Tables That Feature Bearing Friction

Hello Dertonarm,
>The "air-pulse" drive (no pulse would exclude a problem) has some considerable problems while looking close to a theoretical ideal first. It not only will require considerably (really serious...) periphery, but indeed a "assist"-motor to bring the (high mass) platter to requested speed first and than de-coupling.<

Weren't you asking about "all out",no compromise, no commercial consideration approaches? Did I not explain some of the caveats? Yes, the periphery would be expensive, but maybe not as expensive as it appears(remember, this is not about a commercially viable project).
The Onkyo PX-100M eddy current drive turntable does feature an idler drive just to bring it up to speed within half a revolution, then the eddy current drive takes over(and it has a break too). It can be done...
Platter speed needs to be monitored, which in turn can govern the force of the air(or any other driving) "pulse". It will have a VERY slow recovery time, but(that is where my chronometer analogy comes in) the disturbing influence of the drive system could be minimized.

To assess which principle is superior, we'd have to build two(or more) otherwise identical turntables that can be driven by more than one means. I have done this several times many years ago, Chris Brady has done this more recently, so his assesment holds merit, even if some may not agree with all of his peripheral design choices.

I suggest opening another thread to discuss that there is VASTLY more to building an excellent turntable then the drive principle, even though nothing else matters if the record doesn't spin at (as close to)constant speed to begin with.

Dertonarm, I didn't ask you any questions, I just showed that your approach is just as far from or as close to being perfect as some other approaches, at least from a conceptual/theoretical point of view. But that part of the discussion was doomed from the start... and yes, it's not neccessary to repeat yourself yet again.

Nevertheless, have an enjoyable and relaxing Easter weekend!

Frank

Dear dertonarm: Good to hear it, happy holidays.

regards and enjoy the music.
Raul.

I believe some models of Jeep/Chrysler used hydraulic cooling fan motors powered by the P/S pump due to the fact they are quieter.

I would speculate that the main reason for using a hydraulic motor is more to do with the high-temperature environment in which the fan motor must operate, especially if used on the back side of the radiator. At these temperatures, copper conductors get pretty lossy, and when running a 12V motor (drawing 20-30 amps), they start to really add up . . . in windings, commutators, brush leads, wiring, relay contacts, etc. And then you've got make up for those losses in power generation . . . and when a cooling fan is most important is when the vehicle isn't moving, hence engine speeds are low, and the alternator suffers from poor effeciency. In this application . . . hydraulic makes lots of sense.

But for a turntable, both air-vane and fluid-vane motors are far from vibration-free and cogless (go to an auto-body shop and listen to their air-vane-powered tools) . . . so there will be similar challanges as electric magnetic motors. Maybe an expanding-chamber screw-type armature fed by high-pressure hydraulic fluid? Then the problem is that you've got NO speed feedback, not even the fixed-frequency rotating magnetic field in an electric motor, and there's been disapproval voiced for a feedback speed control system.

Believe me, I'm not completely poo-poo'ing the idea, but rather will be extremely impressed if these challanges (and all of the others that I've not thought of) are able to be solved. And of course I'll want to read all about it, so do keep us posted.

Dear friends: IMHO the subject on speed accuracy/stability in TTs are almost addressed and solve by almost all the TT designers and manufacturers. We can take examples like Technics, Denon, Rockport, Walker, Kenwood, Basis, Pionner, SME, Monaco, Sota, Raven, etc, etc, where we find very good numbers on the subject that goes as low as 0.001% ( speed subject ) and figures on SN of 92db or WF of 0.015%.

So one way or the other ( different TT design approaches ) the spedd accuracy and speed stability are already achieved by commercial TTs.

Where I think there are a non-definitive solutions are ( like other people point out ) in self TT isolation and neutral build materials on each commercial TT design out there.

As Dertonarm poin out, the TT must does not have any " sound "/signature by it self that can add some kind of distortions/colorations that affect the cartridge quality sound reproduction, the TT must be " dead neutral ".

If we read any TT subject thread in this forum or in any other one we are reading things like this: the bass in this TT has a better bass that the other TT, it is warmer that the other ones, it is more alive that the others, the high frequencies sounds better, everything sounds lower in record noise, etc, etc, etc.
There is always a TT sound, so these TT are faraway to be neutral ( that is our target like customers. We are full of distortions/colorations to continue to accepting more. )

IMHO two main factors that contribute to those each commercial design TT " sounds/signature " are due to a poor isolation and what were the choose on build materials ( including the arm board ).
I think that is here where the commercial TT designers/builders have the greatest " room " to improve and achieve " neutrality ": for to have a TT running with speed accuracy and stability with out adding/removing almost nothing.

I think that the challenge is a big one but with a lot of rewards when solve for everyone.
The build material issue is critical, you can take how important is when you try different TT mats in your own TT: you have different sound quality level as different are each one mat and its build material.

This build material challenge is enormous if we take in count that exist hundred/thousands of build materials that can be use in the TT manufacture and million of blend/combination materials that could be use it, so not an easy task to have the " answer " but IMHO if we want to have better TTs ( any kind of TT. ) then we have to ask for to the commercial TT builders. I think that the " ball " is in their hands and I hope we can see in the near future ( and can buy ) that " neutral " TTs in favor of the analog music-sound home reproduction.

I know it can do it because I already experienced and " solve " something similar with our tonearm design.

Regards and enjoy the music.
Raul.

Other subject that I would like that the commercial TT designers/builders could address and solve is to have a record " perfect center " mechanism.
This out-off center record hole is a " cancer " in the analog quality performance ( due to an extremely poor build quality of the record industry. ), we need a solution. I think on the TT builders because I don't think that the records industry can " hear " our needs.

There are other " desirable " characteristics that will be welcome in a TT design but for now I think these ones are enough.

Regards and enjoy the music.
Raul.