Author Topic: Con-rod oiling holes  (Read 6559 times)

Online RichardL

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Re: Con-rod oiling holes
« Reply #15 on: 17.08. 2009 12:05 »
Lee,

The hole should be 3/64" or #56 (drill) or very close thereabouts. A piece of stainless wire or part of broken drill bit that is a snug or slight press fit could be epoxied into the hole. Otherwise, maybe just some JB Weld or whatever your favorite high-quality (not "five minute") epoxy, alone, would do the trick.

Richard L.
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Online RichardL

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Re: Con-rod oiling holes
« Reply #16 on: 17.08. 2009 12:57 »
Sorry, one more idea. Maybe, tap to #0-80 thread and permanent Loctite a set screw into the hole (assuming you could source the screw).
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Online trevinoz

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Re: Con-rod oiling holes
« Reply #17 on: 17.08. 2009 22:10 »
Just my two bob's worth, the rods are fitted with the match numbers facing the camshaft.
As to the drilling in the rod, I am pretty sure that the late A65s had both rods drilled so it probably doesn't matter if both are drilled in an A7/10.
Trev.

Offline A10Boy

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Re: Con-rod oiling holes
« Reply #18 on: 04.06. 2010 09:57 »
That pretty much comes back to my view.

Richard, I think I need to say that I would never ever give advice which would risk someones engine. My view was that as the rods came out of a running engine, I would prefer to use them as they were rather than try to glue bits of wire in there, or un-necessarily go and buy replacements.

This place is great for people to ask questions and others give their opinions, but its upto the asker to decide what he prefers. I have found this forum a great help.  *smiley4*

Lee, perhaps you could update us on what you did and hows the bike going ?

Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Online RichardL

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Re: Con-rod oiling holes
« Reply #19 on: 04.06. 2010 11:55 »
Andy,

I think you're right. At the least, I should have put it like, "A fool, such as I, might plug the hole with something, but I am in no way suggesting others should try it."

Thank you for putting this straight.

Richard L.
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Offline A10Boy

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Re: Con-rod oiling holes
« Reply #20 on: 04.06. 2010 14:57 »
That was not a criticism. I'm sure everyone here acts with best intentions.

It would be interesting to hear what Lee did and how his bike is going.

Cheers
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Online RichardL

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Re: Con-rod oiling holes
« Reply #21 on: 04.06. 2010 15:53 »
No problem, we're good.
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Offline beezalex

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Re: Con-rod oiling holes
« Reply #22 on: 04.06. 2010 21:41 »
The only thing that makes sense to me is the idea of cylinder wall lubrication.  I've seen this in many automotive engines in one form or another.  I think that oil being slung is the primary source of oiling for the cylinder walls.  The timing side has a oil coming from the timing side bearing, but the drive side does not.  The rod bearings only produce about 3cc of oil/s from leakage (@ 4krpm) while a 1 mm orifice on the con rod supplied by a 5 mm hole at 60 psi supplies about 10 times as much.  At low rpm, the bearings leak even less, so maybe that's where the problem lies.  I do know that my A65 race bike has no problems running without drillings.  Besides, that's just a spot where cracks can propagate from.

I've had a bunch of people try to tell me it's for flow equalization, but nobody could explain exactly how this works.  Doesn't make sense to me.
Alex

Too many BSA's


Online RichardL

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Re: Con-rod oiling holes
« Reply #23 on: 04.06. 2010 23:03 »
So, how "dry" is that sump. The flywheel runs pretty close to the bottom of the crankcase, and, as I see it, the hole squirts at the side of the flywheel and never has a shot at the cylinder wall. If the flywheel runs in a puddle at the bottom of the crankcase, the spritz from the hole becomes insignificant. Regarding the timing-side bearing, how would that be contributing to throwing oil at the right cyclinder wall other than contributing to the puddle at the bottom? I see it as an oozer not a sprayer.

I'm not making a big arguement for the cause here, it's just fun trying to read the minds of dead people, like some of you will be doing with me some day and asking "What drove him  to write so many G.D. B.S. posts?"
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Offline MG

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Re: Con-rod oiling holes
« Reply #24 on: 05.06. 2010 08:57 »
Quote
I'm not making a big arguement for the cause here, it's just fun trying to read the minds of dead people,...

Totally agree, Richard, so let me add my 2p worth  *smile*:

During the last weeks I've been working on my Matchy basketcase and had a very close look at the yearly engine lubrication mods on the AMC twins (and there were many of them!)
Obviously oil starvation of the lhs cylinder was a big issue for them, as there had been several different attempts to get oil up there, even by having an oil route through a drilling in the cylinder spigot (to be omitted just half a year later due to massive over-oiling of the lhs pot). They ended up with a drilling through the inlet camshaft tunnel (behind the barrels) in order to have oil spill on the lhs flywheel, thus being flung up to the cylinder wall.

