When a gear shift becomes difficult or unresponsive, it often points to several common mechanical issues. The gear lever fork might be loose or bent, causing misalignment. The shift shaft's positioning groove and pin could be worn, leading to irregular steps on the surface that cause the gear to get stuck during shifting. A deformed gearbox or a misaligned shift lever pin can also contribute to this problem. Additionally, if the clutch doesn't fully disengage or the small brake isn't functioning properly, it may lead to shifting difficulties.
Another common issue is when the gear automatically disengages. This usually happens due to excessive wear on the gear end faces, which shortens the meshing surface and reduces contact. If the gear body develops a taper, it can generate axial forces that prevent proper engagement. A broken positioning pin or failed steel ball can cause vibrations, leading to disengagement. Worn fork grooves or a loose fork can also result in axial movement of the sliding gear, causing unexpected shifts.
Gear shifting chaos often occurs due to faulty positioning components, such as a broken spring or a damaged steel ball. Excessive wear on the shift head or its associated shafts, along with worn positioning guides, can also cause erratic shifting behavior.
Unusual noise during operation typically stems from improper gear clearance. If the backlash between gears is too small or too large due to wear, poor meshing can result in noise. Worn bearings, spacers, or insufficient lubrication in the gearbox can also lead to abnormal sounds during use.
For gear repair, several methods are commonly used. One approach is repositioning or flipping the gear 180 degrees if only one side is worn. For example, the final drive reduction gear on the Dongfang Hong-75 tractor has a symmetrical design, allowing it to be flipped for continued use. Another method involves inserting a ring into the gear. If the tower gear consists of multiple parts with uneven wear, individual gears can be replaced by removing the worn teeth and pressing a new ring into place. Welding or drilling is then used to secure the new ring.
For smaller gears operating under low load and speed, the insert method can be applied. This involves cutting a dovetail groove on the gear root and pressing a new tooth into place with interference fit before welding. The surfacing method is suitable for gears with damaged teeth or excessive wear. After cleaning the gear surface and preparing it for welding, the damaged areas are rebuilt using appropriate electrodes. Once repaired, the gear should be tempered to relieve internal stresses.
When repairing the transmission housing, worn bearing seat holes can be restored using a boring insert. The material is typically gray cast iron, and after installation, the inner diameter is machined to standard size. Tolerances must be strictly maintained, with cylindrical deviation not exceeding 0.03mm and parallelism within 0.06mm across the entire length.
Cracks or holes in the transmission case can be repaired using patches, welding, or adhesives. Patch repairs involve drilling around the damage, tapping threads, and securing an iron plate with screws. Welding requires opening a V-shaped groove and using copper-iron or cast iron electrodes. In some cases, epoxy resin is used to fill the damaged area after proper preparation.
Boom Barrier Gate
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