Maximum load on jewel bearings

Discussion in 'Clock Construction' started by dandydude, Feb 1, 2018.

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  1. dandydude

    dandydude Registered User

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    Is there something like a maximum load on jewel bearings? I intend using 1.5mm ID olive hole jewels for the escapement pivots. Would an excessive weight (of crutch rod) damage the jewel bearing?
     
  2. Phil Burman

    Phil Burman Registered User

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    Sapphire has a compressive strength more than 10 times that of steel and of course is extremely hard wearing so I would think not, providing there is no shock loading.

    Do you not mean the pivots for the pallet, if so is this not standard usage?

    Phil
     
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  3. Allan Wolff

    Allan Wolff Moderator
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    I doubt the weight of a crutch rod would be too much. Jewels are used for mainspring barrel arbor bearings in pocket watches which would be much more pressure than anything on a clock escapement.
     
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  4. dandydude

    dandydude Registered User

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    Dear Phil,
    I use an asymmetric crutch and its a little heavy to keep it moving with the pendulum. I was a little concerned with the weight. I intend using olive hole ruby bearings. Does ruby have strength similar to sapphire? (I am totally clueless about this)
     
  5. dandydude

    dandydude Registered User

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    Dear Allan,

    Are you aware of how the assembly of the bearing done in clocks?

    Thanks
    Dandydude
     
  6. gmorse

    gmorse Registered User
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    Hi dandydude,

    They're both the same material, aluminium oxide, or 'alumina'. They just contain slightly different trace elements which determine the colours.

    Regards,

    Graham
     
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  7. jhe.1973

    jhe.1973 Registered User
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    Hi dandydude,

    I agree with Allan that a crutch is unlikely to put enough pressure on a ruby/sapphire bearing to cause any problem.

    This statement may be technically true but in practice it might be misleading.

    Here is a view of some of the jewels that I spun set into their mountings before parting them off from the bar stock while still in the lathe:

    DSC_2204a.JPG

    Using the burnisher in the foreground, this is a process that has to be practiced to develop the required 'touch'. Not enough pressure and the jewel remains loose. Too much pressure and the jewel is crushed.

    Because of the extreme hardness of ruby/sapphire the material is also brittle and the wall thickness of the jewels that we are working with makes them somewhat fragile.
     
  8. John MacArthur

    John MacArthur Registered User
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    Jewels are plenty "strong" for pallet and crutch pivot bearings - they've been used for those for hundreds of years. As Jim says, they can be fragile if you apply point force, or otherwise bash them. Here are pics of my pallet cock jewels in place.
    Johnny
    12DSCN0777sm.jpg 13DSCN0780sm.jpg 14DSCN0773sm.jpg
     
  9. Phil Burman

    Phil Burman Registered User

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    #9 Phil Burman, Feb 3, 2018
    Last edited: Feb 3, 2018
    Hi Jim, it's a bit of an apples and oranges comparison. I think that the applied force is not the same when you press a jewelled bearing into a hole versus the force applied by the weight of the pallet and crutch. When you press a jewel bearing into a hole you will generate tensile as well as compressive forces due to the drag on the side wall of the bearing, which may cause the trailing end to break away. Diamonds are used in hardness testers by pressing them into the material being tested, included hardened steels (copressive force only). In use with a pivot a jewel bearing is only subjected to a relatively small compressive force.
     
  10. jhe.1973

    jhe.1973 Registered User
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    Hi Phil,

    I feel that the question that was originally asked has been answered for dandydude.

    My use of the word misleading was not intended to suggest that you were misleading anyone. I was concerned that others coming to this thread might get the impression that a person could treat a ruby or sapphire jewel the same as an equivalent steel item.

    When mounting jewels, I do not press them into their holes before spin setting so there is no chance of a tension force being generated.

    So as not to hijack this thread, I decided that I would post details in my own thread that discusses my own regulator movements.

    https://mb.nawcc.org/threads/owner-built-precision-regulator.74057/page-4
     
  11. dandydude

    dandydude Registered User

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    #11 dandydude, Mar 15, 2018
    Last edited: Mar 15, 2018
    Dear John,

    Thanks for the images. I wanted to understand how this is done. Is the jewel glued?
    i have attached a sketch to help you understand my question. I have roughly sketched your jewel assembly.
    Why doesn't the jewel come out of the side B?

    Thanks
    Dandy

    IMG20180316005317.jpg
     
  12. John MacArthur

    John MacArthur Registered User
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    Dandy -- It's done like this: The jewel is a snug fit into the chaton (same as bezel), and the small groove around it is burnished over the edge of it with a smooth round-pointed burnisher. Look at the first pic in the #8 post above, and you'll see it
    Jewel setting.jpg Johnny
     
  13. dandydude

    dandydude Registered User

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    Dear John,

    Any particular reason for using straight hole jewel? I intend using olive hole jewel for escape wheel. Doesnt olive hole have less friction?
    I also read that straight holes are stronger, so maybe i would use them for the palets like you have... Is it because of better strength than you have used straight hole bearings?

