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Gas strut dos and don’ts

Here is a list of a few things we recommend when designing your application and mounting our gas struts.

Do

Do mount our gas struts in pairs to prevent side loading.

Do mount our gas struts rod down to ensure that the main rod seal is well lubricated at all times, this ensures that the oil is in the correct position to allow you to benefit from our end of stroke damping. When releasing pressure from your Vari‐Lift gas springs, always let the gas out in small amounts, that way you are less likely to de‐gas the struts past the pressure you require. It is recommended that during storage gas springs are kept rod down.

Do ensure that all of our end fittings are fully screwed down onto the gas springs as this will reduce the chance of the threaded studs being broken off during operation.

Do use ball joint end fittings wherever possible as this will reduce the risk of side loading the gas springs. Whenever using ball joints ensure the ball joint studs are screwed in to the application all of the way up to the spanner flats.

It is always recommended when a heavy object is being lifted up to allow an operator to gain access underneath it, that an Econoloc gas strut is used. This is to ensure the operator’s safety in the event that the gas springs are overloaded or misused.

Don’t

Do not apply solvents to the gas struts as this can wash the lubricating oil off the piston rod and also degrade the seals, which can cause the seals to fail prematurely.

Do not paint the gas struts as this could transfer onto the piston rod which may pass the main rod seal of the gas spring and cause the seals to fail.

Do not grip the piston rod in any way as grooves or damage can cause oil and gas to leak out of the gas strut.

Do not apply anything to the piston rod as this can cause the main rod seal to fail during cycling.

Never pierce or heat gas springs as they act as a pressure vessel. When used correctly and manufactured to our strict manufacturing and engineering procedures, gas springs are very safe.

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Gas strut installation – what you need to know

Considerations for when mounting a gas strut.

Mounting 2.0 Figure Thirteen 207x300 - Mounting - Other Considerations

Crossover

Crossover is the point at which the strut takes over the lifting action (or gravity takes over to close). This will normally be around 10° to 30° from fully closed. In practice, this will vary by several degrees between opening and closing, due to factors such as friction of the internal components of the spring, hinges and end connectors.

Self-Rise & Self-Close

Self-rise is the angle at which the gas spring will lift the lid without any assistance from the operator, similarly Self-close is the angle at which the lid will close without any assistance. In most cases it is undesirable to have the lid open without any operator input (referred to as “instant lift”) because this behaviour is unpredictable to the operator and can allow the lid to open without warning, for example when the P1 force increases above nominal due to elevated ambient temperatures.

Effects of Temperature on Handling

Temperature not only affects the output force, but also the handling forces. The following graphs shows behaviour on an application at 20°C and then again at 65°C. As is seen in the figure below, at 20°C crossover occurs at an opening angle of around 7°, with the handling forces being acceptable in both opening and closing.

Mounting 2.0 Figure Fourteen 300x188 - Mounting - Other Considerations

Crossover at 20°C.

Mounting 2.0 Figure Fifteen 300x188 - Mounting - Other Considerations

Crossover at 65°C.

However, when the ambient temperature increases to 65°C (for example, in the case of an engine cover application), lift will occur almost instantaneously. This behaviour is unpredictable to the operator and can in some cases be dangerous. It can also be seen that the handling effort to close the application increases.

For these reasons it is important that the designer understands what the ambient and “normal” operating temperatures of an application will be so that if necessary a suitable compromise can be made in handling performance.

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Gas strut mounting positions

Understanding gas strut mounting points and positions.

Mounting Points

There are two primary mounting points, the ‘fixed’ and ‘moving’ mounting points. As the names suggest, the fixed mounting point remains fixed, whereas the moving mounting point rotates through an arc as the application opens and closes.

As a rule of thumb when positioning, Camloc start with the moving mounting point approximately 1/3 the length of the lid from the hinge as shown in figure two below:

Mounting 2.0 Figure Two 300x241 - Gas Strut Mounting Positions

Typical mounting points example. This provides an extremely rough guide as to where to place a strut, but if this is developed further it will also give an indication of the size of the required product.

Mounting Orientations

There are two differing mounting orientations available to the designer, these are ‘Push Up’ and ‘Flip Over’ mounting. In both cases, it should always be mounted “rod down” when in the fully closed position to ensure proper lubrication of the seal package.

As a general rule, Camloc’s preferred mounting is the ‘Push Up’ design orientation.

Push Up Design

Mounting 2.0 Figure Eleven 300x251 - Gas Strut Mounting Positions

Identification

This type of mounting can be identified by the fact that the end at the lowest point when closed, remains in its lowest position when fully open. It can also be identified by the moving mounting point being located closer to the hinge than the fixed mounting point.

