QUESTION 2: a) Name the components labelled A, C, D and E. b) Complete the steering circuit in figure 2. c) Explain the operation of the circuit when driving on a straight path.

Here's the solution for Question 2:

a) Name the components labelled A, C, D and E in Figure 2.

• A: Steering Control Unit (or Orbital Steering Valve)
• C: Hydraulic Pump
• D: Double-Acting Hydraulic Cylinder
• E: Hydraulic Reservoir (or Tank)

b) Complete the steering circuit in Figure 2.

To complete the steering circuit:

• Connect the pressure line from the hydraulic pump (C) to the pressure port (P) of the steering control unit (A).
• Connect the two work ports (L and R) of the steering control unit (A) to the two ports of the double-acting hydraulic cylinder (D).
• Connect the return port (T) of the steering control unit (A) to the hydraulic reservoir (E), typically through a filter.
• Connect the pressure relief valve from the main pressure line (between C and A) back to the hydraulic reservoir (E).
• Ensure the suction line of the pump (C) is connected to the hydraulic reservoir (E).

c) Explain the operation of the circuit when driving on a straight path.

When driving on a straight path, the steering wheel is in its neutral position, which means the steering control unit (A) is also in its neutral state. In this position, the internal valving of the steering control unit directs the flow from the hydraulic pump (C) directly back to the hydraulic reservoir (E) through an internal bypass passage. This ensures that no hydraulic fluid is directed to the double-acting hydraulic cylinder (D). Furthermore, the ports leading to the cylinder are blocked, hydraulically locking the cylinder. This prevents any unintended movement of the steering wheels, maintaining the vehicle's straight-ahead direction with minimal power consumption from the pump.