Object Name: upright reciprocating engine model
Dimensions: 33.5 x 27.7 x 14.9 cm (13 3/16 x 10 7/8 x 5 7/8 in.)
Description: This engine stands on a rectangular mahogany base with four brass ball feet. It consists of a pair of horseshoe electromagnets mounted upright, painted green and red. On top, there is a rocking (or vibrating) beam with armatures at each end, formed of U-shaped soft iron pieces that go directly over the electromagnets' poles. One arm connects the beam to the axis of the flywheel, giving its reciprocating motion. There is a pole changer on the same axis. The flywheel is supported by two turned brass columns. Two binding posts on the base were connected to a battery.
This instrument bears an old Harvard number: "6-4-3".
Davis sold this intrument between $10.00 and $20.00 in 1842.
Signed: on plaque: DANIEL DAVIS Jr. / Maker / Boston
Function: The reciprocating action, produced by the pole changer alternating current direction through the electromagnets, is transferred, by the beam, to the fly wheel's rotation.
Primary Sources: Daniel Davis, Jr., Davis's Manual of Magnetism (Boston: Daniel Davis, Jr., 1842), 113-114.
Provenance: From the Department of Physics, Harvard University.
Related Works: Sara Schechner, "Daniel Davis, Jr. and the Electromagnetic Instrument Industry: A Field with Great Potential in the Early 19th Century," unpublished manuscript (1978), available in the CHSI Library (Lib.4884).