Drop Cut-Off Valve and Mechanism Model

This is a wooden model of a very simple variable drop cut-off valve gear in which a poppet valve is lifted by a bell crank operated by a cam. The cam is a cylinder that may be moved parallel to its axis, so as to bring any part of the cam against the follower of the bell crank. The cam is so shaped that the valve will open at the same time for all positions of the cam, but the valve will close progressively earlier or later as the cam is moved along its shaft.
This description comes from the 1939 Catalog of the Mechanical Collections of the Division of Engineering United States Museum Bulletin 173 by Frank A. Taylor.
Currently not on view
Object Name
valve gear, steam engine
valve gear, steam engine, model
Physical Description
wood (overall material)
overall: 6 in x 13 in x 6 in; 15.24 cm x 33.02 cm x 15.24 cm
place made
United States: Rhode Island
ID Number
catalog number
accession number
See more items in
Work and Industry: Mechanical and Civil Engineering
Industry & Manufacturing
Bulletin 173
Engineering, Building, and Architecture
Data Source
National Museum of American History, Kenneth E. Behring Center


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