氣缸旋塞

氣缸是蒸汽機車 上，用於容納推動車輪的活塞。氣缸通常位於車輛前端，左右各一。蒸氣自汽室 供應，並以逆轉機 調節每個活塞循環注入汽缸的蒸氣量。

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.