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Connecting Rods

Connecting rods are subjected to alternating tensile and compressive stresses during engine cycles, making fatigue failure a primary concern. Forging processes are carefully controlled to produce a refined grain structure aligned with the load path, significantly increasing fatigue strength.

Material Specification

Forged Steel (SAE 4340, 300M), Billet Aluminum (7075-T6), or Powdered Metal (for OEM)

Center-to-Center Length

100–300 mm (±0.05 mm tolerance; application-specific)

Big End Bore Diameter

40–80 mm (±0.01 mm honed finish; roundness ≤ 0.005 mm)

Small End Bore Diameter

20–40 mm (±0.008 mm; press-fit or bushed for floating pins)

Big End Width

20–40 mm (±0.02 mm; matched to crank journal width)
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Product Description

Metallurgical treatments such as controlled cooling rates and microalloying elements (e.g., vanadium, niobium) enhance dislocation density and hinder crack nucleation. 

Weight (Individual & Matched Set)

400–1200 g (±2 g for balanced sets; weight sorting available)

Rod Bolt Specification

ARP 2000/CA625+ (M8–M12, 180–220 ksi tensile strength; torqued to stretch specs)

Dimensional Tolerances (Critical Bores)

Big end – ±0.013 mm; Small end – ±0.010 mm; Parallelism ≤ 0.03 mm/100 mm

Surface Finish

Shot-peened (0.8–1.5 μm Ra); Bores – 0.4–0.8 μm Ra; Polished beams (optional)

Certification Standards

ISO 9001:2015, IATF 16949, AMS 6414 (steel), SAE J1397 (aluminum), OEM-specific (e.g., VW 50005)

Technical Advantages

Tight tolerances on bore diameter, center-to-center length, and rod width are essential to maintain bearing clearance and piston motion precision. Advanced CNC machining centers utilizing multi-axis tooling enable the control of geometric parameters within microns. The use of coordinate measuring machines (CMM) and laser scanning ensures dimensional conformity and repeatability batch after batch. The connecting rods alignment and straightness are verified to prevent binding or uneven load distribution, which can induce localized stress concentrations.  

High operating temperatures cause expansion and can alter mechanical properties, impacting clearances and fatigue performance. Alloy composition is tailored to maintain yield strength and modulus of elasticity over a temperature range typically from ambient up to 300°C or higher, depending on the engine type. Heat treatment cycles are precisely engineered to stabilize microstructures, preventing softening or grain coarsening during engine thermal cycles.  

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Industry Applications

Automotive Engines

Transmit reciprocating motion between piston and crankshaft, handling high dynamic loads and rapid load reversals in combustion engines. 

Aerospace Propulsion Systems

Provide critical mechanical linkage in aircraft piston engines, enduring high thermal gradients and fatigue stresses during cyclic flight operations. 

Marine Diesel Engines

Transfer power within large bore diesel engines, designed to withstand corrosive environments and sustained high torque over extended durations. 

Industrial Compressors

Facilitate piston movement in reciprocating compressors, requiring precise alignment and high fatigue strength under continuous cyclical loading conditions.

Agricultural Machinery

Operate in diesel and gasoline engines of tractors and harvesters, subjected to variable loads and harsh environmental factors. 

Construction Equipment

Connect pistons and crankshafts in heavy-duty engines powering excavators and loaders, designed for durability under high vibration and shock loads. 

Connecting Rods

Structural Design and Finite Element Analysis (FEA) Validation

Connecting rods are engineered with optimized cross-sectional geometries to balance strength, stiffness, and weight. FEA simulations evaluate stress distribution under combined bending, tensile, and compressive loads to identify critical stress hotspots. This allows for material removal in low-stress regions and reinforcement in high-stress areas, achieving maximum strength-to-weight efficiency.

Surface finish quality directly impacts the fatigue life and frictional losses of connecting rods. Precision grinding and honing processes achieve surface roughness below 0.4 µm Ra on bearing journals to reduce lubricant film breakdown. Shot peening induces beneficial compressive residual stresses on critical surfaces, increasing resistance to crack initiation.

Connecting Rods

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Having Doubts? Our FAQ

Check all our Frequently Asked Question

How does Frigate ensure the material quality of connecting rods used in high-performance engines?

Frigate sources alloy steels with certified chemical composition and traceability to maintain consistent quality. Each batch undergoes rigorous spectrometry and mechanical testing for tensile strength and hardness. Advanced forging processes are applied to control grain flow and reduce internal defects. Material properties are verified through microstructure analysis and non-destructive testing before machining. 

What machining technologies does Frigate use to maintain tight dimensional tolerances?

Frigate employs multi-axis CNC machining centers with real-time monitoring systems to achieve micron-level precision. Coordinate measuring machines (CMM) verify bore diameter, length, and surface finish during and after machining. Process parameters are optimized to minimize thermal distortion and maintain geometric stability. This precision machining ensures proper bearing fit and reduces engine vibration. 

How does Frigate control fatigue life in their connecting rods under cyclic loading?

Frigate uses heat treatment cycles such as quenching and tempering to optimize the strength and toughness balance. Shot peening is performed to induce compressive residual stresses on high-stress surfaces. Finite element analysis (FEA) guides design improvements by predicting stress hotspots and fatigue behavior. This integrated approach extends service life under demanding engine conditions. 

What surface finishing techniques are applied by Frigate to improve wear resistance?

Surface grinding and honing processes achieve a fine finish with surface roughness typically below 0.4 microns Ra on bearing journals. Specialized coatings such as molybdenum disulfide (MoS2) or DLC may be applied for reduced friction and enhanced wear resistance. Shot peening also improves surface integrity and fatigue resistance. Corrosion resistance is ensured through passivation or phosphate treatments. 

How does Frigate validate the mechanical integrity of connecting rods before delivery?

Each rod undergoes magnetic particle inspection and ultrasonic testing to detect surface and subsurface flaws. Mechanical testing includes tensile, hardness, and impact tests to confirm compliance with design specifications. Dimensional checks use laser scanning and CMM to ensure adherence to tight tolerances. All inspection data is recorded for full traceability and quality audits.

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LOCATIONS

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

Operations Office

9/1, Poonthottam Nagar, Ramanandha Nagar, Saravanampatti, Coimbatore-641035, Tamil Nadu, India. ㅤ

Other Locations

  • Bhilai
  • Chennai
  • Texas, USA
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Connecting Rods

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