Page 105 - TBIS_15194-2019_(EN)_3nd

TBIS 15194:2019

4.3.14 Chain-wheel and belt-drive protective device
4.3.14.1 Requirement

EPAC shall be equipped with one of the following;
a) a chain wheel disc or drive pulley disk which conforms to 4.3.14.2; or

b) a chain and drive belt protective device which conforms to 4.3.14.3; or
c) where fitted with positive foot-retention devices on the pedals, a combined front

gear-change guide which conforms to 4.3.14.4 shall be used.

4.3.14.2 Chain-wheel disc and drive pulley disc diameter

A chain-wheel disc shall exceed the diameter of the outer chain-wheel, when
measured across the tips of the teeth by not less than 10 mm (see Figure 44).

A drive pulley disc shall exceed the diameter of the front pulley, when measured
across the tips of the teeth by not less than 10 mm (see Figure 45). Where the design
is such that the pedal-crank and chain-wheel are too close together to accommodate

a full disc, a partial disc may be fitted which closely abuts the pedal-crank.

Dimensions in millimetres

1 Chain-wheel disc D2≧D1+10

Figure 44 — Chain-wheel disc

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