Full reverse gear. Additional movement is now imparted to the valve spindle to continue admitting steam for three quarters of the travel of the main pistion. The steam therefore expands from 75% to 100% - if steam is admitted at 150psi 225°C (typical steam chest conditions with a small degree of superheat), it would expand to about 97 psi before it is exhausted. Uses steam at a relative rate of 100%.
Half reverse gear. Additional movement is now imparted to the valve spindle to continue admitting steam for three eightha of the travel of the main pistion. The steam therefore expands from 37½% to 100% - if steam is admitted at 150psi 225°C (typical steam chest conditions with a small degree of superheat), it would expand to about 47 psi before it is exhausted. Uses steam at a relative rate of 50%.
Quarter reverse gear. Additional movement is now imparted to the valve spindle to continue admitting steam for three sixteenths of the travel of the main pistion. The steam therefore expands from 18¾% to 100% - if steam is admitted at 150psi 225°C (typical steam chest conditions with a small degree of superheat), it would expand to about 22 psi before it is exhausted. Uses steam at a relative rate of 250%.
The valvegear is also illustrated atmid gear and 25%, 50% and 100% of full forward gear. For these views click on the relavant link.