I'm a huge fan of LEGO® pneumatics, so the crane has to be lifted by small Pneumatic Cylinders (x189c01). A Small Pump (x191c01) is used in combination with a Technic Engine Crankshaft (2853) in order to achieve a 1L displacement.
Here is the result:
|Small Pump in the middle, two Small Cylinders and the Switch|
|Crankshaft with only 1/2L to use the space efficiently|
I also made two videos of the pump turning and lifting the boom.