tub

A tub is a container, typically made of wood, steel, or iron, used to transport coal or ore vertically up a mine shaft. It holds roughly 8 to 15 tons of material depending on the mine and mineral type, and is attached to a rope or cable connected to a steam-powered or later electric winding engine at the surface. The tub rises and falls in cycles, often paired with a counterbalance system that lowers an empty tub while a loaded one ascends, reducing the engine's work.

Tubs come in several forms. The simple box tub has straight sides and a flat or slightly sloped bottom, designed to tip its contents into a hopper or skip at the shaft head. Some tubs feature hinged bottoms or side gates for easier discharge. In deeper mines, larger capacity tubs called cages or skips replaced smaller wooden tubs, though the term persists in older workings and in colloquial speech among miners. Rope attachments vary: tubs may have lugs cast or bolted to their sides, or they sit in frames that grip them during ascent.

Failure modes are critical. A tub that tilts or shifts during ascent can jam in the shaft, halting the entire operation and risking the safety of workers below. Wooden tubs swell and shrink with moisture, distorting their fit in the shaft; they also rot if not regularly maintained. Metal tubs corrode from water seepage and acid drainage. Rope wear concentrates at the attachment points, so regular inspection of lugs and shackles is essential. A broken rope can drop a loaded tub with catastrophic force, which is why safety regulations demand frequent rope testing and tub certification.

The term reflects its basic form: a tub is simply a large, open container for holding and moving material. Early mine tubs were wooden, resembling domestic tubs or barrels adapted for industrial use. The name stuck even as materials and engineering sophistication changed. Regional variations exist: British mines often called them tubs or corves, while some continental operations used different terms, but the Anglo-American mining lexicon settled on tub.

In the hierarchy of mine equipment, tubs sit between hand-carried baskets used by individual workers and the much larger modern ore cars used in deep hard-rock mines. They represent the transition from surface industry to underground haulage, and their design directly shaped the dimensions of mine shafts themselves. An engineer designing a shaft would specify dimensions around the tub size, since the tub must fit with clearance but minimal waste. Understanding tub capacity and weight was fundamental to calculating winding engine power and shaft depth economics.