Selection and replacement of gas stops for the hood, trunk of a car
Content
Strictly speaking, devices that keep the hood or trunk open are not shock absorbers. These are gas springs that use the properties of gases to store energy when compressed. But since certain damping abilities are present there, and the device itself looks very similar to a conventional automobile telescopic shock absorber, the not entirely accurate designation has taken root and is actively used by everyone except manufacturers.
Purpose of hood and trunk shock absorbers
When opening the lids of the hood or trunk, sometimes you have to overcome considerable effort due to the large mass of metal, glass and mechanisms enclosed in them. A spring mechanism supporting the lid will help to partially relieve the driver's hands of the load.
Previously, springs were made of metal and had significant dimensions and weight. In addition, they needed additional reinforcement in the form of rods and levers, sometimes arranged into very intricate mechanisms. After all, the working stroke of a twisted coil spring or torsion bar is quite limited, and the hood swings open at a large angle.
The introduction of pneumatic stops (gas springs) helped engineers. The gas compressed in them allows a significant difference in pressure in the extreme positions and pre-compression in the form of a plant-loaded amount of air or nitrogen in a limited size of the working chamber. High-quality stem sealing allows long storage and operation without loss of working force.
Varieties of stops for cars
With all the theoretical simplicity of the gas stop, this is a complex device with a carefully designed filling.
In addition to the actual force on the stem, the spring must provide damping of the rapid stroke of the stem in order to avoid shocks in extreme positions and smoothly move the cover between them. Here, additional damping properties are required. The design of the gas stop will become even closer to the suspension strut.
Gas
There is oil in the simplest stops, but it serves only to lubricate the seals. The gas is sealed by a piston with cuffs, and the damping of the stroke of the rod is purely pneumatic, due to the bypass of gas through the piston.
Oil
Purely oil stops do not exist by definition, because it is a gas spring. In some applications, fluid springs are used, but this is not the case for cars. The liquid compresses very limitedly, so it is difficult and irrational to use such an effect in the boot lid stop.
The concept of oil stops most likely came from the technology of suspension shock absorbers, where only oil is really used, and there is no elastic element.
Gas-oil
The most common scheme of automobile gas springs as stops for the trunk and hood. An additional oil chamber is located between the piston rod and the seal, which improves the tightness of the high pressure air chamber and provides a soft damping of speed at the end of the rod stroke.
When the piston moves, its speed is limited pneumatically, and when it enters the oil area, the damping force increases due to a sharp increase in viscosity.
The most popular brands - TOP-5
The subtleties of the design and production of durable gas stops are not given to all companies, which made it possible to form the top five, although there are actually many more manufacturers.
- Lesjofors (Sweden), according to many, the best manufacturer of springs and gas stops for cars. At the same time, the price is far from prohibitive, and the range covers almost all makes and models of cars.
- The wedge (Germany), a brand related to Swedish, now these products are represented by one company. It is difficult to say which of them is in the lead, both brands are worthy, the choice can be made more quickly by price and range.
- Stable (Germany), a specialized supplier of gas springs, including the conveyors of the German Big Three. This alone speaks volumes about the quality of the product.
- J.P. Group (Denmark), fairly high-quality budget products. Despite belonging to the middle price segment, products can be purchased and installed.
- Fenox (Belarus), inexpensive stops with acceptable quality. A wide selection, optimal for domestic cars.
How to choose stops for the hood and trunk
It is not necessary to buy original spare parts. Car manufacturers don't make their own gas springs, they have better things to do.
All they do in the aftermarket is pack a product bought from a specialized company under their own brand and charge twice or more the price. Therefore, it is wiser to find out from the catalogs the cross-numbers of non-original parts from a well-known company and save a lot.
How to replace the hood damper
If the part is not original and does not fit according to the cross number, then you can verify its compliance by measuring the length of the stop in the open and closed state. But this is not enough, all springs have different forces.
You can mistakenly purchase a part that cannot lift a heavy hood even in summer (the hardest time for compressed gas is winter with its low temperatures) or vice versa, the lid will tear from your hands, deform and resist when closing. Possibly a jammed lock.
The replacement process itself will not be a problem. Fasteners are easy to access, clear and intuitive. The old stop is removed, the cover is propped up, after which the upper and lower fasteners of the new one are successively screwed on.
It is better to work with an assistant, since the new stops are very tight, it will be inconvenient to hold the stem and rotate the fastening screw at the same time.
Replacing the trunk lid stops
The procedures are completely similar to the hood cover. Temporary support of the heavy tailgate must be securely and carefully, as injury may occur. An assistant is highly desirable, especially in the absence of experience.
The stop swivel should be lubricated prior to installation using silicone multipurpose grease. An open end wrench is used to loosen the ball head screw.
