CLASSIFICATION OF ENGINES.
Q. You implied that there is some other difference between single acting and double acting engines, than that which lies in the use or exclusion of the crank? A. Yes; single acting engines act only in one way by the force of the steam, and are returned by a counter weight; whereas double acting engines are urged by the steam in both directions. Engines, as I have already said, are sometimes made double acting, though unprovided with a crank; and there would be no difficulty in so arranging the valves of all ordinary pumping engines, as to admit of this action; for the pumps might be contrived to raise water both by the upward and downward stroke, as indeed in some mines is already done. But engines without a crank are almost always made single acting, perhaps from the effect of custom, as much as from any other reason, and are usually spoken of as such, though it is necessary to know that there are some deviations from the usual practice. Next >> |
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