File:Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish (1871) (14576623489).jpg

Identifier: sponsdictionaryo05spon (find matches)
Title: Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish
Year: 1871 (1870s)
Authors: Spon, Edward Byrne, Oliver Spon, Ernest
Subjects: Engineering
Publisher: London, New York : E. & F.N. Spon
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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radii. In this case the number of the teeth mustbe lessened, and consequently the pitch increased, until the division can be exactly made. Noinconvenience can result from modifying in this dü-ection the dimensions of the teeth. We have selected as our example the case of two shafts forming an acute angle : the methodof drawing is the same in all cases ; but the most general case is that of two shafts placed at rightangles to each other. Endless Screw and Pinion.—When it is required to communicate the continuous circular motionof a shaft to another not situate in the same plane, the endless screw and pinion may be employed,if the given axes are at right angles and near each other. The discussion of the principles upon which the construction of this gear rests would lead usinto a somewhat complicated theory, which we will pass by for the sake of considering the drawingfrom a practical point of view. The data are reduced to the work and, consequently, to the forceF to be transmitted.
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It is generally required to obtain one revolution of the pinion to a determinate number ofrevolutions of the screw. In this case, the number of teeth on the pinion is equal to the numberof revolutions of the screw. But the distance of the teeth is calculated for the force to be trans- 1638 GEAEING. mitted and remains invariable ; therefore it is necessary to make the radius of the pinion dependupon the number of teeth ; this cannot be, however, unless the distance of the axes be unlimited.It must be remarked that in almost all cases, the screw drives the pinion, the object being anincrease of force at the cost of speed. Knowing the maximum work to be transmitted, we may determine the pitch of the pinion,which is also that of the endless screw. The radius of the solid portion of the screw may be takenas a function of the pitch, since it is also dependent on the force. It is usually obtained bymultiplying the pitch by 5, and dividing the result by 2. To execute the trace we must takeA a

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