Saitreg Fuel Nozzles Fuel Nozzles and Pumps

Gmc Fuel Pressure Regulator

Gmc Fuel Pressure Regulator

Drum Brake

History

The modern automobile drum brake was invented in 1902 by Louis Renault, though a less-sophisticated drum brake had been used by Maybach a year earlier. In the first drum brakes, the shoes were mechanically operated with levers and rods or cables. From the mid-1930s the shoes were operated with oil pressure in a small wheel cylinder and pistons (as in the picture), though some vehicles continued with purely-mechanical systems for decades. Some designs have two wheel cylinders.

The shoes in drum brakes are subject to wear and the brakes needed to be adjusted regularly until the introduction of self adjusting drum brakes in the 1950s. In the 1960s and 1970s brake drums on the front wheels of cars were gradually replaced with disc brakes and now practically all cars use disc brakes on the front wheels, with many offering disc brakes on all wheels. However, drum brakes are still often used for handbrakes as it has proven very difficult to design a disc brake suitable for holding a car when it is not in use. Moreover, it is very easy to fit a drum handbrake inside a disc brake so that one unit serves as both service brake and handbrake.

Early type brake shoes contained asbestos. When working on brake systems of older cars, care must be taken not to inhale any dust present in the brake assembly. The United States Federal Government began to regulate asbestos production, and brake manufacturers had to switch to non-asbestos linings. Owners initially complained of poor braking with the replacements; however, technology eventually advanced to compensate. A majority of daily-driven older vehicles have been fitted with asbestos-free linings. Many other countries also limit the use of asbestos in brakes.

Self-applying characteristic

Drum brakes have a natural "self-applying" characteristic. The rotation of the drum can drag either or both of the shoes into the friction surface, causing the brakes to bite harder, which increases the force holding them together. This increases the stopping power without any additional effort being expended by the driver, but it does make it harder for the driver to modulate the brake's sensitivity. It also makes the brake more sensitive to brake fade, as a decrease in brake friction also reduces the amount of brake assist.

Disc brakes exhibit no self-applying effect because the hydraulic pressure acting on the pads is perpendicular to the direction of rotation of the disc. Disc brake systems usually have servo assistance ("Brake Booster") to lessen the driver's pedal effort, but some disc braked cars (notably race cars) and smaller brakes for motorcycles, etc., do not need to use servos.

Drum brake designs

Drum brakes are typically described as either leading/trailing or twin leading.

Rear drum brakes are typically of a leading/trailing design(For Non Servo Systems), or [Primary/Secondary] (For Duo Servo Systems) the shoes being moved by a single double-acting hydraulic cylinder and hinged at the same point. In this design, one of the brake shoes will always experience the self-applying effect, irrespective of whether the vehicle is moving forwards or backwards. This is particularly useful on the rear brakes, where the footbrake must exert enough force to stop the vehicle from travelling backwards and hold it on a slope. Provided the contact area of the brake shoes is large enough, which isn't always the case, the self-applying effect can securely hold a vehicle when the weight is transferred to the rear brakes due of the incline of a slope or the reverse direction of motion. A further advantage of using a single hydraulic cylinder on the rear is that the opposite pivot may be made in the form of a double lobed cam that is rotated by the action of the parking brake system.

Front drum brakes may be of either design in practice, but the twin leading design is more effective. This design uses two actuating cylinders arranged so that both shoes will utilize the self-applying characteristic when the vehicle is moving forwards. The brake shoes pivot at opposite points to each other. This gives the maximum possible braking when moving forwards, but is not so effective when the vehicle is traveling in reverse.

The optimum arrangement of twin leading front brakes with leading/trailing brakes on the rear allows for more braking force to be deployed at the front of the vehicle when it is moving forwards, with less at the rear. This helps to prevent the rear wheels locking up, but still provides adequate braking at the rear when it is needed.

