Custom Connecting Rod Manufacturer
Connecting Rod
China Simis Company is a specialized OEM custom manufacturer of high-integrity Connecting Rods. Serving as the vital link between the piston and the crankshaft, the connecting rod converts the immense pressure from combustion into the rotational force that drives the engine. Its failure, usually due to fatigue, is catastrophic.
Connecting Rods are subjected to the highest and most complex stresses in an engine: cyclical tension (inertia) and compression (combustion) loads, high-cycle fatigue, and lateral bending. We utilize Precision Forging (for maximum performance) and High-Accuracy Casting to produce components from Alloy Steel, Carbon Steel, Titanium Alloy, Aluminum Alloy, and Ductile Iron, guaranteeing maximum fatigue strength, optimal weight distribution, and micrometer-level bore geometry.
What manufacturing processes are used for connecting rods?
Forging remains the dominant process for high-performance rods, while casting methods are selected for specific material properties and cost requirements.
| Manufacturing Process | Material Focus | Connecting Rod Type & Key Advantage |
| Precision Closed-die Forging | Alloy Steel (AISI 4340), Carbon Steel, Titanium, Aluminum Alloy. | High-Performance/Heavy-Duty Rods; mandatory process to create continuous fiber flow along the highly stressed I-beam profile, maximizing fatigue endurance and resistance to buckling. |
| Investment Casting | Carbon Steel, Titanium Alloy. | Specialized/Near-Net-Shape Rods; used for complex, small-volume alloy rods where forging dies are prohibitively expensive, or where difficult-to-machine alloys are required. |
| Sand Casting / Shell Mold Casting | Ductile Iron (QT series). | Low/Moderate Performance Rods; suitable for low-cost, low-stress industrial applications, focusing on structural stability and manufacturing cost. |
| Heat Treatment | Alloy Steel, Carbon Steel, Titanium. | Quenching & Tempering (Q&T) or Solution Treatment is performed to achieve the optimal balance of high yield strength and toughness necessary to prevent fracturing under load reversal. |
| Fracture Splitting (Cracking) | Alloy Steel, Carbon Steel. | Specialized Machining. The big end bore is scored and then hydraulically fractured, creating a precise, unique mating surface that significantly improves bearing stability. |
How to Select Connecting Rod Materials?
The material must provide exceptionally high strength-to-weight characteristics, as the rod's inertia forces increase exponentially with engine speed (RPM).
| Material Type | Primary Performance Requirement | Typical Connecting Rod Application |
| Alloy Steel (Forged) | Maximum tensile and compressive fatigue strength for long-life, heavy-duty diesel engines. | Standard for high-reliability automotive and truck engines. |
| Aluminum Alloy (Forged) | Excellent strength-to-weight ratio and high thermal conductivity (heat dissipation). | High-performance street/race engines and motorcycles. |
| Titanium Alloy (Forged/Cast) | Ultimate strength-to-weight ratio; lowest possible inertia forces at extreme RPM. | Formula racing and aerospace applications where cost is secondary to performance. |
| Carbon Steel (Forged/Cast) | Good yield strength, high durability, and cost-efficiency. | General passenger vehicle engines and medium-load industrial equipment. |
| Ductile Iron (Cast) | Good strength and durability, high cost-efficiency. | Low-performance or structure-sensitive industrial equipment. |
What Precision Machining and Quality Assurance Measures Ensure Connecting Rod Reliability?
The accuracy of the rod's geometry is paramount for bearing lifespan, oil film maintenance, and the overall longevity of the engine.
·Center-to-Center Distance:
The distance between the small end (piston pin) and the big end (crankshaft journal) must be held to the tightest tolerance (e.g.±0.02mm) to ensure correct compression ratio and proper piston height.
·Bore Geometry (Roundness):
Both the small end and big end bores must be precisely honed to achieve perfect roundness and surface finish, crucial for the formation of a stable hydrodynamic oil film in the bearings.
·Weight Matching:
In multi-cylinder engines, rods are machined to strict mass tolerance (e.g. ±1g) within a set to ensure perfect dynamic balance and smooth, vibration-free high-RPM operation.
·Non-Destructive Testing (NDT):
All critical connecting rods undergo mandatory MPI (Magnetic Particle Inspection) after forging and final machining to certify the absence of surface cracks, particularly in the highly stressed regions around the bolt threads and the transition fillets.
