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LP12 Bearing Change

V

Vinny

pfm Member
Has anyone changed only the bearing to a Cirkus, rather than used the kit (which includes a sub-platter)? Noticeable change in how the deck performs?

Long shot - has anyone heard a LP12 with a Cirkus bearing, with an old sub-platter and with a new? How do they compare?

I have read comments that the Cirkus kits have "matched" bearings and sub-platter, implying something like an optimal fit, one inside the other. Which, to be honest, sounds unlikely, although the logistics of doing that might help explain the near £500 for the kit. Certainly most dealers are convinced that bearing and sub-platter shaft are matched.

I haven't trawled the www to find the article, but what read at the time that I read it, as an apparently authoritative comment, was that the sub in the Cirkus kit is actually a different design (slightly heavier/different geometry). In that article, matched bearing and shaft were not mentioned.
 
New cirkus bearings and inner platters are more accurately machined. The major part of the improvement comes from changing the bearing housing, this is a different design and is a more rigid housing.

I would recommend changing both the housing and the inner platter at the same time due to wear patterns etc. There are still some who prefer the old non cirkus bearing but I find the new one distinctly more accurate. Not to say you can't put together a pleasant sounding older player but if you're looking for better performance then the cirkus bearing is a decent improvement.
 
Machining small, high aspect ratio, possibly blind, bores in non-metals, to very high accuracy to match the accuracy of a machined metal mating part..................... do I believe this?

(Probably centre-less) Grinding the metal part to high accuracy - not a major problem.

Do I believe that a metal shaft moving at slow speed in a lubricated non-metal sleeve bearing, with minimal opportunity for contamination, wears significantly, even over 1000's of hours' use, especially if you understand how effective lubricants work?

Do I believe that most of it is good, even very good, Linn sales spiel?

Can I believe that something about the Cirkus kit is a worthwhile upgrade to an LP12 - certainly.
 
I can't remember the manufacturing process for the inner platter/spindle, but I recall there were a lot of processes involved. Each one contributed to both the overall dimensional accuracy, surface finishing/hardening etc and it is actually an extremely well made component. Compared to the overall price of the new decks and components, it's good value.

In terms of wear, I've examined some of them under high magnification and of course the thrust pad and spindle tip do wear but it is at quite a low rate which tends to suggest the original manufacturing process was well conceived.
 
Manufacture of the sub-platter will require several processes for sure, all very mundane ones in engineering terms.

I have never been a planner for a metal-bashing shop, and not cut up a sub-platter, but the spindle will probably be induction hardened as slightly over-size and then ground to size. It will probably be shrunk/freeze-fitted to a reamed hole in the the rough-machined platter and then the platter finish-machined to the spindle, using the spindle as the datum.
Probably the cheapest way to produce blanks for the platter itself would be casting.
The whole thing might then be balanced kinetically - that would be easy to determine - just look for balancing marks (odd and isolated areas of grinding/machining), on the underside of the platter.
 
The platter is cast from mazak alloy. That's no secret. And although the Linn is nicely made, it is also subject to a bullshit factor even higher than £2-3k 'worth' of toroidal transformer in an otherwise empty box that NAIMees lust after.

I also seem to recall being told that the Cirkus is bolted to the subchassis at several million ft/lb by former Glaswegian Shipyard Riveters using a 20 yard long high tensile bar and an FBH.
So there's no chance of a DIY fix.

..I don't believe that either. :D
 
Can't see the point of putting a new bearing to and old spindle/inner platter though. Suppose it depends on if the inner is worn and by how much.
 
Mullardman said:
I also seem to recall being told that the Cirkus is bolted to the subchassis at several million ft/lb by former Glaswegian Shipyard Riveters using a 20 yard long high tensile bar and an FBH.
So there's no chance of a DIY fix.

..I don't believe that either. :D
Click to expand...

Me neither. BS B B. even a more modest version makes no sense.
 
Vinny said:
Has anyone changed only the bearing to a Cirkus, rather than used the kit (which includes a sub-platter)? Noticeable change in how the deck performs?

Long shot - has anyone heard a LP12 with a Cirkus bearing, with an old sub-platter and with a new? How do they compare?

I have read comments that the Cirkus kits have "matched" bearings and sub-platter, implying something like an optimal fit, one inside the other. Which, to be honest, sounds unlikely, although the logistics of doing that might help explain the near £500 for the kit. Certainly most dealers are convinced that bearing and sub-platter shaft are matched.

I haven't trawled the www to find the article, but what read at the time that I read it, as an apparently authoritative comment, was that the sub in the Cirkus kit is actually a different design (slightly heavier/different geometry). In that article, matched bearing and shaft were not mentioned.
Click to expand...

I don't think the bearing housing (which bolts to the subchassis and contains the sleeve and thrust plate) is manufactured in matched sets with the inner platter/spindle. In fact, Linn does sell both replacements (as well as the subchassis) separately as individual pieces. The "Cirkus" subchassis is slightly different from prior versions, as the point where the bearing attaches with three bolts is twice the thickness of the earlier subchassis. The Cirkus bearing housing itself has a slightly higher lip to compensate for this added thickness in the subchassis.

