to endure extremely high temperatures, as well as keeping the metal in a molten state over extended periods of time. The vessel can be pivoted along its longitudinal axis to empty the pig iron into a ladle. The name is derived from the vessel's resemblance to a torpedo. Vinegar cars A vinegar car is a specialized type of tank car designed to transport vinegar. The largest such car built was built by Morrison Railway Supply Corporation in 1968. The car's underframe included all of the modern facets of freight car design including roller bearing trucks and cushioning devices built by FreightMaster, while the tank that rode on it, made of Douglas fir, had a capacity of . The car, in what has been called 'the largest wooden tank car ever built', took 18 months to build. The Reinhart Vinegar Car can be seen at the Toronto Harbourfront Museum. Vinegar is now moved in ordinary tank cars lined with glass, plastic, or alloy steel. "Whale belly" cars In the early 1960s, the Union Tank Car Company introduced a series of "whale belly" tank cars which offered increased capacity. These cars carried from in CSOX #31084 to as much as in GATX #96500, which had been conceived as a 'rolling experiment' of sorts. The largest tank car ever placed into regular service, UTLX #83699, was rated at . It entered service in 1963 and continued to be used for over twenty years. GATX 96500 is now on display at the National Museum of Transportation in Saint Louis, Missouri. This car is in length, weighs empty, and rides on four two-axle trucks to distribute the additional weight. It was used to transport such diverse substances as liquefied petroleum gas (LPG) and anhydrous ammonia. Safety Where AAR couplers are fitted, the AAR type "F" coupler is preferred as these are less likely to become separated in a derailment and become a puncture hazard for other tank cars. A type "E" coupler that has shelves over and under the coupler that prevent the coupler sliding out of position after a derailment is used on some hazardous materials tank cars. In addition, some types of tank cars have a second end plate visible from the exterior, to further avoid end punctures. It is also preferable if each tap (valve) is recessed within the body of the tank so as to present a reduced knock-off hazard during