This is a 66-tooth replacement delay sector gear for an IBM/Simplex secondary clock. The sector works in conjunction with a correction solenoid to initiate the hourly and daily time-correction cycles in a Hansen movement used in IBM/Simplex synchronized clock systems (see the last photo). The original delay sector was made of copper-plated steel. The portion of the sector that first comes into contact with the steel minute pickup ratchet of the Hansen movement typically experiences the greatest wear. Since new replacement delay sectors are difficult to obtain and appear to be no longer manufactured, I decided to create a replacement.

Due to the precision and material strength requirements of this sector, it is intended to be manufactured by CNC machining or electrical discharge machining (EDM), rather than by selective laser melting (SLM) 3D printing.

To reduce future wear of the pickup ratchet, I chose to manufacture the part from brass, which has better self-lubricating properties and it less hard than steel. In addition, the sector can be easily re-manufactured and replaced if necessary. The brass sector shown in the photos was sponsored by PCBWay and was produced using wire-cut EDM. Although EDM produces a slightly less smooth tooth finish than CNC machining, it is a much more economical method for achieving this level of precision.

The photos show the sector mounted on the rack that attaches to the solenoid of the clock mechanism, as well as the original darker copper-plated steel sector and the new brass sector for comparison.

For more information about IBM/Simplex secondary clocks, please visit my website and my Thingiverse page.