turnsheet

A turnsheet is a circular or semicircular metal plate, typically 4 to 6 feet in diameter, laid flush with the floor of a mineshaft or underground passage. Its upper surface is smooth and slightly dished to allow a minecart's wheels to roll across it without catching. The plate pivots on a central pin or journal bearing so that a loaded or empty cart can be swung through a wide arc, redirecting it from one rail line to another without manual uncoupling or complex track switching.

In practice, a miner or surface worker pushes the cart onto the turnsheet, then applies force to the cart's side to rotate the entire plate beneath it. The friction between the plate and the cart's wheels provides enough grip for the operation. Once the cart has been swung to face the desired direction, it is rolled off onto the waiting track. The method avoids the expense and complexity of traditional points and crossovers, which require precision engineering and regular maintenance.

Variants and Placement

Turnsheets were most common in coal mines and metal mines during the nineteenth and early twentieth centuries, though they remained in use longer in smaller or more isolated operations. Some were fixed permanently in drifts or headings; others were portable and moved as working faces advanced. Cast iron was the standard material, chosen for its strength under repeated impacts and its resistance to rust in damp conditions. The plate's thickness typically ranged from 1 to 2 inches.

The device worked well for hand-operated carts moving at walking speed, but became obsolete as mines shifted to mechanical haulage and larger rolling stock. Modern mines with powered locomotives and standard gauge track have no use for turnsheets. However, the term survives in mining history and heritage documentation, and examples are sometimes encountered during the restoration or archaeology of old workings.

The turnsheet's simplicity made it attractive in remote or developing mining regions where specialized foundry work was difficult to obtain. A blacksmith with basic metalworking skills could fabricate one from salvaged plate or scrap iron. Despite its crude appearance, a well-made turnsheet could function reliably for decades with only occasional maintenance: periodic oiling of the pivot and scraping away of accumulated debris.