27-12-2012, 12:19 PM
INCREASING FUEL EFFICIENCY AND WEIGHT REDUCTION IN DISC BRAKES
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ABSTRACT
Today’s technology is in need for speed, but at the same time we need safety as well. For safety, we need deceleration to the maximum extent. These two things are moreover contradictory factors. To attain the maximum speed of the engine, the efficiency should be increased. So, to decelerate these high speed engine we need an effective braking system. At present we have disc brakes made of cast iron. The cast iron disc brakes have high gyroscopic effect as well as it fails in wet conditions sometimes. Moreover this is much heavier and thus reduces
initial acceleration and causes more fuel consumption. In this paper, we are introducing the ceramic disc brakes which will overcome all the disadvantages of cast iron disc brakes. The implementation of ceramic disc brake show 61% weight reduction when compared to the conventional cast iron disc brakes. Apart from saving fuel, resulting in better and lower emission for the same mileage, this also means a reduction in unsprung masses with a further improvement of shock absorber response and behavior. In this paper, we have practically implemented the ceramic disc brake in two wheeler and tested the weight factors and fuel consumption factors.
INTRODUCTION
One of the most important control system of an automobile is brake system. They are required to stop the vehicle within the smallest possible distance and is done by converting kinetic energy of the vehicle into heat energy which is dissipated into atmosphere. The disc brake or disk brake is a device for slowing or stopping the rotation of a wheel while it is in motion. A brake disc is usually made of composites such as reinforced carbon-carbon or ceramic-matrix composites. This is connected to the wheel or the axle. To stop the wheel, friction material in the form of brake pads (mounted on a device called a brake caliper) is forced mechanically, hydraulically, pneumatically or electromagnetically against both sides of the disc. Friction causes the disc and attached wheel to slow or stop.
CONSTRUCTIONAL FEATURES
Two types brake discs are generally used the solid type and the ventilated type. The ventilated type more efficient since it provides better cooling. But they are thicker and heavier than solid type, they are liable to wrap at severe braking conditions, the dirt accumulates in the vents which affects cooling and apart produces wheel imbalance. The materials used for the manufacture of disc are Aluminum, Cast iron and ceramic. Cast-iron disc is the heaviest part of a brake - about 8 kg each, or 32 kg per car. Aluminum alloy discs are used in the Lotus Elise. Though light, they were less resistant to heat and fade, thus more powerful Elises still employ conventional cast-iron disc.
In contrast, carbon-fiber disc is most heat-resisting yet is by far the lightest, however, it requires very high working temperature, and otherwise braking power and response will be unacceptable.
PROPERTIES OF CARBON-CERAMICS:
Ceramics are inorganic, non-metallic materials that are processed and used at high temperatures. They are generally hard brittle materials that withstand compression very well but do not hold up well under tension compared to the metals. They are abrasive-resistant, heat resistant (refractory) and can sustain large compressive loads even at high temperatures. The nature of the chemical bond in the ceramics is generally ionic in character, and the anions play an important role in determination of the properties of the material. Typical anions present are carbides, borides, nitrides and oxides. The different types of ceramics are clays, refractories, glasses etc.
MANUFACTURING OF CERAMIC BRAKE DISCS:
In the earlier days, the brake discs were made from the conventional brittle ceramic materials would have disintegrated into a thousand pieces under slightest pressure.
In the earlier days, long carbon fibers were used. Later the use of short carbon fibers increased the efficiency. The composites for producing fiber reinforced ceramic brake discs are short carbon fibers, carbon powder, and resin mix. The process involves first compressing the carbon fibers, carbon powder and the resin mix together and then sintering at 1000 degree Celsius. In the furnace a stable carbon frame work created. This consists of carbon fibers in a carbon matrix. Once cooled this material can be ground like wood and the break disk obtains its final shape. Together with silicon the ground break disk blank is then inserted into the furnace a second time. The pores in the carbon framework absorb the silicon melt like a sponge; the fibers themselves remain unaffected by this process.
The ceramic material is created when the matrix carbon combines with liquid silicon. This fiber reinforced ceramic material cools over night and the gleaming dark grey break disk is ready.
CONCLUSION:
Ceramic brake discs due to its advantages over the conventional brake discs are going to be the brake discs for cars in future. The special combination in the ceramic brake discs had turned the conventional brake disc into a material most suited for making brake discs. In our project, we have tested the weight and fuel consumption factors of a two wheeler with ceramic disc brake system. It is noted that the ceramic disc brake system contributed less weight and consumed less fuel for the same mileage.