The brake drum itself is frequently made of cast iron, although some vehicles have used aluminum drums, particularly for front-wheel applications. Aluminum conducts heat better than cast iron, which improves heat dissipation and reduces fade. Aluminum drums are also lighter than iron drums, which reduces unsprung weight. Because aluminum wears more easily than iron, aluminum drums will frequently have an iron or steel liner on the inner surface of the drum, bonded or riveted to the aluminum outer shell.

Advantages

Drum brakes are still used in some modern cars because of some engineering and cost advantages. Drum brakes allow simple incorporation of a parking brake. They are often applied to the rear wheels since most of the stopping force is generated by the front brakes of the vehicle and therefore the heat generated in the rear is significantly less. Drum brakes are also occasionally fitted as the parking (and emergency) brake even when the rear wheels use disk brakes as the main brakes. In this situation, a small drum is usually fitted within or as part of the brake disk also known as a banksia brake.

In hybrid vehicle applications, wear on braking systems is greatly reduced by energy recovering motor-generators (see regenerative braking), so some hybrid vehicles such as the GMC Yukon hybrid and Toyota Prius use drum brakes.

Disadvantages

Drum brakes, like most other types, are designed to convert kinetic energy into heat energy via the process of friction. This heat is intended to be further transferred to atmosphere, but can just as easily transfer into other components of the braking system.

Brake drums have to be large to cope with the massive forces that are involved, and they must be able to absorb and dissipate a lot of heat. Heat transfer to atmosphere can be aided by incorporating cooling fins onto the drum. However, excessive heating can occur due to heavy or repeated braking which can cause the drum to distort, leading to vibration under braking.

The other consequence of overheating is brake fade. This is due to one of several processes or more usually an accumulation of all of them.

1. When the drums are heated by hard braking, the diameter of the drum increases slightly due to thermal expansion, this means the brakes shoes have to move farther and the brake pedal has to be depressed further.

2. The properties of the friction material can change if heated, resulting in less friction. This is usually only temporary and the material regains its efficiency when cooled, but if the surface overheats to the point where it becomes glazed the reduction in braking efficiency is more permanent. Surface glazing can be worn away with further use of the brakes, but that takes time.

3. Excessive heating of the brake drums can cause the brake fluid to vapourise, which reduces the hydraulic pressure being applied to the brake shoes. Therefore less retardation is achieved for a given amount of pressure on the pedal. The effect is worsened by poor maintenance. If the brake fluid is old and has absorbed moisture it thus has a lower boiling point and brake fade occurs sooner.

Brake fade is not always due to the effects of overheating. If water gets between the friction surfaces and the drum, it acts as a lubricant and reduces braking efficiency. The water tends to stay there until it is heated sufficiently to vapourise, at which point braking efficiency is fully restored.

Disc brakes are not immune to any of these processes, but they deal with heat and water more effectively than drums.

Drum brakes can be grabby if the drum surface gets light rust or if the brake is cold and damp, giving the pad material greater friction. Grabbing can be so severe that the tires skid and continue to skid even when the pedal is released. Grabbiness is the opposite of fade: when the pad friction goes up, the self-assisting nature of the brakes causes application force to go up. If the pad friction and self-amplification are high enough, the brake will stay on due to self-application even when the external application force is released.

Re-arc'ing

Before 1984, it was common to re-arc brake shoes to match the arc within brake drums. This practice, however, was controversial as it removed friction material from the brakes and caused a reduction in the life of the shoes as well as created hazardous asbestos dust. Current design theory is to use shoes for the proper diameter drum, and to simply replace the brake drum when necessary, rather than perform the re-arcing procedure.

Adjustment

Early drum brakes (before about 1955) required periodic adjustment to compensate for drum and shoe wear. If not done sufficiently often long brake pedal travel ("low pedal") resulted. Low pedal can be a severe hazard when combined with brake fade as the brakes can become ineffective when the pedal bottoms out.

