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To help understand some basic concepts of hydraulics in relation
to our use of machines using hydraulics to do work, we will do a
series on basic hydraulics and understanding of principles and terms
using graphics and text to help us see the principles applied.
Machines were invented to help man do work. One can easily relate
to a machine that has helped man produce food. Take for example
the ox drawn plow and how it has evolved over time to be replaced
by tractors with air conditioned cabs pulling hardened steel implements
tilling the soil so that we can grow food. Or how about the bulldozer
or some variance of it with a piece of steel mounted on the front
to push and move dirt about so we can have nice flat highways. Most
all modern machinery today uses hydraulics to do work so as to make
our lives easier. One more example and we will move on. The ease
with which we drive and steer our cars today is because of hydraulics.
The automatic transmission is a hydrostatic transmission and power
steering is hydraulically assisted steering.
Hopefully
we are more connected to "hydraulics" now that we have
some examples of the subject. We will need to define some terms
so that our understanding of hydraulics is not hampered.
- Force:
Capable of producing a change in the motion of mass. It can
cause a body (mass) to move or is also capable of retarding
or stopping a body.
- Pound:
One typical unit for measuring force here in the United States.
- Resistance:
A force which retards or stops movement. Friction and inertia
are examples of resistance.
- Energy:
A force which can cause a mass to move.
- Inertia:
Being the reluctance of a body to change its motion.
- Forms
of Energy: Mechanical, heat, electrical, light, chemical and
sound.
- Conservation
of Energy: The Law of Conservation of Energy states that, "Energy
cannot be created, or destroyed." However, energy may change
form.
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Example:
Electrical energy changes when a light bulb is plugged into
an outlet to become light and heat. An electrical fan plugged
into the same source of power is now changed into mechanical
energy, which propels our unseen air to heat or cool us. |
- Kinetic
Energy: Energy that is moving, as in a flywheel. Not all, but
most forms of energy must be in a state of kinetic energy before
work can be done.
- Potential
Energy: Is stored energy such as a dam full of water waiting
to be released so it can turn turbines which will produce mechanical
energy which will produce electrical energy.
Example:
A 12 volt battery is said to have a 12 volt potential, potential
energy that is stored until the circuit is completed and energy
flows from the battery.
- Work:
is moving a mass or body of weight through a distance. Hence,
machines that do work for us. Example, a backhoe that lifts
a bucket of dirt up and out of a hole.
- Foot-Pound:
is the unit of measurement for work.
- Pound:
= lb., pounds = lbs., abbreviated
- Description
of Work: Work (ft.lbs.) = distance moved (ft.) x force exerted
(lbs.)
Example
of work: A backhoe bucket filled with 2,000 lbs. of dirt is lifted
5 feet, then 10,000 ft.lbs. of work has been done.
- Description
of Power: Power = distance moved (ft) x force exerted (lbs).
time (seconds)
Backhoe
example: if the backhoe lifted 2,000 lbs. 5 feet in 5 seconds,
then
10,000 ft. lbs. = 2,000 ft. lbs. of work was done per
second.
5 seconds
- Horsepower:
James Watt discovered that a horse could lift 550 pounds one
foot in one second. Thus the term horsepower, in this case;
1hp. (horsepower)
- Description
of Horsepower: HP = distance moved (ft.) x force exerted (lbs.)
÷ 550
Time (seconds)
Following
through with our backhoe example:
5 ft. x 2000 lbs. ÷ 550 =3.636 HP
5 seconds
We will continue in our May/June newsletter.
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