do not include the equipment needed for unloading. However, since these cars do not have hatches for unloading the products shipped in them, railroads must use rotary car dumpers (mechanisms that hold a car against a short section of track as the car and track are slowly rotated upside down to empty the car) or other means to empty them. The term "bathtub" refers to the shape of the car. The "Double Rotary" coal gondola is required in this consist. The "Double Rotary" referring to this car that has rotary couplers on both ends instead of one end. Coil car The coil car is a modified gondola designed specifically for carrying coils of metal. Track ballast gondolas Track ballast gondolas carry ballast. These gondolas are side tipping. Lorry or mine car An open railroad car (gondola) with a tipping trough, often found in mines. Known in the UK as a tippler or chaldron wagon and in the US as a mine car. See also Corf Minecart Mineral wagon Mine railway Quarry tub Railgon Company Well car References Freight rolling stock