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Old 1st February 2006, 01:30 PM   #1
dod996 is offline dod996  United States
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Default Tonearm pivots

How do the pivots and bearings work on Rega and Origin tonearms? Also what are they made of?

Thanks

Tony
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Old 1st February 2006, 01:37 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

they are high grade ball races allegedly. Stainless steel I presume,
though miniature ball races can use tungsten carbide balls similar
to the balls used in the end of Biro's.

/sreten.
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Old 1st February 2006, 01:48 PM   #3
dod996 is offline dod996  United States
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Default Ball Race

Is "precision ball races" refering to a ball type thrust bearing or a standard ball bearing?

Tony
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Old 1st February 2006, 03:35 PM   #4
sreten is offline sreten  United Kingdom
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I'd expect them to be fairly standard ball bearing for sideways loads,
I wouldn't expect them to be thrust bearings under significant load,
though you would think a combination of the two would be best.

/sreten.
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Old 2nd February 2006, 03:31 PM   #5
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Hi, the bearings in the RB250 and 300 are actually very *low* grade, a fairly cheap, unbranded shielded. flanged radial miniature ball race of ABEC 3 spec. If that sounds a bit mean, they are actually the right choice for the job.

You can get very high-spec direct replacements (eg SKF abec 5 or 7) for just a few pounds from suppliers like RS components, but there's no point in replacing them with anything better using the standard mounting method because the way that the bearings are mounted and set up needs the loose tolerance of ABEC 3. To use a finer spec means using a different mounting method. Even then, I found that ABEC5 was a better for this application than ABEC7 which are very closely toleranced, need very precise alignment and still need maybe 50 hours bench running in to be free enough for this kind of use. The standards were set for using the bearings at their rated loads rather than just waggling around with a few gramms of tonearm. From memory, I think the Rega bearings are rated at something like 70kg at 50,000rpm!

I've been doing bearing replacements on Regas:
http://www.william-reed.net/audio/
and I've recently developed a method of making bearing carriers that can be user set-up and adjusted to *very* fine limits, like well under 0.0001", without using ultra-high-precision machining. This is letting me use very high-precision ceramic bearings on composite carbon fibre shafts. Haven't finished it yet, but as it's taking so long it had better work! That bit's not on the site yet, but I'll try to get photos up soon.

regards, Jeff
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Old 2nd February 2006, 03:51 PM   #6
dod996 is offline dod996  United States
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Default Tonearm pivot

Thanks Jeff that is exactly the info I was looking for. I'm considering building or upgrading a tonearm for a new project.
By the way your machine work looks excellent.

Tony
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Old 2nd February 2006, 03:52 PM   #7
dod996 is offline dod996  United States
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Default Tonearm

Jeff have you ever tried jewel bearings?

Tony
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Old 2nd February 2006, 05:08 PM   #8
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Hi, I had started out ball races because i have been modifying Rega arms and that's what they used. I have just started to use small (10mm OD) ceramic ball bearings that are probably too expensive for most manufacturers at about 20 Euro a pair, but OK for a one-off, especially when you look at the price of a bit of tonearm wire!

I'm not sure about jewell bearings, they are tiny and very light which could be a major advantage but my own view has been that the bearing should be capable of transmitting energy from the arm to the mounting rather than isolating it. This might be a factor in the difference between the sound of pivoted and unipivot arms. I do know there are a lot of different kinds of jewell bearings but I don't know where to buy them in the UK.

If it will be useful, I can look up the RS part number for a bearing that is a straight swop for the standard RB250 ones - I just don't have it to hand at the moment.

regards, Jeff
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Old 4th February 2006, 01:53 AM   #9
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Jeff,

I would be very interested in the part number!

By the way, I see on your website that you polished the paint off the rega arms. How did you do this??

Regards,
Matthias.
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Old 6th February 2006, 12:39 PM   #10
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Hi, I'll look up the part number tonight as I saved the packets they came in.

The paint comes off the Rega arm very easily with ordinary paint stripper, I used "Nitromors" brand. This is much quicker than sanding or scraping it off.

Personally, I wouldn't recommend removing the paint unless you intend to either re-paint or laquer the arm tube at the end of your modifications or if you are adding some kind of internal resonance control like cross bulkheads or the foam filling that Michel use. This is because the bare arm tube is very resonant and the rather thick coat of paint actually helps to damp it. A bare, unmodified armtube rings like a bell!

regards, jeff
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