Landing Module, Vertical Drive Tower and Gravity Motor.
The Landing Module (LM) is subject to vertical motion drives both from thrust demands and from the gravity motor. These two drive inputs are combined via a central differential gear assembly which then provides an output chain drive to the Vertical tower. Thrust and Gravity will usually oppose each other, but they could also work together should the player decide to conduct a suicide mission!
Thrust demand input is covered in detail in the sections on "Variable Speed Drive's" and "Lander Control And Sensing Unit"
This drive input feeds into the differential from the right.
The Gravity motor and gearbox feeds in from the left. The gearbox has two speeds which are selectable by the player to provide a "level select" feature - easy level (Mars Gravity) and hard level (Earth Gravity).
Mars Gravity is roughly a third of that on Earth. So, the gearbox offers a 1:1 ratio and a 1:3 ratio accordingly. The selected ratio is engaged by energising an electro-mechanical clutch. Both clutches and motor are disabled until the Start Button is depressed, so until this happens, the LM remains "locked in orbit"
The Vertical motion chain drive enters at the bottom of the tower via a 5:1 reduction gear. This drives the lower sprocket of a final chain drive to the top of the tower. The chain links to a travelling carriage which carries the upper pantograph link, and of course the Landing Module, up and down the tower.
Also at the lower end, a step-up gear arrangement drives a centrifugal speed switch - part of the safety element for the "Crash or Land" logic. Limit switches at top and bottom of the tower prevent over-travel of the drive systems.
The LM has a thrust flame feature which operates at all altitudes and attitudes. When the thrust lever is pushed forward, a jet flame appears below the LM. This is actuated by a cord system passing up the pantograph, to a swivelling link on the LM shaft. The photos show the final part of the mechanism to extend and retract the flame.