Announcing my latest Lego project: a walking dragline.
A dragline is a type of excavator which uses a bucket suspended by cables from the end of a boom and the front of the machine.
A walking dragline rests on a circular tub and does most of its work while stationary. In order to move it uses to feet that come down, lift and pull the crane back.
These machines are used mainly in large open pit mines. They are themselves very large: a typical bucket contains 100 cubic yard of dirt. Total machine weight is measured in thousands of tons.
Here is a link such a machine at work. You can see the erection of such machine here.
I will not model a specific machine as my main goal is to build a functional model in a scale suitable for the Lego minifigs (about 1:50). The model will have four main powered functions: walk, slew and bucket motion (two winches).
The electrical system will be custom built. This provides several advantages: full rado control, use of the transformers as ballast, reliable high power available.
The machine, like the real ones, will be electrically powered through a long power cord. While the real machines use high voltage (several thousands of volts), mine will have a standard 110V cable. This cable will go through the pivot point using a Mercotac slip ring. The upper works will contain three transformers: two 20V units and one 5V unit. While the 5V unit will power the radio receiver and drive logic, the 20V will be used to power the motors, wired in series two by two trough a pair of H-bridge chips from Allegro.
The radio control system will be based on a cordless gamepad controller for PC manufactured by Logitech. I picked this product because I worked on its development and I have access to its schematics and firmware source code. This part of the project will not be documented on this site.