Chapter 8 Machines
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Mechanism
A mechanism is a way of changing one kind of effort into another
kind of effort. For example, a C-clamp holds two pieces of wood together
while glue sets. Rotary motion in the screw is changed to linear motion to
apply pressure. See Figure 8-56.
Mechanisms can be combined to form machines. Their advantages
include:
• Changing the direction of an effort
• Increasing the amount of effort applied
• Decreasing the amount of effort applied
• Applying an effort to a place that is otherwise hard to reach
• Increasing or decreasing the speed of an operation
Machines change one kind of energy into another and do work. The
amount of work done is approximately equal to the amount of energy
changed.
Work = (Energy Change)
= Effort × Distance Moved in
Direction of Effort
For example, how much work is done to move a 50 lb. resistance a
distance of 5′?
Work = 50 × 5
= 250 ft.-lb.
gure 8-56. A C-clamp is
an example of a mechanism.