Author Topic: Con Rod Oil Hole  (Read 1181 times)

Offline berger

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Re: Con Rod Oil Hole
« Reply #15 on: 12.12. 2018 19:55 »
we have a starter, cheers kiwipom *beer*

Online RichardL

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Re: Con Rod Oil Hole
« Reply #16 on: 12.12. 2018 20:04 »
I have pictures somewhere of me fixturing my soon-to-be-left Thunder rod for drilling.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline BigJim

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Re: Con Rod Oil Hole
« Reply #17 on: 12.12. 2018 22:28 »
I'll be trying to construct an opinion whilst i'm in the pub! Come on Bergs, fess up, which way are you leaning. Smart money says you'll leave it well alone,nail it on and get to the pub.
Am looking forward to the Christmas do, fancy dress as usual?
 *beer* *computer* *countdown* ::hh::
Jamie,  Supporter of Distinguished Gentleman's Ride

Offline berger

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Re: Con Rod Oil Hole
« Reply #18 on: 12.12. 2018 23:23 »
I am not leaning at all at the moment jim, but will be on Friday *countdown* ;). as the new number 2 said in the prisoner - we want information!!! all I want is a view on this across some of the forum members to see what they have done or would do with these modern rods, I am sure there will be some edumacating answers to ponder on over a gallon of black&tan. like why if its not needed  do they still go to the trouble of putting holes in the shells *dunno2* *conf2*

Online RichardL

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Re: Con Rod Oil Hole
« Reply #19 on: 13.12. 2018 04:51 »
I have pictures somewhere of me fixturing my soon-to-be-left Thunder rod for drilling.

Richard L.

I guess the above says my answer is "yes" to drilling, but, before I wrote that, I wrote the following, which, somehow, didn't post.

You have to promise to consider the source but (again) my answer is "yes". Kiwipom's statement from SRM seems contradictory. Promoting oil flow has to be seen as a good thing and, therefore, the hole leans more toward the "necessary" than "unnecessary." No one has ever said the hole would hurt anything,  that I recall. Personally, I believe in the oil flow theory. At one time, I did conjure up an unsupported idea that bubbles in the oil could stack up as foam on the left end of the sludge trap, creating a cushin against which oil did not flow easily. I have no proof of this, nor anyone with a real BSA brain agreeing.

Richard L.

Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online JulianS

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Re: Con Rod Oil Hole
« Reply #20 on: 13.12. 2018 10:29 »
The book "BSA Twin Motor Cycles" from the 1950s by BSA Technical manager D W Munro gives the account as to why the drilled rod was introduced. The drilling was used until the end of the pre unit A series.

The first A65s were made without the drilling but it was reintroduced in early 1965.




Online muskrat

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Re: Con Rod Oil Hole
« Reply #21 on: 13.12. 2018 10:47 »
G'day fellas.
Without the benefit of the internet back in 81 I rebuilt my plunger with the hole pointing outwards. My thinking it would lube the roller bearing. Did countless miles like that. A freshen up about 10 years ago it was put in the "right" way. Again lots of trouble free riding. In the 90's (still without the web) I raced my 57 A7SS with std 40 year old rods. Broke lots of things but never a rod. In about 05 she grew up into the A10 Cafe, still with std rods. A few years ago she dropped a valve and was rebuilt with R&R rods, no hole. Only done about 10K miles but all sounds good.
My only reservation with the hole is oil pressure not flow. To my way of thinking (probably only me and I'm no engineer) a plain bearing needs pressure as well as flow, a roller/ball bearing needs flow. With that hole we are loosing pressure. Flow would be important if we are loosing pressure due to worn out timing side bush, too much end float or worn big ends and that hole.
Cheers
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Offline berger

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Re: Con Rod Oil Hole
« Reply #22 on: 13.12. 2018 13:31 »
richardL and julianS very interesting thankyou!! muskrat you are crazier than dutch- if that is possible *doubt* , i wasn't expecting that when I opened the link  *lol*

Online chaterlea25

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Re: Con Rod Oil Hole
« Reply #23 on: 13.12. 2018 21:00 »
Hi All,
I will have to make the decision to drill or not to sometime soon too *conf2* *conf2*

Suppose the engine has been standing for some time, does the oil within the crank sludge tube /chamber drain away?
(I would think it does to some degree depending on were the crank comes to rest)
When the engine is started up again, oil is pumped into the the crank chamber to expel the air through the big end bearings
Would the drilling in the rod assist bleeding the air from the crank  better than not having a drilling there*????* *????* *????* *????*

John
1961 Super Rocket
1963 RGS (ongoing)

Online duTch

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Re: Con Rod Oil Hole
« Reply #24 on: 13.12. 2018 22:30 »

 
Quote
muskrat you are crazier than dutch- if that is possible *doubt* , i wasn't expecting that when I opened the link  *lol*..

