Hole in nearside con-rod

[muskrat]

An aside - I bought R and R rods around 10 years ago and quickly disguarded them as they did not have the oil hole and because the had been made with 6.5 inch centres, some 1 mm longer than the correct BSA dimension.

I fitted Thunder rods which had one drilled and were the correct dimension.

Are they making the R and R rods to the correct specification now?

G'day Julian.
I rebuilt the Cafe about a year ago with R&R rods. I didn't bother with the hole but did put a 1mm base plate under the barrels. Still hard to kick over but I can't comment on the need for the hole (haven't done more than 50 miles!
40 years ago I built the A7 plunger with the hole facing the drive side bearing thinking it would oil the bearing. 40 years on the bearings looked almost new.
Cheers
Cheers

[berger]

i put thunder rods that hadn't been drilled in the berglar build and got brother to drill the hole i know i would have fkt it up , 

[RichardL]

So a hole was cut in the engine case and a perspex window was fitted and then they saw it was insufficient lubrication to the left piston.

In no way trying a vigorous defense of the bubbles theory, but I think it’s safe to say that they couldn’t put a window in the crankshaft. We know oil can take on bubbles . If they get into the sludge trap, where do the go? Do they become a compressible volume of gas reducing the fluid pressure that can be developed? Any more than two questions would appear "vigorous." For some reason there is a modicum of comfort in grasping at straws.

Richard L.

[Rex]

40 years ago I built the A7 plunger with the hole facing the drive side bearing thinking it would oil the bearing. 40 years on the bearings looked almost new.

Five years or so ago I did the same, mainly because Drag's crappy diagram of the time showed it this way. Checking Drag's site today I see that it's now a much better (probably BSA) diagram there now with the oil hole facing "inwards" towards the crank.
Oh well, probably won't make a jot of difference either way, though I'll check it again in forty years...maybe.

[CheeserBeezer]

An aside - I bought R and R rods around 10 years ago and quickly disguarded them as they did not have the oil hole and because the had been made with 6.5 inch centres, some 1 mm longer than the correct BSA dimension.

I fitted Thunder rods which had one drilled and were the correct dimension.

Are they making the R and R rods to the correct specification now?

Thanks Julian!
Just measured them, they're 6.5" and should be 6.468" = 6 15/32. I am told by a qualified engineer that somebody at R+R made an assumption that they should be 6 1/2".....wrong! BSA often worked in 32nds of an inch, hence the rod length specified is 6.468", i.e 1/32 short of 6 1/2". The R+R rods are going back from whence they came!

[Sakura]

Thanks Julian!
Just measured them, they're 6.5" and should be 6.468" = 6 15/32. I am told by a qualified engineer that somebody at R+R made an assumption that they should be 6 1/2".....wrong! BSA often worked in 32nds of an inch, hence the rod length specified is 6.468", i.e 1/32 short of 6 1/2". The R+R rods are going back from whence they came!
[/quote]


The Carrillo rods in my RGS are 6.5" centre to centre, which is the same as an A65. Again, I queried this with Fred Carrillo, hid poor answer was that everyone wants a high comp ratio. He also said that was all he made so I fitted them with 8 to 1 pistons. Not ideal but I'm pretty sure I'm never going to get a rod through the crankcase, which is important on a RGS.

[RichardL]

Are the R&R billet rods made by Thunder Engineering, or vice-versa, or are they both making the same thing? I've always believed mine are Thunder. If Thunder does make the R&R product, then I'd have to assume I have the extra 1/32". (Maybe that explains my sore right knee.) Assuming mine are 6-1/2" (a little too much trouble to disassemble the engine to find out), they appear to be working fine. You'd think I would recall if the pistons came up above the top of the barrels, but I don't. Maybe I'll have the head off this winter and check it. In any case,  is it a surety that the extra 1/32" is a problem? I guess it could affect timing by measurement through the plug hole, but isn't BTDC BTDC regardless of the length of the rod?

Richard L.

[berger]

well richard TDC is TDC before TDC is before so it doesn't matter what rod, my thunder rods were bang on not longer than old BSA

[JulianS]

When I assembled my engine with the R and R  I found the pistons kissed the piston crowns.

Engine had GPM pistons, Spitfire cam and the head, fitted with the big inlet valve, had been skimmed because it was not completely flat.

So I wasted my money on R and R.

It does seem quite suprising that a reputable manufactureer makes such a basic mistake.

My Thunder rods are made to the correct dimension.

[JulianS]

R and R dont make Thunder rods. Thunder Engineering is based in Leicester, England.

First photo show BSA rod on the left anf R and R rod right.

Second photo shows the Thunder rods which went into my A10.

[berger]

and here we have thunder A7 and BSA A7 rods

[BagONails]

Those Thunderous rods look pretty meaty Bergs. Is there a big difference in weight to the originals?

[CheeserBeezer]

Just ordered some for my A10. The R+R rods I had are 0.81mm too long when compared with a standard big bearing rod. My measuring equipment may not be the most high-tech but, having measured a number of original rods, they are all at least 0.75mm shorter than the R+R rods. I have raised this with the supplier who says they have never had any R+R rods returned to them on the basis that they are too long. According to another source, it is suggested that R+R rods, across centres, are 6.5" whereas BSA spec is 6.468, or 6 15/32 give or take a thou.

[KiwiGF]

Those Thunderous rods look pretty meaty Bergs. Is there a big difference in weight to the originals?

I fully looked into the weight issue….see https://www.a7a10.net/forum/index.php?topic=6086.msg41598#msg41598

[limeyrob]

BSA Service Sheet 215 Issued Oct 1949, Revised August 1956: (Last para at bottom of page)
"When fitting new liners it will be noticed that each half has a small central hole.  Originally only one drilled liner was used. The left hand con-rod has a bleed hole supplement the lubrication of the cylinder bore.  This should be positioned so that it faces the flywheel"

So we know that from August '56 engines were being fitted with hole/con-rods and anyone rebuilding an engine was to fit a con-rod on the left with a hole to the flywheel side.  I wonder how many engines were built by people who did follow the service Sheets?