Vintage DD turntables. Are we living dangerously?

Lew, re:
"I am surprised that one good oil would be noticeably superior to another good oil in a tt turning at most 45rpm", studying fluid mechanics would indicate that the toughest lubrication applications are slow speed as opposed to high speed where lubrication "wedge" can be easily generated by the fast moving parts.
That is why slow turning gears use high viscosity lubricants with extreme pressure additives to reduce wear and minute "welding" of the gear parts.
This is basic lubrication.
Viscosity is part of the equation. Another part is film strength and anti friction agents to support moving parts at high pressure.
The lubrication of a tiny ball bearing moving against a disc at slow speed is actually a tough application. It's like stilettos: The pressure of the bearing is fairly high (P=F/A) where A (area) is very small and F (force) is not insignificant and the slow 33 or 45 RPM is not sufficient to easily build a fluid film between the ball bearing tip and the disc.
A good lubricant can help since reducing friction in this point will benefit in less noise which transfers from the spindle to the platter.
Just my thoughts and personal experience.
Stop times are dictated by viscous shear (internal friction of the fluid layers) and asperity contact at the tip of the bearing. The higher the lubricant's film strength the less the asperity contact would be a factor and stop times will be dictated by viscous shear. That is why adding weight didn't really change our results with RP.

Nice Post Doron.....😘

Doron,

+1
I have read your post a couple of times. Made me think!
Thanks.

Halcro,

When your Acromat arrives, you will notice that it has square edges. Looking at the inside of the base of the raised edge on the platter, you will see that there is a slight radius. Because the Acromat's diameter is a tight fit when placed in the lip of the Victor's platter,this radius to square corner bothered me so I did slightly chamfer (bevel), the underside edge of the Acromat so that I wasn't worried about interference (the square corner riding a radius). I might have been overreacting to a possible non-existent problem but had I not done something, I would have thought about this for ever. Anyway, the Acromat sands very easy so take my comments only as something to consider.
Hope you like what it brings to the party! (grin)

Regards,

Doron, You obviously know your stuff when it comes to lubricants. Thank you for the information, some of which I once knew but had forgotten. Your last remark is the focus of my question: Do you mean to say that there is some fundamental difference in the way Royal Purple (RP) motor oils are formulated as compared to Redline motor oils which would account for the reported observation that RP 5W30 sounded better than Redline 20W, other than viscosity? My point was that the difference in sonics observed the the OP might have been due entirely to the difference in viscosity between the two oils. Do you think yes, or no? It was after that when I made my ignorant remark about slow motor speed.

You must realize that if you say RP oils are superior to Redline for use in a typical TT, then at least several of us are going to run out and buy RP motor oil. I've got the Redline 20W in my Kenwood L07D. By the way, I'm not interested that much in "stop times". I don't know what it means for a tt platter. A very low viscosity lubricant (I can imagine) might allow for long stop times (at first) while also doing damage to the bearing in the process.