Weekend Steam

Click on photo to enlarge. An advertisement in an old American Thresherman magazine illustrates the advantages of return flue boilers. In addition to better efficiency than locomotive style boilers, the operator had the advantage of easier maintenance; and less skill and care was needed to stoke the fire in a return flue boiler. In locomotive style boilers the fire had to be maintained evenly over the grates to avoid cold spots. A dead spot in the fire would allow cold air to cool the flue sheet at the front of the firebox, resulting in leaks around the end of the flues. Someone would then have to crawl into the firebox to roll the flues, which is not easy when working in the confined space of the firebox. The engine had to be pretty well cooled before anyone could go into the firebox, so this meant downtime.

The flues on a return flue boiler could be accessed easily if they leaked, and causing a leak by sloppy firing technique was much less likely. There are also fewer parts to fail in return flue boilers. In spite of the advantages of the return flue system, locomotive style boilers were much more popular on traction engines; the most common reason cited is that the operator did not have the smoke stack in his face radiating heat and exhaust noise. I think that is probably correct, although some early return flue engines had a bad record of exploding due to poor design. This surely influenced both builders and customers.

Stories written by the men who ran traction engines often break into discussions of the ease or difficulty of maintaining steam while working an engine. I have read many stories in old steam magazines and have never seen any negative comments on firing a return flue engine.

Compare the complexity of this locomotive style boiler to the return flue Huber in the advertisement above.