Trunk engines and monitor compromises

Trunk engines kept a long stroke within a low machinery profile, but they were not a universal success. Their performance depended on the boiler pressure and metallurgy available, and by the 1870s higher pressures made jamming or catastrophic failure serious limits. The design's history cautions against dismissing an old idea when its materials and supporting systems may have been the true constraint. Ericsson's vibrating-lever arrangement for monitors answered a different problem by balancing two horizontal cylinders around the center of a very small hull. Its shafts and extra levers reduced the weight imbalance of a conventional trunk engine, but only American and Swedish warships used the configuration before maintenance demands helped other engines supplant it.