Self adjusting brakes may use a mechanism that engages only when the vehicle is being stopped from reverse motion. This is a traditional method suitable for use where all wheels use drum brakes (most vehicles now use disc brakes on the front wheels). By operating only in reverse it is less likely that the brakes will be adjusted while hot (when the drums are expanded), which could cause dragging brakes that would accelerate wear and increase fuel consumption.

Self adjusting brakes may also operate by a ratchet mechanism engaged as the hand brake is applied, a means suitable for use where only rear drum brakes are used. If the travel of the parking brake actuator lever exceeds a certain amount, the ratchet turns an adjuster screw that moves the brake shoes toward the drum.

The manual adjustment knob is usually at the bottom of the drum and is adjusted via a hole on the opposite side of the wheel. This requires getting underneath the car and moving the clickwheel with a flathead screwdriver. It is important and tedious to adjust each wheel evenly so as to not have the car pull to one side during heavy braking, especially if on the front wheels. Either give each one the same amount of clicks and then perform a road test, or raise each wheel off the ground and spin it by hand measuring how much force it takes and feeling whether or not the shoes are dragging.

Use in music

A brake drum can be very effective in modern concert and film music to provide a non-pitched metal sound similar to an anvil. Some have more resonance than others, and the best method of producing the clearest sound is to hang the drum with nylon cord or to place it on foam. Other methods include mounting the brake drum on a snare drum stand. Either way, the brake drum is struck with hammers or sticks of various weight.

It is also commonly used in steelpan ensembles, where it is called "the iron."

References

^ a b c d e f g h i j k l m n o p q The AA Book of the car, 1976

See also

Balancing machine

Brake lining

Brake bleeding

Hydraulic Disc Brakes

v  d  e

Automotive design

Part of the Automobile series

Body

Framework

Automobile platform  Body-on-frame  Bumper  Cabrio coach  Chassis  Continental tire  Crumple zone  Dagmar bumpers  Decklid  Fender  Fender skirts  Grille  Hood  Hood scoop  Monocoque  Overhang  Pillar  Pontoon fenders  Quarter panel  Shaker scoop  Spoiler  Subframe  Tonneau

Compartments

Trunk/Boot/Dickie  Hood/Bonnet

Doors

Butterfly doors  Canopy door  Gull-wing door  Scissor doors  Sliding doors  Suicide door

Glass

Greenhouse  Power window  Quarter glass  Sunroof  Windshield/Windscreen  Windshield/Windscreen wiper

Other

Bumper sticker  Curb feeler  Hood ornament  Japan Black paint  Monsoonshield  Nerf bar  Tire/Tyre  Tow hitch  Truck accessory

Exterior

equipment

Lighting

Daytime running lamp  Headlamp  Hidden headlamps  High-intensity discharge lamps  Retroreflector  Sealed beam  Trafficators

Legal and other

Motor vehicle theft  Parking sensors  Vanity plate  Vehicle Identification Number  Vehicle registration plate  Vehicle horn   Windshield/Windscreen washer fluid  Wing mirror

Interior

equipment

Instruments

Backup camera  Boost gauge  Buzzer  Carputer  Electronic instrument cluster  Fuel gauge  Global Positioning System and Automotive navigation system  Head-up display  Idiot light  Malfunction Indicator Lamp  Night vision  Odometer  Radar detector  LIDAR detector  Speedometer  Tachometer  Trip computer

Controls

Bowden cable  Cruise control  Electronic throttle control  Gear stick  Hand brake  Manettino dial  Steering wheel  Throttle

Theft deterrence

Automatic vehicle location  Car alarm  Immobiliser   Power door locks  VIN etching

Safety & seating

Airbag  Armrest  Automatic seat belts  Bench seat  Bucket seat  Child safety lock  Rumble seat  Seat belt

Other

Air conditioning  Automobile accessory power  Car audio  Car phone  Center console  Dashboard  Flat tire  Glove compartment  RF connector  Power steering  Rear-view mirror  Sun visor

