How much do you know about trailer balance beams and shaft pins?

In recent years, affected by the quality of load and market demand, many local users in Zhangzhou have replaced the original dump trucks with four fronts and four rears and four rears and eight rears with semi-trailers. This also makes many masters very distressed. They will also consider second-hand cars when choosing a car. Today we will talk about the inspection and maintenance of trailer suspension components.

Profit is reduced, buying second-hand cars is the kingly way

Before starting the topic, let me introduce the car selection of Master Wang. Recently, he bought two second-hand 13-meter flat-bed semi-trailers. These two cars were purchased from Nanping. They were originally used to transport goods such as bamboo and wood chips. , Master Wang also adopts the method of new trailers and old trailers for the collocation of operating vehicles. Second-hand trailers can greatly reduce the input cost.

A two-year-old local brand trailer like this only costs 50,000 yuan, which is nearly half of the price difference compared with a new trailer. Its self-weight is about 6.5 tons. Master Wang also bought it to transport coal and bagged cement. After careful calculation, it is true that second-hand trailers are more cost-effective, and the damage of new trailers does not seem to be directly proportional to the actual profit.

Then, after buying a second-hand trailer, in addition to maintaining the floor, railings, and columns of the cargo box, the axles, tires, circuits, and brake systems must be maintained or replaced. Master Wang’s car is equipped with Guangdong Fuhua The axle is quite suitable for heavy-duty scenarios. However, during the inspection process, the repairman also found a problem. This suspension part is relatively easy to be ignored.

Generally, everyone will check whether the steel plate is in good condition, but as long as the semi-trailer is not a "hundred-ton king", the suspension system will not be damaged when driving on regular cargo, national highways, and high-speed road conditions. The trailer, the balance beam and the axle pins all had a lot of wear and tear, so he guessed that it might be because the previous owner was engaged in the transportation of bamboo and wood chips, which was more common in mountainous areas, and the uneven road surface caused greater wear and tear on heavy-duty vehicles.

What are balance beams and pivot pins

Conventional trailer suspension structures are mostly seen in leaf springs, airbag suspensions and a rare rubber suspension. In terms of economy and load capacity, leaf spring suspensions are of course more advantageous, and balance beams and pivot pins are exactly leaf springs. As part of the suspension structure, let me introduce their functions and damage symptoms separately.

(1) Balance beam: The balance beam of the trailer is located in the middle of the front and rear two sets of leaf springs. Its working principle is like a "seesaw". As the fixed point of the steel plate floating frame, it also plays a role in balancing the bearing capacity between the axles. , so that when the vehicle is driving on undulating roads, the force on each axle is more even.

Generally, the balance beam is not easy to be damaged. Many of them are caused by the heavy load, which causes the steel plate floating frame and the top of the balance beam to wear too much, and all the force is applied to the shaft pin, which is like a "traction pin". "The role is the same, the steel plate bracket and the balance beam are combined together.

Common balance beam damage occurs on heavy-duty vehicles, and cracks appear directly on the top of the balance beam. After all, this is a fixed part of the chassis structure, and it has been welded when the trailer leaves the factory. If it is a standard For the loaded model, it is almost free of replacement for life, as long as the shaft pin and bearing hole are welded and replaced.

(2) Shaft pin: In fact, from a structural point of view, the shaft pin and the balance beam should be integrated. The reason why they are introduced separately here is precisely because attention needs to be paid when replacing the balance beam. If the balance beam is not worn by the base It is too serious, and the bearing hole cannot be repaired by welding. It only needs to replace the shaft pin, and its appearance looks like a circular shaft.

During work, the shaft pins are used to combine and limit the activity range of the balance beam and the steel plate floating frame. Even if it is a cylinder, I believe everyone has heard the saying, "As long as the hard work is deep, the iron pestle can be ground into a needle", and it will not last for a long time. During maintenance and replacement, the shaft pin will also lose its roundness due to wear and tear, thus losing the role of balance.

After dismantling the shaft pin of the balance beam of Master Wang’s trailer, he found that the shaft pin had been deformed, and the circular bearing hole on the balance beam was also worn into an oval shape by the shaft pin due to the heavy wear and tear accumulated over time. It can be seen that the previous owner of the car extremely neglected its maintenance, and even the basic butter was seldom beaten, which led to the current situation.

Replacement costs and maintenance intervals

The reason why Master Wang prefers the old national standard leaf spring suspension is precisely because of its good load-carrying capacity and cheap maintenance. Compared with the airbag bridge, it is more suitable for transporting heavy and rough goods. On the contrary, the airbag bridge It is only useful for Lvtong, express delivery, and daily necessities transportation, and the types of goods they target are different.

