Transforming motion, transcending expectations
Connecting rod is probably the most dynamically stressed component in the IC engine due to the rapid changes in direction that both its ends are subject to. It forms the link between the piston and the crankshaft and any failure of the connecting rod will almost certainly cause catastrophic damage to the engine. AutoGRACE® brand connecting rods have been trusted by customers globally for many decades to perform reliably under the most demanding conditions.
Connecting rods serve following functions in an IC engine:
Size Range of Piston Rings in AutoGRACE® Brand
| SPECIFICATION | FROM | TO |
|---|---|---|
| Weight (kg) | 0.3 | 12.0 |
| Center-to-Center Distance (mm) | 85.0 | 320.0 |
| Big End Diameter (mm) | 30.0 | 110.0 |
| Small End Diameter (mm) | 10.0 | 70.0 |
Garima Global supplies components for a wide variety of on-road, off-road, industrial and stationary applications such as: automotive (light duty) and light commercial, trucks (heavy duty), tractors (agricultural), earthmoving and construction machinery, generators, irrigation pumps, and defence / special purpose vehicles.
The brands for which we manufacture and export aftermarket products are Caterpillar, Chevrolet, Chrysler, Citroen, Cummins, Daewoo, DAF, Daihatsu, Detroit Diesel, Deutz, Fiat, Ford, Hino, Honda, Hyundai, International, Isuzu, Iveco, John Deere, Kamaz, Kia, Komatsu, Kubota, Land Rover, Leyland, Lister Petter, Lombardini, Mack, Mahindra, MAN, Massey Ferguson, Mazda, Mercedes Benz, Mitsubishi, Navistar, Nissan, Onan, Perkins, Peugeot, Renault, Scania, Suzuki, Tata, Tatra, Toyota, Ursus, UTB, Volvo, Yanmar and Zetor, amongst others.
Garima Global also export parts for air-brake compressors like Wabco, Bendix, Knorr, Cummins, Clayton Dewandre, Mercedes, Midland etc.
Garima Global has developed an extensive range of components for engine, braking, transmission, suspension, steering, chassis, electrical, lighting and other automotive sub-systems. To assist our customers with choosing the right product for their requirements we have published comprehensive catalogs with engine / vehicle models, interchange with references of OEMs and other popular aftermarket brands, fitment dimensions and other technical data. We strongly encourage you to contact us with your specific requirements so that we can email you the relevant catalogs, and we look forward to starting a mutually beneficial business relationship with you soon!
Connecting Rods may be categorized based on manufacturing process, applications, materials, method of splitting the big end cap etc. and AutoGRACE® brand has developed a comprehensive range no matter what kind of connecting rod you require.
The big end of the con rod is machined to separate the cap from the rest of the rod. This cap is then bolted to the rod with special high strength bolts. During engine assembly, the cap is unbolted, big end bearings are installed on the big end between the crank pin and the con rod and the cap is re-bolted to the rod. Various techniques have been developed to split the big end of the con rod.
The cap is simply machined and cut away from the rod. The parting faces are then milled or polished so that a clean flat interface is obtained. Though simplest to manufacture, this arrangement puts greater shear stress on the bolts during operation unless dowel pins or sleeves are used to restrict lateral motion between rod and cap.
Similar to a machined face, interlocking teeth are cut into the parting face of both the cap and the rod. This eliminates the possibility of lateral movement between them and thus lowers shear stress on the bolts.
A laser is used to generate a notch on the big end bore at the location where cap-rod split should occur. The rod is then “cracked” or “split open” in a breaker drift at a high speed. The biggest advantage is that the rough and naturally interlocking interface prevents lateral movement so there is no need for additional guiding / locking mechanisms like dowel pins. Also machining cost of the parting face is eliminated completely.
The parting plane between the rod and the cap is perpendicular to the center-to-center axis of the con rod.
Where the crank pin is especially large, the big end is split at an angle to the center-to-center axis. This allows the large con rod big end to slide into the cylinder liner for installation but the position of the rod must be checked carefully especially for in-line engines. This design is more popular in V engines.
The thickness of the small end is same throughout its length. It is a simple design into which a regular cylinder shaped bushing can be fit easily.
To increase the surface area in contact between piston pin and con rod, the small end may be tapered towards the top. The wider base spreads the forces over a bigger surface area of the small end bush in high pressure engines. However, the trade-off is that additional machining is required for the taper cut, and changing the bush during engine overhaul requires more care. Also tapered bushes are generally more expensive.
