I worked a lot on this part. I made several versions. There is not so much place in the boxes.
I had already choose Boom and carrier color. Then the only possible color was yellow (free parts...). At begining, superstructure was completely yellow, but it looks very massive. Then I created the black line to decorate the model.
Superstructure is easily removable from carrier. It's fit on
the carrier's turntable and lock by three red axle 12. Internal
design of superstructure is a bit complicated by this choice,
because I need to left free space for axle to go through.
Superstructure internal faces, near the winches, are made with
strong stacking (beam, plate, plate, beam...), and is beam interlocking.
Boom and A-frame are removable : boom with a red axle, A-frame with 2 technic friction pins.
As the crane is a mix between two different models (crawler
crane Terex and telescopic crane Demag), I had some scale inconsistencies.
Superstructure scale was 1/22 and truck is 1/17, then driver cabin
was too small. I rebuilt it bigger and now it looks fine.
I also add a driver and a new seat. Seat is adjustable.
Winches
: 3 versionsSuperstructure is made in 3 parts : left box with driver cabin, middle part with winches, and right box. In each box are placed winche's drives. In first version, there were only 3 winches. To wind up cables I use wheel rim, without tyre. I need great demultiplication to drive winches. You can see here the most compact reduction I can make. You get a strong torque, but it's quite slow (on big winches there is more than 15m of wire ! Wind up time are long !).
I tried to manage a gear box with 2 speed.
It works, but frictions are important, and brake the drive. The
speed isn't higher than first version, and I lost lot of torque.
Then I made a new version, with 4 winches ! Boxes are completely full with drives, reductions, electric switches and wire, axles way...
On top of boxes, I put klaxon, lights, exhaust pipe and winches control lever.
CounterweightsThe crane has 3 removable counterweights : a central one plus
2 auxiliaries. They are separately transported, in order to maintain
the truck under 12mTon by axle on the road. Installation procedure
is : 1. Crane is placed and take off on its outriggers. 2. main
boom is fixed and lift. 3. Central counteweight is take from transport
truck to the crane, and put just behind 
truck's
cabin. 4. auxiliary couterweights are fix to the central one.
5. superstructure turn and take off counteweight.
Counterweight are Lego boxes, fill up with lead blocks, especially cast in fitting dimensions.
A-frameA-frame is use to lift boom. It doesn't need to work fast,
but to be very strong (it works in compression mode). I use pulleys
demultiplication (10 pulleys). Those pulleys cause me lot of problems.
I started using Lego pulleys, fixed with this technic pin :
But pulleys are overhanging and don't turn easily under charge.
As I dont want to modify Lego parts, I have built myself specific
pulleys. They are thin, loose pulleys, with a big gorge.
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Booms |