The 6-pin connector, extending from the front steering unit:
The opened-up steering unit gearbox showing the motor and potentiometer:
The opened-up gearbox and contents from another angle:
The complete gearbox unit, with the back piece, the contents, and the front cover. The front cover contains the gears that attach to the external arm:
The contents of the front cover of the gearbox:
The back of the gearbox with the motor and potentiometer in place:
The complete gearbox, in two pieces:
The complete closed gearbox:
The following video demonstrates the gear operation that takes place within the gearbox covering (I apologize for the probably-too-short length of the video):
With the gearbox apart, the physical connections for each of the wires in the 6-pin connector were inspected. The connector's wires, from left to right are (1) brown, (2) red, (3) orange, (4) yellow, (5) green, and (6) blue. Wires 1, 2, and 3 are connected to the potentiometer, while wires 4, 5, and 6 are connected to the motor. Wire 1 is connected to the middle terminal of the potentiometer, and wires 2 and 3 are connected to the side terminals. Wires 4 and 6 are connected to the DC motor terminals, and wire 5 is connected to the motor's metal casing (ground).
The resistance between wires 2 and 1, and wires 3 and 1 vary as the potentiometer is turned, while the resistance between wires 2 and 3 remains constant. The constant, and maximum resistance between wires 2 and 3 was measured as approximately 4.9 kiloohms.
With the gearbox unit out of the truck chassis, resistance measurements were taken for the turning arm in left and right extreme positions, and the approximate center position between wires 2 and 1, and wires 3 and 1. With the arm in the extreme left position, the resistance between wires 2 and 1 was 4.51 kiloohms, and the resistance between wires 3 and 1 was 0.57 kiloohms. With the arm in the extreme right position, the resistance between wires 2 and 1 was 0.49 kiloohms, and the resistance between wires 3 and 1 was 4.62 kiloohms. In the center position, the resistance between wires 2 and 1 was 2.54 kiloohms, and the resistance between wires 3 and 1 was 2.67 kiloohms.
A document containing these measurements is located on Google Documents and can be viewed by following this link.
With these measurements, I placed the steering gearbox unit back into the truck chassis. The gearbox is situated between the left and right sides of the housing for the front driving mechanism. The driving mechanism entirely encapsulates the steering gearbox with only the 6-pin wire exposed to interface with the motor and potentiometer in the gearbox. Photos of the gearbox and front driving mechanism are shown below.
The approximate location of the steering gearbox in the driving mechanism:
The opened-up front driving mechanism:
The closed front driving mechanism with the 6-pin wire exposed:
With an understanding of how the existing front steering system operates, I plan to design and build circuits to detect when the wheels have been turned to an extreme position, and to prevent any attempt of turning further than this (to prevent the gears from grinding). In addition, I'd like to be able to turn to an exact position and quickly re-center the wheels.
