magneto-electric bell demonstration

magneto-electric bell demonstration

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Motor, D.C., Joseph Henry or Davis, Electro-Magnetic Engine (Bell striking machine), about 1848? A permanent horseshoe magnet is affixed to a wooden base with brass feet. An armature shaft turns in the center of the magnet with an electromagnet turning between the poles. Brushes are applied to a small commutator, and the armature shaft turns a geared wheel causing a hammer to ring a metal gong. Ref: Daniel Davis, Manual of Magnetism, (Boston 1848), 214-15, fig. 147. Old #152115 from SI Collection of Apparatus. See also 1989.0743.341 for another example.
From Davis, 1847: "Revolving Bell Engine. This instrument, represented in Fig. 147, is similar in principle to [cat# 323370], the U-magnet, however, being inverted, so that the revolving electro-magnet is near the baseboard; the pole-changer is on the axis below it. There is, in addition, an arrangement for striking a bell, which is fixed above the magnet. To the axis of the revolving bar is attached an endless screw; this screw acts on a toothed wheel, which is provided with a pin projecting laterally, for the purpose of moving the hammer. As the wheel turns, the pin presses upon the handle of the hammer, raising it from the bell until it is released by the pin at a certain point of the revolution; when a spiral spring, fixed to the handle, impels the hammer against the bell.
If the wheel has 100 teeth, as in the cut, the electro-magnet must revolve 100 times in order to produce one revolution of the wheel, and consequently one stroke upon the bell. The velocity of the rotating bar is measured by counting the number of strokes in a given time ; it may make 100 or more revolutions in a second. In order that the motion of the wheel may raise the hammer, it is necessary to transmit the battery current so that the bar shall rotate in the proper direction."
Currently not on view
Object Name
electric motor
electric bell
Other Terms
Motor; Magnetic Devices; Electromagnetic Devices; Electromagnetic Devices
Date made
C. 1848?
date made
ca 1850
Henry, Joseph
Newman, I.
overall: 13 1/2 in x 4 1/4 in x 6 in; 34.29 cm x 10.795 cm x 15.24 cm
ID Number
catalog number
accession number
Credit Line
from the Smithsonian Institution Collection of Apparatus, thru William C. Winlock
See more items in
Work and Industry: Electricity
Data Source
National Museum of American History
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