98 G

THEORY AND PRACTICE OF ENGINEERING.

Book II.

Fig. 1445.

Fig. 1446.

Let de be the crank of the axis of rota-tion d; this crank is equal to half thechoid of the arc abefg; an iron rodsuspended at f to another/^, which turnsround the point h, while the point e ofthe crank goes from l to e , from e to m,and from m to n ; the point f of the rodhf goes from i t of from / to $, and froms to k : consequently k i should be equalton/. The shuttle should pass over thearc a b in the same interval of time; thedistance ai is divided into two parts, irand r a ; the part/^ of the rod efg equaltori, and another rod gp, equal toar,which is placed as the figure indicates, insuch a manner that its extremities canturn freely at g and p of the rod efg, andof the radius cp of the shuttle; the latterwill pass over the arc a b with a velocitywhose variations will depend on the ratio between/# and g p.

Let a b be an axis which receives from the mover an alternate circular motion;n and m two wheels fixed to the axle ah, both together,but placed in opposite directions ; c, d, and e are threetoothed wheels, the two first having two equal diame-ters, which turn freely on the axle a b, and carry the twocatches p and q, engage the third e, whose axis is pro-perly supported ; the axis a b, by its circular alternate mo-tion, will act successively on the two wheels c and d; theywill soon assume a circular continuous motion, and as thistakes place in opposite directions, the wheel e willalways turn in the same direction; thus the circularalternate motion of an axle or wheel may be transformed into a continuous circular mo-tion of another axle or wheel, the second being perpendicular to the direction of the first,and the plane of the second also perpendicular to the plane of the first.

Let ah be the axis corresponding to one of the two cylinders, F or G ; c, the counter-poise; n o the axis of rotation of the vertical rod, which sustains the counterpoise ; q a rodperpendicular to the vertical rod and the axle; tsr the axle of the small machine: nothingis easier, as we have said already, than to cause the rod rsto make a single revolution round the axle de, whilst the axleab makes any number of revolutions we please: now sup-pose that the axle rs elevates itself, the counterpoise cwould find itself in the vertical which passes throughno ; an instant after it will fall to p ; the motion of rotationof the axle ab will change its direction; the axle sr willalso turn in a contrary direction, and meet the rod q above,drawing it from above downwards, and make the counter-poise c pass towards v

Suppose the axle AB terminated by a square rod, gh , which fits freely an openingmade in the centre or the pulley G, sustained by a collar, provided its motion of rotation isnot affected; the movable screw m is furnished with a fork or lever, an endless cordembraces the axles m,n, and the pulleyG, by means of the pulley H. Thecircular motion of the axle mn is thencommunicated to the pulley G, and con-sequently to the axle A B ; this axle inturning will mount or descend freely, ifwe suppose that the screw m mounts;the lower branch ml of the fork willmeet the lever oq of the counterpoiseP, and will cause this counterpoise tofall towards the right of the plane ofthe figure. The axle mn will at theinstant take a motion in a contrarydirection; the screw m will descend,and the upper branch ik of the fork willmeet the lever oq , and acting on it will

conduct the counterpoise, and will make it fall on the other side in the time given.

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Fig. 1447.

Fig. 1448.

Fig. 1449.