MECH ANIC ’S CORNER ◗ EDDie konrad
Force and Motion ◗ Hydraulic systems used on our equipment provide a means of remotely controlling a wide range of components by transmitting a force through a confined fluid. The basic principle behind any hydraulic system is very simple; pressure applied anywhere to a body of fluid causes a force to be transmitted equally in all directions, with the force acting at right angles to any surface in contact with the fluid. This is also known as Pascal’s Law. Pascal’s Law (from Blaise Pascal, 1623 to 1662) comprises a set of principles formulated in 1648 and states that pressure applied to a confined fluid at any point is transmitted, undiminished, throughout the fluid in all directions and acts upon every part of the confining vessel at right angles to its interior surfaces and equally upon equal areas. Pascal’s Law is the basic principle behind any hydraulic system. The word “hydraulics” generally refers to power produced by moving liquids. Modern hydraulics is defined as the use of confined liquid to transmit power, multiply force or produce motion. In figure 1, we have two pistons with different sizes; the left piston has a radius of 0.5 inches while the right piston has a radius of 3 inches. The area of the two pistons is calculated with the following formula: Pi x r2. The area of the left piston is therefore 3.14, while the area of the piston on the right is 28.26. The piston on the right is nine times larger than the piston on the left. So, if you apply a 100-pound downward force to the left piston, a 900-pound upward force will appear on the right. The only catch is that you will have to depress the left piston nine inches to raise the right piston one inch. Hydraulic systems contain the following key components: Fluid – usually hydraulic fluid. Reservoir – to store the fluid and act as a heat dissipater. Hydraulic pump – to convert mechanical energy into hydraulic energy by forcing hydraulic fluid, under pressure, from the reservoir into the system. Fluid lines – to transport the fluid to and from the pump through the hydraulic system. These lines can be rigid metal 40 greenMaster | www.golfsupers.com
Pascal’s Law is the basic principle behind any hydraulic system. The word “hydraulics” generally refers to power produced by moving liquids.
tubes or flexible hose assemblies. Hydraulic valves – to control pressure, direction and flow rate of the hydraulic fluid. Actuators – to convert hydraulic energy into mechanical energy to do work. Actuators on golf course equipment usually take the form of hydraulic cylinders or gear pumps, hydraulic gear motors etc. While there are different kinds of pumps, actuators, valves, etc., the basic design of the hydraulic system is essentially the same for all our equipment.
How do hydraulic circuits and components, used in turf equipment, work?
If we look at a gear pump, it might look the same as a gear motor. However, the difference is the gear pump draws oil in from the reservoir and forces it into the line, while oil is forced into the gear motor from the pump and returned into the reservoir. To make a system work, valves or spool valves are used to open or close hydraulic lines, therefore allowing hydraulic fluid to enter gear pumps or gear motors, or simply
cycle fluid to the reservoir in a neutral position. The purpose of hydraulic fluid (oil) is not only to transfer power, but also to cool internal parts, lubricate moving parts and carry contamination to the filter. Hydrostatic systems make further use of Pascal’s law. Hydrostatic systems were developed for their simplicity. They use no gears or clutches, usually have single lever control and are easy to install. Another advantage is maneuverability. There is a faster response than with other transmissions and, therefore, hydrostatic systems can be used for dynamic breaking and rapid reversals. Working on hydraulic systems can be very dangerous because hydraulic systems must store fluid under high pressure. Three kinds of hazards exist; burns from the hot, high pressure spray of fluid, bruises, cuts or abrasions from flailing hydraulic lines and injection of fluid into the skin. Safe hydraulic system performance requires general maintenance. Proper coupling of high and low pressure hydraulic components and pressure relief valves are