Question 1

What Is Bearing Crush?

Accepted Answer

For those who regularly travel on mass transit rail networks such as the London Underground or the New York Subway, the word 'crush' will have its own and possibly unpleasant connotation. Just as tightly packed in a car as another person squeezes before the doors close, the experience, especially during peak travel times, is not quickly forgotten.

But when applied to the technologies of shell bearings, it is not a good idea to 'crush'; it is absolutely necessary. When adding semi-shell bearings to a cylinder block main bearing housing, even the most visually impaired can't help but notice that at first sight, the bearing doesn't seem to fit. Laying the half-shell across the half-moon of the cut-out makes the bearing proud several millimeters after only a slight pressure clip.

Referred to in engineering parlance as the 'free spread,' it is designed to hold the shell in place during engine manufacturing. The more observant, however, may notice that even when seated, the shell is still a little proud, and the position remains in place no matter how hard you try.

Believe it or not, I've heard of some engine builders actually filing this flush to the level of the clamping face. This is completely wrong. Bearing crush, as it is called, is included for a number of reasons because when clamped together, the compressions in the bearing shells provide highs resistances to the shell turning or progressively creeping in the direction of the crankshafts, as well as supports thin and otherwise flexible structure during use.

Question 2

Bearing Crus:

Accepted Answer

The term crush refers to the external force created by the part of the bearing that is exerted over the housing bore when the bearing parts are held in place. This extra material keeps the outer diameter of the bearings firmly against the housing bore when the assembly is torqued to specification.

By increasing surface contact between the bearing and the connecting rod housing bore, crushing reduces bearing movement, helps compensate for bore deformation, and aids in heat transfer. In simple words, the bearing crush is what keeps the bearing in place. Think of it as putting a 10-pound thing in a five-pound bag.

Tactile or locator tabs on the shell that the saddle fits are only meant to locate the bearing during assembly.When the crush is perfect, slightly elliptical bearing spheres conform to a perfect circle when rotated into place. In this way, the crankshaft rotates properly. However, when excessive crushing occurs, the additional compressive force causes the bearings to bulge inward on the parting lines, causing side pinching.

Question 3

Checking of Bearing Crush:

Accepted Answer

With the bearing shell fitted and the two main cap bolts torqued, the bearing shell insert is forced to conform to the tunnel shape of the block. The quality of the bearing fit is ascertained by checking the 'bearing crush.' Undo and remove one bolt either one &, starting at 0.075 mm / 0.003 in the feeler gauge, see if the feelers gauge will go into the gap between the cap and the block.

The exacts sizes of the gap can be determined using a series of feeler gauges. The acceptable range is 0.075mm/0.003in to 0.015mm/0.006in. If no gap is visible when the bolt is released, then there are something wrongs with the bearing shells; they will effectively be loose as no bearing crush will be present. Such situations are not acceptable - try another's set of shells.

If the gap is greater than 0.20mm/0.008in it means that there is too much crush, which is unacceptable as the party line is likely to result in deformation. One set of spheres has to be changed for another. Alternatively, the desired bearing crush can be achieved by mixing and matching existing shells.

Question 4

Misassembly of Bearing Crush:

Accepted Answer

ometimes, failure is the result of simple installation errors. For example, if the bearing half without an oil hole is improperly placed in a position where the hole is required, that magazine will receive no lubrication. Another type of assemblies error may also be seen.

If connecting rods or main bearing caps are installed in the wrong position or the bearing is not installed securely, the lubrication will be insufficient and cause failure. Careful installation procedures are critical in every aspect of engine manufacturing; careless errors are always costly.

Question 5

Debris of Bearing Crush:

Accepted Answer

The Debris, such as dirt or dust, can cause considerable damage to the bearing surface. If it is in the lubrication system, the dirt will usually leave peripheral scratches and will often remain lodged in the surface of the bearing.

Always be sure to thoroughly flush the lubrication system before reconnecting the engine to avoid engine bearing damage. If engine parts are not thoroughly cleaned, dirt can also wreak havoc.

Question 6

Insufficient Lubrication:

Accepted Answer

The Complete lack of lubrication in the crankcase usually leads to seizure of the engine bearing and complete failure. But, experts say, the more frequent issue regarding lubrication is simply insufficient oiling. The absences of a proper oil film will result in metal-to-metal contacts, sometimes to just one bearing or often to several of them.

When the bearing is damaged by oil starvations, you will get a very shiny surface and evidence of wiping. Remember, oil film failure can be observed on bearings in different ways.

Check for things like a blocked oil passage, a bad oil pump, improper bearing selection or installation, oil seal failures, fuel dilution due to frequent blowing of fuel and air behind the piston rings, or foaming or aeration, ironically—overfilled crankshaft by one.

What Is Bearing Crush | Bearing Crus | Checking of Bearing Crush