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Re: A65 problem with rings sealing
koncretekid #815786 07/10/20 3:33 pm
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Very nice looking bike, I craved this Clubman look for a very long time.
When you finally sort out your engine you will have lots of fun with it.
If you have small port head with it it's even more fun riding fast.

Last edited by Adam M.; 07/10/20 3:34 pm.
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Re: A65 problem with rings sealing
Andy Higham #815898 07/11/20 4:02 pm
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Originally Posted by kommando
If the journal has the bearing lining stuck to it then hydrochloride acid will remove the Aluminium/tin and not touch the steel crank. Not sure if it work on bronze material. Tip I picked up from Briggs engines with a Aluminium rod which seizes on the crank.
The 2-stroke racer boys used to bring a small bottle of Muriatic acid (dilute hydrochloric) with some swabs with them to the races to clean the aluminum off their bores in case of a seizure.
Originally Posted by Mark Z
Amazing (and fortunate) that you could seize a rod to the crank without snapping the rod and/or putting it through the piston or the case!

Left big end seizure is typically due to oil starvation and nothing to do with the upper engine.

Inspect the crankcase very carefully. When I trashed a lower (due to oil starvation; I won't go into that here), I didn't notice the two little partial punch-outs at 4:00 and 8:00 until someone else (who knew what to look for) pointed them out. But my conrod was loose, not seized.

Sorry to hear you're "back to the drawing board".
Luckily it was a soft seizure as I was slowing for a corner on the 2-lane at the beginning of a planned 120 mile round trip. I could feel the motor slowing down and downshifted into neutral while pulling off into a nice driveway. Also lucky that I was only 5 miles from home and I had the "retriever" set up and ready to come after me - - I had made a rear carrier for my old van with jack-up attached to load up the bike.
[Linked Image from i.postimg.cc]

Originally Posted by Andy Higham
Please tell us you don't intend to re use that rod
Andy, I'm aware of the problem of re-using any aluminum connecting rods if you don't know their history, as aluminum has no defined fatigue life and I have no way of checking them. So I've located some NOS 1971 rods which I believe are better, shot peened finish, but the seller makes no mention of left or right. Did BSA do away with the pee hole in 1971? Or is that hole really necessary?

Tom


Life's uncertain - go fast now!
Re: A65 problem with rings sealing
koncretekid #815905 07/11/20 4:36 pm
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The hole is not needed.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
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Re: A65 problem with rings sealing
Mark Z #815908 07/11/20 4:58 pm
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Originally Posted by Mark Z
Inspect the crankcase very carefully. When I trashed a lower (due to oil starvation; I won't go into that here), I didn't notice the two little partial punch-outs at 4:00 and 8:00 until someone else (who knew what to look for) pointed them out..

Where are those punch-outs and what are they for, please?


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Re: A65 problem with rings sealing
Nick H #815930 07/11/20 8:11 pm
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Originally Posted by Nick H
Originally Posted by Mark Z
Inspect the crankcase very carefully. When I trashed a lower (due to oil starvation; I won't go into that here), I didn't notice the two little partial punch-outs at 4:00 and 8:00 until someone else (who knew what to look for) pointed them out..

Where are those punch-outs and what are they for, please?

Oh, no, they're not SUPPOSED to be there; they were made by the loose connecting rod. (4:00 and 8:00 are the two closest points to the rod.) My point was that the damage to the case was not obvious at first glance. Fortunately, the camshaft had worn down to the point that the engine quit before grenading


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
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Re: A65 problem with rings sealing
koncretekid #815983 07/12/20 12:40 pm
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ARE YOU USING SYNTHETIC OIL, ARE THE RING CHROME PLATED. EITHER OF THESE THINGS WILL MAKE IT HARD FOR THE RINGS TO SEAT THEMSELVES.


I APOLOGIZE FOR THE USE OF CAPS. I CAN ONLY TYPE WITH MY RIGHT HAND SO USING THE SHIFT KEY IS BEYOND MY CAPABILITES.

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1965 BSA A65 Lightning Rocket "Clubman" (restored)
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Re: A65 problem with rings sealing
koncretekid #815989 07/12/20 2:32 pm
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Quote
Andy, I'm aware of the problem of re-using any aluminum connecting rods if you don't know their history, as aluminum has no defined fatigue life and I have no way of checking them. So I've located some NOS 1971 rods which I believe are better, shot peened finish, but the seller makes no mention of left or right. Did BSA do away with the pee hole in 1971? Or is that hole really necessary?

