“I have a motion problem” can mean different things. Do you need:
Lift-assist components (like gas springs) and hydraulic dampers aren't necessarily substitutes for one another. They look very similar, but don’t be deceived – the distinction matters.
Choosing gas springs and dampers isn’t necessarily an either/or decision. To determine what type of motion control your heavy-duty design needs, read on. In some cases, the answer might be “none of the above” – we’ll cover that too.
|
Gas Spring |
Hydraulic Damper |
|
|
Primary |
Assist movement and lifting |
Control speed of movement |
|
What It Addresses |
User-unfriendly loads |
Load moves/closes too quickly |
|
Design Concern |
Usability, force required, safety |
Controlled closing, safety |
The primary purpose of a gas springs is to move or support a load through controlled force. A gas spring can add the “muscle” necessary to make a heavy lid, gate, or other moving equipment less of a burden on the end user.
Their job isn't totally limited to making something easier to lift; gas springs can also provide some damping. That means they can help control the motion as the component reaches the end of its stroke.
A hydraulic damper controls the speed of a moving component. Rather than helping lift or support a load, its primary job is to resist motion so a lid, door, or other component doesn't move too quickly.
In some applications, that controlled movement is mostly adding quality of “feel” to the user – more of an added benefit than a requirement. In other heavy-duty designs, damping is a must for safety or equipment-protection.
Make sure to discuss with your hardware manufacturer up-front whether you want damping features in your assembly, and what role they’ll play.
Because gas springs can offer some measure of damping, there’s usually no reason for springs and dampers to exist in the same design. So, which do you need? Here’s a cut-and-dry explanation:
For a product designer, the need for a gas spring often comes back to safety.
If a lid or gate is too heavy for the intended user to operate comfortably, there's a chance they won't use the product as intended. In other words, they’ll find workarounds (i.e. a bartender using a broomstick to prop up a quartz bar flap). If that load isn't properly controlled, the sudden slamming can create a serious safety concern. And you don’t need us to tell you injuries create disruption to service, staffing snafus, and insurance claims you’d rather not deal with.
For marketing and customer satisfaction reasons, you also want gas springs simply for the sake of easy operation. After all, you don’t want an end user avoiding your product because it’s too heavy for them to handle comfortably.
A refrigerator or cabinet door that closes smoothly carries a different perception than one that swings or slams abruptly. Adding damping can provide the soft-close feel that customers love.
Again, sometimes damping is more necessity than luxury. In specific designs, damping is required to prevent impact damage to:
Imagine a heavy weight that’s suspended by a cable in the ceiling. Push it too fast, and you essentially create a wrecking ball. That’s the type of movement you can get from a heavy, counterbalanced lid if someone moves it quickly. It can result in hard impacts at the hinge stops or supporting structure. Dampeners can slow this motion to prevent damage to the structure and nearby people.
There are several paths to arriving at the wrong motion control hardware.
Sometimes it’s a matter of not understanding the technology enough, which causes the designer to paint an inaccurate picture of the load they’re trying to manage.
Designers with less experience in motion control will occasionally miscalculate the weight of the item that needs lift-assistance or counterbalancing. This tends to be a tripping point for architects (think bar top design) more so than engineers.
Besides weight, accurate sizing may require:
Wrong inputs can leave you with hardware that technically “fits” the application but doesn't produce the movement you expected.
Underestimating the load can keep a motion control component from behaving the way you want.
Let’s say you’re using a spring assist that was meant for a 100 lb. load. If you install a spring on a 150 lb. quartz flip-up countertop, it won’t perform effectively – not even close. That flip-up component is going to swing downward far faster than intended because the lid’s force is stronger than the spring’s force.
It’s important to be accurate in either direction.
It’s common for product makers to overengineer a specific part because they want to err on the side of safety. However, bigger or stronger doesn’t automatically mean safer when it comes to kinetics.
Just like underestimating, this will significantly throw off the counterbalance’s performance. What that looks like to the user depends on the geometry and mechanism, but possible symptoms include:
Gas springs and dampers are nice supporting pieces you can use to add a specific behavior to a motion control design. However, their limited cycle life means they shouldn’t automatically be the primary answer in a heavy-duty application.
|
Augment Your Existing DesignBoth gas springs and dampeners can be used not only as standalone solutions, but also as a way to augment heavy-duty motion control devices.
Example #1: A drop gate mechanism. A fold-down gate needs constant controlled force, along with some damping, due to the unique linkage used to eliminate the need for a piano-style hinge. In this case a gas spring is a good choice to assist lifting and slow the gate’s descent.
Example #2: A lift gate. Need to accommodate a design with a longer desired cycle life than those that use traditional lift gates? Soft-close dampers can guide the lid back into position for a more refined user experience. A standard lift gate comes with an exposed hinge, so there is a trade-off here.
|
Before deciding whether a gas spring, damper, or another control device belongs in your design, identify what the moving component actually needs to do.
Start with these questions:
Getting these answers straight first makes it easier to determine whether a gas spring or damper belongs in the design at all. In some cases, one can be a useful addition to a larger motion control mechanism rather than the mechanism doing all the work.
To recap: Lift assistance deals with the force/weight problem. Damping deals with the speed/motion problem.
It’s old habit for engineers to intentionally overestimate because it feels like the safe thing to do. But bad data in either direction can prevent a counterbalance from behaving the proper way.
In the end, choosing a component starts with understanding what motion you're trying to create or control. To get more education on heavy-duty motion control and counterbalancing, grab our free guide: