Beyer Peacock used the Hadfield system which was capable of being worked either by steam or compressed air. London, Virtue and Company Ltd. Many American locomotives were built, or retro-fitted, with power reverse, e.g. Smaller stationary steam engines generally have a fixed cutoff point, while in large ones the speed and power output is generally governed by altering the cutoff, frequently under governor control using an expansion valve or trip gear. Once the valve has closed, steam trapped in the cylinder expands adiabatically.
I know that when a steam loco starts to move, the cut off needs to be 100% for maximum torque, but when at full speed it can be set at less than 50%. This is known as expansive working. Political / Social. The steam engine is the only thermodynamic engine design that can provide its maximum torque at zero revolutions. The Ragonnet power reverse, patented in 1909, was a true feedback controlled servomechanism.
Several engineers then tried them, including William Dean of the GWR and Vincent Raven of the North Eastern Railway, but they found them little to their liking, mainly because of maintenance difficulties: any oil leakage from the locking cylinder, either through the piston gland or the cock, allowed the mechanism to creep, or worse “nose-dive”, into full forward gear while running. [Wikipedia On a steam locomotive the adjustable cutoff of steam at the inlet valve is controlled by the reverser. The two pistons of the steam reverser can be seen at the extreme left on this Bulleid Merchant Navy class locomotive. Ransome-Wallis, Patrick (2001). ( Log Out /  Disadvantages are that, because the lever must rest at one of the notches, fine adjustment of the cutoff to offer best running and economy is not possible. More steam is admitted for a longer part of the piston travel-distance to start heavy trains. But, since there will still be unexploited pressure in the cylinder at the end of the stroke, this is achieved at the expense of engine efficiency. The BEST Steam Locomotive & Transportation Links…. In steam engines for transport it is desirable to be able to alter the cutoff over a wide range.