Automobile Dual Braking ~ 1955 NASA Langley Research Center

more at http://quickfound.net/

A 1950s look at braking problems in automobiles and how NASA Langley Research Center is leveraging technology to address the issues.  A look at the modern vehicles and heavy traffic congestion in the Hampton Roads region is worth viewing.

Much of the original work associated with this film was conducted at the Landing Loads Track.  Tests using a modified vehicle were conducted at the NASA Wallops Flight Facility.

Although most work was conducted for aircraft, much of the lessons were also directly applicable to automobiles.

For more on the Landing Loads Track, see http://crgis.ndc.nasa.gov/historic/1257

Langley Film #L-900

Originally a public domain film from NASA, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.

The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

https://en.wikipedia.org/wiki/Hydraulic_brake

Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/

A hydraulic brake is an arrangement of braking mechanism which uses brake fluid, typically containing glycol ethers or diethylene glycol, to transfer pressure from the controlling mechanism to the braking mechanism...

In a four-wheel car, the FMVSS Standard 105, 1976; requires that the master cylinder be divided internally into two sections, each of which pressurizes a separate hydraulic circuit. Each section supplies pressure to one circuit. The combination is known as a dual master cylinder. Passenger vehicles typically have either a front/rear split brake system or a diagonal split brake system (the master cylinder in a motorcycle or scooter may only pressurize a single unit, which will be the front brake).

A front/rear split system uses one master cylinder section to pressurize the front caliper pistons and the other section to pressurize the rear caliper pistons. A split circuit braking system is now required by law in most countries for safety reasons; if one circuit fails, the other circuit can still stop the vehicle.

Diagonal split systems were used initially on American Motors automobiles in the 1967 production year. The right front and left rear are served by one actuating piston while the left front and the right rear are served, exclusively, by a second actuating piston (both pistons pressurize their respective coupled lines from a single foot pedal). If either circuit fails, the other, with at least one front wheel braking (the front brakes provide most of the braking force, due to weight transfer), remains intact to stop the mechanically damaged vehicle. By the 1970s, diagonally split systems had become common among automobiles sold in the United States. This system was developed with front-wheel-drive cars' suspension design to maintain better control and stability during a system failure.

A Triangular split system was introduced on the Volvo 140 series from MY 1967, where the front disc brakes have a four-cylinder arrangement, and both circuits act on each front wheel and on one of the rear wheels. The arrangement was kept through subsequent model series 200 and 700.

The diameter and length of the master cylinder has a significant effect on the performance of the brake system. A larger diameter master cylinder delivers more hydraulic fluid to the caliper pistons, yet requires more brake pedal force and less brake pedal stroke to achieve a given deceleration. A smaller diameter master cylinder has the opposite effect.

A master cylinder may also use differing diameters between the two sections to allow for increased fluid volume to one set of caliper pistons or the other.

A proportioning valve may be used to reduce the pressure to the rear brakes under heavy braking. This limits the rear braking to reduce the chances of locking up the rear brakes, and greatly lessens the chances of a spin...