Jingle Bell Liners

A_HRD

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VOC Member
I've just been reading the latest MPH (808, May 2016) and note with interest the letter from Edward Renyard of New South Wales, who is complaining about the current manufacture of Vincent cylinder liners. He is absolutely right that they are now far too loose in the crankcase mouth, several thous loose in fact. Why is this now considered the norm? Who made the change and for what engineering reason? Or is it just a "production easement" so that the manufacturers don't have to machine another high precision surface?

Like Edward, I simply can't fathom why the original factory tight fit has recently been dispensed with. Surely, having a big gap in the crankcase mouth would mean that:
1. There will no longer be a proper pressure feed of oil for the piston skirt; most of the oil would flow twixt case and the outside of the liner into the crankcase!
2. This in itself would cause a significant temperature gradient from the front to the back of the lower liner surface - causing undue stresses.
3. Much of the lower part of the liner would be unsupported meaning that it could distort in a variety of ways possibly leading to the beginnings of a seizure.
4. Worse still, with engine vibrations ever present, there could be some resonant frequencies produced which could shatter the lower part of the liner.
5. The liner, being one of the hottest parts of the engine, will no longer have any benefit from the huge heat-sink which is the crankcase.

So before I go the trouble of making my own properly-fitted liners, someone please tell me, and Edward, just what are the advantages of these new Jingle Bell Liners. We are listening.......

Peter B
Bristol, UK
 

vibrac

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VOC Member
Before listing the advantages perhaps it would benifit to identify the sources there are more than one I am sure
 

chankly bore

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Non-VOC Member
Before listing the advantages perhaps it would benifit to identify the sources there are more than one I am sure
The local Spares Scheme here in Victoria has a volume of correspondence, including observations from P.E.I., which drew attention to this fault over 30 years ago. We are still awaiting a reply.
 

1660bob

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VOC Member
I`m not convinced it is an issue at all, in fact I read somewhere that it is a BAD idea, as even a mildly tight fit is bound to distort the lower half of the liner a little by flexing it, mucking up the skirt /liner clearence-and surely the tight fit would ease as the alloy cases heat up and expand in comparison to the steel liner anyway, dispensing with all but very tight fits (those that distort the liner in the first place). I agree a CLOSE fit is best for oil transfer, but my liners, done by Maughans (extra thick wall/V. tight in muff) are positively loose in the cases, so some if not most of the cylinder oil supply will ooze out at the bottom of the skirt for sure. Result of this? The bike goes like stink and does not smoke or burn oil, I have seen no ill effect whatsoever in 900 odd miles since re-build.
Most engines, (nearly all?) have no sort of "fit" of the liner into the cases and run fine with no dedicated oil feed to the thrust side at all. The amount of big end oil flinging up into the underside of the piston, and entering the oil control ring via the piston drillings in the bottom of the ring channel,lubes the cylinder sufficiently in my view.
I think any cylinder oil oozing between liner/casing will make its way down to the bottom of the liner and be whipped away by the spinning flywheels and immediately flung off up into the bottoms of the cylinders with all the other oil passing out of the big ends. It will be flung to the wrong side of the cylinder (non thrust) of course but i think there will be enough flying around to wet everything sufficiently.
My `55 AJS 500 had a cylinder oil feed, with drilled barrell and an annular channel in the top of the crankcase mouth, supplied direct from the pump. On the `56 model it was deleted by the factory, and i now run a later `56 on non drilled barrell. I blanked off the cylinder supply closer to the pump, as it now had nowhere to go, reasoning that now more would go to the main/ big end, and from there be flung up into the barrell anyway, that was 20 years ago, no issues yet........ Bob C.
 

vibrac

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VOC Member
Well we dont know where (or when!) Mr Renyard got his liners but we do know Maughns are "loose in case" and I have never worried about the fit .When I discovered that Ben could get more points in the championship by coming second on a 500 rather than first on a 600 I had a top hat liner made to fit the 600 crankcase mouth to use a 500 barrel and that is just a smooth light push fit and I never botherd with cylinder oil supply either- but it does make for extra support:p
 
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