PO Box 19, Coolspring, Pennsylvania 15730
We found a story in the Rough & Tumble Engineers' newsletter about a very rare engine that had been on display there last summer, courtesy of the Coolspring Power Museum. So, we wrote to Preston Foster at the museum who was kind enough to reply with the following explanation and photos.
The Harvard engine in the Coolspring Power Museum came from the collection of the late Neils A. 'Andy' Kruse of Park Ridge, Illinois. Andy died November 28, 1986. He had a very extensive collection of engines numbering about 225.
Andy had been an early supporter of the Coolspring Power Museum, and his wife Ruth and son Nelson thought it fitting that the engine should go to CPM for permanent display. This engine came to CPM in 1987. Though the engine was restored and was in sound mechanical condition, it never ran as designed.
Dr. John Wilcox, a director at CPM, has long had an interest in seeing how the engine did govern. In 1995 the engine was hauled to his home in Delaware, Ohio, and he did a very complete rebuild of the engine. With some machining help from fellow director, Preston Foster, John returned this engine to factory design running specifications. This engine now runs as it did when it left the factory and even possibly better.
Total credit for this very time consuming project goes to John.
The following is a drawing that explains how the engine governs and shows a section of its construction:
Charles A. Stickney Company, St. Paul, Minnesota.
Design circa 1900. Sold by Sears, Roebuck as 'Harvard' 19024903.
Stickney Vacuum Governing System: Under power, governing valve is open. To initiate an idle cycle, governing valve is pressed shut for a short time at beginning of intake stroke, resulting in these events:
1) Intake Stroke. Main valve open. Increasing vacuum bounded by governing valve and exhaust check. Vacuum holds governing valve shut against its spring.
2) Compression Stroke. Main valve shut. Decreasing vacuum in cylinder. Maximum vacuum is maintained between main valve, governing valve, and exhaust check. This vacuum holds governing valve shut.
3) Power Stroke. Main valve shut. Increasing vacuum in cylinder.
4) Exhaust Stroke. Main valve open. Decreasing vacuum everywhere. Governing valve pops open near end of stroke, unless pressed shut to initiate another idle cycle.
The Stickney Junior is the only engine known to govern on this principle.