 Welcome to the video Hydraulic Cylinder Speed. The speed at which the piston rod of a hydraulic cylinder moves is based on two factors. First, the size of the cylinder bore, which is the area inside the cylinder in which the piston moves, and second, the rate at which the hydraulic fluid flows into the cylinder. The following are the customary units of measurement in the United States. Abbreviations will be used in the calculations to determine the cylinder speed. The area of the cylinder bore is given in inches squared. The abbreviation for area is A. The flow of the fluid is listed in gallons per minute, or GPM. The abbreviation for flow is Q. The velocity of the piston rod is measured in inches per minute. The abbreviation for velocity is V. A conversion factor is used for equations that calculate the speed at which the piston rod moves. The constant number, 231, which represents the number of cubic inches in one gallon, is placed in the formula. Two calculations are required to determine the extension rate of the cylinder. Calculation one, find the bore size of the cylinder, which is also the piston area, using the following equation. Piston area equals pi times the diameter of the piston squared divided by four. Calculation two, find the speed at which the piston rod extends. Velocity or extension rate of the piston rod equals 231 times the flow rate divided by the area of the piston. What is the extension speed of the piston rod of a cylinder with a bore diameter of three inches when the hydraulic pump produces 10 gallons per minute? Step one, calculate the piston area as shown here. The piston area is 7.065 inches squared. Step two, calculate the extension speed as shown here. The extension speed is 327 inches per minute. The rate at which the piston retracts is faster than its extension rate. The reason for the difference is that there is less volume inside the cylinder on the side of the piston that has the rod. Three calculations are required to determine the retraction rate of the piston. Piston area equals pi times the diameter of the piston squared divided by four. Area of the rod equals pi times the diameter of the rod squared divided by four. Velocity or retraction rate of the piston rod equals 231 times the flow rate divided by the difference of the piston and rod areas. What is the retraction speed of the piston rod of a cylinder with a bore diameter of three inches and a rod diameter of one inch when the hydraulic pump produces 10 gallons per minute? Step one, calculate the piston area as shown. Step two, calculate the rod area as shown. Step three, calculate the retraction speed as shown. The retraction speed is 367 inches per minute. Now, check your knowledge by answering these three questions. Pause the video if you need more time to answer. Given that the flow rate of the hydraulic fluid from the pump is the same, the piston rod will extend slower than it retracts. The piston rod retracts faster than it extends because there is less volume of fluid to fill on the rod side than on the other side. The number of cubic inches of hydraulic fluid in a one gallon container is 231. You have completed this video. Hydraulic cylinder speed.