Not quite so
Most aluminium alloys will fail by fatigue in around 10,000,000 cycles at ambient temperature on a standard rotating fatigue test.
Note this is a material property & not a finished product property
Elevating the temperature extends this substantially because the stress cracks can self heal by movements along the slip plains.
Much like copper aluminium is FCC and as such has slip plains along all the 111 axis so has 12 active slip planes which is why it is so soft.
But con rods do have a finite life . The last figures I have seen are roughly 150,000,0000 cycles at 5,000 rpm is around 30,000 hours
And once again these are calculated figures and assume no stress raisers and a constant cycling rate and are for a modern 7000 series alloy
In real life you would not want to go above 1/2 those cycles .
Now in the UK where a ride of more than 3 hours will have you in the sea, not such a problem but in places like the USA or Australia not worth the risk .


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Re: A65 problem with rings sealing
koncretekid #815998 07/12/20 4:48 pm
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30,000 hrs with a 50% drop takes you to 15,000 hrs. 5000 rpm is near 70 mph in top for a powerful twin but lets drop that to 35 mph for lower gears and smaller engines.

15,000 hrs at 35 mph give you a life of 525,000 miles.

So USA or Aus is not an issue.

Re: A65 problem with rings sealing
koncretekid #816013 07/12/20 6:14 pm
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Someone on here, possibly Pete Russell, quoted Triumph rod life to be something like 12 hours at 7,000 rpm.

Rod life when you’re turning the crankshaft with a spanner is probably infinite.

How long do rods last when you ride around on the road, mostly between 3,000 and 5,000 rpm? Nobody knows. There will be much less stress on the rods at 5,000 rpm than at 7,000 rpm.


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Re: A65 problem with rings sealing
koncretekid #816016 07/12/20 6:34 pm
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I don’t doubt that WM has something valuable to say here, but the entire calculation is suspect.

To start, I suspect that “roughly 150,000,0000 cycles” is meant to mean 150 million? (or was the extra zero deliberate with misplaced comma?).

So 150,000,000 cycles divided by 5000 rpm (cycles per minute) = 30,000 minutes = 500 hours (only 2 hours a day for 8 months say).

Even adding the extra “0” to make it 1500 million cycles still only makes it 2 hours a day for 80 months (less than 7 years).

It doesn’t make sense to me. And that is assuming 5000rpm. Unless whizzing across Australia at high speed most of the time, as I expect one does on an M20, or racing, it simply doesn’t fit with reality.

I think this analysis is either incorrect and/or completely inappropriate to the use of conrods in our application, irrespective of the country involved.

Re: A65 problem with rings sealing
koncretekid #816017 07/12/20 6:43 pm
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Ok all those cycles, but what is a cycle?


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Re: A65 problem with rings sealing
koncretekid #816020 07/12/20 7:26 pm
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I naively assumed it meant stress cycles?
Wouldn't that be one stretch and compression cycle = 1 360 deg rotation?

Re: A65 problem with rings sealing
koncretekid #816021 07/12/20 7:31 pm
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Rotation at what speed?

Doesn’t the load on the rod vary with the square of rpm?


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Re: A65 problem with rings sealing
koncretekid #816022 07/12/20 7:40 pm
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WM said it in his post, 5000rpm.

Re: A65 problem with rings sealing
koncretekid #816034 07/12/20 9:19 pm
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Nearly all stress analysis is done with perfect specimen - - no nicks, scratches, or any kind of stress risers. Steel fatigue tests show that as long as the stresses are not more than 50% of the ultimate tensile strength, it will last indefinitely. Aluminum on the other hand will fail at some number of stress cycles. The other consideration is impact loading, which is dependent upon the intensity of the stress over the period of time to which it occurs. So a blow up, for example, might induce an extremely high stress over a very short period time, hence it breaks immediately, or not. So buying used connecting rods is always a crap shoot, not knowing what they were subjected to.

Following is an example of a failure of a frame tube on my Bonneville Land Speed BSA B50 partial streamliner after only 2 years and very few hours. Why did this frame member fail? (and upon disassembly, I found 7 cracks in the frame.) The stresses seem very low, and it is steel. But here is the proof that it failed in much fewer cycles than it should have.

[Linked Image from i.postimg.cc]

So the best thing is to buy new. I already have another A65 motor which appears to have low mileage because it is still on original pistons. Do I use the connecting rods, or buy new?

Tom

Last edited by koncretekid; 07/12/20 9:22 pm.

