FORE:Slotting machines with vertical cutting movement differ from planing machines in several respects, to which attention may be directed. In slotting, the tools are in most cases held rigidly and do not swing from a pivot as in planing machines. The tools are held rigidly for two reasons; because the force of gravity cannot be employed to hold them in position at starting, and because the thrust or strain of cutting falls parallel, and not transverse to the tools as in planing. Another difference between slotting and planing is that the cutting movement is performed by the tools and not by movement of the material. The cutting strains are also different, falling at right angles to the face of the table, in the same direction as the force of gravity, and not parallel to the face of the table, as in planing and [135] shaping machines.
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FORE:There is, however, a principle in hydraulic machinery that must be taken into account, in comparing it with positively geared mechanism, which often leads to loss of power that in many cases will overbalance any gain derived from the peculiar action of hydraulic apparatus. I allude to the loss of power incident to dealing with an inelastic medium, where the amount of force expended is constant, regardless of the resistance offered. A hydraulic crane, for instance, consumes power in proportion to its movements, and not as the amount of duty performed; it takes the same quantity of water to fill the cylinders of such cranes, whether the water exert much or little force in moving the pistons. The difference between employing elastic mediums like air and steam, and an inelastic medium like water, for transmitting force in performing irregular duty, has been already alluded to, and forms a very interesting study for a student in mechanics, leading, as it does, to the solution of many problems concerning the use and effect of power.
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FORE:Prout came up smiling in the course of the next afternoon. He was disposed to chaff his prisoner in a mild kind of way.
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FORE:
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FORE:CHAPTER XVII. MACHINERY FOR MOVING AND HANDLING MATERIAL.
FORE:Dick echoed the cry. Jeff had already caught the threat of that swamp below them. They could not risk going a foot lower. The pilot opened his throttle, picking up climbing speed to the roar of his engine.
FORE:Pneumatic machinery, aside from results due to the elasticity of air, is analogous in operation to hydraulic machinery.
FORE:Prout dutifully returned the following evening, but Lawrence had nothing fresh to offer. He still clung to his new theory, but it was not sufficiently developed for practical use. And he didn't want to be laughed at, he said.In the mouth of a broad channel they touched water and ran out of momentum with the wings hovering over the grassy bank to either side.
FORE:Lawrence stepped into the garden, Mamie welcomed him eagerly. No books of hers were half so popular as the novelist's impromptu stories.
