482
KINEMATICS OF MACHINERY.
a. Joints (for forming links).
I. Elements in pairs or in links.
I. Rigid Elements.
Eivets and riveted joints, Keys and keyed joints, Strained joints,
Screws and screwed joints, pass- ing into
Screw and nut (used for their
motions), Pins,
Bearing-blocks, Shafts and axles, Fixed couplings, Levers (simple), Cranks,
Levers (compound), Connecting-rods, Crossheads and guides, Friction- wheels, Toothed-wheels, Fly-wheels.
Whether moveable couplings and clutches should not be treated along with fixed couplings may be questioned, for we have already seen that in general, when their parts are in gear, they simply form parts of rigid links. It must be remembered, however, that these higher couplings contain in themselves numerous subordinate parts, levers, clicks, brake-blocks and so on, and present on this account greater difficulties to the student than the others. For the same reason they require, to a considerable extent, a special treat- ment dependent upon the nature of their details, and we are therefore justified in placing them rather among the complete mechanisms than here. Let us now go on to the second class of constructive elements, and their simplest arrangement in chains.
II. Flectional Elements.
a. Tension organs by themselves I I and their arrangement
and used with chain-closure. | ^ orc *s / j n CTear j n(T
Chains
