Scale choice and original design respectI wasn't satisfied with my first carrier, the I start a complete new one.
Scale choice and original design respectThe first carrier was too small. I decide to use bigger wheels
(type 24x43, 84mm diameter). I also decide to respect as well
as it's possible a constant scale and original design of the truck.
Scale is given by wheels dimension : in reality, they are 1m40
diameter. So scale is 1/17.
The truck is 18cm width (22 Lego units), 70cm long (88LU) and 11cm high on the plate part. I work based on an original Demag drawing with general dimensions, converted in desired scale.
Chassis rigidityChassis strictly respect, on all its length, the stacking rule to get strong interlocking with vertical beam (see first carrier for picture).The stacking is : beam, plate, plate, beam, plate, plate, beam...
They are lot of interlocking beams, distributed on all the chassis. It's very important to be as rigid as possible, from the turntable to the outriggers. If the chassis twist under charge, the crane precision decrease a lot, particulary when you take of a charge.
I specially work on outriggers design : they
are fully integrated in carrier, and move in very strong boxes.
Those boxes are able to support high torques wich occurs during
lifting.
See here for outriggers deployment
AC120 carrier is very easy to control while approaching lifting place. It use a fonction to move separatly axles 1+2 and axles 3+4. But to do that, you need a retractable axle 3. (see on picture below). I've build this specific axle 3, handly retractable.
Axles 2, 3 and 4 are driving axles. Differentials on each one. I didn't manage suspensions on axles (no room enough...). I use 8880 wheels for steering and driving axles.
See here photos during chassis construction
On first carrier, steering wasn't
OK : there where important differences between front and rear
wheels. Then I use a long transmission line. Each axle have its
own demultiplication system (1/3) to drive the rack. Transmission
line is turning faster, I got less torque and less deformation.
I did not found room to manage a gear box to disconnect front
axles from rear axles.
Axles 1 and 5 turn more than 2 and 4. Drag links are shorter
on those axles.
Superstructure has to be well-fixed to the crane. Technical solution is the same than first carrier. But, I'm not sure it's the best way to do that. When crane is under charge, with counterweight, it shocks during rotation. Dennis Bosmann has manage it by directly driving turntable with no-end screws. It's not easy to do that for my truck beause of supperstructure design.
Electric
drivesChassis is fully motorized. 3 drive axles, 4 steering axles, superstructure rotation. Regarding the machine weight, I use a non Lego motor for main drive. Despite the high power of this motor (12W), I had to get big demultiplication.
Steering drive has been constructed after the photo, at right.
Superstructure drive is under the chassis, and transmission to turntable use a chain (see it on picture at to of this page).
After drives, I worked on the cabin, starting by front inclined plan. I made it without verifying aspect and scale. For the moment I get a kind of "sovietic" design ! I have to work on it !
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