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New Girlir mponents for Hydraulic and Air Braking

18th September 1964
Page 80
Page 81
Page 80, 18th September 1964 — New Girlir mponents for Hydraulic and Air Braking
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FIVE items of braking equipment to new designs have been introduced by Girling Ltd. Included in these are a tandem master cylinder, two hydraulic two-leading-shoe brake units (a rear and a front), an air-operated wedge brake unit and what is termed a Duo-Servo brake unit.

The tandem master cylinder—designated T.V.C.V.—consists of two separate and complete hydraulic cylinders in series to provide independent operation on the front and rear brakes of a vehicle. (A photograph of the new unit is reproduced on page 180 of this issue.) The new twoleading-shoe brake units are the HLS/S, front and H2LS, rear. The former is to the existing design but incorporates some important improvements, In this design there are two internal wheel cylinders, each operating directly on one shoe, and recently shoe-to-shoe springs have been added to give a more positive and quicker shoe retraction. The springs are also of a much lower fitted load-80 lb, against 220 lb.—and are therefore more easily moved and refitted. Shoe tip adjust:nt, in place of a snail cam" on a .st in the shoe web, has been introduced provide more positive adjustment and and seals, now fitted on the pistons, are. designed to reduce seal friction.

The rear hydraulic unit is designed for use on medium-to-heavy types of commercial vehicle and has been introduced to give improved efficiency and safety. Two internal, diametrically opposite double-acting wheel cylinders operate the two leading shoes. The pistons act through fully articulated pushrods direct onto the shoes and this produces a twoleading-shoe factor in both forward and reverse directions. The handbrake mechanism is entirely independent up to the shoes and is actuated by a wedge expander parallel to one wheel cylinder. I he expander actuates two forged-steel shoe carriers.

The Duo-Servo brake unit is designed for lightand medium-weight cornmercials and takes advantage of the servo effect from the revolving drum to .obtain a self-servo-action on the coupled shoes. The two shoes are anchored to the backplate by a pin, and actuation of the service brake is by means of a single doubleacting wheel cylinder on application. The wheel cylinder pushrods move both the primary and secondary shoes against the rotating drum, the primary shoe by tendency to move wlth the drum applying a considerable load to the adjuster screw. This ;a turn transmits the load to the secondary shoe which, being hard -against an anchor pin mounted in the back plate, is forced harder onto the drum with a force in excess ofthat applied by the wheel cylinders. A separate shoe-actuation linkage is incorporated for the handbrake, this taking the form of a cantype expander. The new air-operated wedge brake unit is suitable for vehicles of 12 tons gross and above and uses the two-leading-shoe principle. • Diaphragm chambers fit directly to the brake and also provide for a direct-acting handbrake. The wellknown Girling single-point adjuster is employed. •

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