113 Brake shoe expanders and adjusters

11.3.1 Self-adjusting sector and pawl brake shoe mechanism (Fig. 11.10(a, b and c)) With this leading and trailing shoe rear wheel brake layout the two shoes are actuated by opposing twin hydraulic plungers.

A downward hanging hand brake lever pivots from the top of the trailing shoe. A toothed sector lever pivots similarly from the top of the leading shoe, but its lower toothed sector end is supported and held in position with a spring loaded toothed pawl. Both shoes are interlinked with a strut bar.

Hand brake operation When the hand brake lever is applied the cable pulls the hand lever inwards, causing it to react against the strut. As it tilts it forces the trailing shoe outwards to the drum. At the same time the strut is forced in the opposite direction against the sector lever. This also pushes the leading shoe via the upper pivot and the lower toothed pawl towards the drum. The hand brake shoe expander linkage between the two shoes

(bl New lining; foot brake applied

Fig. 11.10(a-c) Self-adjusting sector and pawl shoes with forward full hand brake

(bl New lining; foot brake applied

Fig. 11.10(a-c) Self-adjusting sector and pawl shoes with forward full hand brake therefore floats and equalizes the load applied by each shoe to the drum.

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