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Help Please Kommando!
#792431 12/09/19 3:49 am
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Hi Kommando (and any other person who can help).
I was at a friends house today---he is restoring a 1967 BSA Hornet.
There is a strange sort of erosion/delamination on one of the big end bearing shells.
I have tried to show it on the attached photos---apologies for the poor quality of the photos--it was difficult to get the lighting/contrast correct (and I am not a good photographer at the best of times).
The other half shell on that con rod was totally unaffected as were both half shells on the other con rod.
I think the shells were the originals as the BSA part number was stamped onto the shell at the back.
Also on the back was another stamping which was a circle within which was a V and a P---I assume that this means that the shells were made by Vandervell Products.
Any explanation/views on this would be very welcome.
Thanks in advance for your views/information.

Attached Files Shell 1.jpgShell 2.jpgShell 3.jpgShell 4.jpg
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Re: Help Please Kommando!
Tridentman #792438 12/09/19 7:00 am
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Never seen that on a half shell. Looks like water corrosion polished by wear. Maybe galvanic...but that would be in both shells.

Some parts are high, some are pitted?

More experience than I can offer is required.


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Re: Help Please Kommando!
Tridentman #792439 12/09/19 7:02 am
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A lack of lubrication may do that. Engine reconditioners have charts on stuff like that, looking on the net the type of erosion seems present with bearings lacking oil.

Either way it's not reusable, and the crank needs going over, trap removing and cleaning, pins measuring, linish or regrind, and a later high capacity pump is worth getting. And a gauge is worth fitting to make sure its always got sufficient oil pressure.


mark
Re: Help Please Kommando!
Tridentman #792441 12/09/19 7:12 am
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.
acid corrosion , overheating and centrifical loading .
the bearings should be replaced .
.

Last edited by quinten; 12/09/19 7:13 am.
Re: Help Please Kommando!
Tridentman #792443 12/09/19 8:19 am
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Top shell so highest concentration of combustion forces is at the area where the Whitemetal lining has departed, so with its low melting point it was just the wrong bearing for a high performance engine and its fatigue strength was breached.

Quote
Bulk Loss–Bulk loss can be termed a crater, pitting, pothole or cracking depending on the size
and form of the damage. Each of these forms represents a deep feature, defined as having a
depth in excess 6 times the local minimum film thickness.


Corrosion in Whitemetal is normally seen with a black deposit in the bottom of the hole, there is no sign of that. There are signs of overload in the form of wiping at the ends of the bearing consistent with overheated Whitemetal caused by oil film being breached and direct journal to bearing contact.

[Linked Image from michellbearings.com]


Appearance

Cracks on the surface in the most heavily loaded region.
Cracking on the bearing surface extends down to and parallel to the bond line.
Detachment of the bearing material from near the bond line.
Cause

Can be as a result of vibration from the machine or rotating element
The fatigue limit of the softer bearing material has been exceeded caused by excessive dynamic loads.
Manufacturing defects causing cyclical loading, e.g. collars swash-plating and out of round journals.

Was the shell from the driveside where the oil supply is weaker than the timing side ?

Re: Help Please Kommando!
Tridentman #792462 12/09/19 4:59 pm
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Guys--thanks for the feedback so far--extremely useful.
I am trying to find out if the failed shell was drive side or timing side.
The crank journals are in very good condition--very smooth with no sign of scoring.
The failed shell had pitting and what looks like delamination.
There was nothing above the nominal original surface-- it was all pitting and/or delamination.
At first I thought that the delamination might have started at the oil hole but this is not the case.
Immediately surrounding the oil hole the top laminate is intact for about 40 thou.
One contributory factor is the oil pump assembly.
We looked at that very closely.
The DPO had put 4 washers on the crank before the oil pump worm drive.
Not sure why he had done that but the oil pump retaining stud holes in the crankcase had been Helicoiled so perhaps these had been drilled eccentrically compared with the original stud holes.
This then might have affected the mesh between the worm drive and the pump --maybe causing the pump output to be affected and then potentially affecting the shell bearing.
All hypothesis of course.
BTW--Kommando--does the V superimposed on the P in a circle denote Vandervell?
And what source would you recommend to get new shells to the Glacier spec?
Again--thanks in advance for the help.

