Often compressors are connected to a bank of large, high-pressure cylinders to store compressed gas, for use at peak times.

The high-pressure cylinders were internal and worked the first coupled axle.

Compound engines which use the exhaust from high-pressure cylinders to power low-pressure cylinders.

These cylinders are positioned above the two main high-pressure cylinders, which drive the main wheels.

The quantity of steam generated was however more than the high-pressure cylinders could cope with.

A 6th one was built, but had 2 sets of high-pressure cylinders, and was not a compound mallet.

The rear set of drivers with their high-pressure cylinders is fixed in the plate frame of the loco.

Smith improved on this by developing a three-cylinder compound system with one high-pressure cylinder inside and two low-pressure cylinders outside.

Smart tires would primarily be used with active suspension, a system developed by Lotus that uses computer-controlled, high-pressure hydraulic cylinders.

This made the locomotive unnecessarily complicated and placed the high-pressure cylinders directly underneath the cab, making it uncomfortably hot, especially in summer.