Page:The Kinematics of Machinery.djvu/598

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�KINEMATICS OF MACHINERY.

�becoming conaxial. If the chain be then placed on a we obtain Watt's planet-train, Fig. 432, the motions in which we have already examined ( 105). Following the name which Watt gave to the mechanism ( C" 6 <7 z ) a we may call the chain itself (C" 6 '(7 ) the planet-wheel chain.*

���FIG. 435.

�FIG. 436.

�(2.) If we make 1*5 = 3*4, a=b, and the two wheels also equal, so that the links c and d are equal and similarly placed, the whole chain becomes symmetrical about the line 6 '2, Fig. 433, and placed on e it gives us Cartwright's parallel motion.

(3.) We can make the lengths 5*1, 1/2, 2'3 and 3'4 uri-symmetri- cal, but by suitably proportioning them, and giving the wheels a particular diametral ratio, we obtain, by placing the chain on e, a mechanism in which 2 moves approximately in a straight line, Fig. 434. This arrangement is that proposed by Maudslay. The path of 2 is very nearly straight if the link d be not allowed to swing through too large an angle.

(4.) We obtain important special cases by making single links infinite. Let us do this first with b and a, using at the same time the simplification employed in Watt's planet-train, namely, making the length 1/5 *= 0. We obtain in this way such a chain as is

before us, and so does not come into consideration here.
 * The planet-wheel train used by Galloway was more complex than the chain

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