Rod-Orientation

Unless a means is utilised to lubricate the rod, then the strut should always be mounted rod down to ensure proper lubrication of the main seal. The main drawback of this mounting position is the additional strength required in the application being lifted, particularly the hinge; this is due to increased cantilever of the lid from the support provided by the strut.

Damping

The major advantage with this type of mounting and rod down orientation is that it provides consistent damping at the end of the stroke. This is due to oil always being at the bottom of the tube; thus, damping will always occur at the same point in the lift cycle.

Flip-Over Design

Mounting 2.0 Figure Twelve 300x267 - Gas Strut Mounting Positions

Identification

This type of mounting can be identified by the end at the lowest point of the strut when closed, rotates to the highest point when fully open. It can also be identified by the moving mounting point being located further away from the hinge than the fixed mounting point

Rod Orientation

Unless a means is utilised to lubricate the rod then it is advised to mount rod down, ensuring proper lubrication of the main seal in the closed position.

Damping

The main drawback of this mounting position is the lack of damping control throughout the stroke. At the start of the stroke, the oil is at the bottom around the main seal. As the horizontal position is passed, the oil begins to run down the tube towards the tube end.

Along this point it will meet the piston moving up through the tube. When the piston meets the oil, extension will be slowed until the oil has passed through. At this point, the extension speed will increase and will reach the end of the stroke with no damping.

The advantage of this design is that it places less strain on the hinges than the push up design.

Mounting: Crossover, Self-Rise & Self-Close

Mounting 2.0 Figure Thirteen 207x300 - Gas Strut Mounting Positions

Crossover

Crossover is the point at which the strut takes over the lifting action (or gravity takes over to close). This will normally be around 10° to 30° from fully closed. In practice, this will vary by several degrees between opening and closing, due to factors such as friction of the internal components of the spring, hinges and end connectors.

Self-Rise & Self-Close

Self-rise is the angle at which the lid is lifted without any assistance from the operator. Similarly, self-close is the angle at which the lid will close without any assistance. In most cases, it is undesirable to have the lid open without any operator input (referred to as “instant lift”). This behaviour is unpredictable to the operator and can allow the lid to open without any warning, in instances where the P1 force increases above nominal due to elevated ambient temperatures, for example.

Effects of Temperature on Handling

Temperature not only affects the output force, but also the handling forces. The following graphs shows behaviour on an application at 20°C and then again at 65°C. As is seen in the figure below, at 20°C crossover occurs at an opening angle of around 7°, with the handling forces being acceptable in both opening and closing.

Mounting 2.0 Figure Fourteen 300x188 - Gas Strut Mounting Positions

Gas Spring and gas strut installation handling forces chart. Crossover at 20 degrees Celsius. Angle of opening (Degrees) vs. force (N).

Crossover at 20°C

Mounting 2.0 Figure Fifteen 300x188 - Gas Strut Mounting Positions

Gas Spring and gas strut installation handling forces chart. Crossover at 65 degrees Celsius. Angle of opening (Degrees) vs. force (N).

Crossover at 65°C

However, when the ambient temperature increases to 65°C (for example, in the case of an engine cover application), lift will occur almost instantaneously. This behaviour is unpredictable to the operator, in some cases proving dangerous.

It is also evident that handling effort to close the application increases. For these reasons it is important that understanding of what the ambient and ‘normal’ operating temperatures of an application will be, so if necessary, a suitable compromise can be made in handling performance.

Mounting: Dampers

Should dampers be mounted rod up or rod down? The answer to this is dependent on whether the damper is a compression or extension damper; each having specific orientations and should be mounted as follows:

Mounting 2.0 Figure Nineteen - Gas Strut Mounting Positions

Extension damper and compression damper side by side comparison. Extension Damper (Left), Compression Damper (Right).

Extension Dampers

Extension dampers should be mounted ‘rod down’ to ensure consistent damping throughout the stroke, if these are mounted ‘rod up’, this will result in little or no damping.

Compression Dampers

On the contrary to extension dampers, compression dampers should be mounted ‘rod up’ to ensure damping is consistent throughout. If instead they are mounted ‘rod down’, this will again result in little to no damping. Lubrication of the main seal is not a problem due to the high volume of oil used in the damper.

Mounting: Practical Application

Unused Stroke

Camloc’s preference when positioning is to allow 10mm of unused stroke. The reason for this is to allow for the stack up of manufacturing tolerances in the application, preventing “bottoming out” before the lid is fully closed.

Mounting 2.0 Figure Sixteen 163x300 - Gas Strut Mounting Positions

10mm of unused stroke example.

