One of Robinson's first developments was the class 11B, which was intended to meet the increased demands of new lines. They were similar to the class 9J “Pom-Poms” freight locomotives and were therefore also called “Pom-Pom Bogies”. On some lines they could reach an average of 60 mph (97 km/h). In terms of power, they were soon outperformed by Robinson's newer designs and rebuilt. Only two locomotives received a new saturated boiler and became class 11C. Between 1909 and 1927, all other locomotives were rebuilt with a different boiler, which was delivered directly with a superheater from 1913. The last ones were able to remain in service until 1950. 