Inverted bearing question

Inverted bearing question

Postby Lcoblentz3 » Sat Sep 08, 2018 11:44 pm

My annual maintenance is coming up on my Prime. If I decide to try and rotate the ball of the inverted bearing to a new position, how is this best accomplished? As I recall, it is pretty firmly seated into the shaft.
Prime #880, Soundsmith Aida, Yamaha C-80, Yamaha M-40, Campbell/Holtz Anthology speakers
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Re: Inverted bearing question

Postby Peer Gynt » Sun Sep 09, 2018 4:41 pm

There is no reason to do this. The mating surfaces currently in contact should be lapped and compatible.

Just do the recommended lube.
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Re: Inverted bearing question

Postby Brf » Mon Sep 10, 2018 9:24 am

The only reason to rotate or replace the inverted ball bearing is due to wear. If your ball bearing has developed a flat spot, it is more than likely that your Prime's PEEK thrust plate is worn as well and should also be replaced. A properly lubricated bearing is your best defense against premature wear.
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Re: Inverted bearing question

Postby Lcoblentz3 » Tue Sep 11, 2018 12:09 am

Thank you for the replies. I don’t anticipate any flat spotting at this point. I was thinking that if there was any, a slight rotation of the ball would provide a new surface. I had thought about the PEEK disk, but wasn’t certain what to do about that. I have performed annual maintenance and lubrication, so doubt there will be a problem. Thanks again!
Prime #880, Soundsmith Aida, Yamaha C-80, Yamaha M-40, Campbell/Holtz Anthology speakers
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Re: Inverted bearing question

Postby Lcoblentz3 » Wed Oct 10, 2018 8:17 pm

Well, so much for hoping for the best. The PEEK disc is dimpled and the bearing has a rough spot on it. I have new ceramic balls on the way. Now, what do I do with the PEEK disc? Certainly doesn’t appear to be easily removable.
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Re: Inverted bearing question

Postby Brf » Thu Oct 11, 2018 10:57 am

Lcoblentz3 wrote:Well, so much for hoping for the best. The PEEK disc is dimpled and the bearing has a rough spot on it. I have new ceramic balls on the way. Now, what do I do with the PEEK disc? Certainly doesn’t appear to be easily removable.


A local machine shop will be able to remove the thrust plate, but personally, I would send it into VPI and let them perform the service.
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Re: Inverted bearing question

Postby Peer Gynt » Thu Oct 11, 2018 11:15 am

1. Does the Classic use a PEEK thrust plate?

2. And how does a hard ball wear flat against PEEK?

No Lube? Transporting TT w/o removing platter? Dirt on ball?

Just curious. My sense is that PEEK might reduce noise when in good condition, but it seems like life issues would trump the early service potential noise advantage.
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Re: Inverted bearing question

Postby Peer Gynt » Thu Oct 11, 2018 11:18 am

If the ball is really a ceramic, I guess wear debris would turn it into a mortar and pestle situation.

How often does this bearing need to be replaced? And do current models have this characteristic too?
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Re: Inverted bearing question

Postby Brf » Thu Oct 11, 2018 12:49 pm

Peer Gynt wrote:1. Does the Classic use a PEEK thrust plate?


Yes

Peer Gynt wrote:2. And how does a hard ball wear flat against PEEK?
No Lube? Transporting TT w/o removing platter? Dirt on ball?


PEEK and Stainless steel have a similar hardness, therefore, wear will manifest on both contact surfaces. The bearing has approximately 25,000 pounds per square inch of pressure, therefore, improper or inadequate lubrication, contamination, heat, etc will cause increased friction which will result in premature wear.

Peer Gynt wrote:Just curious. My sense is that PEEK might reduce noise when in good condition, but it seems like life issues would trump the early service potential noise advantage.


PEEK is easily machined, can take a high level polish, exhibits excellent wear resistance and has excellent damping properties which makes it an excellent choice for a bearing thrust plate. IMHO, due to the nature of the VPI bearing being inverted, the bearing needs more periodic cleaning and re-lubing than the specified once per year to ensure a long life expectancy.

Peer Gynt wrote:If the ball is really a ceramic, I guess wear debris would turn it into a mortar and pestle situation.


No, the current bearing ball is Stainless Steel. Some users replace the SS ball with a Silicon Nitride (Si3N4) ball which is non-porous, non-magnetic, non corrosive and much harder than SS. The non-porous nature of Si3N4 allows them to be manufactured to a higher grade than SS which allows them to operate with less lubrication and friction. Since Si3N4 is much harder than PEEK, the PEEK thrust plate will wear more than the ball

Peer Gynt wrote:How often does this bearing need to be replaced? And do current models have this characteristic too?


Most VPI tables use the same bearing material and configuration, therefore, wear should be consistent for all tables using the 20lb classic platter. Wear will also be dependent on usage and lubrication. To increase wear resistance, I've changed out the PEEK thrust pad for sapphire and the SS ball for Si3N4. My table's original bearing lasted 1.5 years, but my platter weighs around 30lbs.
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Re: Inverted bearing question

Postby Peer Gynt » Thu Oct 11, 2018 3:01 pm

Brf wrote:PEEK and Stainless steel have a similar hardness, therefore, wear will manifest on both contact surfaces. The bearing has approximately 25,000 pounds per square inch of pressure, therefore, improper or inadequate lubrication, contamination, heat, etc will cause increased friction which will result in premature wear.

PEEK is easily machined, can take a high level polish, exhibits excellent wear resistance and has excellent damping properties which makes it an excellent choice for a bearing thrust plate. IMHO, due to the nature of the VPI bearing being inverted, the bearing needs more periodic cleaning and re-lubing than the specified once per year to ensure a long life.

.... the current bearing ball is Stainless Steel. Some users replace the SS ball with a Silicon Nitride (Si3N4) ball which is non-porous, non-magnetic, non corrosive and much harder than SS. The non-porous nature of Si3N4 allows them to be manufactured to a higher grade than SS which allows them to operate with less lubrication and friction. Since Si3N4 is much harder than PEEK, the PEEK thrust plate will wear more than the ball.

Most VPI tables use the same bearing material and configuration, therefore, wear should be consistent for all tables using the 20lb classic platter. Wear will also be dependent on usage and lubrication. To increase wear resistance, I've changed out the PEEK thrust pad for sapphire and the SS ball for Si3N4. My table's original bearing lasted 1.5 years, but my platter weighs around 30lbs.


Your answers don’t lead me to your conclusions. The maintenance interval you describe would be considered unacceptable by most design engineers.

PEEK would not even be on my list of good choices for a thrust bearing. Neither would stainless steel.
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