Four-axle Mobile Crane with Two-stage Telescopic Boom

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(Click on any image to enlarge it)

Mobile Crane #3, picture 1


  • First 2 axles steerable
  • Last two axles drive a V8 engine
  • All four axles with suspension
  • Four independent supports: extendable in width and height
  • Revolving upper structure
  • Boom liftable with Pneumatic cylinders and extendable by a gear rack
  • Quadruple pulley for hook
  • Fully detailed drivers and crane operators cabin

The only thing the third mobile crane has in common with the second one are the wheels.
These are now mounted on four indepenent, fully suspended axles. Steering works by the flashlights via flex system cables on the first and second axle. The first axle has a greater steering angle than the second.

Mobile Crane #3, picture 2

The picture on the right shows the crane with fully extended boom.
Lifting works with two old Pneumatic cylinders. They are a bit weak but with the help of two airtanks (mounted on the chassis between the axles) it works. The telescope is extended by a crank, mounted on top of the boom which drives a gear rack.
On this pic you can also see the supports. They are extended by a gear rack too. In the height you can adjust them with threaded 10' axles. See in addition to this my building hints section about threaded axles.
The hook is lifted by a quadruple pulley. Because the official LEGO hooks don't fit two wedge belt wheels I mounted them between two side plates which are connected to the hook.
Revolving of the upper structure works with a crank which is located at the back end of the chassis.

Mobile Crane #3, picture 3

The left picture shows some of the details of the model. These include a fully working V8 engine which is driven by the two last axles. Extendable axles connect the third axle with the engine and the fourth axle with the third. Because of the suspension the axles have to be extendable. I solved this problem by using a transmission driving ring which connects two axle connectors.
More details include a cabin with a working steering wheel which is adjustable. There are also exhaust and air intake pipes beside the engine compartment which is openable.
Two ladders are located on the chassis. They are needed to get up to the crane operators cabin. The cabin features a detailed seat and levers as well as pedals.

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