Wednesday, 23 January 2013

Central unit construction

At this stage work on the central carrier unit began with the upper ring of the central turntable coming first:
Main machine pivoting structure

The very strong triangular central frame which bolts onto the turntable ring followed:
Central arm support
The sides of the box girders shown above are created entirely out of two mm. gauge steel plates as this unit will support over 400 kgs.

Then came the central barrel-like structure which supports the whole weight of the upper rotating machine arms.  This was created out of 32 bulkheads with girder frames and fully plated with 1mm gauge plate.  These measured 40 holes by 16 holes each.  The outer skin was created by overlapping 0.6mm gauge plates to give an overall skin thickness of 1.2mm.  A very high screw-density was used so that the unit was a close to weld-strength as possible.  The upper and lower annular faces were created using 32 eleven by seven hole plates as was the matching turntable ring show above.  

The roller race between the above units was created from 65 solid brass train wheels based on Meccano's 1.125 inch-diameter wheel but wider, and with deeper flanges.  This roller race will carry a live weight of about 450 kgs.  

An initial attempt at fabricating (from Meccano strips) the rails on which the wheels run was not very successful.  The motion was too jerky.  I replaced this by a single strip of 25x3 mm mild steel, needing only one join.  The action is now much smoother and the rails stronger.
Roller race

 At this stage the barrel-like toroidal structure was placed on trestles and the three supporting projections were created out of 2mm gauge plates.  Each of these carries a 20 mm diameter high-tensile threaded rod.  These rods pass down into three bridge-like structures which carry the 12 main crawler units.

Also attached to the outside of the toroidal main frame are the outer features of this unit, such as, the electric substation with 5 transformers, the large box-like structure at the front and the personnel control room at the rear.
Electrical sub-station
Main supporting bolt

Receiving conveyor in main unit
Personnel access stairs

Another view of personnel stairs

Conveyor belt exiting main body

Control Room
 Also projecting outward from below the main body is a very strong cantilver arm which will carry the off-loader arm.  The 2mm heavy-gauge plates were used to create this.  As seen below this cantilever arm hangs from the outer skin of the main body, which is specially re-inforced to take the load.
Cantilever arm

A transformer

Cantilever arm

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