10 third basics mechanical movements description and applications

31. Worm or endless screw and a worm wheel. This effects the same result as 29 ; and as it Is more easily constructed, it is oftener used.

32. Friction-wheels. The surfaces of these wheels are made rough, so as to bar as much as possible ; one is sometimes faced with leather, or, better, with vulcanized India-rubber.

33, Elliptical spur-gears. These are used where a rotary motion of varying speed is required, and the variation of speed is de-termined by the

relation between the lengths of the major and minor axes of the ellipses.

34. An Internally toothed spur-gear and pinion. With ordinary spur-gears (such as represented in 2,0 the direction of rotation is opposite ; but with the internally toothed gear, the two rotate in the same direction ; and with the same strength of tooth the gears are capable of transmitting greater force, because more teeth are engaged.

35. Variable rotary motion produced by uniform rotary motion. The small spur-pinion works in a slot cut in the bar, which turns loosely upon the shaft of the elliptical gear. The bearing of the pinion-shaft has applied to it a spring, which keeps it en-gaged ; the slot in the bar is to allow for the variation of length of radius of the elliptical gear.

36. Mangle-wheel and pinion—so called

from their application to mangles—converts continuous rotary motion of pinion into re-ciprocating rotary motion of wheel. The shaft of pinion has a vibratory motion, and works in a straight slot cut in the upright stationary bar to allow the pinion to rise and fall and work inside and outside of the gear-ing of the wheel. The slot cut in the face of the mangle-wheel and following its outline is to receive and guide the pinion-shaft and keep the pinion in gear.

37. Uniform into variable rotary motion. The bevel-wheel or pinion to the left has teeth cut through the whole width of its face. its teeth work with a spirally arranged series of studs on a conical wheel.

38. A means of converting rotary teiniren, by which the speed is made uniform during a part, and varied during another part, of the revolution.

39. Sun-and-planet motion. The spur-gear to the right, called the planet-gear, is tied to the center of the other, or sun-gear, by an arm which preserves a constant dis-tance between their centers. This was used as a substitute for the crank in a steam en-gine by James Watt, after the use of the crank had been patented by another party. Each revolution of the planet-gear, which is rigidly attached to the co/meeting-rod, gives two to the sun-gear, which 1.8 keyed to the fly-wheel shaft.