In most circuits that use cylinders, designers arbitrarily set parameters such as stroke, force, cycle time, mounting styles, mounting orientation and maximum system pressure - if they have not already been determined by the required mechanical function. Because force and maximum system pressure usually are known, it is easy to use a cylinder catalogue to pick the minimum bore required.. From this point, things such as pump flow, pipe size, piston rod column strength, stop tube requirements, acceleration and deceleration times, and natural frequency can be calculated. Most cylinder manufacturers provide charts and/or formulas to simplify these calculations, but inexperienced designers often overlook them.

Admittedly, in applications where speed and force are low and the stroke is short, many of the parameters listed above are unimportant. However, it would be helpful to have all these facts available on every application just to make sure the actuator is specified correctly. With software called HydraCyl, your computer can quickly give you all these answers.

The software runs on any IBM_compatible computer with MS-DOS 3.1 or later or Win3.1/Win95 platforms. It produces values for all of the cylinder parameters in metric or English units. The software is easy to use because it notifies you if incorrect data is entered or if more information is needed. Keyboard or mouse inputs simplify access.

When you start HydraCyl, the first window-like screen appears (with any information from the last cylinder analysis in place). A menu bar across the top of the screen shows the input categories available: Cylinder to work with screen information; Analysis to perform different tasks; and Help to get on-screen assistance about how to use HydraCyl software.

The first information input is Dimensions under Cylinder from the menu bar. The data on the screen is based on standard square-end tie-rod hydraulic cylinders for medium- or heavy-duty applications. All you need to do is to select the cylinder and rod diameter you want and the enter OK. Note that this information can be changed at any time so different bore and rod combinations can be checked against different operating parameters.

Operating Parameters is the next selection under Cylinder. They include Stroke, Flow, Extending Speed, Extending Time, retracting Speed, Retracting Time, Supply Pressure, Extending Force, Retracting Force, Applied Mass, and Cyl-Valve Distance. The data that can be input here is limited by the relationship among parameters. For example, if gpm figure is given, speed and time for extending or retracting are locked out. Or if pressure is specified, extend and retract force cannot be input. The software allows speeds up to 200 fpm or 40 ips maximum. Under Mounting Type, several pivot attachments are available. The different mounts are described in a box below the selection brackets and can also be seen graphically by clicking on View Different Mounting Types. All mounting styles are designed by appropriate National Fluid Power Association standard M letters and numbers.

Next comes Mounting Orientation, still under Cylinder menu. Six selection brackets show different cylinder and rod hookups and actions. When a selection is made a description of that choice appears in a box below. The angle between axes 0X and 0Z must be specified. By clicking on the View Orientation Diagrams, it will become obvious what angle increment is required here. For a vertical cylinder with rod down, an angle of 180° would be entered. Also on this screen is a place to put in the Coefficient of friction for the cylinder and machine members. When all selections on this screen have been made, click on OK to select this data and go back to the main menu.

The last selection under Cylinder is Hydraulics Pipe (Tube). The screen that comes up from this selection is used to pick out a pipe size. An experienced designer might arbitrarily choose a diameter and wall thickness. Someone with little or no experience would either have to figure the correct size or guess at something close. Because these choices can be changed and the problem figured again, a pure guess is not as dangerous as it sounds.

After all parameters are set, click on Analysis on the menu bar, then on Perform Analysis, to make the software compute all cylinder data. If you should try to Perform Analysis, before all information is entered, the software will alert you with a beep and the missing menu item will appear on screen.

Information on:

- cylinder area,

- displacement volume,

- force, acceleration and deceleration time,

- pump flow,

- extending and retracting line flow,

- pipe flow velocity for both lines, both directions,

- stop tube requirements,

- column strength,

- natural frequency,

- minimum pressure and minimum distance for extending and retracting

- minimum braking pressure both compartments when cylinder is running ahead of pump

are all detailed on eight different screens. Any of the data can be altered and refigured again as often as needed. A printout can be made each time new data is entered and analysed.

Anyone who designs circuits with hydraulic cylinders can have greater confidence in their finished product after using HydraCyl. The software does almost all the calculations with minimum time invested, and operating problems due to incorrect specifications are practically eliminated.

You are welcome to use supplied free and fully functional Test Drive of Hydracyl for cylinders up to 2 inches.

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