Assembling and handling of cracked connecting rods
Important information to avoid damage
Information on use
Cracked connecting rods are extremely important for engine efficiency, as these connect the crankshaft to the pistons and transfer huge forces. The crack technique, as it is known, allows for an extremely exact fit precision between the connecting rod cap and the connecting rod shank. However, to avoid damage and ensure durability, a few other points must be adhered to during assembly, in addition to cleanliness in the work area. This article sets out what these are.
Cracked connecting rods are a central component in engines; they connect the crankshaft to the pistons and efficiently transfer the gas forces and inertial forces to the crankshaft. In the case of cracked connecting rods, the large connecting rod eye is split into two parts in a controlled manner, resulting in an excellent fit precision between the connecting rod cap and the connecting rod shank. This technique, known as cracking, offers a precise effective connection between the components and ensures high strength and load-bearing capacity in engine operation. But this precision can only be maintained if the correct procedures are followed during handling and assembling.
What is a cracked connecting rod?
When cracked connecting rods are manufactured, the large connecting rod eye is first produced as a component in one piece. It is then broken into two parts along a predetermined separation plane (cracking the connecting rod). This process enables an extremely high fit precision between the two parts of the connecting rod. To ensure that the parts continue to work together perfectly after assembly, they are marked with a pairing number that ensures that only parts that go together are connected to each other.
Important notes on assembly
To assemble cracked connecting rods correctly, the necessary precision must be maintained at every step. One particularly important point is cleanliness in the work area: Even the smallest of dirt particles can cause problems during assembly. Before assembly, make sure that the connecting rod caps and connecting rod shanks are correctly assigned. If there are no markings, apply markings with a paint pen to avoid confusion.
Preparation for assembly
- Cleaning: The work area must be free of impurities to prevent damage to the separation planes on the connecting rods.
- Securing: To prevent damage to the connecting rod, it must be properly secured before disassembly.
- Markings: The upper and lower parts of the connecting rod must be correctly marked to ensure correct assembly.
Cleaning the separation planes
The fracture surfaces or separation planes of the cracked connecting rods are particularly delicate and must be cleaned carefully. These surfaces must never be wiped or treated with aggressive detergents, as this could impair the precision of the fitting bolts. Only special detergents such as brake cleaner should be used for cleaning. Direct contact with hard objects should also be avoided, as this can result in a notch effect that can impair the strength of the connecting rod.
Another important detail is that no particles must get onto the separation planes when the bearing shells are assembled. Special tools can be used for this purpose, which help to install the bearing shells precisely and cleanly.
Avoid impurities and damage
The fracture surfaces must be thoroughly cleaned and checked before assembly. One requirement for proper assembly is that particles that could increase the notch effect or reduce the strength of the component must not get onto the surface. To prevent impurities from becoming lodged in the contact areas of the fracture surfaces, the connecting rod should only be transported with the connecting rod cap and hand-tightened connecting rod bolts.
When using materials to prepare the connecting rods, it is crucial that the parts be made of steel or other high-strength materials that can withstand the high loads in engine operation. In addition, care should be taken that the internal cross-section of the parts is correct to ensure the necessary strength and cylinder shell surface for effective power transmission.
Important points for assembly and handling
- No damage to the fracture surfaces: There must be no mechanical impact on the separation planes that could impair the fit precision.
- No oil on the fracture surfaces: During assembly, make sure that no oil gets onto the cracked separation planes. If oil gets into the pores it can cause hydraulic compression.
- Securing before measurement: When the connecting rods are measured, the bearing cap should always be fitted and hand-tightened to prevent the connecting rod base becoming deformed.
Summary
The precise manufacture and assembly of cracked connecting rods is essential for the durability and performance of the engine. High strength and a precise fit are achieved by handling the separation planes correctly, and carefully preparing the connecting rods. The cleanliness and correct handling of the materials are crucial to avoid notch effects and damage to the connecting rods, and to ensure the effective connection between the components that is needed. Following the procedures set out minimises the risk of damage and ensures the long and reliable use of engine components.
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