Portal  Category

v  d  e

Powertrain

Part of the Automobile series

Hybrid powertrains

Hybrid vehicle drivetrain

Transmission

Automatic transmission  Clutch  Continuously variable transmission  Differential  Direct-Shift Gearbox  Drive shaft  Dual clutch transmission  Easytronic  Electrohydraulic manual transmission  Electrorheological clutch  Epicyclic gearing  Fluid coupling  Gear stick  Hydramatic  Limited slip differential  Locking differential  Manual transmission  Manumatic  multitronic  Parking pawl  Roto Hydramatic  Saxomat  Semi-automatic transmission  Super Turbine 300  Torque converter  Transaxle  Transmission control unit  Turbo-Hydramatic  Universal joint  Zeroshift

Suspension

Anti-roll bar (sway bar)  Axle  Axle track  Beam axle  Camber angle  Car handling  Coil spring  De Dion tube  Double wishbone  Hydragas  Hydrolastic  Hydropneumatic  Independent suspension  Leaf spring  Live axle  MacPherson strut  Multi-link suspension  Panhard rod  Shock absorber  Swing axle  Toe angle  Torsion bar  Trailing arm  Unsprung mass  Watt's linkage  Wheel alignment  Wheelbase

Steering

Ackermann steering geometry  Caster angle  Kingpin  Oversteer  Power steering  Rack and pinion  Torque steering  Understeer

Brakes

Anti-lock Braking System  Brake bleeding  Brake fade  Brake fluid  Brake lining  Disc brake  Drum brake  Electronic Brakeforce Distribution  Electronic Stability Control  Engine braking  Hydraulic brake  Hydraulic fluid  Inboard brake  Parking brake  Regenerative brake  Vacuum servo

Roadwheels

and tires (tyres)

All-terrain tyre  Alloy wheel  Bias-ply tire  Contact patch  Custom wheel  Drive wheel  Hubcap  Mud-terrain tyre  Paddle tires  Radial tire  Rostyle wheel  Run-flat tire  Schrader valve  Slick tyre  Spinner  Tire code  Tire Pressure Monitoring System  Tread  Treadwear rating  Tweel  Whitewall tire  Wire wheels

Portal  Category

Categories: Vehicle braking technologies | Vehicle parts | BrakesHidden categories: Articles needing additional references from July 2008 | All articles needing additional references
About the Author

I am a professional writer from China Manufacturers, which contains a great deal of information about quran mp3 player , radar detector canada, welcome to visit!

Fuel Pressure Regulator $72.99 Fuel Pressure Regulator;

Competition Fuel Pressure Regulator $128.99 Competition Fuel Pressure Regulator; 2 Port; Gasoline; 20 psi;

Edelbrock Pro-Flo EFI Systems Fuel Pressure Regulator $54.99 Fuel Pressure Regulator

Inline Fuel Pressure Regulator $154.99 Inline Fuel Pressure Regulator; Up To 300 gal. Per Hour; 3-12 psi Range;

Fuel Pressure Regulator Diaphragm Kit $61.99 Fuel Pressure Regulator Diaphragm Kit; Gasoline; 5-Port Return Style;

Fuel Pressure Regulator Spectre Fuel Pressure Regulator 2517 $36.49 spectre universal fuel pressure regulator chrome 1-5.5 psi adjustment 0.25 in. 0.31 in. and 0.38 in. barb fittings designed to regulate fuel pressure to an approximate desired pressure for use on vehicles with less than 10 psi not for use on fuel injected vehicles auto parts warehouse has extensive spectre fuel pressure regulator catalogs.we are now offering free shipping on all spectre fuel pressure regulator orders over $50.00. our secure spectre fuel pressure regulator catalog is available every hour of everyday. shop with confidence for all your spectre fuel pressure regulator needs. spectre fuel pressure regulator are in stock and available today. save upto 60% off dealer price on your next spectre fuel pressure regulator purchase. our online catalog contains a wide selection of the oem and aftermarket parts you need at unbeatable prices