. American engineer and railroad journal . e, with the crosshead between them. Thiscrosshead is a wide one with pins at its ends for the connectingrods that lead to the cranks on the fly-wheel shaft. The pistonrods are not connected directly to the crosshead, but are bothkeyed to a block held in the crosshead by the vertical pin shown inFig. 3. This permits the crosshead to swivel slif^htly and thus ad-just itself to the lengrth of the connecting rods without strainingthe piston rods. There is also a slight vertical adjustment pro-vided by means of this same block to compensate for the wearing
. American engineer and railroad journal . e, with the crosshead between them. Thiscrosshead is a wide one with pins at its ends for the connectingrods that lead to the cranks on the fly-wheel shaft. The pistonrods are not connected directly to the crosshead, but are bothkeyed to a block held in the crosshead by the vertical pin shown inFig. 3. This permits the crosshead to swivel slif^htly and thus ad-just itself to the lengrth of the connecting rods without strainingthe piston rods. There is also a slight vertical adjustment pro-vided by means of this same block to compensate for the wearingdown of the crosshead and guides. In a steam cylinder using steam expansively, the greatest forceis exerted during the early part of the stroke, while lu an aircompressing cylinder the power required is 1 irgely in the secondhalf. Instead of providing heavy fly-wheels to absorb and giveout power in different parts of the stroke, the inertia of the re-ciprocating parts is utilized for this purpose. The piston rods AND RAILROAD JOURNAL. 179. Fig. 3.—Sectional View of Norwalk Compound Air Compressor Driven by a Compound Steam Engine. and crosshead represent in the aggregate considerable weight, sothat it requires most of the power of the steam over and abovethe air resistance at the beginning of the stroke to start them for-ward at the required speed. At the end of the stroke, when thesteam has become weak by expansion, tlie power stored up inthe momentum of these reciprocating parts is given out in usefulwork, and the parts are brought to a state of rest by expendingtheir force upon the air in the compressing cylinders. The weightof these parts is purposely made sufficient to give the desired re-sult, consequently the flywheels can be made comparativelylight and there are no heavy strains to be transmitted betweenthem and the pistons. The valves on the inlet cylinder are of the Corliss type, and itwill be seen that both inlet and discharge valves are mechanicallyactuated. The s
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
