USS Pompano (SS-181) - Engine Problems

Engine Problems

Six boats were built in this group, with three different diesel engine designs from different makers. Pompano was fitted with H.O.R. (Hooven-Owens-Rentschler) 8-cylinder double-acting engines that were a license-built version of the MAN auxiliary engines of the cruiser Leipzig. Owing to the limited space available within the submarines, either opposed-piston or, in this case, double-acting engines were favoured for being more compact. Pompano's engines were a complete failure and were wrecked during trials before even leaving the Mare Island Navy Yard. Pompano was laid up for eight months until 1938 while the engines were replaced. Even then the engines were regarded as unsatisfactory and were replaced by Fairbanks-Morse opposed piston engines in 1942.

Pompano's engines were a unique prototype of the H.O.R. engine, having 8 cylinders. An inherent problem with double-acting cylinders, owing to the piston rod reducing the piston area on one side, is an imbalance in the force on each side of the piston. The H.O.R. engines were plagued by vibration, and other, problems as a result. While Pompano was still being built, the Salmon class submarines were ordered. Three of these were built by Electric Boat, with a 9-cylinder development of the same H.O.R. engine. The 9-cylinder arrangement was an attempt to re-balance the engine, so reducing the overall effect of vibration across the engine. Although not as great a failure as Pompano's engines, this version was still troublesome and the boats were later re-engined with the same General Motors 16-248 two-stroke V16 Diesel engines as their sister boats. Other Electric Boat constructed submarines of the Sargo and Seadragon classes were also built with these 9-cylinder H.O.R. engines, but later re-engined.