How to Calculate the Fluid in a Horizontal Cylinder

Horizontal cylinders filled with fluid aboard a boat usually are filled with hydraulic fluid. They generally are the hydraulic cylinders used to control the position of the rudder, the external drive or the outboard motor. Their hydraulic volume varies, depending on the position of the hydraulic piston head in the cylinder. This means the amount of fluid in the cylinder at any given time may be expressed as a percentage of the cylinder's total volume.

Things You'll Need

  • Inside micrometer
  • Tape measure
  • Machinist's rule
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Instructions

    • 1

      Measure the inside diameter of the cylinder wall using a inside micrometer. Divide the diameter by 2. Multiply the diameter by itself. Multiply the result by 3.14; the result is the area of the base of the interior of the cylinder. For example, if the inside diameter is 1.25 inches, divide 1.25 by 2, which equals 0.625. Multiplied by 3.14, the result is 1.96, the area of the base of the interior of the cylinder.

    • 2

      Measure the length of the cylinder's interior with a measuring tape. Multiply the length of the interior by the area of the base of the interior. This is the total volume of the cylinder. If the cylinder's interior is 13 inches long, multiply this by 1.96. The result, 25.51, is the volume of the cylinder in cubic inches.

    • 3

      Measure the thickness of the hydraulic piston head, using a machinist's rule. Multiply by the area of the base of the cylinder; in this case, 1.96. If the piston head is 0.5 inches thick, 1.96 time 0.5 equals 0.98. Subtract this from the total volume to yield the volume of the cylinder when in use: 25.51 minus 0.98 equals 24.53 cubic inches.

    • 4

      Measure the length of the ram -- the rod connected to the hydraulic piston head. Divide each increment of the measure by the total measurement. For example, if the ram is 12 inches long, each inch of the rod equals 8.3 percent of the total length. When the ram is fully extended, the volume of the horizontal hydraulic cylinder is about 24.53 cubic inches. When the ram is 50 percent extended, the hydraulic volume is 12.27 cubic inches. When the ram is fully compressed -- all the way into the cylinder -- the hydraulic volume is nil.