This meant that the majority of condensation – and therefore vacuum creation – took place outside the heated drum. This allowed the main piston cylinder to remain at a temperature where water could quickly be pressurised.
The second improvement was the introduction of an extra steam valve. The added valve increased the power of the engine as it capped and inserted low-pressure steam into the upper part of the main piston cylinder.
This sped up vacuum creation, increasing the piston’s downstroke power and, as a result, its actions per minute.