The maintenance and replacement cycle of the balance beam bearing hole and shaft pin of the ordinary leaf spring suspension depends on the driving road conditions and the number of kilometers. The original owner of Master Wang’s trailer has been worn out for two years. The kilometers are consistent, of course, the road it was originally used on is too bad, and if the bumpy steel plate crunches all day long, it is another story.

If it is standard-load transportation, the operating conditions are mainly high-speed road conditions and supplemented by national road conditions, and the round-trip heavy load is about 34-35 tons, then the maintenance cycle of the shaft pin is about 10,000 kilometers, and it needs to be lubricated with butter to make it Butter can protect the shaft pin. When buttering, you can also check the gap between the shaft pin and the balance beam bearing hole. If it is loose, it means that it is time to replace it.

According to the description of the repairman, the safe replacement cycle of the above operating conditions is one year or 200,000 kilometers. The balance beam bearing hole and the shaft pin are replaced as a whole, so as to avoid tire eating and strong beating of brake tires. , if the trailer has ABS, it will also affect the effect of ABS.

Many car owners are worried that repairing the car will delay the delivery timeliness. The maintenance and replacement of the balance beam and the axle pin depends on the degree of wear and tear. Master Wang put the two trailers in the repair shop for a day, and they all replaced them. According to the master repairman It is said that the removal speed of the balance beam shaft pin depends on whether the rear bolts are rusted or not. If they are rusted, they cannot be unscrewed. They can only be directly cut violently by gas welding. One day, the balance beam bearing hole of the trailer is seriously damaged and has already lost its roundness. , you have to replace the welding socket again, which is time-consuming.

Replacement expenses: Many card lovers are concerned about the cost of maintenance and replacement. Here is a brief list for your reference (prices vary from place to place, for reference only). The cost of repairing the balance beam bearing hole and shaft pin of a single trailer is: ordinary The three-axis trailer has a total of 4 balance beam bearing holes and pins, with a pair of structures on the left and right sides. The local labor cost is 50 yuan for a single replacement, and the material cost for a single pin is 60 yuan. All replacement (including buttering) ) is about 500 yuan, and the two cars of Master Wang are 1,000 yuan.

Usually, a single buttering is 60 yuan for the whole vehicle, including parts such as the turntable, drive shaft, steel plate lifting lug, etc. Especially after buying a new melon car, the whole car must be buttered and maintained. New cars are maintenance-free. This is a big misunderstanding. Overall, the cost is not high. Compared with other faults, these two small things are inconspicuous, but they are very fatal.

What are the side effects of damage to the balance beam bearing hole and shaft pin?

To be honest, many domestically-made trailers now remove the ABS of the original car, pull out the wires, and then install it back after the annual inspection. The braking force of the vehicle is reduced, especially when the balance beam bearing hole and the shaft pin are abnormally worn.

The first thing that brings is the difference in bearing capacity between the axles. When you can't associate the braking system with the suspension system, it is their "insufficient coordination that leads to failures". When the vehicle is loaded or heavily loaded, the load distribution of the three axles is uneven, and when the vehicle is braking, the wheels with smaller bearing capacity will be more likely to lock up.

When the vehicle slows down in an emergency, the wheels of the trailer are locked and there will be crazy bouncing. Even if the brakes are adjusted to the same level on the three axles, it is useless. Reduce the braking force, if the domestic ABS anti-lock braking system is installed, then the problem will be even more serious.

It directly leads to the out-of-control performance of the four-channel ABS anti-lock braking system. The principle is that when the wheel with a small bearing capacity is locked, other wheels that are not locked will be misjudged by the ABS system and actively reduce the braking force, which will eventually lead to vehicle failure. The emergency braking distance is greatly extended, which is especially dangerous in rain, fog, ice and snow weather.

Therefore, when the wheels have the above-mentioned tire eating, abnormal locking and ABS anti-lock braking system performance failure, check the balance beam bearing holes, shaft pins and steel plate floating frames on the suspension structure in depth, and combine the actual operating conditions with appropriate Reduce the cycle of buttering and overall replacement, and prevent excessive wear and tear of the trailer suspension structure.

Summarize

Again, a vehicle is composed of countless parts and components. Failure of any part will cause the vehicle to be unable to drive. Therefore, to maintain a car, you must not only be able to drive, but also be able to maintain and inspect the vehicle. When the vehicle is faulty, it will be discovered early , Repair early to avoid major damage caused by small faults, so as to obtain greater profits in the era of small profits.

                                                                                                                                                   This article is reprinted from Xiao Lu from Truck House, if there is any infringement, please contact the author to delete