Model of Theodore Judah Surveyors Compass

I constructed this compass over a week or so in January of 2020 for the purpose of demonstrating traditional 19th century surveying at the California State Railroad Museum. They have an original compass apparently used by Theodore Judah on display. It is assumed he used it in his surveys of the Sierra for the original transcontinental railroad in the 1850's. My compass is NOT a replica, but rather a reconstruction in the spirit of the original based on materials I had on hand, Judah's original compass, and practical considerations for an instrument that could be shown to and used by adult and school-age visitors to the museum. 

The compass body was cut with a jig saw from  1/4" oak veneer plywood to a pattern inspired by the original compass. The size was constrained to fit an old Craftsman replacement surveyors compass box (cast pot-metal with plastisized paper card and scale, screw operated arrest and scale adjustment for declination). The compass is set into an aluminum ring (originally recovered from an old hard drive, with a notch cut into one side to accommodate the compass arrest and set screws  tapped into three locations and holes drilled for four wood screws to hold it onto the body). A bullseye level recovered from an old instrument is substituted for the east-west single vial on the original compass. For convenience an adapter to allow the compass to be mounted on a standard camera tripod with a hole was turned from stock 2" brass round stock, drilled a tapped to fit a 1/4" 20 tpi screw and attached with four small machine screws via tapped holes. Finally, the two sights (single beveled hole for the fore-sight and an oval hole with wire on the far-sight) were fabricated from some rectangular brass microwave conduit and and attached with an alignment screw and thumbscrew each.

The made to fit case was then fabricated over the following week from scrap lumber and miniature cabinet hardware found in my shop. The sides were cut from light hardwood from a broken CD storage rack. The top was cut from 5/32" hardwood plywood, while the bottom was cut from two sheets of 1/4" mahogany paneling glued together with one fitted into the box and the other covering the side-edges. Small chunks of Luan "mahogany" were then cut, drilled and notched to fit the compass body and sight vanes. A furniture pad and two felt pads were glued to the inside lid to secure the compass and vanes.