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Machines and mechanisms

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The transformation of one of the simple motions, such as rotation, into any other motions is often conveniently accomplished by means of a cam mechanism A cam mechanism usually consists of two moving elements, the cam and the follower, mounted on a fixed frame. Cam devices are versatile, and almost any arbitrarily-specified motion can be obtained. In some instances, they offer the simplest and most compact way to transform motions.

A cam may be defined as a machine element having a curved outline or a curved groove, which, by its oscillation or rotation motion, gives a predetermined specified motion to another element called the follower . The cam has a very important function in the operation of many classes of machines, especially those of the automatic type, such as printing presses, shoe machinery, textile machinery, gear-cutting machines, and screw machines. In any class of machinery in which automatic control and accurate timing are paramount, the cam is an indispensable part of mechanism. The possible applications of cams are unlimited, and their shapes occur in great variety. Some of the most common forms will be considered in this chapter.

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gear or cogwheel is a rotating machine part having cut teeth, or in the case of a cogwheel, inserted teeth (called cogs), which mesh with another toothed part to transmit torque. Geared devices can change the speed, torque, and direction of a power source. Gears almost always produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a simple machine. The teeth on the two meshing gears all have the same shape.[1] Two or more meshing gears, working in a sequence, are called a gear train or a transmission. A gear can mesh with a linear toothed part, called a rack, producing translation instead of rotation.
The gears in a transmission are analogous to the wheels in a crossed, belt pulley system. An advantage of gears is that the teeth of a gear prevent slippage.

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"What is the most common probable cause for machine malfunction?"
Machines fail for a variety of reasons. Likewise, not all failures are the same. The term "machinery failure" or "malfunction" usually implies that the machine has stopped functioning the way in which it was intended or designed. This is referred to as “loss of usefulness” of the machine or component. For instance, if a pump is installed to pump 100 gallons of oil per minute but over time can no longer keep up and now only pumps 75 gallons per minute, this is a loss of usefulness of the asset.

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Torque: Something that produces or tends to produce rotation and whose effectiveness is measured by the product of the force and the perpendicular distance from the line of action of the force to the axis of rotation.

Consider the lever shown in Figure 1-1. The lever is a bar that is free to turn about the fixed point, A, called the fulcrum; a weight acts on the one side of the lever, and a balancing force acts on the other side of the lever.

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Motion: a change of position or orientation.

1.2.1  Motion Along a Straight Path

We begin our study of motion with the simplest case, motion in a straight line.

1. Position and displacement along a line
The first step in the study of motion is to describe the position of a moving object. Consider a car on an east-west stretch of straight highway. We can describe the displacement of the car by saying "the car is 5 kilometers west of the center town". In this description, we specified two factors, the original point of measure and the direction of the displacement.

2. Velocity
We can define the velocity of an object moving steadily as its displacement per unit time:

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The Meaning of Torque

Torque (also called moment — mostly by engineers) is calculated by multiplying force and distance. The SI units of torque are newton-meters, or N*m (even though these units are the same as Joules, torque isn't work or energy, so should just be newton-meters).
In calculations, torque is represented by the Greek letter tau: τ.
Torque is a vector quantity, meaning it has both a direction and a magnitude. This is honestly one of the trickiest parts of working with torque because it is calculated using a vector product, which means you have to apply the right-hand rule. In this case, take your right hand and curl the fingers of your hand in the direction of rotation caused by the force. The thumb of your right hand now points in the direction of the torque vector. (This can occasionally feel slightly silly, as you're holding your hand up and pantomiming in order to figure out the result of a mathematical equation, but it's the best way to visualize the direction of the vector.)
The vector formula that yields the torque vector τ is: