Section 21.—CIRCULAR AND RECIPROCATING MOTION.

[392]. The ordinary type of piston-rod and crank motion as universally used.

[393]. Watt’s substitute for the above, or “sun-and-planet” gear. Note that the crank shaft revolves twice for each double stroke or revolution of the engine. The crank being a loose link only, the planet wheel does not revolve.

[394]. Epicycloidal parallel motion and crank. The pinion is one-half the diameter of the wheel on pitch line, and the connecting pin is fixed on the pitch line of pinion.

[395]. Bernay’s patent crank motion; radius of crank = stroke × ·25.

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[396]. Slot and crank motion. The pin usually runs in a sliding block.

[397]. Segment pinion and double rack motion.

[398]. Rack and pinion. The pinion is sometimes made so as to be driven on one stroke and run loose on the other, by a clutch or ratchet motion, such as [Nos. 1135], [1178], or their equivalents. See [Section 62].

[399]. Hydraulic multiplying gear. See also [Section 42].

[400]. Slotted crosshead and disc crank. The pin runs in a sliding block in a groove in the covered crosshead.

[401]. Stannah’s patent, works vertically; the fly-wheel centre A oscillates on the end of a link B, allowing the crank pin to run in a straight line.

[402]. Screw and fly nut. May be made to produce continuous rotary motion by fitting the nut with a clutch motion similar to [1135] or [1178], so as to grip the wheel only on one stroke.

[403]. Friction gear; the pinion is driven by the reciprocating rod and runs loose on the out stroke, the weighted lever with roller giving frictional grip on the in stroke.

[404]. Lever and roller crank pin.

[405]. Treadle motion, with cord and spring. For continuous rotary motion the pinion must be fitted as described with [No. 402].

[406]. Ball and socket crank motion. The crank pin is always horizontal.

[407]. Segment lever, with cord and pulley.

[408]. Double geared cranks, used for driving rotary blowers, &c.

[409]. J. Warwick’s patent; circular motion converted into reciprocating by a diagonal sheave grooved as shown; the crank arm centre is in line with the centre of the sheave, as shown in dotted lines.

[410]. Rolling sectors, with thrust motion to crank pin. Used in Outridge’s box engine with double pistons; this gives a constant rectilinear thrust to the crank pin at all points in the stroke, and no part is in tension.

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[411]. Weight and multiplying pulleys, used for clock motions, driving any light machines, &c.

[412]. Oscillating clutch arm and ring, silent feed motion.

[413]. Slot and roller motion for crank. The crank pin has a friction roller, which runs in a covered slot in the crosshead.

[414]. Trammel gear; one revolution of the wheel to two double strokes of piston.

[415]. Segmental vanes (in a semicircular case), driven by a disc crank and pin, running on the upper centre, giving motion by links to two arms fixed to the two vanes, which have independent motion. Used as a pumping or blowing machine.

[416]. Circular into reciprocating motion by revolving arm A carrying the two pinions, the point at end of arm B describes a vertical line four times the length of arm B, the large wheel C is fixed, and motion is given to the arm B. May be used as a piston rod and crank motion.

[417]. Trammel gear; the slotted cross moves in a right line.

[418]. Slot link and treadle, driving the pinion on both strokes by friction on the inside of link alternately at the upper and under sides.

[419]. Chain and roller treadle motion.

[420]. Reciprocating wheel and crank motion.

[421]. Velocipede pattern foot treadle.

[422]. Double crossheads, separated by distance rods so arranged as to allow the crank and connecting rod to work between them. See [No. 681].

[423]. Mangle rack and pinion reciprocating gear. The rack moves in a right line, the pinion working round it by moving up and down the slot at each end of the travel of the rack.

[424]. Mode of connecting an oscillating lever by a sliding joint to any reciprocating part, such as a steam hammer head, engine crosshead, &c. See [Nos. 893, 894].

[425]. Suspended treadle motion.

[426]. Eccentric and sliding bush motion for a double piston engine.

[427]. Rocking lever motion by gearing and a tied crank pin. The upper pinion drives the crank disc on the middle centre at each revolution, of which the lever with the gearing attached oscillates from side to side as shown.

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[428]. Crank pin and slotted lever for giving a variable speed to the connecting rod. See [No. 1195].

[429]. Side gudgeon crank motion.

[430]. Bell crank and disc crank motion, the bell crank centre having horizontal as well as vertical movement.

[431]. Worm wheel and screw reciprocating motion by means of a tied crank pin. Useful for slow speeds.

[432]. Treadle, cord and pulley crank motion.

[433]. Circular into reciprocating motion, or vice versâ.

[434]. Another form of sun-and-planet gear. The ring is stationary, and the bush on which the planet wheel revolves is slotted to fit the ring; the planet wheel is fixed to the connecting rod end.

[435]. Bent shaft and arm motion.

[436]. Reciprocating motion by a return thread screw and lever.