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Drum Brakes 28.5.1. Brake Layouts There are two types of drum brakes, such as externally contracting and internally expand­ing. External contracting brakes are preferred for automatic gearboxes. The internal expanding type, along with a drum, is commonly used in braking systems of vehicles. The drum brakes, used with light vehicles, are hydraulically operated. These brakes are commonly used for the rear wheels to complement a disc system at the front. This disc/drum layout permits the front wheels to undertake more braking effort. In addition, the compatibility of a mechanical hand-brake with a drum brake makes this type an obvious option for rear brakes. Various shoe arrangements in use include : • Leading and trailing shoe (L&T) • Two leading shoe (2LS) • Duo-servo. 28.5.2. Leading and Trailing Shoe (L&T) The layout of a leading and trailing shoe brake is presented in Fig. 28.14. This arrangement uses a pair of shoes pivoted at a common anchor point. The free ends of both sh

Brake Fluid A brake fluid meets the international standards set in the United States by the Society of Automotive Engineers (SAE) and Department of Transportation Federal Motor Vehicle Safety Standard (FMVSS). The major characteristics of a brake fluid include : (a) Low viscosity. The brake fluid must flow easily over a wide temperature range and be able to operate in very cold conditions. (b) Compatibility with rubber components. Besides resisting corrosion of metal parts, it must be chemically non-reactive to the rubber seals etc. It must be non-injurious to the system. (c) Lubricating properties. It must reduce friction of moving parts, especially rubber seals. (d) Resistance to chemical ageing. It should have a long storage life and be stable when in use. (e) Compatibility with fluids. It must be compatible with other fluids of its type. if) High boiling point. Most braking systems use a glycerin-alcohol (glycol) fluid with additives to meet the required specifications. Because of

Blinding Flashes Leave Astronaut's Eyes Damaged Dark Sky, Bright Sun. Credit: STS-82 Crew, NASA. by Patrick L. Barry for NASA Science News Huntsville AL (SPX) Oct 25, 2004 Gazing out of their space capsules, Apollo astronauts witnessed sights that humans had never before seen. They saw the breathtaking view of the Earth's bright blue disc against the inky black of space. They saw the far side of the Moon. They also saw strange flashes of light inside their eyeballs! Since then, astronauts aboard Skylab, the Shuttle, Mir, and the International Space Station have all reported seeing these flashes. No need to call Agents Mulder and Scully of The X Files, though: what the astronauts are experiencing is space radiation zipping through their eyes like subatomic bullets. When a "bullet" strikes the retina, it triggers a false signal that the brain interprets as a flash of light. Needless to say, this is not good for your eyes. Years after returning to Earth, many

Blogger Buzz: Support Haiti Disaster Relief Like many of you, we watched in horror as news emerged from Haiti about yesterday's disastrous earthquake. For those of you who publish your blog with Blogger, we built a couple of widgets that make it easy to invite your readers to contribute money to the Red Cross's international disaster relief effort. Pick a size that best fits your sidebar: After clicking the appropriate button, select which of your blogs you want to add the widget to, then click "Add widget". The Red Cross assures us that 100% of the money raised is going to disaster relief efforts in Haiti — we and they thank you for your support! Not on Blogger? Be sure to visit the Red Cross's Haiti banners page with banners that you can add manually, or visit Google's page containing information about relief organizations, news and contact info relating to the earthquake.