When a freight train comes, dozens of tons of weight will fall on the rail first and then be transmitted down. You sit in the car and look out of the window, mostly just at the two bright rails, rarely looking down. In fact, how this force is finally dispersed depends on what is padded under the rail to a large extent.
The force is transmitted layer by layer down. The wheel presses the rail, the cushion under the rail presses the bottom, the cushion presses the crushed stone and the subgrade, each layer divides a little, and the force that finally falls on the foundation is much smaller.
In this layer, the sleepers are dry to take over the work.
The difference between the soft and hard cushions comes out. Take walking as an analogy. Wear hard-soled shoes and step on the gravel. The bottom of the foot is sore. It's much easier to go down the same road with double soft bottom. The same holds true for orbit. If the cushion is rigid, the wheel will bounce back as it was when it hit the wheel. The rail will push against the wheel and the wheel will push back, making both ends tired. The cushion is a little elastic, and the situation is different. The impact is first absorbed, and then the force transmitted downward is much gentler.
The elasticity of wood is not null and void. It has numerous thin cells stacked together, the cell wall is thick and tough, can be slightly compressed when stressed, force pull back and back to the original state. This structure enables the wood to bear pressure and rebound. It is not easy to simulate it.
There must be a degree of softness. It is too soft to support, the rail cannot be pressed up and down, and the line shape cannot be maintained. The advantage of wooden sleeper is that it is soft enough to give way and hold. Pine wood is also related to this much, long fiber, good toughness, and cannot be dispersed. Soak the oil through the fiber gap before going onto the road, and the wood should have the same elasticity, but a layer of moisture-proof and anti-corrosion primer is added.
The benefits of elasticity finally fall on both ends. One end is steel rail. The rail is afraid of repeated repeated efforts. The impact is repeated and the interior changes slowly. The cushion underneath can remove some impact and the load on the rail is lighter. The other end is the wheel and car body. The wheel will be slightly bounced after being rolled, and the loose parts will be slower. It cannot be seen once or twice. It has been running for one or two years, and the difference is written in the maintenance record.
Some people will ask whether the elasticity will be worse and worse with such pressure every day. As long as the moisture-proof and anti-corrosion measures are taken in place, and the fiber is not damaged by blisters and gnawed by bacteria, the elasticity can be maintained all the time. This is why the wooden sleeper on the track should be soaked with oil first. The purpose of oil soaking is to make it worse and to improve hardness to some extent.
A flexible track also has the advantage that it is easy to maintain a smooth line. Where there is a little height difference, the wooden sleeper can be pasted by its deformation, so as not to make the whole line suddenly become pointed. The car runs stably, and the goods loaded on the car are less subject to bumping.
The concrete sleeper runs another way, which is hard in itself and elastic mainly by the rubber pad under the rail. Hard has its advantages. It is used for a long time and I don't have to worry about it at ordinary times. Wood has its own purpose in this softness.
This elasticity plays a different role in different scenarios. The private siding of the mine area is densely loaded with heavy traffic and enough load. It runs back and forth dozens of times a day, and the accumulated force of the cushion is very obvious. The track on the bridge has a finer requirement for smoothness, the cushion is softer and the vibration on the bridge body is less. For curves, turnouts and other stress-bearing sections, the turning margin of wooden sleepers shall prevail.
A train passed safely and steadily, the upper rail and the lower wheel were less stressed, and the black wood in the middle did the work silently. For the oil-immersed sleepers made by Qingdao Tiehan, pine is selected, which can be soaked in oil thoroughly. The elasticity is still the same as the old one. The moisture-proof layer is also well done. When delivered to the line, the rails and wheels are better.