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Re: A65 problem with rings sealing
koncretekid #816043 07/12/20 10:13 pm
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What is the the engine year of production?
I had been using original rods of my 70 A65 for 10 years and some 24000 km without a problem and the next guy is using them now for 3 years, so I believe those late rods are very well made. And I wasn't just puttering around on this bike it had seen 70 - 80 mph quite regularly, sometimes 90 during longer trips.You are just make sure they are not oval at the big ends, that's all.

Re: A65 problem with rings sealing
koncretekid #816047 07/12/20 10:32 pm
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Hi Tom,
The fracture on the frame tube in your photo started at the end of the weld, having the bracket meeting the tube at 90 degrees concentrates the stress , If you had the bracket shaped with convex curved sides so that it meets the tube with a gradual slope the stress is spread along the tube
I believe it is better to add brackets and gussets etc to the side of the tubes rather than to the centre to avoid fractures
I had a frame down tube crack where the steering stop weld ended, along with welding the crack I added metal to the stop so it tapered gradually down to the down tube meeting it further along from the failure point. That was over 20 years ago and its been fine since

Good Luck with the A65 rebuild
John

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Re: A65 problem with rings sealing
koncretekid #816048 07/12/20 10:38 pm
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Replacing the rod is one thing, but the big question is why did it seize in the first place. Likely scenario would be oil starvation. What caused that, worn timing side bush, worn rod bearings or plugged sump trap are some possibilities. I'd also be looking for evidence of piston seizure. Simply installing a new rod and not addressing the root cause of the failure is asking for another blowup possibly with significant damage to the cases the next time. Would highly recommend putting an oil pressure gauge on it when starting it up after rebuild.

Last edited by htown; 07/13/20 12:12 am.

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Re: A65 problem with rings sealing
triton thrasher #816062 07/13/20 3:22 am
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Originally Posted by triton thrasher
Ok all those cycles, but what is a cycle?

A stress cycle for a con rod is actually every time it goes through TDC or BDC .
And there are two different stresses the rod is subjected to.
There is strait compression & tensionwhich is most pronounced at TDC & BDC and then there is a bending moment that is greatest at mid stroke and swaps from left to right depending on weather it is an up stroke or down stroke.

When determining the fatige life of a MATERIAL a rod with a cross section of 1 sq inch x 14" long is supported with 12" hanging out of a chuck and 10lbs hanging off the end of it.
The rod is polished.
The machine is rotated till the rod fails
We used 12" exposed length & 10 lbs for ease of calculations
When we went metric these changed for the same reason but nowhere that I worked had metric gear.

The other stndard test is for a rod spinning between centers with a bearing in the middle
The sample is rotated at fixed speeds then a load is applied to the bearing and is incresed till the rod fails .
The results get plotted on a graph with stress on one axis & number of revolutions on the other, called a S-N curve
Con rods are particularly difficult to do the maths for as the stresses on the rod are highly variable over each cycle.
When selectings a MATERIAL for a cyclic stress application you start by looking at the S-N curve and checking that the MATERIAL you are using is well below the curve for the life proposed service life of the item at the stresses that you have calcualted it will be subjected to.

I really did not want to hyjack the thread, if curious minds need to know more, search " S-N curves for cast (or forged ) aluminium alloys "
The important thing to know is RODS HAVE A FINITE SERVICE LIFE and any BSA on the roads today will be way past the design life of the parts that went into the engine.
Try & find an A 7/10 crank that does not have a nice big fatigue cack right around the drive side journal.


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Re: A65 problem with rings sealing
triton thrasher #816064 07/13/20 3:58 am
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Originally Posted by triton thrasher
Rotation at what speed?

Doesn’t the load on the rod vary with the square of rpm?

It is way way more complicated than that but yes stresses do vary proportional to engine speeds but from memory ( i.e. too lazy to check ) it is exponential relationship not a simple squared one.
At TDC exhaust the stress on the rod is the momentum of the piston & pin.
Similarly at BDC induction stroke.
TDC on compression stroke is of course different as is BDC power stroke.
TDC on ompression/power stroke will be an amplitude change in compressive force and BDC may either be an amplitude change or a compression/tension cycle depending upon weather the charge is still pushing the piston down or the cankshaft is dragging it down at BDC.


