parallel motion protractor
Date: 1942
Inventory Number: 2003-1-0127
Classification: Protractor
Subject:
Maker: Charles Bruning Company (founded 1897)
Cultural Region:
Place of Origin:
Dimensions:
instrument: 7.5 × 53.2 × 26.5 cm (2 15/16 × 20 15/16 × 10 7/16 in.)
case: 10.3 × 58.5 × 31 cm (4 1/16 × 23 1/16 × 12 3/16 in.)
Accessories: plywood case; 3/4 inch wrench; black metal end pieces
DescriptionThe drafting machine is stored in a rectangular, varnished plywood case that opens with two brass hinges along one of the long edges. There are two metal hooks on the front of the case that hook onto two pins in the front edge of the lid to keep the case closed. There are two short plywood pieces fixed perpendicular to the back edge. There are also five small round stumps with black felt padding fixed to the inside of the case lid. These extra pieces serve to protect the instrument pieces and hold them in place when the case is closed.
The drafting machine consists of two steel arms that intersect at one end and four discs: one at each free end of the arms and two at their intersection point. The two discs at the intersection point are connected to a shared steel cylinder of smaller diameter such that both arms pivot, making the angle between the arms variable. One of the free-end discs is steel, with a black axle. The other two are black steel on a metal axis. Two thin black steel bars connect the intersection disc with each of the free end discs. The thin bars run parallel to the main steel arms. The black steel disc at the free end of the other arm is unmarked. Beneath it is a black steel platform with squared edges.
The uncovered steel disc at the free end of one arm is in two parts: a base fixed disc, with a rotating smaller disc on top. The base disc has a 360°scale engraved around its circumference. There is a small engraved line for each degree, every fifth and tenth line is slightly longer, and every tenth degree is also engraved with the appropriate numeral, beginning with 0° and ending with 350°. There are two round extensions emerging from the outside circumference of the disc. One of them emerges from the 270° mark and has a small hole drilled through the center. The other emerges from the 45° mark and also has a hole drilled through it and a wing nut screwed into it. The smaller top disc is unmarked except for a small arrow every 90°. The black plastic axle of this disc has a smoothly serrated edge, attached with three screws to the top disc. Turning the axle turns the top disc. Underneath the arm to which this disc is attached is a clear ruler with inch and centimeter scales marked on it in black. The ruler is attached by a pivot such that it can rotate with the steel disc as its center.
The drafting machine comes with a small black steel wrench, two rectangular end pieces, each with three raised edges, and a steel black cylinder with a small round handle.
The drafting machine consists of two steel arms that intersect at one end and four discs: one at each free end of the arms and two at their intersection point. The two discs at the intersection point are connected to a shared steel cylinder of smaller diameter such that both arms pivot, making the angle between the arms variable. One of the free-end discs is steel, with a black axle. The other two are black steel on a metal axis. Two thin black steel bars connect the intersection disc with each of the free end discs. The thin bars run parallel to the main steel arms. The black steel disc at the free end of the other arm is unmarked. Beneath it is a black steel platform with squared edges.
The uncovered steel disc at the free end of one arm is in two parts: a base fixed disc, with a rotating smaller disc on top. The base disc has a 360°scale engraved around its circumference. There is a small engraved line for each degree, every fifth and tenth line is slightly longer, and every tenth degree is also engraved with the appropriate numeral, beginning with 0° and ending with 350°. There are two round extensions emerging from the outside circumference of the disc. One of them emerges from the 270° mark and has a small hole drilled through the center. The other emerges from the 45° mark and also has a hole drilled through it and a wing nut screwed into it. The smaller top disc is unmarked except for a small arrow every 90°. The black plastic axle of this disc has a smoothly serrated edge, attached with three screws to the top disc. Turning the axle turns the top disc. Underneath the arm to which this disc is attached is a clear ruler with inch and centimeter scales marked on it in black. The ruler is attached by a pivot such that it can rotate with the steel disc as its center.
The drafting machine comes with a small black steel wrench, two rectangular end pieces, each with three raised edges, and a steel black cylinder with a small round handle.
Signedengraved on an instrument tab: U.S. NAVY, BuShips / (N) 18540, 1942 / BRUNING-WALLACE NEW YORK
Inscribedstamped in light blue ink on the bottom right-hand corner of case lid: TRA 68
hand-written in black ink on case lid: A76 - 558 / 17M-100
hand-written in black ink on case lid: A76 - 558 / 17M-100
FunctionThis drafting machine was designed to combine the qualities and capacities of a straight edge, a triangle, a scale, a T-square, and a protractor. It was used for making maps, drafting, and architectural plans.
A discussion of the parallel motion protractor is available here.
A discussion of the parallel motion protractor is available here.
