Main bearing wear..
Discussion
Flat plane cranks were notorious for shaking the engines to bits in the comp SD1 engines! We have worked over a year or two with TN Racing who use their own flat plane cranks http://tn-racing.com/
Bearing cap movement on the V8s can also evidence the problem you show. We had a coupl of guys in the unit explaining how, when they worked at Perkins, BMW paid for research to turn the old SD1 into a diesel, the engines were so flexible it was unbelievable! The two guys developed the cross bolted mains in 3.5 blocks which Rover later used in the bigger engines.
One of our customers, Mick Richards, fabricated a girdle to fit between the sump and block to help reduce flexing in his early 90s championship dominating TR8.
Peter
Bearing cap movement on the V8s can also evidence the problem you show. We had a coupl of guys in the unit explaining how, when they worked at Perkins, BMW paid for research to turn the old SD1 into a diesel, the engines were so flexible it was unbelievable! The two guys developed the cross bolted mains in 3.5 blocks which Rover later used in the bigger engines.
One of our customers, Mick Richards, fabricated a girdle to fit between the sump and block to help reduce flexing in his early 90s championship dominating TR8.
Peter
Jhonno said:
Excellent. Thank you for that. The smiley in my post above was meant to gently indicate my opinion of the comments so far in this thread. However my own surmise for the actual reason for the wear pattern in the cap side of the bearing could only be verified by a photo of the shell in the block which I expected to show normal wear. So now let's get into it.In a normal shell bearing the wear pattern should be concentrated mainly in the centre of the U, extending to about 2/3 of the length of the shell and diminishing or disappearing towards the split line of the shell. The reason for this is simple. Most of the forces on the crank from the pistons act in the up and down plane rather than side to side so near the split line of the cap and shells there should not be much contact. When there is contact near the split line then it is generally because the shell has been pinched in laterally by dirt or burrs under the shell or some distortion in the housing.
However your shell only showed wear on one side. It is absurd to suggest this could be caused by vibrations, crank balancers or anything similar. For that to be the case the crank would have to bend significantly right within the 1 inch width of a single journal which is solid metal. It is preposterous. You could take a 1 inch length of solid steel or iron 2 or more inches in diameter and not be able to bend it one iota with the forces acting inside an engine.
So the problem had to be in that specific cap or the vanishingly unlikely case that the crank journal had been ground bigger on one side than the other.
The answer is therefore simple. The shell was pinched in a bit at the split line just on one side by a burr or dirt right at the edge of the worn side leading to most of the contact being on that side of the shell and also accounting for why the contact extended up to the split line.
Mignon said:
Jhonno said:
Excellent. Thank you for that. The smiley in my post above was meant to gently indicate my opinion of the comments so far in this thread. However my own surmise for the actual reason for the wear pattern in the cap side of the bearing could only be verified by a photo of the shell in the block which I expected to show normal wear. So now let's get into it.In a normal shell bearing the wear pattern should be concentrated mainly in the centre of the U, extending to about 2/3 of the length of the shell and diminishing or disappearing towards the split line of the shell. The reason for this is simple. Most of the forces on the crank from the pistons act in the up and down plane rather than side to side so near the split line of the cap and shells there should not be much contact. When there is contact near the split line then it is generally because the shell has been pinched in laterally by dirt or burrs under the shell or some distortion in the housing.
However your shell only showed wear on one side. It is absurd to suggest this could be caused by vibrations, crank balancers or anything similar. For that to be the case the crank would have to bend significantly right within the 1 inch width of a single journal which is solid metal. It is preposterous. You could take a 1 inch length of solid steel or iron 2 or more inches in diameter and not be able to bend it one iota with the forces acting inside an engine.
So the problem had to be in that specific cap or the vanishingly unlikely case that the crank journal had been ground bigger on one side than the other.
The answer is therefore simple. The shell was pinched in a bit at the split line just on one side by a burr or dirt right at the edge of the worn side leading to most of the contact being on that side of the shell and also accounting for why the contact extended up to the split line.
Ollie from TN Racing tells me..... main thing with flat plane V8 is the second order vibration that you cannot get rid of without a balance shaft. The key is ensuring that the counterweights of the crank are matched perfectly to the piston and rod weights. Ours is within a couple of grams and we don't get the bolts trying to undo themselves like others experience.
Peter
Peter
We have had good results, especially on V8s with Rattler pullies.
http://vibrationfree.co.uk/sterling-rattler/shop-2...
Peter
http://vibrationfree.co.uk/sterling-rattler/shop-2...
Peter
Mignon said:
Jhonno said:
The answer is therefore simple. The shell was pinched in a bit at the split line just on one side by a burr or dirt right at the edge of the worn side leading to most of the contact being on that side of the shell and also accounting for why the contact extended up to the split line.PeterBurgess said:
We have had good results, especially on V8s with Rattler pullies.
http://vibrationfree.co.uk/sterling-rattler/shop-2...
Peter
Thank you for that link! Interesting company I shall look into..http://vibrationfree.co.uk/sterling-rattler/shop-2...
Peter
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