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Spindle oil

What oil are people using to lubricate their spindle bearing?
scottht
herman
2,282 posts
 
Sean, while I respect your opinion on most matters, after looking into this a little more deeply, just about everything you said turns out to be wrong.

Your diamond cutting glass analogy makes no sense. The stylus isn't "slicing" through the vinyl, it rides along the surface following the modulations already cut into it, and just because the stylus is harder than the vinyl doesn't mean there isn't any friction. It is well documented that the stylus temperature can easily reach in excess of 100 degrees celsius. Where do you think that heat comes from? I'm guessing friction, and the drag caused by that friction must be dealt with.

You are also confused about the differences in viscous damping and friction. "Friction is the enemy of any well designed product that requires motion. After all, friction generates more heat, causes more wear, requires more force and is nothing more than lost energy." Viscous damping is not causing the bearing to wear away.

Your idea about instantaneous speed correction is completely incorrect. The motor doesn't and can't correct for every tiny variation in speed that would be caused by the stylus and there isn't a turntable in the world that uses the motor controller to do this.

It won't work for the same reason that motor driven, servo controlled linear tracking tonearms won't work. With the tonearm you are constantly trying to correct for something that has already happened so the arm is always out of postion. Same thing with the system you advocate. Even if you could build a controller fast enough to keep up, in order for it to compensate for the variations in stylus drag it would have to be able to predict when they will occur, and that's not going to happen.

So how can you overcome these variations in drag caused by the stylus when you can't predict when they will occur? One way is to introduce another source of drag into the system (such as viscous damping) that is far greater than the stylus drag, and while the motor is working to overcome this induced steady state drag it will in effect ignore the tiny variations caused by the stylus. To use an electronic term you may be familiar with, they are swamped out.

This is not poor engineering. It is a brilliant, simple, elegant solution to the problem.
shasta
155 posts
 
100 deg C/212F on a stylus tip?? Yow, can you find a thermocouple small enough to fit on a cantilever? Can you get a handheld infrared gun with a small enough beam pattern? Can you measure this with an infrared thermography device??

Back to lubes; the more I think about it, I wonder how many square inches of contact area are on the tip of the spindle bearing and it's contact plate. Mighty small... Seems to me like this is going to have to be a regular maintenance item - lubing the spindle bearing.
sean
6,231 posts
 
Herman: If the stylus wasn't "scraping" its' way through the vinyl troughs, it wouldn't be generating heat at the tip. That heat is wasted energy due to unnecessary friction. It's pretty simple when you break it down.

Amplitude modulations in the vinyl surface should simply produce vertical displacement of the cantilever. This vertical displacement is the result of energy transfer, which produces voltage from the cartridge and the accompanying music from your phono stage. There is some horizontal deflection also as there are various amplitude passages that occur in one channel that don't occur simultaneously in the other channel. This is what gives us output in the individual right / left channels.

As such, the "friction" between the stylus and the vinyl groove comes from the fact that the stylus is NOT centered in the mass majority of grooves. As a result, the cantilever is constantly being twisted rather than being pushed up and down on loud to quiet passages or side to side during left to right / right to left signal changes. This is how records get "worn out" due to the "cutting action" of the diamond "dragging" across the sides of the grooves, not through the center of the grooves.

If you can align the stylus in a fashion that it stays relatively centered in the grooves, you'll find that surface noise is drastically reduced and stylus' will last a LONG time. Then again, you can't ever hope to achieve this type of performance from a pivoted arm due to the very nature of the design.

As to your comments about servo's, they can be made quite fast and quite good. Compared to a pivoted arm that can only be correct in two places ( at best ) along the entire side of an LP, i'll take a well designed servo controlled linear tracker any day of the week. I would rather have something that was "very close" most of the time as compared to something that was "rarely correct" at best due to the law of averages.

As far as introducing more drag to compensate for other drag, that sounds like complimentary colourations to me. Neither is "right", but you end up with something that is bearable. It's not necessarily "good", but it works. Like i said, you can throw money at a design, but that doesn't make it good. It might be better than others of similar design, but that doesn't make it good. It just makes it slightly better than "poor" because it isn't quite as obvious due to the blatant errors being covered up. Sean
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herman
2,282 posts
 
Sean, your seeming inability to even hint at the possibility that you might be wrong makes it impossible to discuss this in a logical manner. I'm leaving the topic after this.

First you claimed that the stylus was "slicing" through the vinyl like a diamond cutter through glass. When I point out you are wrong because it is "riding along the surface" you change to "scraping," which is in effect exactly the same thing I just said, and make a condescending remark like I don't get it. You should go into politics.

The heat isn't generated simply because the stylus isn't centered. It comes from the stylus tracking the modulations. Heavily modulated grooves produce more heat than lightly modulated ones no matter how well centered the stylus is. Centering has nothing to do with it.

This is a well proven fact, not an opinion. You are wrong. No matter how many times you put forth the centering argument, you will still be wrong.

Also, there isn't a manufacturer in the world that uses a servo motor controller to compensate for instantaneous stylus drag. Why? It won't work. No matter how fast, servos will always be reacting to something that happened in the past. Again, not an opinion. It is a fact that you are unwilling to acknowledge.

All servo controlled linear arms to date have been inferior to other designs for the same reasons. This is also a fact. I do believe given the advances in servo motors since the attempts in the early 80's, and the speed of todays microprocessors, that it should be possible to build one that will work well. Perhaps combining the tracking capabilities of the newer laser tonearms as the feedback to the controller along with high speed processors might work. The laser tracker could be positioned ahead of the stylus, in effect predicting where it needs to be instead of reacting to it being where it shouldn't be. Feel free to use and develop that idea.
eldartford
4,262 posts
 
Herman...There are servos, and there are servos. The faults you cite can be avoided. The microprocessor controlled linear tracking arm on my Sony PS X-800 TT maintains tracking angle within 0.05 degree across the entire disc, even when the groove spacing is variable. No pivoting arm can do this.

By the way, like all linear tracking arms, many other problems such as skating force are eliminated entirely.

But this was supposed to be about spindle oil. Damping, viscous or otherwise, can stabilize a servo that tends to oscillate. Consider the shocks on your car...without them you would bounce a lot. Speed regulation in the presence of variable friction is the job of the platter inertia, at least at a frequency higher than what can be followed by the speed control servo of a direct drive table. If there is no speed control servo, there will be some slowing down.
However, the stylus drag variation is so small, and turntable motors so powerful, relative to the drag they overcome, that I doubt any noticable slowdown actually occurs.
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