Apparently, both the thicker subchassis mounting area and the more massive Cirkus bearing housing are the key contributors to the improved performance of the Cirkus bearing. The inner platter/spindle is identical in spec to prior versions. Most dealers insist on replacing all three components when doing a Cirkus conversion, but over on the Linn forum, there is a tribologist (who seems knowledgeable about such things) who asserts that as long as the inner platter/spindle has not been subject to abuse/abnormal wear, there is no need to replace it. Many others shouted him down, but his statements on the subject make sense to me.

As an aside, while these Linn upgrades certainly are not cheap, they don't seem out of the realm of ordinary for high-end audio gear. For example, a new LP12 inner platter/spindle costs approx. US $400; VPI charges US $1,000 for a new 'Classic' aluminum platter and I believe that even the third-party "Groovetracer" subplatter for Rega 'tables is US $275 now. Avid and SOTA upgrades also cost a pretty penny.
 
Would you put new disc pads on scoured worn brake discs? Surely same would apply to the bearing and spindle if badly worn or spotted. Got to give a better result surely. The bearing being a fundamental part of a turntable.
 
I think that proves my point in post 8, and shows that you have not read posts 3 and 10.

The two things are so very different, you are not comparing apples with oranges, more like comparing apples with herrings, although I don’t see anyone here suggesting that a spotted spindle be re-used.

FYI, the answers to my question in post 3 are – no, no and yes.

As implied by VG, and the “tribologist”, and me, the chances of there being wear are close to minute, certainly in terms of the OD of the spindle, less so with the thrust pad and spindle tip, which, unlike the bore and OD, will take substantial loads, albeit, if the lubricant is correctly chosen and the bearing not allowed to run dry, they should not actually touch (hence my reference to knowing how lubricants work) .
 
Poppy cock, I am an engineer, worked in engineering since a lad, metal on metal will wear regardless of lubricant, granted a turntable is not like say a car engine, when I changed to a circus bearing there was noticeable wear, obviously letting the bearing run dry will accelerate wear noticeably. Putting a new bearing with a worn spindle is madness.
 
What is?
Machining non-metals to anything like the tolerances achievable in metals is a non-starter.
Loads on the OD of the spindle are tiny.
Correctly chosen lubricants form a film, bonded to the two (or more) mating parts, that will withstand tons of pressure per square mm. Metal on metal, properly lubricated, does not happen.
Wear of a hard part with a soft part does not happen (spindle within a Linn bearing), unless there is contamination with hard contaminant, or over a massively long time - what happens then is that the hard contaminant or the hard wear product of the hard part, embeds in the soft part, which then acts as an abrasive. In the case of a bearing running at 33 or 45 rpm, there is VERY unlikely to be any significant wear products generated in any normal lifetime.

You obviously do not know much about lubricants, and a lot besides, engineer or not.............

So far we have a vote of 4 to 1
 
Vinny said:
Correctly chosen lubricants form a film, bonded to the two (or more) mating parts, that will withstand tons of pressure per square mm. Metal on metal, properly lubricated, does not happen.
Click to expand...
That is an easy assertion to prove or disprove. Just test for electrical continuity between the spindle and the bearing. My thinking is that even thick grease will not separate a point contact. But then, what do I know? I'm neither an engineer nor materials scientist.

Vinny said:
Wear of a hard part with a soft part does not happen (spindle within a Linn bearing), unless there is contamination with hard contaminant, or over a massively long time - what happens then is that the hard contaminant or the hard wear product of the hard part, embeds in the soft part, which then acts as an abrasive. In the case of a bearing running at 33 or 45 rpm, there is VERY unlikely to be any significant wear products generated in any normal lifetime.
Click to expand...
Do we know as fact that the thrust pad of the LP12 bearing is made of a softer metal than the spindle? If so, then I'm inclined to agree with you.
 
I am completely unconvinced by the conductivity argument - it only takes a mono-layer.........

People only ever consider the OD of the spindle - crazy, but true.

In the case of an LP12, the spindle is steel, the bearing liner is not, and that is what most of the discussion here revolves around (pardon the pun again).
 
If you fit all three items, new, at once, then they will work to the manufacturers spec. In fact they are guaranteed to do so and the manufacturer will replace them if not.

Much as I disagree with Linn's pricing policy (ie if it sounds like a £1000 improvement then that's what we will charge even if the R&D costs have been recovered and it only costs a tenner to make) I can't see the point in skimping and having to take the deck to bits several times to get it to work properly and having no warranty on the single item fitted.

The subchassis is different to properly match the new type bearing housing so you won't get the full benefit without it. Mine must be over 20 years old by now and many 1000's of hours so I guess I've had my money's worth (though it was probably well under £200 then)
 
Vinny said:
I am completely unconvinced by the conductivity argument - it only takes a mono-layer.........

People only ever consider the OD of the spindle - crazy, but true.

In the case of an LP12, the spindle is steel, the bearing liner is not, and that is what most of the discussion here revolves around (pardon the pun again).
Click to expand...
Who's fixated by the OD? I'm not.

My assertion is simple. If the thrust bearing is metal and is in contact with its metal housing, then electrical continuity will prove or disprove metal-to-metal contact.

What are you asserting about this "mono-layer". That oil conducts electricity if the film is thin enough, or something else?
 
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