There are numerous little devices and shop expedients which are desirable, and for which the boy will find uses as he progresses.

We devote this chapter to hints of this kind, all of which are capable of being turned out or utilized at various stages.

Figs. 58. 61. Belt Lacing

Lacing Belts

To properly lace a belt is quite an art, as many who have tried it know. If a belt runs off the pulley it is attributable to one of three causes: either the pulleys are out of line or the shafts are not parallel or the belt is laced so it makes the belt longer at one margin than the other.

In Fig. 58 the lacing should commence at the center hole (A) of one belt end and lace outwardly, terminating at the hole (B) in the center of the other belt end, as shown in Fig. 58.

In Fig. 59 the lacing commences at A, and terminates at the hole (B) at the edge. This will be ample for all but the widest belts.

Fig. 60 is adapted for a narrow belt. The lacing commences at one margin hole (A), and terminates at the other margin hole (Z)

Fig. 61 shows the outside of the belt.

Fig. 62. Bevel Gears Fig. 63. Miter Gears Fig. 64. Crown Wheel Fig. 65. Grooved Friction Gears Fig. 66. Valve Fig. 67. Cone Pulleys Fig. 68. Universal Joint

Fig. 62. Gears. - This is something every boy ought to know about. Fig. 62 shows a pair of intermeshing bevel gears. This is the correct term for a pair when both are of the same diameter.

Miter Gears

In Fig. 63 we have a pair of miter gears, one being larger than the other. Remember this distinction.

Fig. 64. Crown Wheel. - This is a simple manner of transmitting motion from one shaft to another, when the shafts are at right angles, or nearly so, without using bevel or miter gears.

Fig. 65. Grooved Friction Gearing. - Two grooved pulleys, which fit each other accurately, will transmit power without losing too much by friction. The deeper the grooves the greater is the loss by friction.

Fig. 66. A Valve Which Closes by the Water Pressure. - The bibb has therein a movable valve on a horizontal stem, the valve being on the inside of the seat. The stem of the handle has at its lower end a crank bend, which engages with the outer end of the valve stem. When the handle is turned in either direction the valve is unseated. On releasing the handle the pressure of the water against the valve seats it.

Fig. 67. Cone Pulleys. - Two cone pulleys of equal size and taper provide a means whereby a change in speed can be transmitted from one shaft to another by merely moving the belt to and fro. The slightest change is available by this means.

Fig. 68. Universal Joint. - A wheel, with four projecting pins, is placed between the U-shaped yokes on the ends of the approaching shafts. The pins serve as the pivots for the angles formed by the two shafts.

Fig. 69. Trammel Fig. 70. Escapement Fig. 71. Device for Holding Wheel Fig. 72. Rack and Pinion Fig. 73. Mutilated Gears Fig. 74. Shaft Coupling

Fig. 69. Trammel for Making an Ellipse. - This is a tool easily made, which will be of great service in the shop. In a disc (A), preferably made of brass, are two channels (B) at right angles to each other. The grooves are undercut, so that the blocks (C) will fit and slide in the grooves and be held therein by the dove-tailed formation. Each block is longer than the width of the groove, and has an outwardly projecting pin which passes through a bar (D). One pin (E) is movable along in a slot, but is adjustable at any point so that the shape of the ellipse may be varied. The end of the bar has a series of holes (G) for a pencil, so that the size of the ellipse may also be changed.

Fig. 70. Escapements. - Various forms of escapements may be made, but the object of all is the same. The device is designed to permit a wheel to move intermittingly or in a step by step movement, by the swinging motion of a pendulum. Another thing is accomplished by it. The teeth of the escapement are cut at such an angle that, as one of the teeth of the escapement is released from one tooth of the escapement wheel, the spring, or the weight of the clock, will cause one of the teeth of the escapement wheel to engage the other tooth of the escapement, and give the pendulum an impulse in the other direction. In the figure, A is the escapement, B the escapement wheels and a, b, the pallets, which are cut at suitable angles to actuate the pendulum.

Fig. 71. Simple Device to Prevent a Wheel or Shaft prom Turning Back. - This is a substitute for a pawl and ratchet wheel. A is a drum or a hollow wheel and B a pulley on a shaft, and this pulley turns loosely with the drum (A). Four tangential slots (C) are cut into the perimeter of the pulley (B), and in each is a hardened steel roller (D). It matters not in what position the wheel (B) may be, at least two of the rollers will always be in contact with the inside of the drum (A), and thus cause the pulley and drum to turn together. On reversing the direction of the pulley the rollers are immediately freed from binding contact.

Fig. 72. Racks and Pinions. - The object of this form of mechanism is to provide a reciprocating, or back-and-forth motion, from a shaft which turns continually in one direction. A is the rack and B a mutilated gear. When the gear turns it moves the rack in one direction, because the teeth of the gear engage the lower rack teeth, and when the rack has moved to the end its teeth engage the teeth of the upper rack, thus reversing the movement of the rack.

Fig. 73. Mutilated Gears. - These are made in so many forms, and adapted for such a variety of purposes, that we merely give a few samples to show what is meant by the term.

Fig. 74. Simple Shaft Coupling. - Prepare two similarly formed discs (A, B), which are provided with hubs so they may be keyed to the ends of the respective shafts. One disc has four or more projecting pins (C), and the other disc suitable holes (D) to receive the pins.