氣缸旋塞

Cylinders are steam engine components that house pistons that propel the vehicle. Typically, there are two cylinders in the front of the vehicle, one on each side. They are alternately fed steam from the steam chest , with every full rotation of the driving wheels, in the amount set with the cutoff .

Steam in cylinders pushes the pistons inside, mechanically linked to the driving wheels, propelling the vehicle. The used steam is then expelled through a blastpipe, where it mixes with smoke from the firebox in the smokebox, and together they are exhausted to the atmosphere through a chimney.

因為氣缸與鍋爐和火箱有段距離，當氣缸中不再有蒸汽注入時會迅速冷卻。氣缸中的蒸汽會很快地凝結成水，而由於水不像蒸汽能被壓縮，當足夠的水聚集在氣缸中並被活塞推動時，它會使氣缸受損並導致災難性的動力系統損壞。

To prevent this, steam engines come equipped with cylinder cocks. They are usually operated by a lever from inside the cab , and allow water to be expelled from the cylinders. However, since steam escapes through the cocks too, they should only remain open for a short time, typically just a few seconds, when the vehicle begins moving from a standstill.

Cylinders can also fill with water if the boiler is overfilled , or from running the vehicle with the cutoff set in the opposite direction.