Some background:
The model of the Halfling Soup Tank "Kathleen" was built by Chad Mierzwa, with parts of the classic steam engine model. It was used by Mat Ward and Gav Thorpeduring the "Revolt in Mootland," a game report/special scenario in the White Dwarf of February 2006. Presumeably one of the lost Steam Tanks, it was armed with a soupcannon and had its own rules for the scenario.
The Halflings used the Soup Cannon in their revolt against the "Mad" Elector Marius Leitdorf of Averland (2502 IC), which had degenerated into a war of extermination. This indiosyncratic "Soup Tank" was probably based on one of the lost Steam Tanks of the Empire and, like the notorious Hot Pots could burn enemies with boiling hot soup, against which even full plate armour proved no protection. In addition, the Soup Tank was able to simply overrun enemy troops, and probably helped to ensure (together with the Ogres of the Feastmaster tribe and Lumpin Croop's Fghting Cocks) that the demoralized Halflings survived the revolt after their defeat in the Battle of Wassernah. As a result of the events, the Elector of Averland was reprimanded by the Emperor himself, who sent him champion, Ludwig Schwarzhelm, to bring him back to his senses.