Page 43 - Demo

Page 43.Alvis Three Litre Shop Manual - T.A. 21 and T.C. 21BRAKESThe brakes of the ALVIS THREE LITRE are of the Lockheed hydraulic type operating inside drums of 11%u201d diameter and 21/4%u201d wide, providing an exceptionally large friction area. The two leading shoe front brakes, and leading and trailing rear brakes, give extra power and lighter pedal effort for forward retardation, while retaining the advantage of one leading shoe when braking in reverse. The rear brakes are in addition mechanically operated by the pistol grip hand brake, independent of the %u2019hydraulic system.The foot pedal operated master cylinder of the integral barrel type, containing a reserve supply of fluid, generates a hydraulic pressure which is transmitted through pipe lines to the two wheel cylinders between the front brake shoes and the one wheel cylinder between the rear brake shoes. The master cylinder, like each wheel cylinder, has a single piston provided with a rubber cup to maintain the pressure and prevent loss of fluid.When the brake pedal is depressed the pressure generated is transmitted with equal force to all the wheel cylinders. Each front wheel cylinder piston operates against the leading tip of its respective shoe, the trailing tip locating itself against the closed end of the other cylinder, both shoes being free to slide and centre themselves.The single cylinder on each rear wheel operates against the leading shoe which is free to slide against a fixed anchor block at the bottom of the back plate. The trailing shoe is located in a similar manner between the anchor block and the closed end of the wheel cylinder, making both shoes selfcentring, and is operated by the reaction of the leading shoe against the brake drum, the wheel cylinder being free to slide in an elongated slot in the back plate.When the brake pedal is released the pistons are forced back into the wheel cylinders by the brake shoe pull-off springs, and the displaced fluid is passed back into the master cylinder.HHydrauaulicic Flui uidIt is advisable to check the level of the hydraulic fluid every 2,000 miles, and top up, if necessary, to maintain the level at approximately ( 1/2%u201d ) below the filler neck of the master cylinder. The master cylinder is mounted beneath the bonnet on the driving side of the chassis.If it is found that the level has dropped considerably the pipe lines and connections should be inspected for leaks in the system, which should in any case be checked periodically, taking care not to over-tighten the unions.The air vent in the filler cap must be kept clear, otherwise the brake shoes are liable to drag.Only genuine Lockheed brake fluid should be used for topping up and cleaning internal parts, as other fluids are likely to prove injurious to the component parts of the system.Brakake AdjuustmtmenttWhen the car is assembled the length of the rod between the brake pedal and the master cylinder is adjusted to give approximately ( 1/2%u201d ) free movement at the pedal pad, and should never need alteration. This free movement can be felt by gently depressing the pedal by hand and if it is not apparent it may be found that the brake pedal is fouling a displaced carpet or some other obstruction.Each wheel cylinder is provided with a %u2018Micram%u2019 adjuster, located between the piston and the brake shoe. Briefly this consists of a double serrated snail cam mounted on a spindle on which the brake shoe is located, the serrations on the periphery of the cam engaging with a ridge formed on the back of the %u2018Micram%u2019 mask. When the spindle is rotated in a clockwise direction with the aid of a screw-driver, the distance between the shoe and the piston is increased, and the lining moves nearer the drum. The serrations retain the cam at the desired setting and