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Unknown "S"

Front View Rear View Side View
Front View Rear View Side View
Front View: Open for Rigging Rear View: Open for Rigging
Front View: Open for Rigging Rear View: Open for Rigging

Technical Details

I acquired my Unknown "S" from Bill Boehle at 2008 Old Timers Reunion.

The Unknown "S" is a home-made bobbin that is 203 mm tall, 38 mm. wide, and 38 mm. thick. Mine weighs 245 g.

The two side plates are made of 34.7 by 3.1 mm. 6061-T6 aluminum. The lower ends of the side plates are bent to converge at the attachment point, which consists of a 12.1 mm. beveled hole in each side plate. One side plate pivots to allow threading the rope. That plate pivots on the lower bollard, while a notch cut in the plate clears the bolt holding the upper bollard in place.

The bollards are 16 mm. lengths of 38 mm. aluminum rod. The upper bollard is bolted to the fixed plate with a 1/4-20 x 1-1/8 UNC bolt that passes through the bollard about 6 mm from the bollard center. The side of the bollard next to the fixed side plate is chamfered. The lower bollard has a 1/4" socket head cap screw and washer passing through its axis; this holds the swinging side plate on. What comes out of the other side of the fixed side plate is 5/16-18 UNC. Without disassembling the bobbin, I cannot tell why neither bollard turns on the side plate.


Bill did not know who made this bobbin, but there was an "S" painted on some of the equipment in the gear set that these came from. As for when it was made, I can speculate - but speculate only. The February 1968 N.S.S. News showed a drawing of a European bobbin; perhaps this bobbin was made as a result of that article?

The chamfering on the top bollard was probably on the original aluminum rod used to make the bobbin, since I can think of no reason to intentionally add it. Neither bollard has a groove, so the rope can run against the side plates. Judging by the wear marks, the original owner may have only used this bobbin once or twice.