provided to the driver so that he can change from conventional to crab steering depending upon the vehicle speed.
The project procedure is presented in the form of flowchart below:
Fig. 3.1 Flowchart of Actual Work
3.1 PROBLEM DISCUSSION:
3.2 DISCUSSION OF VARIOUS MECHANISMS:
Initially, it was considered to connect the front and rear wheels directly using a rack and pinion mechanism in which, the motion of the front wheels will be transmitted completely to the rear wheels using two Dumb-Bell shaped gears which will act as the pinion. The two dumb-bell gears are connected via the same rack.
This mechanism would be installed on one side of the vehicle, and was intended to accomplish both crab and conventional steering effects on its own. But then due to the fact that, the angles of turning of the rear wheels are different in crab and conventional steering, the mechanism was deemed irrelevant for the stated purpose.
Later after many deliberations, it was decided that our purposes will be met accurately if the mechanism can be installed on both sides of the vehicle, connecting both sets of front and rear wheels, with one set performing crab steering and the other performing conventional steering effect.
3.3 FINAL MECHANISM:
In our design, we employ one basic set of linkages. This linkage connects the FRONT and REAR wheels at both sides of the car. One set of linkages produce the CRAB Steer effect and the other set produces the Conventional Steer effect. When one type of steering is required, the other type is made dysfunctional.
Each set of linkage consists of:
• TWO Dumb-Bell shaped Gears, one for each wheel.
• Rods to connect the wheels to the Gears.
• One Lengthy rod with teeth cut in its outer surface, which runs throughout the length of the vehicle, connecting the front and rear Gears.
• A box like structure used for the purpose of breaking the contact between the toothed rod and the gear, thus rendering the linkage ineffective.
Each of the Dumb-Bell Gears, as the name suggests, has two gears at the top and bottom respectively.
The top gears of each dumb-bell gear is connected to the wheels by toothed rods, replicating a Rack-and-Pinion setup. Likewise, the two bottom gears of the...