Preventing Instant Lift

Positioning the moving mounting point so that it creates an over-centre condition when the lid is closed will aid in reducing instant opening of the lid.

The figure below highlights two examples; one of a position which will lead to instant lift (on the left) and one which is over-centre and will reduce the potential of instant lift (on the right).

Mounting 2.0 Figure Seventeen 242x300 - Gas Strut Mounting Positions

Preventing instant lift spring position example.

Reducing Handling Forces

To help reduce handling forces, the following strategies can be used:

  • Move the mounting point Y1 closer towards the pivot by reducing the stroke.
  • Consider whether the opening angle could be reduced.
  • Move fixed mounting point Y2 to a more suitable location.
Mounting 2.0 Figure Eighteen 81x300 - Gas Strut Mounting Positions

Reducing handling force example.

For more technical information on mounting and other commonly asked queries, head over to our whitepapers section. For information on our product range, please visit our Products Page.

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Our friendly team are more than happy to help. Call +44 (0)116 274 3600.

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Gas strut positioning

There are two differing mounting orientations available to the designer, these are ‘Push Up’ and ‘Flip Over’ mounting. In both cases, it should always be mounted “rod down” when in the fully closed position to ensure proper lubrication of the seal package.

Mounting Orientation

As a rule, Camloc’s preferred mounting is the ‘Push Up’ design orientation.

Push Up Design

Mounting 2.0 Figure Eleven 300x251 - Mounting Orientation

Identification

This type of mounting can be identified by the fact that the end at the lowest point when closed, remains in its lowest position when fully open. It can also be identified by the moving mounting point being located closer to the hinge than the fixed mounting point.

Rod-Orientation

Unless a means is utilised to lubricate the rod, then the strut should always be mounted rod down to ensure proper lubrication of the main seal. The main drawback of this mounting position is the additional strength required in the application being lifted, particularly the hinge, this is due to increased cantilever of the lid from the gas spring support.

Damping

The major advantage with this type of mounting and rod down orientation is that it provides consistent damping at the end of the stroke. This is due to oil always being at the bottom of the tube; thus, damping will always occur at the same point in the lift cycle.

Flip-Over Design

Mounting 2.0 Figure Twelve 300x267 - Mounting Orientation

Identification

This type of mounting can be identified by the end at the lowest point of the strut when closed rotates to the highest point when fully open. It can also be identified by the moving mounting point being located further away from the hinge than the fixed mounting point

Rod Orientation

Unless a means is utilised to lubricate the rod then the spring should always be mounted rod down to ensure proper lubrication of the main seal in the closed position.

Damping

The main drawback of this mounting position is the lack of damping control throughout the stroke.

At the start of the stroke the oil is at the bottom around the main seal, as the spring passes the horizonal position the oil begins to run down the tube towards the tube end, along this point it will meet the piston moving up through the tube. When the piston meets the oil the extension of the spring will be slowed until the oil has passed through, then at this point the extension speed will increase and it will reach the end of the stroke with no damping.

The advantage of this design is that it places less strain on the hinges than the push up design.

Can't find what you're looking for?

Our friendly team are more than happy to help. Call +44 (0)116 274 3600.

Tell us about your project

Can't find what you're looking for?

Our friendly team are more than happy to help. Call +44 (0)116 274 3600.

Tell us about your project

How to improve gas strut handling

Mounting and practical considerations.

Unused Stroke

Camloc’s preference when positioning is to allow 10mm of unused stroke. The reason for this is to allow for the stack up of manufacturing tolerances in the application and prevent the gas spring from bottoming out before the lid is fully closed.

Mounting 2.0 Figure Sixteen 163x300 - Mounting - Practical Considerations

Preventing Instant Lift

Positioning the moving mounting point so that it creates an over-centre condition when the lid is closed will aid in reducing instant opening of the lid.

The images below show examples of spring positions that will lead to instant lift (on the left) and one that is over-centre and will reduce the potential of instant lift (on the right).

Mounting 2.0 Figure Seventeen 242x300 - Mounting - Practical Considerations

Reducing Handling Forces

To help reduce handling forces, the following strategies can be used:

  • Move the mounting point Y1 closer towards the pivot by reducing the stroke.
  • Consider whether the opening angle could be reduced.
  • Move fixed mounting point Y2 to a more suitable location.
Mounting 2.0 Figure Eighteen 81x300 - Mounting - Practical Considerations

For more technical information on mounting and other commonly asked queries, head over to our whitepapers section. For information on our product range, please visit our Products Page.

Can't find what you're looking for?

Our friendly team are more than happy to help. Call +44 (0)116 274 3600.

Tell us about your project