Re: hydraulic jack

[Rick Swanson <swansonr@EMAIL.SANDHILLS.CC.NC.US>]

Kudos to those who have responded to this question.  In a few brief
emails, I have read simple, concise explanations and been provided with
vaulable resources that I can use in class

It happens all the time on this list; that is why I keep listening in.

Cheers,

Rick Swanson
Sandhills Community College

Richard E. Swanson, Ph.D.
Dean of Instruction
Physics Professor
Sandhills Community College, Pinehurst, NC 28374
swansonr@sandhills.edu (910) 695-3715

> > > exit60@CABLESPEED.COM 12/06/02 12:17PM >>>
The mechanical advantage of a hydraulic jack depends on knowing the
actual working *face* area of each piston, which in many cases is
going
to be different from the area you calculate using the diameter (or
radius) of the piston *body*.  You really do need to get inside the
cylinders to see what's going on, as others have suggested.

Accurate diagrams or photos of the working parts of hydraulic jacks
are
hard to come by, but there is a good cutaway engineering drawing of a
bottle jack at <http://www.shjack.com.cn/qyljg.htm>.  I'd be
interested
in hearing about other good online graphical representations that
anyone
on the list knows of.

Also there is a very kewl animated diagram of a working hydraulic
jack,
for which you might find instructional use, at
<http://www.hyjacks.com/anjack.htm>.

Best wishes,

Larry

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Larry Cartwright     <exit60@cablespeed.com>
Retired Physics Teacher
Charlotte MI 48813 USA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Lord, preserve us from the excesses of those
who would do us harm; and preserve us from
the excesses of those who would protect us.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Robert Cohen wrote:
> A student of mine was thinking about hydraulic systems and brought in
his floor jack.  We measured the diameter of the input and output
pistons and the distance each moved during one pass.  We hoped that the
total volume would be the same, i.e., pi r2 h of one would equal pi r2 h
of the other, where h is the distance each piston moved during one pass.
 However, the output volume is 20-25% greater.
> Anyone know what we're missing?