The Spacekeet will be able to track satellites as they fly across the sky. One of the parts required for this is a large dish. The main dish will be a do-it-yourself 120cm wire dish. It is based on a design by the Werkgroep Kunstmanen and drawn by Harry Arends. That design uses an F/D ratio of 0.5, the one I've been building has a ratio of 0.6, which leads to better magnification.
The changes in F/D ratio mean that the curvature of the center radials is altered and this the lengths for those are different than the original plans.
Together with Job de Haas we ordered all the materials at a bulk aluminum merchant and transported the materials on the roof of his car.
We had most of the materials cut to 4m by for transport. We drove them to Peter Smits, a long time member of the Werkgroep, who would help us with the processing of the pieces.
Peter had already built multiple dishes, this 1.20m dish he built in the 90s. It was a useful example on how to do some of the assembly.
Closeup of the assembly of the cross-sections that the wire-mesh can be attached to in order to maintain the parabolic curve.
The radials are placed onto a disk and assembled with nuts and bolts.
The front side mounting disk.
We started off using his self-built roller to bend the 8mm tubing into circles that would form the outer frame of the dish. The total length for this tubing is the diameter of the dish multiplied by pi.
Both the front and back mounting disks where built from sheet material.
They where rough-cut with a plate shear and in the case of the front disk later made fully circular on a lathe.
Afterwards we cut the u-channel aluminum rods that would make the radials to size.
12 pieces for Job's 1m dish and 12 for the spacekeet's 1.2m dish.
Arguably the most difficult part of building the dish is curving the radials. The radials are almost straight towards the center of the dish and then curve outwards. Job had plotted the curvature using * for windows.
The plot was turned into a line graph on which we could compare our results.
Bending happened using the same roller we used to bend the outside frame.
Since it is a manual process we approximated the curvature as much as possible based on the plot
Between the individual radials there are still some that bend back out of shape, these need to be individually hammered into shape.
Perforating the back-side mounting disk with 4mm holes.
Same goes for the front side.
Making a template for the curvature and checking every radial and bending to size
The radials are perforated on two points so they can be attached to the mounting disks
Drilling holes in the radials.
See part two for futher construction details