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"Drum Brakes: Principles of Operation" pt2-2 1983 US Army Auto Mechanics Training Film

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Published on Nov 19, 2011

NEW VERSION in one piece instead of multiple parts, and with improved video & sound: https://www.youtube.com/watch?v=Ft0mG...

More at http://auto-parts.quickfound.net/

"HYDRAULIC BRAKES: PRINCIPLES OF OPERATION, PART 1 (DRUM BRAKES)"

"THIS PROGRAM DEMONSTRATES THE BASIC PRINCIPLES OF HYDRAULIC BRAKE SYSTEM OPERATION. USING THE M151 WHEELED VEHICLE DRUM BRAKE SYSTEM, THE FOLLOWING MAJOR COMPONENTS ARE IDENTIFIED AND SHOWN IN OPERATION: MASTER BRAKE CYLINDER, WHEEL CYLINDERS, BRAKE SHOES AND ASSEMBLY AND BRAKE DRUM."

Public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, clipping reduction, and equalization.
Split with MKVmerge GUI (part of MKVToolNix), the same software can recombine the downloaded parts (in mp4 format): http://www.bunkus.org/videotools/mkvt...

US Army training film TVT 9-66

pt 1: http://www.youtube.com/watch?v=n20sTZ...

http://en.wikipedia.org/wiki/Drum_brake

A drum brake is a brake in which the friction is caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum.

The term "drum brake" usually means a brake in which shoes press on the inner surface of the drum. When shoes press on the outside of the drum, it is usually called a clasp brake. Where the drum is pinched between two shoes, similar to a conventional disk brake, it is sometimes called a "pinch drum brake", although such brakes are relatively rare. A related type of brake uses a flexible belt or "band" wrapping around the outside of a drum, called a band brake.

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...

In operation
Normal braking

When the brakes are applied, brake fluid is forced under pressure from the master cylinder into the wheel cylinder, which in turn pushes the brake shoes into contact with the machined surface on the inside of the drum. This rubbing action reduces the rotation of the brake drum, which is coupled to the wheel. Hence the speed of the vehicle is reduced. When the pressure is released, return springs pull the shoes back to their rest position...

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