Wire Antenna Corner Pulley 4 inch

This is a pulley for use with a wire antenna, typically to be used as a corner pulley with a horizontal full wave loop, aka “sky loop”.  The sheeve diameter is approximately 4 inches (110mm).    The primary design objective was to constrain the wire to prevent it from leaving the sheeve groove and potentially getting caught between the side of the sheeve and the pulley frame.  It should easily accomodate wire sizes from 10awg to 20awg, but I have only used it with 14awg THHN so far.

This is a “split frame” pulley.  With the axle in place, the frame sides can pivot to allow insertion of a pre-strung wire without the need for access to a wire end.  After insertion, attachment of the pull up line through the holes in both frame ends will prevent them from pivoting open.  The holes in the frame ends should accomodate up to an 8mm line.

The  hardware required for assembly is a 608 style bearing and a 20mm M4 cap head screw, preferably stainless steel.  The bearing spacer component is inserted into the bearing during assembly to accomodate use of the M4 screw as an axle.  One frame side has a countersunk hole to accomodate the M4 cap, the other is sized for the M4 screw to self thread.  Depending on your printer settings, some deburring of printed parts (or mechanical persuasion) may be needed to allow insertion of bearing, spacer and screw.

Two versions of the hub are provided, one that is solid and one with “spokes”  the solid version uses about 25% more material than the “spoked” version.  I used 5 walls, 5 top/bottom layers and 20% infill.

The filament used needs to be resistant to weather and UV exposure.  I have been using ASA for my latest pulley prints but PETG may be a resonable alternative for shorter term use.

Print with the flatest side down.  No supports are needed.

Source is provided as F360 and STEP files.

A prior, 3 inch, version can be found here:

https://www.printables.com/model/437051-wire-antenna-corner-pulleys-3-inch