hydraulic machine

The Columbia Encyclopedia, 6th ed.

hydraulic machine

hydraulic machine, machine that derives its power from the motion or pressure of water or some other liquid.

Hydraulic Engines

Water falling from one level to a lower one is used to drive machines like the water wheel and the turbine. The difference in height between the highest and the lowest level is called the head. The amount of work produced per pound of falling water is proportional to the head. Water power can be produced in this way from many natural sources, such as waterfalls and dammed rivers. Where no natural sources are available, an artificial reservoir can be made. When energy is plentiful, it is used to pump water into the reservoir; the water is then available as a power source to drive turbines when energy becomes scarce.

In driving certain industrial hydraulic machines an apparatus called an accumulator is employed to supply high power for short periods of time. One type consists essentially of a cylinder enclosing a piston loaded with weights. When water is slowly pumped into the cylinder, the piston and weights are forced up to a position where they are held. When they are released, they force the water out of the cylinder rapidly, providing the machine with hydraulic power.

Hydrostatic Devices

Water or oil under pressure is commonly used as a source of power for many types of presses, riveting machines, capstans, winches, and other machines. The hydraulic press, or hydrostatic press, was invented by Joseph Bramah and is therefore sometimes called the Bramah press. It consists essentially of two cylinders each filled with liquid and each fitted with a piston; the cylinders are connected by a pipe also filled with the liquid. One cylinder is of small diameter, the other of large diameter. According to Pascal's law, pressure exerted on the smaller piston is transmitted undiminished through the liquid to the surface of the larger piston, which is forced upward. Although the pressure (force per unit of area) is the same for both pistons, the total upward force on the larger piston is as many times greater than the force on the smaller piston as the area of the larger piston is greater than the area of the smaller piston. If, for example, the smaller piston has an area of 2 sq in. and a force of 100 lb is exerted on it, then the force on the larger piston having an area of 50 sq in. would be 2,500 lb (100×50/2=2,500). However, when the pistons move, the distance the smaller piston travels is proportionately greater than the distance the larger piston travels, satisfying the law of conservation of energy. If the smaller piston moves 25 in., the larger one will only move 1 in. The hydraulic press is used, for example, to form three-dimensional objects from sheet metal and plastics and to compress large objects.

The hydraulic jack, also an application of Pascal's law, is used to exert large forces or to lift heavy loads. Like the hydraulic press it consists essentially of two different-sized pistons contained in cylinders that are connected by a pipe. When the smaller piston is moved back and forth by a handle connected to it, it pumps a liquid into the cylinder of the larger piston, forcing the larger piston to move. In this way a weak force applied to the smaller piston can raise a heavy load on the larger one. The hydraulic elevator is also an application of Pascal's law.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

hydraulic machine
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.