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Parking Brake |
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The parking brake holds one or more brakes continuously in the applied
position. The parking brake employs the regular drum brakes on the rear wheel.
Instead of hydraulic pressure, however, a simple mechanical linkage is used to
engage the brake shoes. When the parking-brake pedal is depressed (or, in some
cars, a hand lever is raised), a steel cable pulls taut a tension lever; other
cables draw the brake shoes firmly against the drums. The release knob slackens
the cables and disengages the brake shoes. The parking brake is self adjusting.
An automatic adjuster in the piston moves on the thrust screw to compensate for
lining wear.
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Piston, Rings, and Wrist Pin |
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The piston converts the potential energy of the fuel into the kinetic energy
that turns the crankshaft. The piston is a cylindrical shaped hollow part that
moves up and down inside the engine's cylinder. It has grooves around its
perimeter near the top where rings are placed. The piston fits snugly in the
cylinder. The piston rings are used to ensure a snug "air tight" fit. The wrist
pin connects the piston to the connecting rod. Pistons are made of aluminum,
because it is light and a good heat conductor. The piston head or "crown" is
the top surface against which the explosive force is exerted. It may be flat,
concave, convex or any one of a great variety of shapes to promote turbulence
or help control combustion. In some, a narrow groove is cut into the piston
above the top ring to serve as a "heat dam" to reduce the amount of heat
reaching the top ring. |
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Power Brakes |
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Power brake are of four general types: vacuum suspended; air suspended;
hydraulic booster, and electro-hydraulic booster. Most power brakes use vacuum
suspended units, which contain a large vacuum-powered booster device to provide
the added thrust to the typical power-brake. Pressure on the brake pedal pushes
forward a rod connected to the pistons of the two master cylinders. The pistons
begin forcing fluid into the front and rear brake lines. At the same time, the
brake-pedal pushrod positions the vacuum-control valve so that it closes the
vacuum port and seals off the forward half of the booster unit. The engine
vacuum line then draws off the air, creating a low-pressure vacuum chamber.
Atmospheric pressure in the control chamber then pushes against the diaphragm,
dividing the two chambers. The pressure on the diaphragm, which is locked to
the pushrod, forces it forward, supplying even more pressure on the pistons.
The safe driver is always ready to apply the total force needed to stop their
vehicle, even if the engine quits (removing the power assist). |
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Push Rod |
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A push rod is a connecting link in an operating mechanism. Two examples are the
rod between the valve lifter and rocker arm on an overhead valve engine, and
push rods at the piston ends which apply pressure to the brake shoes. |
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Rear View Mirror |
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The rear view mirror is a wide rectangular mirror that you (the driver) use to
view anything behind the car. You don't have to take your eyes off the road to
turn your head around. On most cars, the rear view mirror has a "day/night"
selection switch that tilts the mirror inside its glass housing without tilting
the exterior glass housing itself. The switch tilts the mirror upward, about
five degrees, to divert the majority of the light striking the mirror up on to
the headliner of the car. The light that you see when the mirror is on the
"night" setting is actually bouncing off the glass housing (a good reason to
keep it clean). The percentage of light reflected into your eyes in the night
position, is very small compared to the amount that would normally be reflected
into your eyes in its normal position. |
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Radial Tyres |
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In radials tyres the ply or ply cords are alligned at 90 degrees to the
circumference. While radials improve performance the fact is that they are not
very good for bad roads and overloading. The suspension of a vehicle has, also,
to be modified to accept radials. Radials offer much better grip of the road
especially on surfaces which offer poor wheel traction like wet of slippery
roads. |
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Radiator |
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The radiator is used to dissipate the heat that the coolant has absorbed from
the engine. It is constructed to hold a large amount of water in tubes or
passages which provide a large area in contact with the atmosphere. It
generally consists of a radiator core, with its water-carrying tubes and large
cooling area, which are connected to a receiving tank (end cap) at the top and
to a dispensing tank at the bottom. Side flow radiators have their "end caps"
on the sides, which allows a lower hood line. While in operation, water is
pumped from the engine to the top (receiving) tank, where it spreads over the
tops of the tubes. As the water passes down through the tubes, it loses its
heat to the airstream, which passes around the outside of the tubes. To help
spread the heated water over the top of all the tubes, a baffle plate is often
placed in the upper tank, directly under the inlet hose from the engine. Sooner
or later, almost everyone has to deal with an overheating car. Since water is
readily available, it is not beyond the ability of most people to add some to
their radiator if it's low. |
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Radiator Cap (Pressure Cap) |
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The radiator cap is more than a cap for your radiator; it keeps your engine
cool by sealing and pressurizing the coolant inside it. It is designed to hold
the coolant in the radiator under a predetermined amount of pressure. If it was
not kept under pressure, it would begin to boil, and soon all the coolant would
have boiled away. However, the radiator (or pressure) cap prevents this from
happening by exerting enough pressure to keep the coolant from boiling. If your
cooling system is under too much pressure, it can "blow its top"! To prevent
this, the radiator cap has a pressure relief valve. The valve has a preset
rating that allows it to take just up to a certain amount of pressure. When you
turn the cap on the filler neck of the radiator, you seal the upper and lower
sealing surfaces of the filler neck. The pressure relief valve spring is
compressed against the lower seal when you lock the cap. The radiator filler
neck has an overflow tube right between the two sealing surfaces. If the
pressure in the cooling system exceeds the preset rating of your cap, its
pressure relief valve allows the lower seal to be lifted from its seat. Then
the excess pressure (coolant, air) can squish through the overflow tube to the
ground or the coolant reservoir. Once enough pressure has been released (the
caps preset rating), the pressure relief valve is again closed by the spring.
The pressure cap can be tested with a cooling system pressure tester, using an
adapter, to make certain that it is living up to its pressure rating. It should
be replaced if it fails the test. It should be noted that most radiator
pressure caps are not meant to be removed, and that the coolant should always
be added through the expansion (overflow) tank. If you happen to remove the
radiator cap from a hot engine, the pressure can cause steam to shoot out and
seriously burn you. |
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Radiator Grille |
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The radiator grille is the part of the body shell on the front of your car that
covers the area where the air enters. The radiator grille can also be part of
the bumper on some cars. The radiator is connected to the shroud for the
radiator, which directs the air that comes in through the radiator grille to
the radiator only. This prevents the air from escaping around the radiator and
failing to cool the engine. On newer cars, the radiator grille has been lowered
to take advantage of lower hood lines, brought about by an effort to increase
fuel efficiency. Older cars had massive grilles, whereas the cars now produced
have smaller more aerodynamic grilles. |
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Radiator Shroud |
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The radiator shroud prevents the recirculation of air around the fan. It is
usually a plastic hood that encloses the fan to guide the air through the core,
and stop it from coming back around and through the fan again. It also protects
you from the fan blades! |
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