This led me to belive that the lhs conrod oil hole must be there for exactly that purpose, being on the lhs and facing the flywheel.
Mr. Hopwood also bothered to design a trough for the camshaft, which is shaped so that surplus oil will be flung towards the crankshaft, thus oiling the cylinders, so I suppose considerations on reducing the cylinder wall/piston sliding friction had been an issue with BSA as well.

As the return oil pump is of much greater capacity than the feed pump, I would say the sump IS dry. Have a look at the oil returning to the oil tank, you will see it is full of air bubbles for this very reason.

Sun is shining, so I'll go for a quick spin now and enjoy the results of Mr. Hopwood's efforts.  *smiley4*

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

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Online RichardL

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Re: Con-rod oiling holes
« Reply #25 on: 05.06. 2010 17:28 »
Mr. Hopwood also bothered to design a trough for the camshaft, which is shaped so that surplus oil will be flung towards the crankshaft, thus oiling the cylinders,

Markus,

So, output from the conrod hole, again, seems to me to be insignificant compared to trough overflow. Like a baby to his mother, I'm clinging to the engineering concept for this hole that I think I understand. That is, pressure and flow to both journals is better balanced by promoting more flow to the end of the path, rather than reducing pressure at the left end via the outlet at the right journal.

So, for those of you who know I'm wrong, allow me to agree with you in advance, without actually giving up my illusion, yet. For those of you who agree with me, we are probably about to be spanked. For those of you with professional training in treating obsessions, HELP!

Richard L.
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Offline MG

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Re: Con-rod oiling holes
« Reply #26 on: 05.06. 2010 19:32 »
Quote
That is, pressure and flow to both journals is better balanced by promoting more flow to the end of the path, rather than reducing pressure at the left end via the outlet at the right journal.

I'm absolutely not questioning that, I would also think that this had been the main reason to add the hole. I was just trying to give an explanation why it should be facing the flywheel on the lhs.

However, as we all know, opinions are like a**holes. Everybody's got one.  *roll*


Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Offline beezalex

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Re: Con-rod oiling holes
« Reply #27 on: 07.06. 2010 14:52 »
This is an interesting subject and I think it's definitely worth contemplating.  I certainly can't claim to know what was going through the BSA engineers' minds when they came up with this, but I do have a pretty firm background in mechanical design and experience with BSA twins so I'm trying work the problem backward on the assumption that there was a logical reason for the addition of the hole. 

Richard asked about the timing side journal:  oil from the timing side journal travels up the counterweight and can the be flung toward the cylinder wall.  Now, I'm going to backpedal a bit on what I said earlier with regards to slung oil lubricating the cylinder walls.  I think only the couterweight will be any good at slinging oil into the bores.  It turns out that the flywheel is no good at getting oil on the cylinder walls bacause the spray comes off the flywheel at a tangent and with the large OD of the flywheel, very little, if any gets in the bores. 

When the pistons are at TDC, however, the oil hole is clear of the flywheel and this turns out to also be the crankshaft position when the oil hole lines up with the bearing feed hole in the crankshaft...and yes, at 50-60 PSI a 1 mm orifice will make a good jet. 

As for the "equalization of flow" thing...the sludge trap basically forms a reservoir at static pressure that supplies the big end bearings.  I don't see how there can be any difference in pressure between the two journals unless the trap is plugged.  All adding a significant hole anywhere in the system does is lower the overall pressure...thus REDUCING the flow from the journals.
Alex

Too many BSA's


Offline MikeN

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Re: Con-rod oiling holes
« Reply #28 on: 07.06. 2010 15:09 »
It turns out that the flywheel is no good at getting oil on the cylinder walls bacause the spray comes off the flywheel at a tangent and with the large OD of the flywheel, very little, if any gets in the bores. 

What makes you say that oil comes off the flywheel at a tangent? I would of thought centrifugal force would fling it off the flywheel radially.
MN

Offline beezalex

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Re: Con-rod oiling holes
« Reply #29 on: 07.06. 2010 15:16 »
It turns out that the flywheel is no good at getting oil on the cylinder walls bacause the spray comes off the flywheel at a tangent and with the large OD of the flywheel, very little, if any gets in the bores. 

What makes you say that oil comes off the flywheel at a tangent? I would of thought centrifugal force would fling it off the flywheel radially.
MN

All particles leaving a round, rotating object depart at a tangent...that's physics.  Ever watch rain water coming off a tire without a mudguard?  F1 cars or bicyles in the rain?
Alex

Too many BSA's