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Joined: Feb 2011
17-02-2011, 08:18 PM
am B.E student, i want full details of hydraulic brakes from basics to latest information and ppt presentation of hydraulic brakes
Joined: Apr 2012
24-09-2012, 02:57 PM
hydra.pdf (Size: 530.68 KB / Downloads: 95)
WHEEL CYLINDER BASICS
Fluid pressure is transferred from the brake pedal through the master cylinder, is power assisted, then is transferred to the
wheel cylinder which applies the activating force on the brake shoes. As the fluid pressure to the wheel cylinder increases,
the cups and pistons are forced apart. In most cases, this force is carried from the piston to the shoes through piston pins.
However, some special shoe configurations do not utilize piston pins. (Example: Wagner Front E-2549.) Two types of
wheel cylinders are commonly used in today's hydraulic brake systems: single-ended and double-ended.
TUBE SEAT CHARACTERISTICS
Both single-ended and double-ended wheel cylinders may be supplied with or without tube seats depending on the type of
hydraulic line connection used. The majority of light and meduim-duty vehicles use 3/8" or 7/16" port sizes. These port sizes
may also contain different thread pitches (ie. 7/16"-20 vs. 7/16"-24). Be careful to identify the thread pitch as well as thread
size. Several metric threaded port sizes (M7, M8, M10, etc.) exist and need to be identified (Figure 3). Cylinders manufactured
with tube seats are not interchangeable with cylinders manufactured for use without tube seats. It is normally not
possible to convert wheel cylinders from one style to the other by removing or adding tube seats.
The wheel cylinder must be serviced whenever brake shoes and linings are replaced. Inspect the cylinder for leakage. A
leak not immediately apparent may be detected by pulling back the cylinder boot. The presence of any brake fluid retention
in the boot is an indication of a leak. A slight dampness may be present from condensation and is not evidence of a
leak. Dripping fluid is evidence of a leak.
Even if there is no evidence of leakage, the wheel cylinder must be internally cleaned as part of a reline operation. This is
necessary since contaminants will have collected behind the cups. If cylinders are pushed back to their initial position
without cleaning, the cups generally will be damaged by this contamination and will start to leak soon. The disassembly
and assembly of the wheel cylinder is described in the reconditioning procedures. It is generally a good practice to recondition
wheel cylinders since the cups, pistons, and boot cost is very small compared to the reline service operation.
Where there is evidence of leakage or parts appear worn on disassembly, then the reconditioning procedure described below
is required. If any doubt exists, replace the entire wheel cylinder.
Loosen the bleeder screw before starting to recondition a wheel cylinder. If it is seized and cannot be loosened, the cylinder
must be replaced. It is a common practice to recondition wheel cylinders without dismounting them. However, some brakes
are equipped with external piston stops which require removal prior to disassembly. Pull the protective dust boots off the
cylinder. Internal parts should slide out. If not, slight air pressure may be applied to the fluid inlet. Parts which cannot be
removed easily indicate a cylinder which has been damaged beyond reconditioning and the cylinder must be replaced.
Light roughness and/or deposits in the cylinder bore can be removed by fine crocus cloth or a light honing. If the bore
cannot be cleaned readily, replace the cylinder. Check the piston clearance after any honing of the cylinder bore (Figure 4).
Replace the cylinder if maximum piston clearance is exceeded. Extra clearance causes brakes to release slowly causing
excessive lining wear. After honing, remove any burrs from the edges of fluid intake and/or bleeder screw ports.
When reassembling the cylinder, be sure to lubricate the new cups and pistons with brake fluid. Insert new cups and pistons
in each end of the cylinder. DO NOT SLIDE THEM THROUGH THE CYLINDER. This could cut the cup as it passes the
inlet ports. Cup lips should always face inward (Figure 5). Many modern wheel cylinders and wheel cylinder repair kits do
not contain cup expanders. These cylinders use a conically wound spring that provides the cup expansion function. During
reassembly be sure not to distort the spring. Spring distortion will cause cylinder leakage.
BRAKE LINES AND HOSES
Hydraulic lines and flexible hoses serve as the arteries of the hydraulic system because they transmit fluid pressure from the
master cylinder to the wheel cylinders and calipers. Even a partial blockage in the lines is detrimental to braking action because
it restricts the flow of fluid. Although applying pressure may force the fluid past the blockage, the affected brake may not release,
or release slowly and drag. During brake inspection, the lines and hoses should be examined for chafing crimps, loose or missing
tie clips, kinks or dents, fluid seepage at connections, and stains around hose ends which indicate leakage.
Joined: Oct 2012
05-11-2012, 02:21 PM
to get information about the topic "hydraulic brakes" full report ppt and related topic refer the link bellow
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