    Regards
    Dandy
     
  14. John MacArthur

    John MacArthur Registered User
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    Dandy -- It's because that's the way they come out when I drill and polish them. I'm not sure I could control the shape and size of an olive hole jewel. I make these myself from raw ruby boules, and each one is slightly different. I'll be posting pictures of this sequence during the construction of my next clock, which I will be starting soon. Stay tuned.....
    Johnny
     
  15. John MacArthur

    John MacArthur Registered User
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    Dandy, I also suspect that my jewels do have a minute amount of olive shape - the way I polish them they would almost have to, even if it was largely imperceptible.
    Johnny
     
  16. dandydude

    dandydude Registered User

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    Dear John,

    Any particular reason for using straight hole jewel? I intend using olive hole jewel for escape wheel. Doesnt olive hole have less friction?
    I also read that straight holes are stronger, so maybe i would use them for the palets like you have... Is it because of better strength than you have used straight hole bearings?

    Regards
    Dandy
    Oh wow!!! I thought you buy stock ruby bearings ... I didn't know you could drill rubies !!! Thats really amazing
     
  17. dandydude

    dandydude Registered User

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    HI Johnny,

    What size are the ruby holes? I am currently experimenting with 1.5mm ID (for the escapements).
    I have tried miniature ball bearings (which gradually failed), PTFE from Igus and now i am upgrading to rubies...
    I clearly know by experience how ball bearings can fail in escapements now
     
  18. John MacArthur

    John MacArthur Registered User
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    Dandy -- My jewels are different sizes - mostly in the 1.25 mm range, to fit the pivots. The front escape jewel is quite a bit larger, over 2 mm I think.
    Johnny
     
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  19. Phil Burman

    Phil Burman Registered User

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    #19 Phil Burman, Mar 18, 2018
    Last edited: Mar 18, 2018
    Hi Dandy, I'm interested in what way they fail? I have used them on the escape wheel arbor but not the pallet arbor and after a year it is still running fine.

    Phil

    PS Erwin Sattler use them extensively so there must be a solution
     
  20. tok-tokkie

    tok-tokkie Registered User

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    Certainly the Sattler self assemble clock uses ball bearings everywhere with the exception of the pallet arbor. That runs in jewels & Sattler supplies oil for them.
     
  21. dandydude

    dandydude Registered User

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    Dear Phil,

    I have used 2mm ID ball races (Japanese made NMB)... at least 3 sets. The ones used for the palets failed much sooner than the ones of the escape wheel. I even tried using fully ceramic ones.
    They just get a bit rough after a bit of use. Currently my palets are running on PTFE plain dry bearings 1.5mm ID. Escape wheels on ball races (2mm ID). Its been working for a month. I wouldn't be surprised if they fail anytime soon. Thats the pattern i have been observing.

    Regards
    Dandydude
     
  22. dandydude

    dandydude Registered User

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    Hi tok tokkie,

    I had read someplace that bearings are not meant to be run in a jerky fashion. I mean a non-continuous (if there's such a word) circular motion. I don't know if thats the reason for the failure. This is why Iam really trying jewels for both arbors.
    I am also going to try to use endstone in both the arbors (all four pivots)... I have never attempted it... which is why i have so many questions.

    Regards
    Dandy
     
  23. dandydude

    dandydude Registered User

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    Hi Phil,

    I also remember i met this really famous clockmaker one time. He said they remove ball races and clean the balls off any lubricant and put them back. They run it dry. I haven't attempted that. Maybe, thats a way of solving the problem.
    There's one other thing... i use shielded races. That could again be a problem...

    Regards
    Dandydude
     
  24. dandydude

    dandydude Registered User

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    Hello John,

    Is this what they call 'the rubbing method' of setting rubies?

    Regards
    Dandydude
     
  25. John MacArthur

    John MacArthur Registered User
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    Hi Dandy -- I would think so.
    Johnny
     
  26. Jim DuBois

    Jim DuBois Registered User
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    you might want to try Rex Swensen's site, he has done a lot of research on using ball bearings in clocks https://drive.google.com/drive/folders/0B6If277wwdHNeGlYdlkteHJUWXM a great paper on his work, there is more, several folks are having very good success with absolutely dry running ceramic bearings
     
  27. dandydude

    dandydude Registered User

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    Dear Jim,

    Thanks for the link. Quite enlightening.

    Thanks
    Dandydude
     

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