Section 88.—VARIABLE MOTION AND VARIABLE POWER.
For variable speed and power by spur gear, see [Sections 84] and [40].
For variable speed and power by bevil gear, see [Section 84].
For variable speed and power by cam gear, see [Section 9].
For variable speed and power by belt gear, see [Section 3].
[1582]. Variable speed belt cones, for crossed belts. Angle of cones should not exceed 15°.
[1583]. Stepped cone gear.
[1584]. Variable throw crank pin. (See Hastie’s Patent, 3561, 1878; Knowelden and Edwards’, 2996, 1858.)
[1585]. Beam motion, with variable fulcrum to alter the proportionate lengths of stroke of driving and driven cylinders. See also [No. 1606].
[1586]. Variable pressure accumulator. Both cylinders are in communication by a pipe, and the pressure varies with the angle between the rams.
[1587]. Wright’s variable gear. The radius of frictional contact of the wheels varies as they are moved closer together or separated.
[1588]. Olmsted’s variable cone friction gear, with intermediate double cone idle wheel instead of belt.
[1589]. Convex and concave cones for open belts.
[1590]. Three speed gear, each separate pair of spur gear being driven by its own belt pulley on separate sleeve pieces.
[1591]. Irregular or elliptical gear.
[1592]. Lever combination to obtain an even tension from a spring throughout its motion.
![[Larger plate.]](#3701448400155979539_plate90lg.png.id-7860056451792221359.wrap-0.html.html){kind=link}
[1593]. Scroll spur gear.
[1594]. Scroll gear for obtaining a variable pull from a weight.
[1595]. Variable friction gear. The pinion can be moved up or down from the centre to the outside of disc to vary the speed.
[1596]. Owen’s compound lever variable pressure air pumps. The pressure increasing and speed decreasing as the pistons rise to the top of their stroke.
[1597]. 2-speed gear by one belt. One loose pulley B carries a transverse mitre wheel, which, gearing into the fixed mitre wheel A, drives the mitre wheel pulley C keyed to shaft at twice the speed of pulley B when the belt is on B; by shifting the belt to pulley C, the speed is 1 to 1. The third pulley is loose for running idle.
[1598]. 2-speed bevel gear with three wheels and sliding shaft, by which either pair can be put into gear.
[1599]. 2-speed bevel gear with four wheels and sliding shaft.
[1600]. Increasing speed cone and screw, friction gear. The cone is driven by frictional contact with the pinion.
[1601]. Variable fulcrum lever, with shifting pin and hole adjustment.
[1602]. Fusee barrel, as used in clocks and watches to equalise the tension of spring on the movement; may also be employed to give a variable speed. The spring is usually similar to [No. 1484], and coiled in the upper barrel.
[1603]. Variable throw crank pin and slot, much used for variable feed motions in combination with some type of pawl and ratchet gear.
[1604]. Variable travel imparted to the piston rod from the crank by altering the point of attachment of the link A to the slot.
[1605]. Variable power pistons, single-acting.
[1606]. Effects the same ends as [No. 1601] or [1585], by shifting the fulcrum point along the slot by means of a screw.
![[Larger plate.]](#3701448400155979539_plate91lg.png.id-3433125738383960600.wrap-0.html.html){kind=link}
[1607]. Variable throw crank pin by means of a jointed crank and radial adjusting screw.
[1608]. Variable throw crank pin by attaching the crank pin to an eccentric disc. See [Section 10].
[1609]. Wind motor-fan or turbine, with variable-angle vanes actuated by a central sleeve and cam or lever gear.
[1610]. Variable friction cone gear; the small friction pinion can be moved radially to and fro to alter the leverage and consequently speed of driving radius from the cone.
In the steam engine, compressed air engine, and gas engine (these being all elastic fluids), the power given out is varied by altering the supply of steam, air, or gas. In the water wheel the power may be varied by altering the quantity of water (or head of water) supplied to the wheel. In the turbine the power can be varied by altering the head of supply water and the angle of vanes; altering the quantity reduces the speed and efficiency. The turbine will not work well under great variations of either head or quantity.
See also [Nos. 736], [722], [723], [1190], [1191], [381], [382], [384], [385], [377], [372], [373]; and [Sections 20] and [40].
For variable pressure or tension by springs, see [Section 80].
Variable balance weights, [Section 20].