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The Mechanical Valve-Gear The valves are located in the steam chests, which are bolted to the top of the casing directly over the first sets of expansion nozzles. The chests, two in number, are on opposite sides of the machine.
The heavy thud of the cross-heads, flashing between their guides, beat time to the clang of the valve-gear, a pump throbbed like a kettledrum, and something tinkled like a high-pitched triangle. All went well, the engines were good and Terrier stubbornly forged ahead. By and by the strain was less marked. The load was getting lighter and after a time Lister let go the wheel and wiped his wet face.
There are besides the mechanical valve-gear the electric and hydraulic, but these will be left for a future article. The Governor
The rods which connect the governor with the valve-gear have ordinary brass ends or heads and are adjusted by right-and-left threads and secured by lock-nuts.
We will consider what is known as the "mechanical" valve-gear, with two sets of valves, one set of five valves being located on each side of the machine. Turn the machine slowly, until the pawls are at their lowest point of travel.
Overhead the dark and bulky cylinders cut against the reflected glimmer on the skylights; below, valve-gear and connecting-rod flashed across the gloom, and the twinkling cranks spun in their shallow pit. One saw the big columns shake and strain as the crosshead shot up and down; the thrust-blocks groaned with the back push of the propeller.
The crankshaft has a single throw, and is made in two parts to allow the cage for carrying the big end-pins of the connecting rods to be placed in position. The casing is in two parts, on one of which the brackets for fixing the engine are carried, while the other part carries the valve-gear. Bolts secure the two parts together.
This is corrected by the governor, but the correction is usually carried too far and the machine slows down. With the stage valve in operation, at a critical point the regulation is uncertain and irregular, and its use has to be abandoned. The mechanical valve-gear does not often get out of order, but sometimes the unexpected happens.
Our daughters are not ashamed to culture flower beds, and while they plant the rose in the ground a corresponding rose blooms in their own cheek. But we need another proclamation of emancipation. The human locomotive goes too fast. Cylinder, driving-boxes, rock-shaft, truck and valve-gear need to "slow up."
Second, the governor weights move outward on a parallel motion opposed directly by spring thrust, thus relieving the fulcrum entirely of spring thrust. Third, the lay shaft driving the governor oil pump and reciprocator is located underneath the main turbine shaft, so that the rotor may be readily removed without in the least disturbing the governor adjustment. The Valve-Gear
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