Made in Russia


Our correspondent visited the first and only enterprise in Russia producing single-tube gas-filled shock absorbers.

Alexander BUDKIN

The Petersburg shock absorbers "Plaza" repeatedly appeared in reports on the operation of editorial cars and already managed to light up in some tests (ЗР, 1997, No. 10; 1998, No. 1). Their price, by the standards of Russian goods, is not small, but they find their fans, first of all, among fans of fast driving. Available for all domestic cars - from the Oka to the Gazelle - and most foreign cars traveling on our roads, although they are most popular with owners of front-wheel drive VAZs.

The main advantages of single-tube gas-filled shock absorbers are the stability of their characteristics and the ability to “respond more quickly” to impacts from the side of the road: they are, as it were, less thoughtful. Here, the cavity with oil in which the piston runs is separated by a movable partition from the cavity with gas (nitrogen) under pressure 20-30 bar (see photo). Gas constantly keeps oil under pressure and does not allow air bubbles to appear during sudden movements of the piston. This property of gas shock absorbers on our rough roads is very handy, but the car is becoming tougher. You can recall another advantage of the "single tube" - a smaller diameter. It is precisely because of this that the Plaza shock absorbers (and only them) are placed on the gas conveyor in the Sable’s front suspension.

Obviously, in a more complex design, compared with the “two-pipe”, it is harder to ensure the operation of the seals. Where in the "oil" shock absorbers it is enough that the liquid does not leak out, in the "gas" it is necessary to keep the pressure comparable to the pressure in the car tire. Moreover, immediately in two movable nodes - the seals of the shock absorber rod and the gas cavity.

What will happen if the gas seal starts to “poison”? Obviously, gas bubbles will appear in the oil and there will be no vaunted stability of characteristics. And if the cuff sealing the rod fails? Here the troubles are more serious. As the oil flows out, gas will occupy a larger volume, pushing the movable baffle closer to the main piston. Sooner or later, this will lead to the fact that at full stroke compression the main piston will begin to reach the septum. Further more. The meeting of the piston with the separation wall will occur with smaller compression strokes until this stroke disappears altogether. After all, the piston can hardly move the baffle. A leaking gas-filled shock absorber will experience a reaction of 150-200 kgf. This will be perceived unambiguously - like a shock absorber jamming. It cannot be repaired - the stock can shoot so that it doesn’t seem enough.

That is why the most critical parts in the “gas” shock absorbers are gaskets. The search for a supplier of these parts and their absolute control before installation in shock absorbers lasts all eight years of the existence of the St. Petersburg enterprise. Today, the following combination is in use: the gas seal is domestic, originally from Moscow, and the most critical oil cuff is the German company Freidenberg with a machined (!) Working lip. It is possible that the place of the latter will soon be taken by the domestic cuff from Balakovo. Cold-drawn pipes are still German, purchased along with domestic ones - of the Pervouralsk plant. If Russian suppliers succeed in ensuring consistently high quality with the necessary volumes of supplies, the transition to their products is not excluded.

The shock absorber models produced in St. Petersburg differ in five main parameters: the diameter of the working pipe, the type of shock absorber (ready-made shock absorber or cartridge for shock absorber struts), one of the two types of design of the working piston valves (single or double acting), the stroke and the initial settings of the shock absorber (number washers in a set of disc springs and initial gas pressure). Buffers are installed in some shock absorbers.

The current production of the Plaza is about 300 thousand shock absorbers per year, and plans are up to 1 million or more. For the successful implementation of such volumes, it is desirable for the plant to reduce prices for its products, and this depends on domestic subcontractors - their ability to supply high-quality components. Another growth component is the desire to expand the assortment further: to master the production of fixed racks used on some foreign cars, earn the trust of manufacturers of “Russian foreign cars” and, possibly, get on their conveyors.

Cartridge for shock absorber strut. Significant bending stresses help to withstand the second pipe. The piston rod with the working piston is fixedly mounted on the outer pipe. In relation to them, the inner pipe with gas, oil and fasteners to the car body is movable. Between the two pipes there are plain bearings (a steel-bronze sleeve coated with fluoroplastic). Bottom, under the inner tube - rubber compression stroke buffers. Under the working piston is a rebound stroke buffer from desmopan. Despite the presence of two pipes, the cartridge refers to shock absorbers of a single-tube type.

A small but very important part is the oil seal cuff. So far, imported.