User's Manual

®
Model No. ME-6984 Theory
3
Theory
Hydraulics is a topic in applied science and engineering that deals with the mechanical properties of liquids. Pneu-
matics is a topic that deals with the study and application of the use of pressurized gas to affect mechanical motion.
Blaise Pascal described the behavior of a fluid (gas or liquid) in a closed container. Pressure applied to an enclosed
fluid is transmitted undiminished to every part of the fluid, as well as to the walls of the container. A hydraulic lift
is an example of a device that demonstrates the principle. A model of a hydraulic (or pneumatic) lift consists of a
syringe that has a large diameter piston connected to another syringe that has a small diameter piston. The pressure
is the ratio of force to area and will be the same throughout the system. For example, if the large diameter piston
has an area five times larger than the small diameter piston, the hydraulic lift will have a theoretical mechanical
advantage of five to one. In other words, a force of 10 N applied to push the small piston into the syringe would
cause a force of 50 N to be applied to push the large piston out of the piston. The large piston does the same
amount of work as is done to the small piston. The distance that the small piston is pushed into the small syringe is
five times more than the distance that the large piston will move out of the large syringe.
About the Components
Syringes
The set has three sizes of syringes (60 mL, 20 mL, and 10 mL), each with a male luer (pronounced “loo-er”) lock
at one end. The luer lock allows the syringe to be connected to couplers (tubing) or valves. There is a retainer ring
on the inside of the large end of the cylinder that helps prevent the piston from being pulled out of the cylinder too
easily.
Hydraulic Cylinder
The hydraulic cylinder is a modified 60 mL syringe with six trunnions (cylindrical protrusions used as a mounting
or pivot point) on the cylinder and two mounting holes on the end of the syringe. The holes allow the hydraulic
cylinder to be mounted between two axles. When the hydraulic cylinder is attached to a structure and a gas (such
as air) or a liquid (such as water) is pumped into the cylinder, the pressurized fluid will cause the piston to be
pushed out of the cylinder. The part of the structure that the piston is attached to will move.
Figure 1: Syringe (60 mL)
Cylinder
Piston
Male Luer
Lock
Volume
Markings
Figure 2: Hydraulic Cylinder
Mounting
Holes
Trunnion
Holes
Cylinder
Piston