Penumbra: Requiem/The Engine

You awaken in front of a laser gate, with only a cog wheel and a ladder visible from where you are.

To save some time, take the cogwheel before you climb down.

Engine and laser gate
The first step is to go through the engine. Climb down two ladders, walk to the end, and enter the engine. You will need to pass through two pistons, and you can easily run through the ring as they are raised. At the third piston, enter the vent on the right to reach a makeshift sleeping area. Turn the valve to stop a spray of steam blocking access to part of the level, and collect the handle from the nearby shelf. Return to the piston and continue right.

Unblock the door by moving the crate. You can now put the handle in the control panel next to the large glass window, and can touch the portal key. Also, take the second handle on the shelf and put it in the panel.

You now need to find the three cog wheels and place them on the cog spokes. The first cog wheel was found at the laser gate, and is placed on the right cog spoke. The second is behind a pipe on the second floor, in the corner just before the round hole, and is placed on the left cog spoke. The third is on the other side of the floor, under a pipe where the steam was spraying, and is placed on the middle spoke. When the cog wheels are in place, press the button next to the machine, and a ball will drop. Roll it into the nearby hole.

Climb down, and use the control panel to move the ball to the destination. Although you can eventually complete the puzzle by randomly playing with the controls, the a quick combination is: Pull left, pull right, push left, push right, push left, pull left, push right, pull left, pull right, pull left.

Artefact
From the second floor, jump from the ladder to the roof of the engine. The artefact is found in the far corner.

Portal keys
You now need to collect to remaining keys. On the side of the floor opposite of the engine, you will see a set of stationary pistons. Press the button on the chain link fence to activate them, and jump across each piston.

The second portal key is on the left path, and doesn't have anything too special.

The third portal key is in the caged area across from the main section. In this area, you will need to jump over the explosive barrels as they roll down. The barrels will also touch you if you wait on the ladder, but can be evaded by waiting until after they fall before starting the climb. When you reach the top, the portal key is in plain sight.

With all three keys, you may now return to the starting area and exit the level.