MECHANICS; 



Barker's mill is a remarkable instance 

 of a continued rectilinear motion pro- 

 ducing: a continued circular one. 



(103.) To convert a continued recti- 

 linear motion into a reciprocating cir- 

 cular motion, ar vice versa. 



Fig. 95 . 



One method of ef- 

 fecting this is by a 

 rack MN, (/#. 95.) 

 in the teeth of which 

 the end B of a lever 

 A B works. As the 

 rack M N descends, 

 the end of the lever 

 falls from one tooth 

 to another, and the end A moves al- 

 ternately up and down in a small circu- 

 lar arc. 



A method of producing either a reci- 

 procating circular motion from a con- 

 tinued rectilinear motion, or a conti- 

 nued rectilinear from a reciprocating 

 circular motion, is represented in Jig. 

 A B C D is a double rack, fur- 



96. 



Fig. 9 



nished with teeth at intervals, the parts 

 of A B, which bear teeth, being opposite 

 to those parts of C D which are free 

 from them ; a b c d is a wheel bearing 

 teeth, corresponding to those of the 

 rack. Suppose the rack in its highest 

 position, and the first tooth b of the 

 wheel engaged with the lowest tooth on 

 the rack CD. As the rack descends, 

 the teeth b a are successively engaged 

 with the corresponding teeth of the 

 rack, and the wheel revolves until the 

 last tooth a is passed by the last tooth 

 of the first set on the rack C D. At 

 this moment the lowest tooth d on the 

 other side of the wheel is seized by the 

 lowest tooth of the first set on the rack 

 AB; and after this, the teeth dc are 

 successively engaged by those of the 

 rack, and the wheel is turned in the di- 

 rection contrary to its former motion. 

 As the rack continues to descend, the 



same reciprocating circular motion con- 

 tinues to be produced in the wheel. 



The motion may be continued with- 

 out limit by using two chains, bearing 

 teeth at intervals, working on two pair 

 of rag-wheels. 



The lever of Lagaroust is a con- 

 trivance by which a reciprocating cir- 

 cular motion produces a continued rec- 

 tilinear one. M N (/g. 97.) is a fixed 

 Fig. 97. 



shaft, in which a centre is placed at C, 

 on which the lever A B works. F G is 

 a rack, which is capable of being raised 

 in the vertical direction. This is effected 

 by two bars D E, D' E', placed on joints 

 at D, D'. When the extremity A de- 

 scends, the point D' rises, and the 

 hook E', being engaged with a tooth of 

 the rack, draws it up. The hook E in 

 this process falls from one tooth of the 

 rack to the tooth immediately under it 

 When B is depressed, and D rises, the 

 same effects take place, but on differ- 

 ent sides of the rack. 



Thus, the reciprocating circular mo- 

 tion of the lever A B produces a conti- 

 nued rectilinear motion in the rack F G. 

 The term continued rectilinear motion 

 here means rectilinear motion which is 

 always in the same direction ; for, 

 strictly speaking, the motion is not con- 

 tinued, since it is intermitting. 



(109.) To convert reciprocating rec- 

 tilinear motion, in one direction and 

 with one velocity, into reciprocating 

 rectilinear motion in another direction 

 and with another velocity. 



1 1' the velocities of the two motions 

 were equal, and the directions in the 

 same plane, this might be effected by a 

 strap passing over a wheel, the part of 

 the strap on one side of the wheel being 

 in one of the given directions, and that 

 on the other side in the other given di- 

 rection. If friction were insufficient, a 



