498 BRAKE SYSTEM TANDEM MASTER CYLINDER (TMC) General: This is a light weight master cylinder with heat treated Aluminum/Cast iron body and with bore anodized. It has rigid steel pistons. This Tandem Master Cylinder, is attached to the transparent plastic brake fluid reservoir which is inserted in to its inlet port, which has baffles to house float of level indicator switch which shows the low fluid level of reservoir and vertical baffles are provided in order to divide the brake fluid of the reservoir in two portions, one is for primary circuit, the other one for secondary circuit. These baffles keep bare minimum fluid on one circuit even if other circuit is drained out. Fluid is circulated separately to primary port and secondary port of TMC due to this division. TandemMaster Cylinder consists of two pistons, four seals, two springs and spring seats. Out of which two seals are fitted on secondary piston and two seals are fitted on primary piston inside TMC bore. Normal Operation: Depression of the brake pedal forces primary piston inside the bore, which in turn pressurizes the brake fluid next to it and actuates brakes connected to primary circuit. Simultaneously secondary circuit gets operated and actuates another set of brakes. One Circuit Operation Primary Failure: Depression of the brake pedal makes primary piston to move inside the bore, but due to failure of primary circuit system can not hold the pressure, also brake fluid next to it will not get pressurized. Still primary piston keeps on moving finally compressing primary piston return spring. When the primary piston return is fully compressed the secondary piston moves and pressurizes brakes connected to secondary circuit. One Circuit Operation Secondary Failure: In this case, the inward movement of the primary piston has little effect in pressurizing the brake fluid in the primary circuit initially, because the initial built up of pressure in the primary circuit causes the secondary piston to promptly yield and move inward without much resistance as the secondary has a leak. Very soon the secondary piston touches the cylinder wall and hence stops moving forward. From this point onwards, the pressure starts building up in the primary circuit which actuates one set of brakes. 1 TMC casting 2 Primary piston assembly 3 Secondary piston assembly 4 Secondary piston stopper 5 Push rod assembly 6 Piston stopper complete 7 Brake oil reservoir 8 Closure plug 9 Spring pin 1 4 5 6 7 8 9 2 3
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