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Mechanical Combi Brake for small scooters |
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A number of small scooters are equipped
with mechanical drum brakes. The mechanical Combi Brake
is a system designed for small scooters. On application
of the left lever, the brakes will work simultaneously
on the front and rear wheels through the equalizer. On
input of low power, however, the front wheel brake efficacy
is checked to bring nosedive closer to the former level
caused by operation of the left lever. Thanks to the system,
a high degree of deceleration is effectively obtained
through a single operation of the left lever. |
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Fluid pressure type Combi Brake for medium-sized models |
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Fluid pressure type Combi Brakes were developed for
large scooters, medium-sized touring bikes and American
custom cruisers. Hydraulic pressure created by application
of the pedal (or the left lever) is conveyed simultaneously
to the front and rear wheel brakes. Similar to mechanical
Combi Brakes, they are equipped with delay valves to cut
hydraulic pressure to assure no brake will work on the
front wheel at input of low power. The hydraulic pressure
type Combi Brake is similarly effective to the mechanical
Combi Brake; a high degree of deceleration can be effectively
obtained by operation of the pedal (or the left lever)
only. |
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Braking force distribution characteristics of combination brakes
to front and rear wheels |
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The above figure shows the braking force distribution characteristics
of the Combi Brake of a certain model, to front and rear wheels.
The axis of abscissa represents the braking force of the front
wheel while the axis of ordinate the braking force of rear wheel.
The curve connecting blue points indicates an ideal braking
force distribution characteristics in case of a single rider
while the same connecting red points the ideal braking force
distribution characteristics in case of maximum loading.
The maximum deceleration on a road surface having a friction
coefficient occurs immediately before the simultaneous lock
of the front and rear wheels. Individual points denote ideal
braking force distribution on a road surface µ. Ideal
braking force distribution characteristics are obtained by connecting
points of ideal braking force distributions of respective friction
coefficients. On a road surface with friction coefficient (µ)
of 0.2 in case of single rider (green circle), for example,
the figure shows that it is better if the braking force on the
rear wheel was made larger than the front wheel. In case of
1.0 (yellow circles), on the other hand, it will be better if
the distribution on front wheel brake was increased.
The riders will make either higher or lower distribution from
the ideal braking force distribution characteristics. Making
higher distribution will indicate that braking force distribution
on rear wheel is larger while making lower distribution will
show the braking force distribution on front wheel is larger.
The dark blue line denotes the braking power distribution characteristics
into the front and rear wheel on operation of pedal (or the
left lever) of the Combi Brake. Being positioned above the ideal
braking force distribution characteristic diagram, the braking
force distribution on rear wheel is larger. On operation of
the right lever, braking force will take place on the front
wheel only so that the distribution will be on the green line
of front wheel braking force line.
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