By far the predominant material used in manufacture of forged con rods. The important grades of steel are given in the table below.
| ELEMENT | SAE1042 1.1186 EN8D/CK40 |
SAE8640 1.6546 40NiCrMo2 |
SAE1045 1.1191 CK45 |
SAE5140 1.7035 41Cr4 |
SAE4140 1.7225/EN19 42CrMo4 |
C70S6 |
|---|---|---|---|---|---|---|
| Carbon (%) | 0.40-0.45 | 0.00-0.43 | 0.42-0.50 | 0.38-0.45 | 0.36-0.44 | 0.68-0.75 |
| Silicon (%) | 0.10-0.40 | 0.15-0.30 | 0.40 MAX | 0.040 MAX | 0.10-0.40 | 0.15-0.35 |
| Manganese (%) | 0.70-0.90 | 0.75-1.00 | 0.50-0.80 | 0.60-0.90 | 0.70-1.00 | 0.50-0.60 |
| Phosphorus (%) | 0.050 MAX | 0.035 MAX | 0.045 MAX | 0.025 MAX | 0.035 MAX | 0.045 MAX |
| Sulphur (%) | 0.050 MAX | 0.040 MAX | 0.045 MAX | 0.035 MAX | 0.040 MAX | 0.045 MAX |
| Chromium (%) | - | 0.40-0.60 | 0.400 MAX | 0.90-1.20 | 0.90-1.20 | 0.10-0.15 |
| Molybdenum (%) | - | 0.15-0.25 | 0.100 MAX | - | 0.25-0.35 | 0.060 MAX |
| Nickel (%) | - | 0.40-0.70 | 0.400 MAX | - | - | 0.080 MAX |
| Vanadium (%) | - | - | - | - | - | 0.030-0.060 |
Used for lower speed engines like diesel pumps and older agricultural engines, in the following grades:
For slightly higher performance requirements following grades of SG Iron may be used for con rods:
For air compressors and automotive brake compressors, pressure die cast aluminum con rods are used extensively since the operating temperatures are much lower and aluminum provides enough strength and rigidity for such applications. By using lightweight aluminum (7068 T6511 or similar grades), compressors become much more efficient.
AutoGRACE® piston rings are manufactured by OEM and OES factories across
India that adhere to the highest quality specifications.
A blank that confirms to certain geometrical parameters like twist, parallelism etc. and has its weight correctly distributed between its two ends is essential for manufacturing a goof quality conrod. AutoGRACE® con rod blanks are controlled within OEM specs because space is constrained in modern engines, and the con rods can foul with the block / crankcase during operation if the blank is wider / longer than the acceptable limit. Connecting rod blanks may be manufactured by one of the following processes.
Most connecting rod blanks for automotive applications, especially heavy duty ones, are forged from steel bars at 1250-1300 deg C under a hammer, generating 200 MPa of compressive stresses on the surface.
Cast iron con rods used for lower speed engines are cast using traditional green sand casting methods. These conrods are lighter than steel connecting rods of the same size, and suffice the requirements of lower speed engines.
This modern manufacturing technique involves melting powder metal in a servo-hydraulic press at 1120 deg C to generate a preform within an accurate weight tolerance of +/-0.5%. The preform is then forged to increase density and decrease component height. Minimum machining is required due to the narrow tolerances that can be achieved in this process.
For compressor applications like air-brakes, aluminium provides adequate strength while being much lighter, and dimensionally accurate blanks can be created using pressure die casting process.
To further enhance material properties like hardness or to relieve the forging stresses, NQT (Normalizing, Quenching and Tempering) as well as other heat treatment processes may be carried out for particularly heavy duty applications.
The blanks are then machined to achieve the required dimensions and weight of the finished connecting rod. AutoGRACE® connecting rods are manufactured on automated production lines to accurately control the geometry of the rod. Both machined and fractured big end type connecting rods are available in the AutoGRACE® brand. For some sensitive applications the con rods are categorized by their weight or center-to-center distance so that similar con rods can be installed in a single engine. This minimizes NVH levels of the engine.
AutoGRACE® con rods undergo stringent checks at our in-house lab before dispatch to our discerning customers globally on the following important parameters, among others:
Our painstaking QC process will ensure that costly claims and returns are eliminated and our customers become the trusted source of connecting rods in their respective markets.
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