Crankless Opposed-Piston High-Speed Diesel Engine


| January/February 1996



Principles of Operation of Piston Diesel Engine

Fig. 74. Principles of Operation, Sterling Crankless Opposed-Piston Diesel Engine. Courtesy of The Sterling Engine Company, Buffalo, New York.

The Sterling Engine Company

1801 52nd Dr., NE, Marysville, Washington 98721

Thought our readers would be interested in this section of the book, Diesel and Other Internal Combustion Engines by Howard E. Degler, published by the American Technical Society in 1937.

Eliminating crankshaft, connecting rods, cylinder heads, gaskets, valves, and camshafts, the Sterling crankless high-speed engine may forecast a revolutionary trend in design. The compactness of the engine and the principles of operation are shown by Fig. 74. The engine has four horizontal cylinders, each containing two opposed reciprocating pistons. Thus the engine is equivalent to the usual two-cycle 8-cylinder diesel engine of corresponding bore and stroke. The cylinders are arranged about a straight drive shaft which carries an inclined disk (also called wabble plate) at each end. The disks are virtually flywheels. The pistons act directly upon the circular disks set angularly upon the shaft, so that the gas pressure transmitted by the pistons forces the disks and shaft to rotate.

The mechanical bearing units which transfer the power from pistons to drive shafts utilize the same principle as the Michell and Kingsbury thrust bearings: that is, from the piston base, a U-shaped bridge passes over the rim of the disk and carries two bearing surfaces.

The thrust surface is a slipper of rectangular shape with babbitt bearing surface, mounted on a half sphere; the other bearing (which serves only to position the piston) is a bronze-faced half sphere. This provides a universal mounting which permits the bridge to adapt itself to any motion of the inclined disk. The bridge is guided by short rods extending through guide holes, Fig. 74.

The engine follows conventional 2-cycle design in that circumferential ports replace valves. Scavenging air is provided by a pressure pump. However, instead of the usual rotary or centrifugal blower, piston type pumps are used, and the piston is mounted directly on the end of the piston bridge rod (left side in Fig. 74). Air is distributed by a simple rotary valve at the left end of the shaft.

David Norstebon
9/26/2009 11:38:16 PM

I am seeking parts for a 1958 Onan engine model ACK-S15/D. this engine has an optional gear drive Fairbanks Morse magneto ignition model PE1-2B69D. I need the magneto drive gear that turns the impulse coupler. It is 2.5" across and has 30 beveled teeth. Anyone know where I could find such a thing.thank you!