10 4th basics mechanical movements description and applications

23. A contrivance for transmitting rotary motion to a movable pulley. The pulley at the bottom of the figure is the movable one; if this pulley were raised or depressed,

the belt would be slackened or tightened accordingly. In order to keep a uniform tension on the belt, a pulley, A, carried ina frame sliding between guides (not shown), hangs from a rope passing over the two guide-pulleys, B, B, and is acted upon by the balance weight, C, in such manner as to produce the desired result.

24. Spur-gears.

25. Bevel-gears. Those of equal diame- ters are termed “ miter-gears.”

26. The wheel to the right is termed a “ crown-wheel ;” that gearing with it is a Spur-gear. These wheels are not much used, and are only available for light work, as the teeth of the crown-wheel must necessarily be thin.

27. “Multiple gearing "—a recent inveb- tion. The smaller triangular wheel drives the larger one by the movement of its at-* tached friction-rollers in the radial grooves.

28. These arc sometimes called “brush- wheels.” The relative speeds can be varied by changing the distance of the upper wheel from the center of the lower one. The one drives the other by the friction or adhesion, and this may he increased by facing the lower one with india-rubber.

29. Transmission of rotary motion from one shaft at right angles to another. The spiral thread of the disk-wheel drives the spur-gear, moving it the distance of one tooth at every revolution.

30. Rectangular gears. These produce a rotary motion of the driven gear at a varying speed. They were used on a printing-press, the type of which were placed ona rectangu- lar roller.