A gas spring is a type of spring that, unlike a typical mechanical spring that relies on elastic deformation, uses gas contained within an enclosed cylinder sealed by a sliding piston to pneumatically store potential energy and withstand external force applied parallel to the direction of the piston shaft. Much larger gas springs are found in machines that are used in industrial manufacturing, i.e. the press tooling industry, where the forces they are required to move are very heavy.
Top Tips for Selecting and Installing Gas Springs for Lifting and Lowering
1. Collect the data you need to size your gas spring properly.
- Locate the center of gravity (M) for your hood or door, typically the center point between the system’s pivot point and handle. This can also be determined from your CAD drawings for more complex doors and hoods.
Measure the dimensions of the door or hood; alternatively, your CAD drawings can provide you with the door or hood measurements in all three dimensions.
Find the radius measurement to your center of gravity (Rw) from the pivot point, located in Step 1.
- Next, measure the radius of your hand force, which is the distance between your pivot point and the handle (RH)
- Find your starting angle (aM)—the angle created between the horizontal level and RM when your hood is closed—by checking it on your CAD drawing or measuring it directly on your application.
You’ll also need the opening angle (a), which is the total angle of rotation from when your hood is closed to when the hood is open.
- Finally, measure your hood weight (m), which may be found in your CAD dat a. Without CAD, this is easily accomplished by using a spring scale during lifting. Note that the distance used for measuring the weight needs to be scaled to RM for an accurate number (multiply measurement by RH and divide by RM).
2. Decide how many gas springs you will be using.
If your hood is wide or cumbersome for any reason, it is recommended that you use two gas springs, one on
either side. This will also prevent you from adding lateral forces into your calculation, which can greatly change
the size and capacity of your final choice.
3. Consider special conditions posed by your environment.
Equipment that operates in high or low temperatures, around abrasive chemicals, or in a place with excessive
dust and dirt, may require special seals, oils, etc. So, at this point, check the manufacturers’ catalogs for specific
characteristics of each gas-spring series they have available. In addition, most manufacturers provide help in
making the right decision. For example, ACE Controls provides an easy-to-use online calculator that asks for
all of the above information and then helps you make the right selection for your application’s needs. For more
complicated applications, ACE engineers are ready to help you specify the right product.
4. Mount the gas spring correctly.
Be sure that the flap hits the end position without end damping. A small amount of oil has been placed in the
pressure tube to assure that the seal is properly lubricated and that the end position is hydraulically damped.
Now, mount the gas spring with the piston rod down. This helps to reduce the extension velocity during operation
and makes sure that the piston dives into the oil.
5. Adjust the pressure in your gas spring for proper usage for your application.
Adjustments are often needed when one of two things happen—either the designer didn’t know the correct
data during the time for specifying the gas spring, or the machine design changed after the spring specifications
were decided upon. If your hood is being pushed back open rather than staying closed, you will have to de-gas
To adjust the gas pressure and extension force, you’ll need to remove the gas spring from the hood. Screw the
de-gas adjustment tool onto the gas spring. Tap the tool to release excess gas, then reattach the spring to the
hood. You can also purchase fully charged gas springs and find the appropriate force by bleeding the gas springs
down if you don’t have all of the necessary information for sizing.
6. Focus on your application.
The keys to selecting and installing gas springs are application specifications and uniqueness. For example,
in an underground distribution system, easy access for servicing is critical. By incorporating two gas springs
to lift heavy covers (mounted with large supply systems), maintenance and repeated operation become easy.
Another application requires gas springs to aid in the prevention of injuries during maintenance work on
harvesting machines. Proper gas-spring selection is key, because they need to be stable under rough operating
conditions. Once again, proper sizing is important when used on helicopter doors, such as those operated for
rescue operations. The proper component provides a defined retraction speed and secure engagement of the
door lock. An integrated end position damper is added to allow gentle closing of the door while reducing wear.