Experience - steps to success

Working on this vehicle has been a great experience. We test drove it quite a few times and each test made us know much more interesting things about it. Initially, we couldn’t reach our estimated power and distance but some changes to the design and distribution of apparatus made it efficient. Some of the major problems we faced are mentioned in brief.

One major change which turned the tide was the introduction of chain drive system replacing the belt driven system. The rubber belt was used to connect the motor shaft and the rear axle with the help of a pulley. As the number of tests increased, the belt began to expand due to the heat produced due to the friction between the motor shaft and the belt. This led to increased power consumption by motor which led to fast discharge of batteries. Also the belt had to be tightened by changing the position of motor which is a tedious job. The chain drive system answered all the queries of the previous system by decreasing friction, no requirement to displace motor, decreasing discharge and no jerk movements or slipping of the belt due to initial start-up.

The selection of a reliable braking system is a very important part of achieving proper vehicle control. We started with disc brakes for both front and rear axles. The front axle brakes are making the design of the steering system complex and it had to be replaced. So, they were changed to drum brakes which are placed inside the tire rim by giving us proper space for the steering. We also replaced the rear brakes with drum brakes but due to lack of professional knowledge on this kind of complex braking, we could not achieve 100 % braking. This had a drastic effect on the morale of the group as it resulted in an accident breaking the entire rear axle into half. Finally, we settled the problem by the use of mechanical disc brakes to rear axle which are mounted on the rear axle beside the pulley. It had a simple operation and selection of proper disc brake helped us by achieving efficient braking.  

Some practical changes include placing the thermocol sheets under solar panels and metal apparatus to damp the sound created during the vehicle run. Using a better insulated wiring in place of regular wires to withstand the heat produced by the high current flow. Distributing the weight of the apparatus innovatively by not clustering all the parts of a specific apparatus at a single place.

Minimum mechanical requirements - Braking

Braking system makes an important mechanical entity to any automobile. An excellent braking system is the most important safety feature of any land vehicle. The main requirement of the vehicle’s braking system is that it must be capable of locking all wheels on a dry surface. Ease of manufacturability, performance and simplicity are a few important criteria that are to be considered for the selection of the braking system. The two main types of braking systems under consideration in this report are Drum and Disc brakes. In case of drum braking there is a high possibility of mud and debris to gather in the space between the shoe and the drum. Same problem is faced in mechanical disc brakes, but not in hydraulic disc brakes. Hydraulic brakes are found to be suitable for all type of terrain. Since, drum brakes are of more cost and they are heavier in weight which greatly increases the weight of solar car we can eliminate it. On the other hand, using hydraulic brakes can be an asset as it is cheap and it is readily available but the drawback was using this system the overall weight of the solar car is increased which makes it harder for the motor (linked to battery to solar panels) to run the car. The discs of brakes are made of paralytic grey cast iron. The material is cheap and has good anti-wear properties. Cast steel discs have also been employed in some cases, which wear even less and provide higher coefficient of friction; yet the big drawback in its case is the less uniform frictional behaviour. Two types of discs have been employed in various makes of disc brakes, i.e. the solid or the ventilated type. Disadvantages of ventilated type discs include usual thickness and heavier than solid discs, In case of severe braking conditions, they are liable to wrap, accumulation of dirt in the vents, which affects cooling, resulting in wheel imbalance, Expensive, Difficult to turn. Turning produces vibrations which reduces the life of the disc. Any of these make no much difference on the solar vehicle mentioned in this report as its overweight cannot go beyond 450kgs to 500kgs. Although in the practical version of the solar vehicle done through this report hydraulic drum brakes are used for the front axle and mechanical disc brakes are used for rear axle for experimentation  it is advisable to opt for hydraulic disc brakes for both the front and back axles as they are economical and reliable.