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In a steam engine, cutoff is the point in the piston stroke at which the inlet valve is closed. On a steam locomotive, the cutoff is controlled by the reversing gear.. The point at which the inlet valve closes and stops the entry of steam into the cylinder from the boiler plays a crucial role in the control of a steam engine.
The reversing lever has a catch mechanism which engages with a series of notches to hold the lever at the desired cut-off position. This means that the operator does not have a full choice of cut-off positions between maximum and mid-gear, but only those which correspond with the notches.
Then, for instance, to calculate the percent of the piston's stroke at which steam admission is cut off: Calculate the angle whose cosine is twice the lap divided by the valve travel; Calculate the angle whose cosine is twice the (lap plus lead), divided by the valve travel
In the simple case, this can be a relatively simple task as in the internal combustion engine in which the valves always open and close at the same points. This is not the ideal arrangement for a steam engine, though, because greatest power is achieved by keeping the inlet valve open throughout the power stroke (thus having full boiler pressure, minus transmission losses, against the piston ...
Collects steam at the top of the boiler (well above the water level) so that it can be fed to the engine via the main steam pipe, or dry pipe, and the regulator/throttle valve. [2] [5] [6]: 211–212 [3]: 26 Air pump / Air compressor Westinghouse pump (US+) Powered by steam, it compresses air for operating the train air brake system.
Period cutaway diagram of a triple-expansion steam engine installation, circa 1918. This particular diagram illustrates possible engine cutoff locations, after the Lusitania disaster and others made it clear that this was an important safety feature. A marine steam engine is a steam engine that is used to power a ship or boat.
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(On some engines the die block was in the top of the link in forward gear. This type was generally used on tank engines, which worked in forward and reverse equally. [6]) Once the locomotive has accelerated the driver can adjust the reverser toward the mid-gear position, decreasing cut-off to give a more economical use of steam.