$3.$ Modify the circuit designed for question $2$ to provide an emergency stop which

will park both cylinders in the extended position $($i$.$e$.$ A $+$ B $+).$

Teesside University Open Learning $($Engineering$)$ TEESSIDE UNIVERSITY $2018$

$4.$ Show, with the aid of a schematic diagram, how an electronic controller could

be included in the circuit designed for question $3$ to control the sequence of

cylinder operation. The circuit should also include a fail$-$safe which should:

$($a$)$ act in the event of a reduced pressure at inlet to the group selecting

valve

$($b$)$ act in the event of a failure of the electric supply and

$($c$)$ park the cylinders in the retracted position.

Explain the operation of the fail$-$safe.

$5.$

$($a$)$ Draw the circuit diagram showing how a bi$-$directional hydraulic motor

can be driven by a unidirectional hydraulic pump with both torque

control and $$meter out$$ speed control.

$($b$)$ Explain the operation of the circuit you have designed in part $($a$)$ above.