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Penn, in their larger engines, generally make the area of the steam trunnion less than that of the eduction trunnion, in the proportion of 32 to 37; and the diameter of the eduction trunnion is regulated by the internal diameter of the eduction pipe, which is about 1/5th of the diameter of the cylinder. But a somewhat larger proportion than this appears to be expedient: Messrs.
In 1840, one of the engines of the Liverpool and Manchester Railway was altered so as to have 1 inch lap on the valve, and 1 inch opening on the eduction side at the end of the stroke, the valve having a total travel of 4-1/4 inches. The consumption of fuel per mile fell from 36.3 lbs. to 28.6 lbs, or about 25 per cent., and a softer blast sufficed.
The area of the steam pipe is usually made less than the area of the eduction pipe, especially when the engine is worked expansively, and with a considerable pressure of steam. In the case of ordinary condensing engines, however, working with the usual pressure of from 4 to 8 lbs. above the atmosphere, the area of the steam pipe is not less than a circular inch per horse power.
The cold water round the condenser will condense some of the steam contained in the eduction pipe, and its place will be supplied by some of the air from the cylinder. The steam valve must again be opened to blow out that air, and the operation is to be repeated until the air is all drawn out of the cylinder.
This disk is fastened down with a screw press, and when the apparatus is thus arranged the eduction cock is opened, and the air pump maneuvered. If the flange did not exist, the air would enter between the mould and the piece at the first strokes of the piston, and the piece would be inevitably broken.
But traduction and eduction are equally inexplicable when it is a question of finding the origin of the soul. It is not the same with accidental forms, since they are only modifications of the substance, and their origin may be explained by eduction, that is, by variation of limitations, in the same way as the origin of shapes.
Near the smoke stack end of this pipe is a valve K or regulator moved by a handle p at the front of the boiler, and of which the purpose is to regulate the admission of the steam to the cylinder; f is a safety valve kept closed by springs; N is the eduction pipe, or, as it is commonly termed in locomotives, the blast pipe, by which the steam, escaping from the cylinder after the stroke has been performed, is projected up the chimney H. The water in the boiler of course covers the tubes and also the top of the furnace or fire box.
In using these rules, all the dimensions are to be taken in inches, and the answers will be found in inches also. Q. Is it a benefit or a detriment to open the eduction passage before the end of the stroke?
A A are the ordinary steam passages to the top and bottom of the cylinder; B B is the ring which rubs against the back of the valve casing, and D is the eduction passage, S S S S shows the limits of the steam space, for the steam penetrates to the central chamber S S by the sides of the valve.
The common opinion was that forms were derived from the potency of matter, this being called Eduction. That also meant in fact nothing, but it was explained in a sense by a comparison with shapes: for that of a statue is produced only by removal of the superfluous marble. This comparison might be valid if form consisted in a mere limitation, as in the case of shape.
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