CALCULATION OF CYLINDER DIAMETER

Given that the load and operating pressure of the system are known, and that a piston rod size has been estimated taking account of whether the rod is in tension(pull) or compression (push), then the cylinder bore can be selected.
If the piston rod is in compression, use the ‘Push Force’ table below.

1. Identify the operating pressure closest to that required.
2. In the same column, identify the force required to move the load (always rounding up).
3. In the same row, lock along to the cylinder bore required.

If the cylinder envelope dimensions are too large for your application increase the operating pressure, if possible, and repeat the exercise.

If the piston rod is in tension, use the ‘Deduction for Pull Force’ table. The procedure is the same but, due to the reduced piston surface area resulting from the piston rod, the force available on the ‘pull’ stroke will be smaller, To determine the pull force.

1. Follow the procedure given for ‘push’ applications as described above.
2. Using the ‘Deduction for Pull Force’ table below, establish the force indicated according to the rod diameter and pressure selected.
3. Deduct this from the original ‘Push’ force. The resultant is the net force available to move the load.

If this force is not large enough, go through the process again but increase the system operating pressure or cylinder diameter if possible. If in doubt, Our design engineers will be pleased to assist.

Piston Rod Size Selection

The selection of a piston rod for thrust (push) conditions requires the following steps to be carried out:

1. Determine the type of cylinder mounting style and rod end connection to be used. Consult the Stroke Factor table and determine which factor corresponds to the application.
2. Using this stroke factor, determine basic length from the equation:
Basic Length = Net Stroke x Stroke Factor
( The Piston Rod Selection Chart, below, is prepared for standard rod extensions beyond the face of the gland retainer. For rod extensions greater than standard’ add the increase to the stroke to arrive at the basic length’)
3. Find the load imposed for the thrust application by multiplying the full bore area fo the cylinder by the system pressure, or by referring to the Push and Pull Force charts.
4. Using the Piston Rod Selection Chart below, look along the values of ‘ basic length ’ and ‘ thrust ‘ as found in 2. and 3. above, and note the point of intersection.

The correct piston rod size is read from the diagonally curved line labeled ‘ Rod Diameter ‘ above the point of intersection.


Long Stroke and Stop Tubes

When considering the use of long stroke cylinders, the piston rod should be of sufficient diameter to provide the necessary column strength.
For tensile(pull)loads, the rod size is selected by specifying standard cylinders with standard rod diameters and using them at or below the rated pressure.

For long stroke cylinders under compressive loads, the use of stop tubes should be considered, to reduce bearing stress. Selection of a stop tube is described.

 

Stop Tubes

The Piston Rod Selection Chart on page T3 indicates where the use of a stop tube should be considered. The required length of stop tube, where necessary, is read from the vertical columns on the right of the chart, by following the horizontal band within which the point of intersection lies. Note that stop tube requirements differ for fixed and pivot mounted cylinders.
If the required length of stop tube is in the shaded region marked consult factory, please submit the following information.

1. Cylinder mounting style.
2. Rod end connection and method of guiding the load.
3. Bore and stroke required, and length of rod extension ( Dimension ‘K’ ) if greater than standard.
4. Mounting position of cylinder. If at an angle or vertical, specify the direction of the piston rod.
5. Operating pressure of the cylinder if limited to less than the standard pressure for the cylinder selected.

When specifying a cylinder with a stop tube, please state the net stroke of the cylinder and the length of the stop tube.