ILLUSTRATING SOME OF THE FUNDAMENTAL DEVICES
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.
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. 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.
[Illustration: _Inside Fig. 58. Belt Lacing_
_Outside Fig. 58. Belt Lacing_
_Fig. 59. Belt Lacing_
_Fig. 60. Belt Lacing_
_Fig. 61. Belt Lacing_]
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 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.
[Illustration: _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. 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 FROM 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.
[Illustration: _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. 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.
Fig. 75. CLUTCHES.--This is a piece of mechanism which is required in so
many kinds of machinery, that we show several of the most approved
types.
Fig. 76. BALL AND SOCKET JOINTS.--The most practical form of ball and
socket joints is simply a head in which is a bowl-shaped cavity the
depth of one-half of the ball. A plate with a central opening small
enough to hold in the ball, and still large enough at the neck to
permit the arm carrying the ball to swing a limited distance, is secured
by threads, or by bolts, to the head. The first figure shows this.
Fig. 77 illustrates a simple manner of tightening the ball so as to hold
the standard in any desired position.
Fig. 78. TRIPPING DEVICES.--These are usually in the form of hooks, so
arranged that a slight pull on the tripping lever will cause the
suspended articles to drop.
Fig. 79. ANCHOR BOLT.--These are used in brick or cement walls. The bolt
itself screws into a sleeve which is split, and draws a wedge nut up to
the split end of the sleeve. As a result the split sleeve opens or
spreads out and binds against the wall sufficiently to prevent the bolt
from being withdrawn.
Fig. 80. LAZY TONGS.--One of the simplest and most effective instruments
for carrying ice, boxes or heavy objects, which are bulky or
inconvenient to carry. It grasps the article firmly, and the heavier the
weight the tighter is its grasp.
Fig. 81. DISC SHEARS.--This is a useful tool either for cutting tin or
paper, pasteboard and the like. It will cut by the act of drawing the
material through it, but if power is applied to one or to both of the
shafts the work is much facilitated, particularly in thick or hard
material.
[Illustration:
_Fig. 75. Clutches_
_Fig. 76. Ball and Socket Joints_
_Fig. 77. Fastening Ball_
_Fig. 78. Tripping Devices_
_Fig. 79. Anchor Bolt_
_Fig. 80. Lazy Tongs._
_Fig. 81. Disc Shears._]
Fig. 82. WABBLE SAW.--This is a most simple and useful tool, as it will
readily and quickly saw out a groove so that it is undercut. The saw is
put on the mandrel at an angle, as will be seen, and should be run at a
high rate of speed.
Fig. 83. CRANK MOTION BY A SLOTTED YOKE.--This produces a straight
back-and-forth movement from the circular motion of a wheel or crank. It
entirely dispenses with a pitman rod, and it enables the machine, or the
part of the machine operated, to be placed close to the crank.
Fig. 84. CONTINUOUS FEED BY THE MOTION OF A LEVER.--The simple lever
with a pawl on each side of the fulcrum is the most effective means to
make a continuous feed by the simple movement of a lever. The form shown
is capable of many modifications, and it can be easily adapted for any
particular work desired.
[Illustration: _Fig. 82. Wabble Saw_
_Fig. 83. Continuous Crank Motion_
_Fig. 84. Continuous Feed_
_Fig. 85. Crank Motion_
_Fig. 86. Ratchet Head_
_Fig. 87. Bench Clamp_]
Fig. 85. CRANK MOTION.--By the structure shown, namely, a slotted lever
(A), a quick return can be made with the lever. B indicates the fulcrum.
Fig. 86. RATCHET HEAD.--This shows a well-known form for common ratchet.
It has the advantage that the radially movable plugs (A) are
tangentially disposed, and rest against walls (B) eccentrically
disposed, and are, therefore, in such a position that they easily slide
over the inclines.
Fig. 87. BENCH CLAMP.--A pair of dogs (A, B), with the ends bent toward
each other, and pivoted midway between the ends to the bench in such a
position that the board (C), to be held between them, on striking the
rear ends of the dogs, will force the forward ends together, and thus
clamp it firmly for planing or other purposes.
[Illustration:
_Fig. 88. Helico-Volute Spring_
_Fig. 89. Double Helico-Volute_
_Fig. 90. Helical Spring_
_Fig. 91. Single Volute Helix-Spring_
_Fig. 92. Flat Spiral or Convolute_
_Fig. 93. Eccentric Rod and Strap_
_Fig. 94. Anti-Dead Center for Foot-Lathes_]
Fig. 88. HELICO-VOLUTE SPRING.--This is a form of spring for tension
purposes. The enlarged cross-section of the coil in its middle portion,
with the ends tapering down to the eyes, provides a means whereby the
pull is transferred from the smaller to the larger portions, without
producing a great breaking strain near the ends.
Fig. 89. DOUBLE HELICO-VOLUTE.--This form, so far as the outlines are
considered, is the opposite of Fig. 88. A compression spring of this
kind has a very wide range of movement.
Fig. 90. HELICAL SPRING.--This form of coil, uniform from end to end, is
usually made of metal which is square in cross-section, and used where
it is required for heavy purposes.
Fig. 91. SINGLE VOLUTE HELIX-SPRING.--This is also used for compression,
intended where tremendous weights or resistances are to be overcome, and
when the range of movement is small.
Fig. 92. FLAT SPIRAL, OR CONVOLUTE.--This is for small machines. It is
the familiar form used in watches owing to its delicate structure, and
it is admirably adapted to yield to the rocking motion of an arbor.
Fig. 93. ECCENTRIC ROD AND STRAP.--A simple and convenient form of
structure, intended to furnish a reciprocating motion where a crank is
not available. An illustration of its use is shown on certain types of
steam engine to operate the valves.
Fig. 94. ANTI-DEAD CENTER FOR FOOT-LATHES.--A flat, spiral spring (A),
with its coiled end attached to firm support (B), has its other end
pivotally attached to the crank-pin (C), the tension of the spring being
such that when the lathe stops the crack-pin will always be at one side
of the dead-center, thus enabling the operator to start the machine by
merely pressing the foot downwardly on the treadle (D).