Rubuta ci gaba don wannan sakin layi - A cikin 1930s H.O.R. ya haɓaka injin dizal mai aiki biyu, da farko ya dogara da injunan MAN na jirgin saman Jamus "Leipzig" amma tare da silinda takwas maimakon bakwai, ya faɗaɗa zuwa silinda tara a cikin fasalin jirgin ruwa na ƙarshe. Tsarin aiki guda biyu ya samar da karin iko daga karamin injin jiki fiye da na al'ada. Duk da haka, H.O.R ta dual-aiki injuna, musamman ma wadanda na USS "Pompano", samu notoriety ga unreliability a cikin jirgin ruwa karkashin ruwa karfi, inda suka aka lakabi " karuwai ". Saboda iyakancewar sararin samaniya a cikin jiragen ruwa, ko dai ya yi tsayayya da piston ko, a wannan yanayin, an yi amfani da na'urori masu aiki guda biyu don zama mafi karami. Matsala ta asali tare da silinda masu aiki biyu, saboda sandar piston tana rage yankin piston a gefe ɗaya, rashin daidaituwa ne a cikin karfi a kowane gefen piston. Injin H.O.R. ya sha wahala daga rawar jiki da sauran matsaloli sakamakon haka. Wannan kuma ya sanya ƙarfin motar ya yi yawa kuma ya sa giya (waɗanda kansu ba a yi su daidai ba) don zubar da hakora, ƙirƙirar rawar jiki, kuma sau da yawa ya sa injin da motar gear ba su aiki. A matsayin misali na matsalolin da rashin amincin injunan H.O.R. ya haifar, Kyaftin Charles Herbert Andrews na USS "Gurnard" ya tuna game da sintiri na yaƙi don tallafawa Operation Torch
"Na yi amfani da uku ne kawai, na ajiye na huɗu don ajiya. Sa'ad da jirgi biyu suka lalace a Tekun Biscay, sai na daina tafiya kuma na koma Scotland".