Re: Help Please Kommando!
Tridentman #792465 12/09/19 5:24 pm
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VP in a circle is Vandervell, so they will be Whitemetal, Triumph and Norton got Trimetallic bearing from Vandervell, why BSA used Whitemetal is beyond my comprehension as even in the 70's Glacier would not recommend it for any application let alone a high performance engine. Suspect it was cost cutting either by BSA or Vandervell, when Glacier took over Vandervell we found out they had been telling some real porkies to sell their bearings.

I would ask John Healy where he sells his Velocette sourced bearings to and use who he names, but there are quite a few new companies selling these bearings, outside of SRM and one other source, whose name escapes me, they are all Al/Sn. SRM and the other source use Trimetallic bearings which are overkill for a road bike. The Aluminium Tin will suffer if the oil is dirty so fit an oil filter in the return line.

The one good thing with Whitemetal is even if it seizes the steel journal will not be touched.


Re: Help Please Kommando!
Tridentman #792480 12/09/19 9:54 pm
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I understand from my friend that the failed shell was on the drive side---so at the end of the oiling line.
Throws an extra question over the oil pump situation I think.

Re: Help Please Kommando!
Tridentman #792527 12/10/19 8:25 am
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Not really, the fix they applied because of seizures due to then unknown stray sparks from the 4CA cam was wrong, adding a hole in the top shell exactly where the load is highest to increase oil flow did nothing for the pressure and compromised the bearing. What they should have done is kept the holeless top shell and reduced the timing side journal hole to direct more oil to the driveside.

Re: Help Please Kommando!
Tridentman #792660 12/12/19 1:36 am
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I have never personally been involved in one of these BSA/4CA situations before.
Am I correct in believing that BSA suffered piston seizures and before they discovered that the real cause was stray sparks from the 4CA points that they tried to increase cooling to the piston underside by drilling the conrod with corresponding holes in the top bearing shell?
So to encourage oil flow to the drive side big end would it make sense to use bottom undrilled shells at the top on both conrods as well as a much more suitable Al/Sn shell material?
Bearing (no pun intended!) in mind that the oil flow does not just lubricate but also cools the bearing.
Just thinking aloud.
Feedback and information to date much appreciated--thank you.

Re: Help Please Kommando!
Tridentman #792682 12/12/19 6:53 am
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Yes they applied a fix to a symptom not to the root cause, not until they strobed the ignition did they then realise the issue and came up with the 6CA but left the oil hole in place. By the 80's you could model the oil flows through a crank and see the effect of hole sizes and position, too late for BSA. On a recent Norton twin rebuild U used 4 plain shells and machined a wide but shallow relief on the top of the con rod big end to direct oil coming out of the journals upwards.

Re: Help Please Kommando!
Tridentman #792683 12/12/19 7:38 am
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Like on these Commando?

[Linked Image from i.postimg.cc]

Honda used two groves on the upper thrust faces of their MotoGP rods.


mark
Re: Help Please Kommando!
Tridentman #792685 12/12/19 8:59 am
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Yes, will post a pic later, mine are shallower but wider, as the milling cutter left a sharp corner I used a small round file to add a rounded corner and then polished the groove.

[Linked Image from i.postimg.cc]

Note the shallow groove has no overlap with the bearing shell, this is narrower than the width of the con rod so you still get full support to the back of the bearing. I have also added 2 other shells to the pic, does not show well but on one I have gently polished the back to get a better contact to the con rod to help the heat get away from the bearing. Glacier Al/Sn AS15 shells have a heat treatment stage to reticulate the tin in the bearing material and the steel gets a brown staining and this reduces back contact but still within design limits, polishing gets you better contact.

Last edited by kommando; 12/12/19 11:00 am. Reason: added pic
Re: Help Please Kommando!
Tridentman #792708 12/12/19 4:30 pm
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Wonder if those grooves do much. There’s a gap all round the sides of the big end.


