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LP12 Spindle

Discussion in 'd.i.y.' started by Vinny, Aug 10, 2017.

  1. Vinny

    Vinny pfm Member

    If you take a look at the tip of the spindle at even low mag', you can see that something like 3mm at the core of the spindle is different to the bulk of the metal.
    I sort of assumed that the spindle was (probably induction) hardened along the length and at the thrust bearing end, and then ground to size and profile.

    But - I have just tried polishing the bearing tip, and it appears to be mighty soft - just a touch with green compound and then blue compound mop has it to a mirror finish. Literally it took me longer to change the polishing mops than it did to polish the bearing. Logically, it looks like the spindle is just hardened along the length/OD.

    Should anyone be worried that this might be damage rather than polishing, green and blue compounds are removing truly minute amounts of metal. Having said that, the OD of the spindle looks absolutely fine and if it wasn't, I am not about to try polishing one outside a lathe ........... which I do not have at home.
     
  2. Bob B.

    Bob B. pfm Member

    Not a good idea. Usually what you will see on the end of the spindle is a small black mark where the oil has hardened due to friction/ heat. Leave well alone. The thrust pad and spindle will have lapped themselves together. You may well change the radius of the spindle causing accelerated wear of the two components. I remember speaking to Martin Dalgleish about this years ago.
     
  3. Vinny

    Vinny pfm Member

    There was nothing on the end of the spindle, just circular "scuff marks". As the spindle bearing "point" is soft, the whole idea must be that it wears very quickly (against the very hard thrust pad) to form a mating contact - not a new idea, far from it, even before the 1970's.

    Polishing the spindle tip to remove the "scuff marks" will do not much apart from removing whatever produced the marks, if it is still there, so long as you are careful to clean things. As I implied - polishing with compound removes microns of metal, not even thou (apologies for mixed units there).

    It does rather make a mockery of the insistence that sub-platters be changed when fitting a Cirkus though, given that apart from neglect producing OD wear of the spindle, any wear will be on the "point"......
     
  4. Bob B.

    Bob B. pfm Member

    What is the phrase I am looking for. Oh yes. 'Be it on your own head'

    Bob.
     
  5. Vinny

    Vinny pfm Member

    Sounds, what is the word that I am looking for? Oh yes, "blissful" right now.

    Understanding some basic engineering and material science helps :)

    Where else but within the insanities of hifi would anyone recommend running a scored bearing on degraded lubricant crud? BMW, Merc', RR et al obviously have something to learn.
     
  6. Bob B.

    Bob B. pfm Member

    Vinny.
    I was not recommending running a scored bearing anywhere. And I certainly wasn't suggesting to run it in degraded lubricant crud. If the bearing is obviously scored, possible causes are an ingress of dirt in the oil. Or the spindle has been in use for 40 years ? My point is if the bearing is marked that much you need a new assembly. If you change the contour of the tip, and I have seen this done at the factory by a very light abrasive. The tolerances are within microns by the way. Then even cleaning out and adding fresh oil it will never run as quietly as designed. You can also cause precession which will destroy the thrust pad.
     
  7. sq225917

    sq225917 situation engineer

    Last I heard merc didn't recommend you polished worn engine parts by hand.
     
  8. Vinny

    Vinny pfm Member

    Precession cannot affect the thrust bearing and that is what I am talking about. So, this "..........small black mark where the oil has hardened due to friction/ heat" isn't degraded lubricant crud? So what is it precisely?
    I will also state, yet again, that green and blue polishing compound will remove barely microns of material only.
    If you take a look at the tip of an LP12 spindle, the taper that has been machined into the hardened steel is very poorly finished indeed - there is no need for it to be anything else, it does/touches nothing. The entire soft steel centre is completely polished, and I would expect that to have been done with compound - it is fantastically easy and quick to do. Although it is polished, only the extreme tip does anything anyway.

    How many point thrust bearings are there in a car engine?

    I will say again - only within the lunacy of hifi would this sort of debate reign.
     
  9. Mynamemynaim

    Mynamemynaim pfm Member

    Vinny
    Have to agree with you
    No point at all supplying a new inner platter with a cirkus other than to perpetuate the mith that these are hi precision parts and have to be matched together...and also to make a few quid out of the whole cirkus upgrade kit ...with springs and belts and bushes all ( obviously) vital to fit at the same time
    It's a bit of silver steel rod running in a bush...let's not get too excited about it..
     
  10. Bob B.

    Bob B. pfm Member

     
  11. Bob B.

    Bob B. pfm Member

    Trust me. It is not done by hand.
     
  12. sq225917

    sq225917 situation engineer

    Maybe I'm out of touch but every LP12 bearing spindle i've seen, pre and post cirkus is one piece of one material. The tip is mirror polished.
     
  13. Bob B.

    Bob B. pfm Member

    Yep. That is correct. And I have seen a few as well. And the lathe idea is even more ludicrous.
     
  14. chiily

    chiily PFM Special Builder

    Really? It gets that hot? I'm coming from a position of complete ignorance, but is there enough force and energy to burn the oil hard? Wouldn't the residue effect the bearing's performance?
     
  15. chiily

    chiily PFM Special Builder

    Cos I'm curious, how is it done?
     
  16. Bob B.

    Bob B. pfm Member

    As I have said. Years ago I had numerous discussions with Martin on the bearing. Just imagine all that mass rotating on a relatively small single point. He did tell me the temperatures involved but I can't be accurate enough. I am sure they were in the 100s of degrees though. That is why there were developments in the oils used leading up to the black oil. This was at the time the liners in the bearing housing were also changed to PEEK. It is also why I like the idea of the Tranquillity as I am sure it will reduce the forces dramatically. If I am wrong on this blame Linns chief mechanical designer at the time.
     
  17. chiily

    chiily PFM Special Builder

    With those temps I would expect oils that could cope with the temps of engine turbo not to burn, harden or leave deposits. I thought Linn oil was based on a fully synthetic engine oil with added slippy stuff?

    I would think there would be a great deal of pressure at the top but vanishingly small friction...
     
  18. You might want to read a few posts on the linn forum regarding the changes linn made a couple of years ago to the production process of the Cirkus bearing.
    If you have crud you have bearing tube contamination most likely a old deck thats not been looked after.:rolleyes:
     
  19. You obviously have know idea what you are talking about.:rolleyes:
     
  20. Gaius

    Gaius Trade: Stiletto by Tangerine

    ^^^ The bearing and inner platter should be regarded as a set, a couple, they work in tandem together, to replace one without the other is ill advised. Not a myth.
     

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