How do connecting rods get oil

Many engine builders are beginning to lean back toward tighter clearances. That means the minimal oil film on the rod journals must have full pressure behind it to maintain full lubrication under the heavy pounding it absorbs. They are also moving to synthetics and lighter weight oils, all of which requires optimum integrity of the oil film on each rod journal.

Straight shot oiling provides the solution and it is available on all modern crankshafts like those provided by K1 Technologies. About Us Contact Us. K1 Technologies. Keeping a race engine alive requires adequate lubrication! The connecting rods and main bearings, some of the most stressed components in an engine, cannot live without proper oil pressure even for a brief moment.

The welding rod passing through the journals shows the straight-shot path from the main journal to the rod journal. This view shows how each main journal feeds an adjacent rod journal on either side of it. Oil is fed to each of the main journals through passages in the block. After oiling the mains, oil pressure is directed through the straight-shot oiling to each of the rod journals.

The crankshaft is supported by a very thin film of oil on babbit-style bearings such as these. The minute amount of oil film requires perfect oil pressure for the crank to survive. In the top and bottom dead centre where the piston stops to redirect, the film thickness becomes minimal and mixed lubrication may exist.

To realize a good head transfer from the piston to the cylinder, an optimal sealing and a minimum of oil burning, a minimal film thickness is desirable. The film thickness is kept minimal by a so called oil control ring. This ring is situated beyond the piston rings so that the surplus of oil is directly scraped downwards to the sump. The oil film left on the cylinder wall by the passage of this ring is available to lubricate the following ring.

This process is repeated for successive rings. On the up stroke the first compression ring is lubricated by the oil left behind on the cylinder wall during the down stroke. This is the reason why, despite of frequent replenish of oil, oil change remain essential or even become more essential. Cams and followers. The loads of No. Under the same engine speed, the maximum loads of connecting-rod bearing and all main bearings in an engine operating cycle increase basically with the increase of engine load, and the maximum loads of connecting-rod bearing and all main bearings in an engine operating cycle take place at full engine load.

The journal axis orbits of all bearings are calculated by the dynamic method in the lubrication analyses of all connecting-rod or main bearings [ 32 ]. If the effect of the oil film inertia is not considered, the motion of the journal axes of bearing conforms to the Newton second law, that is,. The lubricating oil flow-rate Q 1 from the front-end plane of bearing and the lubricating oil flow-rate Q 2 from the rear-end plane of bearing are given by.

The journal axes orbits, maximum oil film pressures, minimum oil film thicknesses, end leakage flow-rates and frictional coefficients of connecting-rod bearing and No. In different engine operating conditions, there are major differences of the lubrication performance of bearings, and there are obvious differences in the changes and numerical values of the journal axes orbits, maximum oil film pressures, minimum oil film thicknesses, end leakage flow-rates and frictional coefficients of bearings in an engine operating cycle.

When the engine load is same, the maximum oil film pressure of connecting-rod bearing in an engine operating cycle is decreased generally with the increase of engine speed, and the maximum oil film pressure When the engine load is same, the changes of the maximum oil film pressures of all main bearings in an engine operating cycle is different one another with the change of engine speed. The maximum oil film pressures of No. When the engine load is same, the minimum oil film thicknesses of connecting-rod bearing and all main bearings in an engine operating cycle do not have the same change one another with the change of engine speed.

When the engine speed is same, the maximum oil film pressures of connecting-rod bearing and all main bearings in an engine operating cycle are increased generally with the increase of engine load, but the maximum value of the maximum oil film pressures of No.

The minimum oil film thicknesses of all main bearings do not have the same change with the change of engine load, the minimum values of the minimum oil film thicknesses of Nos. When the engine speed is same, the average frictional power losses of connecting-rod bearing and all main bearings in an engine operating cycle do not change obviously with the change of engine load.

The average frictional power losses of connecting-rod bearing and all main bearings in an engine operating cycle are generally increased slightly with the increase of engine load in addition to the individual engine loads. In addition, the corresponding comparisons between the lubrication performance of connecting-rod bearing and the one of main bearings at same engine operating condition shown in Tables 4 , 5 , 6 , 7 , 8 , 9 show that, the maximum oil film pressure of connecting-rod bearing in an engine operating cycle is larger than those of all main bearings, the minimum oil film thickness of connecting-rod bearing in an engine operating cycle is smaller than those of all main bearings, and the average frictional power losses of connecting-rod bearing in an engine operating cycle is smaller than those of all main bearings.

Also, there is the corresponding difference between the lubrication performances the maximum oil film pressure, minimum oil film thickness and average frictional power loss in an engine operating cycle of all main bearings one another at same engine operating condition, and some difference is larger. In different engine operating conditions, there are great differences of the loads of connecting-rod and main bearings. When the engine load is same, the maximum load of connecting-rod bearing appears at the lower engine speed, the maximum loads of some main bearings appear at the lower engine speed but the others appear at the higher engine speed.

When the engine speed is same, the maximum loads of connecting-rod bearing and all main bearings appear at the full engine load. In different engine operating conditions, there are obvious difference of the lubrication performance of connecting-rod and main bearing. When the engine load is same, the maximum oil film pressure of connecting-rod bearing at lower engine speed is larger obviously than the one at higher engine speed; the change of the maximum oil film pressure of each main bearing with the engine speed is not the same; the smaller values of the minimum oil film thicknesses of connecting-rod bearing and all main bearings appear generally at higher engine speed; the maximum average frictional power losses of connecting-rod bearing and all main bearings happen at higher engine speed.

When the engine speed is same, the maximum oil film pressures of connecting-rod bearing and main bearings increase generally with the increase of engine load; the minimum oil film thickness of connecting-rod bearing happens at the full engine load, the minimum oil film thicknesses of some main bearings happen at the full engine load but some other happen at the lower engine load; the average frictional power losses of connecting-rod bearing and all main bearings do not have evident change with the change of engine load.

Under the same engine operating condition, the maximum oil film pressure of connecting-rod bearing is larger than the one of main bearing; the minimum oil film thickness of connecting-rod bearing is smaller than the one of main bearing; the average frictional power loss of connecting-rod bearing is smaller than the one of main bearing.

There are the larger difference between the lubrication performances of main bearings one another under same engine operating condition. Therefore, it is not comprehensive and reasonable that only the lubrication performance of a certain connecting-rod bearing or main bearing at rated engine operating condition is analyzed.

It is necessary to analyze simultaneously the lubrication performance of connecting-rod bearing and all main bearings in different engine operating conditions in the design of engine.

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