Thompson Steam Engine Indicator
notes: label: Description
content: The American Steam Gauge Co. of Boston, Massachusetts, manufactured this steam engine indicator, serial number 1875. J.W. Thompson patented this style of indicator on August 31, 1875, patent number 167,364.
label: Description
content: An engine indicator is an instrument for graphically recording the pressure versus piston displacement through an engine stroke cycle. Engineers use the resulting diagram to check the design and performance of the engine.
label: Description
content: A mechanical indicator consists of a piston, spring, stylus, and recording system. The gas pressure of the cylinder deflects the piston and pushes against the spring, creating a linear relationship between the gas pressure and the deflection of the piston against the spring. The deflection is recorded by the stylus on a rotating drum that is connected to the piston. Most indicators incorporate a mechanical linkage to amplify the movement of the piston to increase the scale of the record.
label: Description
content: When the ratio of the frequency of the pressure variation to the natural frequency of the system is small, then the dynamic deflection is equal to the static deflection. To design a system with a high natural frequency, the mass of the piston, spring, stylus, and mechanical linkage must be small, but the stiffness of the spring must be high. The indicator is subjected to high temperatures and pressures and rapid oscillations, imposing a limitation on the reduction in mass. Too stiff a spring will result in a small displacement of the indicator piston and a record too small to measure with accuracy. Multiplication of the displacement will introduce mechanical ad dynamic errors.
label: Description
content: The parameters of the problem for designing an accurate and trouble free recorder are such that there is no easy or simple solution. Studying the variety of indicators in the collection shows how different inventors made different compromises in their designs.
label: Location
content: Currently not on view
place: label: place made
content: United States: Massachusetts
setName: label: See more items in
content: Work and Industry: Mechanical and Civil Engineering
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content: Engineering, Building, and Architecture
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content: Work
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content: Industry & Manufacturing
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content: Indicators
creditLine: label: Credit Line
content: Gift of Department of Mechanical Engineering, University of Illinois, Urbana, IIlinois
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MC.316801
label: catalog number
content: 316801
label: accession number
content: 228496
label: patent number
content: 2547
objectType: label: Object Name
content: indicator, steam engine
physicalDescription: label: Physical Description
content: wood (case material)
label: Physical Description
content: metal (overall material)
label: Measurements
content: overall: 4 5/8 in x 8 5/8 in x 7 in; 11.7475 cm x 21.9075 cm x 17.78 cm
label: Measurements
content: walnut case-from catalog card: 4 1/2 in x 7 1/4 in x 9 in; 11.43 cm x 18.415 cm x 22.86 cm