parallel motion protractor
Date: circa 1940
Inventory Number: 2003-1-0128
Classification: Protractor
Subject:
Maker: Charles Bruning Company (founded 1897)
Cultural Region:
Place of Origin:
Dimensions:
closed: 54.6 × 16 × 10.5 cm (21 1/2 × 6 5/16 × 4 1/8 in.)
Description:
The drafting machine consists of two steel arms that intersect at one end and four steel discs: one at each free end of the arms and two at their intersection point. The two discs at the intersection point are connected above and below by a steel cylinder such that both arms can pivot, making the angle between them variable. There are two elliptically shaped black rubber bands: each is wrapped around the intersection steel disc and one of the two free end discs, paralleling the black arms.
One of the free-end discs is black with another, larger steel disc fixed on the bottom of it. A thin, flat steel tape extends from the side of this disc. This bottom steel disc is attached by a pivot and so can rotate around the disc. The disc at the free end of the other arm is black and has a perpendicular rectangular attachment with a whole through each end on the bottom.
One of the free-end discs is black with another, larger steel disc fixed on the bottom of it. A thin, flat steel tape extends from the side of this disc. This bottom steel disc is attached by a pivot and so can rotate around the disc. The disc at the free end of the other arm is black and has a perpendicular rectangular attachment with a whole through each end on the bottom.
Signedengraved in instrument arm: BRUNING-WALLACE DRAFTER / CHARLES BRUNING CO. INC.
Inscribedengraved on instrument arm: 473
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, navigation, and drafting plans.
A discussion of the parallel motion protractor is available here.
A discussion of the parallel motion protractor is available here.