  *eek* *fight* I think I represent that..... *beer*

 
Quote
.......Suppose the engine has been standing for some time, does the oil within the crank sludge tube /chamber drain away?
(I would think it does to some degree depending on were the crank comes to rest)........

 I've suggested before that as the oil feed holes are in the *sides* of the Big-end journals (ie; @ 90˚ to T/B-DC), if the throw is below horizontal, then at rest it should in theory hold a certain amount of oil....until it rolls up past horizontal and at rest, any oil in the crank would in theaory start to seep out the big-end feed holes, or back down to the T/S main bush, where it will seep out over time ....so best to leave at BDC if parked up for extended periods.....on the other hand.... *conf2*..... *beer*

 So, with regard to the Conrod hole, the way I see it, is the hole only coincides with the above mentioned journal-feed holes momentarily *at 90˚* before/after TDC ie- when the crank throw is horizontal either way, so a very short time to catch an extra shot of lube......so there's not a constant extra steam anyway...can't see any problem having the 'ole, and mine's still running fine after most days in 6 years

 Fairly sure my Thunder Rods have the 'ole, and facing the flywheel (but not planning a search in the foreseeable future)- but may have a photo on an old camera....
              *beer*
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Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline berger

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Re: Con Rod Oil Hole
« Reply #25 on: 13.12. 2018 23:12 »
hang on call me thick but the oil pump is supplying the journal shells  through the big end holes all the time the engines running , so the oil can come out of the con rod hole all the time weather it's in line with the ole or not *whistle*

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Re: Con Rod Oil Hole
« Reply #26 on: 13.12. 2018 23:57 »
G'day berger.
That's my thoughts as well.
I can see the thinking the 'ole would promote flow as any fluid will find the easiest escape route and there are a few as I said earlier. All this adds to the loss of pressure.
Our motors would nearly always come to rest with the pistons rising, the compression stops them. The journals would be at about 45 degrees btdc or thereabouts. I would imagine over time all/most of the oil would drain away either through the big ends or main bush. *conf2*
Cheers
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Re: Con Rod Oil Hole
« Reply #27 on: 14.12. 2018 00:02 »
 
 Musko got in while I'm struggling with the phone.... but here goes again

'Yes' to the above,  ( you're  thick .....*smile*-  nah just joking)
' Yes' to the rest., I think I said the hole provides just an *extra* squirt at those times, and not a constant stream ( from the rod hole)....

 
Quote
....when the crank throw is horizontal either way, so a very short time to catch an extra shot of lube......so there's not a constant extra steam anyway.....
   *beer* *beer*
 
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Tomcat

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Re: Con Rod Oil Hole
« Reply #28 on: 14.12. 2018 05:57 »
I reckon that at some time an engine or two failed on the left cylinder so adding that hole was a knee-jerk reaction. The left side, being further away from the oil supply may have been in need of slightly more jollop squirting about, especially on a worn engine.


Yep, this is the reason for the hole. In Bert Hopwood's book 'Whatever Happened T T B MC I' He tells of the first A10s grabbing the left piston. No one could explain the reason and one of the Development Engineers said " If we had a window in the engine, we could see why." So they cut a hole in the cases and put in a perspex window to find very little oil in the area. So the fix was a small hole in the LHS Con Rod.
'48 A7 '59 SR '74 850 Commando TDM900

Online chaterlea25

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Re: Con Rod Oil Hole
« Reply #29 on: 14.12. 2018 17:36 »
Hi All,
Another thought  *ex*
Engine oil quality has improved massively since the 1950's,
So maybe the reason that bikes are running with rods without the oil hole happily for many thousands of miles
is due to better oil quality  *????* *????*

John
1961 Super Rocket
1963 RGS (ongoing)