Perhaps it is starting to be a little more obvious now why when an engine maker found a bore/stroke ratio that worked, they tended to keep using the same ratio.
Remember when the A 50/65 rods were being designed it was either a trial & error process or days with smoking slide rules


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Re: A65 problem with rings sealing
kommando #816067 07/13/20 4:34 am
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Originally Posted by kommando
30,000 hrs with a 50% drop takes you to 15,000 hrs. 5000 rpm is near 70 mph in top for a powerful twin but lets drop that to 35 mph for lower gears and smaller engines.

15,000 hrs at 35 mph give you a life of 525,000 miles.

So USA or Aus is not an issue.

Actually I made a boo boo because there are 2 stress cycles per revolution, brain was not working.
35 mph might be an average speed in Scotland but it is standing still in OZ.
I average better than than on the WM20.
I doubt you would find many California riders under 70mph unless there was a big car with lights on the roof sitting on their rear wheel. mad
Before I moved out west & my riding drastically reduced I was putting in around 20,000 miles a year on the WM20 .

I should have know better that to throw in some very rough numbers on this list. ohno
Also remember there is idleing time , gear changing and clutch slip and a pile of things that can add lots of cycles over time.
I also did not consult S-N curves particularly as I don't know what alloy BSA actually used so everything was meant to be rough & very approximate .
The take home is whoever advised Tom that aluminium does not have a definite fatigue life was wrong, it does and it is quite short .
It just happened that on a different forum they were discussng rod materials & one of them dropped in link to a paper on a 7000 series rod which was 1.43 x 10 (7) ( can't do superscripts.).
The only alloy I had significant experience with was AS601 which was the only alloy allowed to be used in OZ for cast wheels before we signed our death warrant & joined in the world free trade agreement so now wheels can be made from putty.
AP601 has a stress life of 1,000,000 cycles @ 50% UTS and we made AS601 ingots which had to be certified ( p= primary metal S = secondary metal )
AP 601 is a slight variation of the UK BP 601 and the S variants of both have more specificed impurity tollerances because you get pick up of things like chrome when remelting old wheels.


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Re: A65 problem with rings sealing
koncretekid #816071 07/13/20 7:52 am
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Thanks. So the rod will break after so many cycles, at 50% of the load that would break it in one cycle?

Am I applying 50% of the ultimate tensile strength when I ride the bike?

Pistons are aluminium too, with cycled loads applied to them. So is the crankcase, if it comes to that. Worrying, isn’t it!


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Re: A65 problem with rings sealing
koncretekid #816074 07/13/20 8:34 am
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Now that I have some idea what to search for, this comes up.

[Linked Image from i.postimg.cc]

The flat part of the line on the right is interesting. There’s a stress level that will cause failure in 100,000,000 cycles, which isn’t really very many cycles. Then there’s a lower level of stress which causes no failure at all, no matter how many cycles.

From. https://eurocodes.jrc.ec.europa.eu/doc/WS2008/EN1999_7_Kosteas.pdf


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Re: A65 problem with rings sealing
koncretekid #816075 07/13/20 9:43 am
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"The take home is whoever advised Tom that aluminium does not have a definite fatigue life was wrong, it does and it is quite short ."

Just for the record, I do know that aluminum has a definite fatigue life. What I said was that aluminum does not have defined fatigue life but maybe I should have said that aluminum rods have an unknown remaining fatigue life. My point was that we do not know where we are on that curve when the rods have been previously used; maybe 100,000 cycles or maybe 100,000,000 cycles, or worse yet, maybe they came from a motor that had been raced in anger, or had even been thru a blow-up.

And yes, pistons, too, may be beyond their "best before date", but we usually replace them anyway because they wear out. Rods simply do not show signs of the number of cycles they've been thru. Lots of them for sale on eBay.

I hope to complete the disassembly today and I'm expecting a failed oil pump because the oil I drained from the sump (1/2 cup) was dirtier than the oil that came from the tank, although the oil in the tank would have gone thru the new oil filter I installed.

Is there a thread on this forum about installing an oil pressure port on the pre-'69 motors?

Tom


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Re: A65 problem with rings sealing
koncretekid #816080 07/13/20 11:57 am
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Hi OT, This has been an interesting thread. Sorry for the seizure. I won't comment about the rods but I do have an oil port on my 1966 race bike. I had to do it in order to feed the turbo. Just measure to make sure it is in the right place before the oprv and that it will clear the frame. A 1/8 pipe thread will do the job. Until recently I did not use a gauge because I did not want to know but I was just getting nervous and now use it for testing and will remove it when on the track.
BTW nice bike! With all the spare time I have been giving my street bikes a little long neglected love. Cheers, PRT

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