Letters & Miscellanies

Fairbanks-Morse Rings, Waukesha Engines, Wajax Pump and Engine Show Poetry

| June/July 2004

Fairbanks-Morse Piston Rings

In regard to query 39/5/7 in Flywheel Forum in the May 2004 issue about piston ring retainers cast into Fairbanks-Morse pistons: It is very important that they be retained and used, if the engine is to retain compression.

The purpose of the protrusions is indeed to keep the rings from rotating in the ring grooves. On the horizontal engines, especially in the larger engines with bores over 4 inches, the rings will tend to rotate. This results in numerous problems. First, if the ring ends are all in alignment compression can escape the combustion chamber. Secondly, The escaping gases will create hot spots in the cylinder, drying the oil and creating more wear on the cylinder. Finally, blow-by pressure will blow the oil supplied by the oiler for the piston and wrist pin back into the oiler -or worse, out the vent and onto spectators and the engine. The oiling to the wrist pin on the FM engine is marginal at best, and a loss of oil will quickly lead to bearing failure at the wrist pin. Insufficient oil on the rings accelerates wear, resulting in deterioration of compression, and it all just snowballs.

The FM 6 HP engines also have locaters, and one I owned had the locaters filed off. The wrist pin failed three times in four years, the rings twice. All four times the piston was removed, and all the rings had rotated to ends-up position. It wasn't until I worked on a second 6 HP that I saw what was missing from my engine. By all means, keep the retainers.

The ends of the original rings were cut at a slant, and retainer grooves were cut into the bottom edge of the ring. On straight-cut rings, I ground a groove into the ring, approximately 3/4-inch from the ring end to help preserve compression. I hope this helps.

26 Mott Place Rockaway, NJ 07866, mackmotr@aol. com

Fairbanks-Morse Compressor

The Fairbanks-Morse engine in the April 2004 Gas Engine Magazine is definitely a Model M Waukesha. I once had a small generator with an FM tag on the diesel engine that drove it, but the engine was an Onan.