Forklifts play an important role in modern enterprise logistics and have become one of the main transportation tools in production logistics. Due to funding issues, many "over aged" old-fashioned forklifts are still struggling to operate, and some technical failures have also followed, causing certain impacts on production and serious safety hazards. Especially for many forklift companies, the supply of old product components has almost stopped, making it difficult to find in the market. So, many parts in maintenance need to be solved by customers themselves to ensure the normal maintenance of forklifts and meet production needs.
Taking an old Yichang CPQ3 3T forklift from a certain unit as an example, the rear steering tires of the forklift were rubbing against the fuel tank on the frame, which was very serious and caused it to be unable to drive. Repairing these forklifts has become an urgent task. But if we were to purchase a new forklift frame assembly and replace the original forklift frame, it would require more than 10000 yuan in funding. Repairing these old-fashioned forklifts at this cost would not have much value. Therefore, it is urgent to find the simplest and most cost-effective way to repair these faults.
The unit technician identified the cause of the problem by inspecting the vehicle body:
(1) The original structure of the forklift has a low ground clearance for the rear counterweight. The connection between the counterweight and the frame is achieved by hanging the upper front end of the counterweight at two points on the left and right sides of the frame, and the middle part is tightly attached to the rear end face of the frame by its own weight. When stationary, the counterweight tends to move forward at any time.
(2) The overall structure of the frame itself, except for the two fuel tanks, is welded with 20mm thick steel plates, especially the rear end of the frame, which is welded after hot forming. Its structural shape reflects insufficient rigidity during use, causing severe geometric deformation.
(3) The steering rear axle assembly is connected to the frame through a pin shaft. After use, the two pin hole bushings on the pin shaft and axle, as well as the two pin holes on the frame, have severe wear. In daily maintenance, it is mainly necessary to replace the pin shaft and bushing to restore their fit requirements, while the two holes on the frame cannot be repaired after wear and tear.
(4) Forklifts often operate on complex road surfaces and environments. Due to the low height of the counterweight from the ground, slight carelessness can lead to collisions with objects on the ground, especially when reversing due to poor visibility. In this way, impact loads are often applied to the two points where the middle of the counterweight block is in close contact with the frame. Over time, this causes the geometric shape of the rear of the frame to deform, thereby driving the entire rear axle to shift forward.
(5) Due to the frequent bumps on complex road surfaces, forklifts accelerate the wear of the connecting pins and bushings between the rear axle and the frame, as well as the two pin holes on the frame, causing the entire body to sink and reducing the distance between the counterweight and the tires.
(6) Due to the sinking of the vehicle body and the forward displacement of the rear axle, friction between the tires and the fuel tank occurred. Light tires often wear out; Heavy forklifts are difficult to drive, and the tires are completely unable to turn.
After a detailed inspection and analysis of the problems with the forklift, three solutions were proposed and analyzed and compared separately.
(l) To fundamentally solve the problem, it is necessary to calibrate the frame and repair the pin holes to restore them to their original technical state. However, the calibration of the frame is too difficult because the steel plate at the deformed part is 20mm thick and needs to be heated to a temperature that is prone to metal deformation. Using fire at the fuel tank is definitely unsafe and can easily cause accidents; In addition, there is no technical data at all, and the process is incomplete. Even if it can be calibrated, the effect may not be ideal; In addition, the repair of the pin hole requires boring the worn part and adding a lining, and boring the hole requires disassembling the forklift and lifting the frame assembly onto the boring machine for processing, which is somewhat difficult.
(2) Contact the original manufacturer to order an old-fashioned forklift frame assembly and replace the deformed frame. But the manufacturer specializes in producing an old-fashioned frame, which requires a longer processing cycle; Moreover, it requires a considerable amount of funds, as well as transportation costs, parking time, repair hours, and other indirect losses that may affect production. Therefore, this method is not advisable.
(3) In response to practical problems, after repeated analysis and comparison, it is believed that as long as efforts are made to increase the distance between the tire and the counterweight, and between the tire and the fuel tank, the problem of mutual friction can be solved. Cut off all the two pin holes on the frame, design and manufacture a groove shaped bracket with a 20mm thick steel plate, weld it to the cut position, and move the entire rear axle 40mm backwards; Due to the welding of this part below the cut area and on the upper side of the rear axle, it has the effect of improving the vehicle body, thereby increasing the distance between the counterweight and the tire by 30mm. According to this plan, the problem of friction between the tire and the fuel tank was completely solved, and after a period of operation, the effect was very ideal.
Using the above method, the problematic vehicle was repaired and modified. The entire process only took one week, and two groove shaped brackets were designed and manufactured at a total cost of only 100 yuan. This enabled each forklift worth more than 70000 yuan to be restored to use, solving the urgent production needs and saving a lot of money. At the same time, it saves transportation costs, parking and maintenance hours, as well as significant indirect losses recovered for unit production.