Amateur Loctite enthusiast.
Re: Help Please Kommando!
Tridentman #792709 12/12/19 4:43 pm
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The clearance to the edge of the journal flange for the rod is a lot smaller so then the groove will do more than it looks capable of in the pic, in effect it will wipe the oil accumulating on the sides of the journal flange and direct it upwards. I was of 2 minds as to bother but it was easy to do. This was on a Norton, other cranks will have different dimensions and clearances.

Re: Help Please Kommando!
Tridentman #792710 12/12/19 4:53 pm
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I wonder if in marginal situations the scavenge tube could be shortened slightly. This would raise the oil level slightly allowing the flywheel dip in the oil and distribute it up the bores.


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Re: Help Please Kommando!
Tridentman #792711 12/12/19 4:58 pm
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Triumph shortened the scavenge tube on the 650's in the mid 60's to add oil to the sump. On BSA Unit Singles there is a flywheel wiper cast into the crankcases to remove oil from the flywheel, will have to look and see where it then directed to, from memory its into the sump.

Re: Help Please Kommando!
Tridentman #792714 12/12/19 5:03 pm
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If Triumph were trying to solve their exhaust cam wear problem by shortening the scavenge pipe, it didn’t work.


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Re: Help Please Kommando!
Tridentman #792791 12/13/19 12:32 pm
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This is part of the ultimate BSA drive-side piston/bore oiler type rod. It's 3 piece, the cap, plus front and back shaft sections, only one side holds the L/end and piston, and a bolt holds each section to the cap, (why two bolts to each rod I guess.)

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]


mark
Re: Help Please Kommando!
Tridentman #792797 12/13/19 1:35 pm
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The B25 rod oil hole is also a crack propagation point, but at least by buying a late Daytona rod you can get one with no hole. No such option on the A65 unless you go non OEM.

Re: Help Please Kommando!
Tridentman #792805 12/13/19 3:13 pm
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That photo of the rod reminds me of an experience with one of the forerunners to the A65.
My first bike was a BSA Bantam but in 1963 an uncle offered me a 1960 BSA A7 Shooting Star as he was buying a new bike.
I bought the bike which was frighteningly fast after a Bantam.
But after a few days I decided to see "what it would do" so heading for the local downhill by pass.
At about 75 mph there was a tremendous bang and I coasted to a stop.
The drive side con rod had made a neat 3" X 3" hole in the crankcase.
That was my first (of many) engine rebuilds.
I lived in Rugby (UK) which at the time housed two big companies making steam turbine generators.
BTH (later GEC) employed 12,000 people and English Electric employed 10,000.
The father of a friend was the superintendent of the machine shop at BTH (in West Midlands terminology "The BTH").
He had also raced a 1938 BSA Empire Star in the years immediately after the war--so knew bikes.
He taught me how the strip and rebuild a motorcycle engine.
He took the crankcase half into work, left it in the big trike bath for a couple of days and then got one of their top welders to weld in a piece to fill the hole.
It was totally oil tight.
Kept that bike for many years but then sold it for an A10 with chair when the family came along.
Sorry to bore you!

Re: Help Please Kommando!
Tridentman #792812 12/13/19 4:14 pm
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Didn't bore me. Wish I had known that dude when my Thunderbolt threw its rod. Made a 2x4 hole though. In 1970. Was told it was unrepairable.


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Re: Help Please Kommando!
kommando #792856 12/13/19 10:30 pm
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Originally Posted by kommando
The B25 rod oil hole is also a crack propagation point, but at least by buying a late Daytona rod you can get one with no hole. No such option on the A65 unless you go non OEM.



Just use 2 timing side rods.
My 72 A65 engine came out of the factory with that arrangement. (when i rebuilt it i left it as is)
Also the late steel capped rods didn't have the oil holes.
The oil holes were not only on the a65 they were a carry-over from a10's etc. as i remember.

Re: Help Please Kommando!
Tridentman #793099 12/16/19 6:00 pm
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these shells have failed due to overload, so retard ignition ( a little bit) or run higher rpm's at a lower load. I've seen a lot of shells with this damage in diesel engines running at high loads. also my MG LMII suffered the same damage, to much throttle at low revs.
regards A


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