What Are the Key Application Fields of High-Integrity Connecting Rods?
Automotive engines connecting rod
Alloy steel and carbon steel connecting rod is widely used in cars, trucks, and commercial vehicle engines. Closed-die forging combined with quenching and tempering ensures high fatigue resistance, bending strength, and wear performance. Precision machining of bearing surfaces and small-end bores provides smooth rotation, accurate alignment, and reliable torque transfer under repeated high-speed cycles.
Motorcycles connecting rod
Carbon steel and aluminum alloy connecting rod is applied in motorcycle engines and high-performance scooters. Forging and heat treatment enhance fatigue resistance, torsional strength, and vibration damping. Machining ensures precise fit, smooth movement, and consistent power transmission under high-speed operation.
Racing engines connecting rod
Titanium alloy and high-strength aluminum alloy connecting rod is used in racing cars, motorcycles, and motorsports applications. Closed-die forging and heat treatment provide exceptional strength-to-weight ratio, fatigue resistance, and impact performance. Precision machining ensures smooth engagement and reliable operation under extreme high-speed and high-load conditions.
Ship engines connecting rod
Alloy steel and carbon steel connecting rod is applied in marine engines, including ship main engines and auxiliary engines. Closed-die or open-die forging combined with heat treatment improves fatigue resistance, wear performance, and bending strength. Machining ensures precise alignment, smooth rotation, and reliable torque transmission under continuous high-load conditions.
Aerospace engines connecting rod
Titanium alloy connecting rod is used in aircraft engines and UAV power systems. Closed-die forging ensures lightweight, high-strength blanks. Machining and heat treatment maintain dimensional stability, fatigue resistance, and reliable torque transmission under cyclic high-speed loads.
Industrial engines connecting rod
Carbon steel and alloy steel connecting rod is applied in stationary engines, generators, and industrial machinery. Forging with heat treatment enhances bending resistance, fatigue strength, and wear performance. Machining ensures precise alignment and stable operation under repeated load cycles.
Heavy machinery engines connecting rod
Alloy steel and carbon steel connecting rod is used in excavators, bulldozers, and construction machinery engines. Closed-die forging and quenching-tempering improve impact resistance, fatigue strength, and bending capacity. Precision machining ensures smooth rotation, accurate fit, and reliable power transfer under heavy-duty operation.
Agricultural machinery connecting rod
Carbon steel and alloy steel connecting rod is applied in tractors, harvesters, and planting equipment engines. Forging and heat treatment enhance fatigue resistance, wear performance, and torsional strength. Machining ensures smooth power transfer and reliable operation under repetitive heavy-load cycles.
Mining machinery engines connecting rod
Alloy steel and carbon steel connecting rod is used in mining equipment engines, including haul trucks, drills, and loaders. Closed-die or open-die forging combined with quenching and tempering provides high fatigue resistance, bending strength, and impact durability. Precision machining ensures accurate fit and stable torque transmission under extreme load and harsh conditions.
What Are the Advantages of Simis OEM Custom Connecting Rods?
Partnering with Simis ensures maximum engine reliability, efficiency, and safety:
·Maximum Fatigue Strength:
We specialize in Precision Forging and strict control over heat treatment to achieve the highest possible fatigue endurance limit, preventing the most common mode of rod failure.
·Optimized Weight and Balance:
We utilize advanced CNC contouring and precise final honing to ensure the optimal strength-to-weight ratio and achieve strict weight matching across all units in an engine set.
·Advanced Splitting Technology:
We offer Fracture Splitting services, which creates a superior, self-aligning bearing joint geometry, enhancing bearing stability and eliminating the need for alignment dowels.
·Certified Precision:
We guarantee micrometer-level dimensional accuracy on critical features, including the center-to-center distance and big-end bore roundness, essential for bearing reliability.
How to Get a Quote for Custom Connecting Rods?
China Simis Company is your expert global partner for custom-forged and cast Connecting Rods, engineered for high fatigue life, optimal strength-to-weight ratio, and precise bore geometry.
Please submit your 2D technical drawings, 3D models (showing I-beam profile), and specific requirements for material grade, required fatigue life (cycles), RPM limit, mass tolerance, and bore finish specification to our engineering department for a consultation and detailed quotation.
