Demonstration Model of a Slide Valve for a Steam Engine
name: label: maker
content: Severn-Lamb Ltd.
notes: label: Description
content: This is a demonstration model of a slide valve for a steam engine. By about 1820 such valves had evolved as the simplest devices for controlling the steam inlet and exhaust for a steam engine cylinder. This type of valve was operated by an eccentric that caused it to slide back and forth, alternately opening ports for inlet and exhaust at each end of the cylinder. Inlet steam was cut off when the inlet port closed at a fixed point in the stroke of the engine.
label: Description
content: The speed of the engine was controlled by throttling the steam supply. No provision was made for adjusting the point of cut off while the engine was running. This feature was added in later evolutions of valve designs resulting in increased efficiency and the ability for automatic control of the speed of the engine. Several patent and demonstration models of such variable cut off valves are included in the collections.
label: Description
content: The model was built to operate and show how the valve functioned. It shows a steam cylinder and valve case in cross section. The crankshaft of the engine is at the right of the model, and the eccentric is seen mounted on that shaft. The eccentric operates a crank arm which in turn operates the D valve. A steam pressure versus volume curve is shown below the cylinder. A label at the right of the model describes the functioning of the valve. A separate label on the top of the model case describes the limitations of the valve design.
topic: label: Subject
content: Steam Engines
label: Subject
content: Model
setName: label: See more items in
content: Work and Industry: Mechanical and Civil Engineering
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content: Engineering, Building, and Architecture
label: Exhibition
content: Power Machinery
label: Exhibition Location
content: National Museum of American History
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MC.325394
label: catalog number
content: 325394
label: accession number
content: 253584
objectType: label: Object Name
content: Engine, Steam, Valve Gear
label: Object Name
content: engine, steam, slide valve, model
physicalDescription: label: Measurements
content: overall: 12 in x 18 in; 30.48 cm x 45.72 cm