Cabinet Gas Struts: How Many Newtons Do You Need?

Local fitters call this part amortizator, amartizator, nasos, mebel nasosu or qazlift. They all mean the same thing: a gas spring. It consists of a sealed cylinder filled with compressed gas and a rod coming out of it. The gas constantly pushes the rod outwards; that force lifts the door and holds it open. When you close the door, you push the rod back into the cylinder along with it.

It is used most in kitchen wall units with a lift-up door: the door hangs on hinges along its top edge and the strut supports it from the side. The second place is drop-down flaps: a bar cabinet, a shoe cabinet. There a reverse strut is fitted, which does not lift the flap but slows its descent.

The struts that lift a bed base are stronger and are chosen by a different rule; they are covered separately in bed lift gas springs.

The number in a strut's name is its push force, stated in newtons (N). About 10 N equals one kilogram-force: to compress the rod of an 80 N strut you have to press on it roughly as an 8 kg load would. That is not the weight of the door the strut can hold. The door works as a lever around the hinge, so the same strut lifts one door easily and fails to hold another of the same weight but different dimensions.

The lift-up gas strut is sold in seven forces: 60, 80, 100, 120, 150, 200 and 250 N. Stronger does not mean better. A strut that is too strong throws the door upwards with a jerk, makes it hard to close and overloads the hinges. One that is too weak cannot hold the door open. The aim is to find the force that suits the door.

Four things determine the force you need: the weight of the door (laminated board is light, MDF and a glazed frame are heavy), the height of the door, the points where the strut is fixed to the carcass and to the door, and whether one strut is fitted or two. Moving a fixing point by a few centimetres changes the result, which is why we give no exact table here.

As rough guidance: small, light laminated-board doors usually take 60–80 N, medium ones 100–120 N, and large, MDF or glazed-frame fronts 150 N and above. These are starting figures and have to be checked on the door.

The check is simple. The open door should stay up by itself and not creep slowly down. Once closed, it should not open again when you take your hand away. If the door drops, try one step stronger; if it will not stay closed, try one step weaker.

The basic lift-up strut does one job: it raises the door and holds it fully open. When closing, the door has to be guided all the way by hand, otherwise it may knock against the carcass.

The slow-closing gas strut lifts in the same way but brakes at the end of closing: the hydraulic part inside takes the speed out of the door and it seats without slamming. The chance of a finger being caught between door and carcass is lower too. This type comes in three forces: 60, 80 and 100 N, so it is for light and medium doors. If a front needs more than 100 N, the choice stays within the basic strut range.

Which one to take depends on use. A kitchen cabinet opened many times a day is more comfortable with the slow-closing strut, while a rarely opened top cupboard is fine with the basic one.

In a bar cabinet or a shoe cabinet the flap is hinged along its bottom edge and opens downwards. Here the flap's own weight pulls it down; if you do not hold it, it drops with a bang and damages the hinges and the carcass. The drop-down (reverse) gas strut is for exactly this: it resists as the flap opens and lowers it slowly and smoothly.

The word 'reverse' (tərs) describes the direction of work. An ordinary strut pushes the door in the opening direction, a reverse strut works against opening. That is why one cannot be fitted in place of the other.

The reverse strut comes in two forces: 60 and 80 N. The selection rule is the same: a heavy, tall flap takes the stronger one. The check is also made on the flap: if it still comes down fast, the force is too low; if it does not open fully or will not stay open, it is too high.

A strut is not the only solution. For a drop-down bar flap there is the mechanical arm: when the flap opens, the arm holds it at a set angle, opened to 90 degrees, and the flap is used as a small table. The arm works mechanically, not on gas; its job is to stop the flap dropping suddenly and to support it when open. Check on the product itself whether it goes on the left or the right side and how many pieces one flap needs.

In a tall wall unit a one-piece door rises too high when opened and is out of reach. In that case the front is divided into two horizontal parts and hung on a bi-fold lift mechanism: on opening, the two parts fold in the middle and rise together. Confirm with the seller before ordering that the mechanism suits the size and weight of your front.

Fit the strut with its own brackets and at the points specified for it; moving a fixing by eye cancels out the choice of force. With the door closed, the cylinder should be at the top and the rod at the bottom: in that position the oil inside keeps the seal lubricated. Wide doors usually get two struts, one on each side, otherwise the door twists to one side.

A lift-up door hangs along its top edge on ordinary cup hinges; the sprung plain hinge does the job here. The type is chosen by how the door sits on the carcass, as explained in cabinet hinge types.

The wrong force shows quickly: if the door will not stay closed or opens with a jerk, the strut is too strong; if it drops, too weak. A gas strut is under pressure: it must not be dismantled, drilled or heated. All forces are in the catalogue.

For an overview of every type, see the furniture hardware guide.