- Joined
- Oct 28, 2014
- Messages
- 1,991
I noticed the JS Carrillo rods do not have a spit hole drilled in them. It seems I could blank off the hole by swapping the shell bearings and achieve a higher oil pressure to the rods and rockers.
Can't do that with the shells I have for the JS long rods. Even if you could it wouldn't accomplish anything.
OK, that being the case, I definitely would not do it with a Norton alloy rod. That may just be me though. Understood on the location on the hole on a Norton rod. The JS rod reference threw me.
Those are bright and shiny rods.
Impressive handywork!! Lot of satisfaction doing that kind of thing without power tools. I thought about doing it, but stuck aftermarket rods in my one Norton. I don't have the Brit bike fever as bad as most of you guys do.Fully detailed (no power tools or mops) and seem to remember I went with the RGM shells and AN > bolts. < Even if they were of poor dimensions compared to the OEM bolts)
(RGM bolts in the picture)
In addition you need the max bearing surface area on the top shell as the downward force from the combustion is applied to the top shell so it needs all the help you can give it.as they bleed off high pressure oil from the oil wedge just when it is needed most
I had never thought of thatIn addition you need the max bearing surface area on the top shell as the downward force from the combustion is applied to the top shell so it needs all the help you can give it.
When I worked for a shell bearing maker the development dept had a program where you entered all the parameters for the crank/cod rods/oil pump including oil holes and their position and it predicted the oil film thickness at different revs and degrees of rotation and consequently the predicted life of the bearings. They then gave advice back to the engineers including repositioning of oil holes. One customer was warned his oil hole position on the crank conrod journal compromised the oil film thickness and would shorten the life of the con rod bearing but he refused to move the oil hole as it was just a program on a PC. So the development team ran some tests in the lab using the proposed customer hole position and the development engineers position. The results showed a catastrophic failure on the customer hole position and normal behaviour with the revised position. Presented with the results the hole was moved.The reduction in bearing area is tiny
Its not the fact that the journal hole aligns itself with the bleed hole twice each revolution which it does. Its that it is constantly bleeding off high pressure oil all the time the crank is revolving.The reduction in bearing area is tiny, not to mention the journal oil hole does not line up with the bearing hole until the rod is close to right angles with the throw (around 3:00 / 9:00) maximum torque.
No offence meant and it might be the lighting, but those shells look well beyond their use by date and look older than Methuselah.
The scores look like debris in the oil so the oil clearance might have increased.
Surely being a 360-crank combined with centrifugal force oil will feed the equally positioned journal oil holes.
When I worked for a shell bearing maker the development dept had a program where you entered all the parameters for the crank/cod rods/oil pump including oil holes and their position and it predicted the oil film thickness at different revs and degrees of rotation and consequently the predicted life of the bearings. They then gave advice back to the engine including repositioning of oil holes. One customer was warned his oil hole position on the crank conrod journal compromised the oil film thickness and would shorten the life of the con rod bearing but he refused to move the oil hole as it was just a program on a PC. So the development team ran some tests in the lab using the proposed customer hole position and the development engineers position. The results showed a catastrophic failure on the customer hole position and normal behaviour with the revised position. Presented with the results the hole was moved.
After that I never looked at an oil hole being a tiny item ever again.
Oil film thickness is king.
Oil pressure measured by a oil pressure gauge and the oil film thickness are in some ways completely unconnected. Of course for good oil film thickness you need a good supply of oil, the oil pressure is a good proxy for that but does not tell you what is happening in the gap between journal and bearing. There is a dam of oil created inside this space and its thickness must never get to zero, what effects that dam are many and the measured oil pressure will not tell you wants going on with oil film thickness, only that oil is present. You can currently only measure oil film thickness in a lab.Interesting and you would be the one to answer on the subject based on your background.
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Are we talking about that one worn shell and when did a Commando have high oil pressure.
That could be ignition, it could be excess oil in that cylinder, it could be old age and dirty oil. (It does have evidence of that plain to see) even acid etch from sitting, maybe even excessive idling at low rpms, high mileage etc.
What was the oil pump like, what was the actual across the board oil pressure.
What is the history of the engine.
I am certainly no expert, but where is the actual evidence considering the over 50000 Commando's built and it's not like folk are changing bearings on a regular basis if ever on a lot of bikes.
Did someone do a pressure test (Comstock) with both open and closed rod bleed hole, not to mention Post #8 by Fast Eddie which seems to suggest no difference.
I forget how I installed the RGM shells, probably in the aligned position but won't lose any sleep over it.
View attachment 116860
Very true.Oil pressure measured by a oil pressure gauge and the oil film thickness are in some ways completely unconnected.
The reason those old shells look like they do is because they have been exposed to air after they were removed and the surface has corroded (think of a sheet of lead, scrape a new shiney surface on it, leave it for a few years, nearly ten in this case and then look at it, it won't be shiney then!)Interesting and you would be the one to answer on the subject based on your background.
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Are we talking about that one worn shell and when did a Commando have high oil pressure.
That could be ignition, it could be excess oil in that cylinder, it could be old age and dirty oil. (It does have evidence of that plain to see) even acid etch from sitting, maybe even excessive idling at low rpms, high mileage etc.
What was the oil pump like, what was the actual across the board oil pressure.
What is the history of the engine.
I am certainly no expert, but where is the actual evidence considering the over 50000 Commando's built and it's not like folk are changing bearings on a regular basis if ever on a lot of bikes.
Did someone do a pressure test (Comstock) with both open and closed rod bleed hole, not to mention Post #8 by Fast Eddie which seems to suggest no difference.
I forget how I installed the RGM shells, probably in the aligned position but won't lose any sleep over it.