Vertical Tandem-Compound. A vertical tandem-compound engine, the Willans, is shown in section in Fig. 64. This engine, which was originally manufactured in England, presents some peculiar features. The cylinders have no inlet or outlet ports as is usual in most steam engines. The ports are in the trunks, which are connected to the high and low-pressure cylinders through the ports in the trunk, as shown. The exhaust from the high-pressure cylinder passes into the trunk below its piston and from there to the low-pressure cylinder, the admission and release being regulated by a piston valve which works in a trunk connecting the two pistons. The piston beneath the low-pressure cylinder acts as a guide or crosshead for the upper end of the connecting rod. The pistons and the trunk move as one piece, the trunks taking the place of the steam chest and piston rod. The various piston valves also move as one valve. The valves are moved by an eccentric on the crankpin, and, therefore, the valves move with the pistons.

"Practical Mechanical Engineering"
Edited by Carl S.Dow
American Text-book Co.
Philadelphia, Copyright 1907, Volume III   page1011

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