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#Di_Vito 29/06/2019 In Kronstadt, a unique 19th century bridge - Petrovsky Dokovy - was restored. Assembled from ship armor, on boiler rivets, it has never been repaired for a century and a half. Today’s engineers had to rediscover ancient technologies for themselves, and the operation of installing the span on the supports turned into a special one, requiring jewelry precision. TEXT: Each bridge is unique. But this one is rare even for St. Petersburg. The only surviving turning one: for the passage of ships, it was not lifted up, but taken to the side. Bridge builders are ready to kneel before him, delving into the structure of the mechanism. (tool strikes) It’s hard to believe, but in the 19th century, the bridge was lifted by hand. A gear train was hidden under the granite embankment. And it was so balanced that only two sailors could turn the bridge. We put a wrench on the top nut and just walk in a circle. At the same time, the arch weighs 70 tons, plus a counterweight - 62. Outwardly, it looks like a battleship of the 19th century. It was actually assembled from sheets of ship steel: Tavras, frames on boiler rivets. For a century and a half it seemed that he had no demolition. But the mechanism was out of order, in 2018 it was decided to restore it. The bridge was removed from its place for the first time. And then it became obvious: the restoration of the entire structure is required. Yes, only no drawings, no name of the bridge builder, no technology have survived. Valery MAKAROV - designer of the bridge restoration: “After all, almost all the elements are cast iron. Now, if you look there, there are still such rather complex connectors with voids that are cast from cast iron. So I assure you, now modern masters will not be able to repeat this. Such technologies are simply lost!“ They were afraid to transport the arch to the plant. It was restored right here - on the shore. At the same time, the granite supports were repaired and covered with waterproof mortar. And I had to tinker with the mechanism. Everything seems to be obvious, but how did our ancestors fasten these giant parts without cranes and jacks? One of the most stressful and difficult moments is that workers use huge keys to install such wheels in their places. This is part of the mechanism. The wheel is mounted on these bronze bushings and rotates when the bridge turns. Massive wheels are installed with jewelry precision on a semicircular rail. But this is just a counterweight. The span itself must be placed on the rod strictly vertically. If the axle deforms, the bridge simply won’t budge. Lifting cranes work synchronously. With long pauses: operators take into account gusts of wind. From the outside - everything is very slow and even. But on the fast track you can see how much the structure sways from the slightest wrong movement. 12 hours of tense waiting, and, finally, a few seconds of complete calm. At this moment, the central sector is precisely lowered onto the axis. The wooden flooring has yet to be laid, the pedestrian balcony to be strengthened on the sides of the armored arch, and the mechanism control levers brought out, as was the case in the 19th century. The builders promise to start up traffic in a month, by the Day of the Navy.
