Kuhn loop
The Kuhn loop is a component of a Heusinger control on steam locomotives named after its inventor Michael Kuhn (1851–1903) . At the same time, the term stands for this type of Heusinger control.
Especially in the construction of tender and narrow-gauge locomotives , accommodating the Heusinger controls often caused space problems. The control shaft with the throwing lever required to adjust the control was therefore mounted at the same height as the pivot point of the swing arm. The hanging iron could be dispensed with; the raising lever engages directly in the slide push rod. To ensure the necessary horizontal play, the rear end of the slide pushrod is designed as a loop (Kuhn loop) into which a sliding block rotatably mounted in the throwing lever engages. The Kuhn loop was less common than the classic hanging iron control because of higher production costs. A peculiarity of the Kuhn loop is a steady stone jumping when driving forwards and backwards. For this reason, it was preferred to the suspension iron control for tank locomotives , which for operational reasons also had to drive long distances backwards.
The Winterthur locomotive factory developed a variant of the Kuhn loop . In the Winterthur control , the rocker arm is mounted on the control shaft. The rocker arm and control shaft have a common pivot point.