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07-20-2010 Post does not mapped to Knowledge Tree
Stitch


Behind The Sun
Posts 222
Joined on 01-15-2009

Post #: 1
Post ID: 14042
Reply to: 14042
Idler Drive - Rumbling Into The Future?
fiogf49gjkf0d
When I read the forums I think, there is a coming back from Idler wheels. You know, these units which have the maximum contact for distortion (idler direct to the bearing into the platter). The Radio stations replaced them as fast as possible when DD's were available.
I listened some time ago to a Garrard 501 and I had no idea about these kind of turntables. It was the most horrible performance for me ever, a disaster with Orchestras. The owner loved it, so much rhythm.Now I read something from an OMA company which makes a lot of advertisements, same for a vibrating piece of wood on strings which is called a Tonearm.On the other side I rarely read something from users which have something serious, a table which was clever made, let's say a Basis for example. There is some serious Brain behind which made some interesting solutions (suspension for example, or a low pressure vacuum system..).Did I miss something?


Kind Regards
Stitch
07-20-2010 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 2
Post ID: 14043
Reply to: 14042
The DD, Idler or Belt from 50.000 feet.
fiogf49gjkf0d

Stitch,

the only thing that you are missing is paying attention to the OMA advertisements and truing to recognize behind it any rational beside a pimp yearling own merchandise (in fact it is not his merchandises). I told many times before that brain, ears, knowledge and listening awareness behind that Pennsylvania dirt is sub-acceptable and I would like do not be induced to comment on it again and again. Ironically, there is a manufacture in your country who dealt with the OMA dirt before and who after read my site sent me email with surprise how much I know the OMA under-hood.  He even proposed to upload in the site some of his anecdotes about OMA that in his view would make everyone se that his Pennsylvania dirt is not “nothing” but something that deserve to be squashed and destroyed. I refuse as I do not feel that truth about OMA need any “evidence”.  So, please let keep the OMA out of scope of any further attention. The only thing that would make me happy if a lighting strike the dirt, kill him, burn his house with all crap the he is trying to sell and preferably any single person who deal with him. Is it too much to ask? Jonathan Weiss of Oswaldsmill Audio is an audio equivalent of neo-cons in US politics – he uses the identical methods of capitalizing on fears and stimulation of parochial thinking.

About the Idler Drive turntables. Yes, you never see any serious thinking about it. In the best cases you see the people swear own devotion to idler TT but in all cases I was able to recognize a flows in logic and their desire to advance this or that method of transforms momentum from motor to platter. Can we presume that if DD, Idler or belt TT – all of them made with identical respect to own topology then will produce identically result?  I presume that it might be so, but I am not certain.

I have seen a few years back an article in Russian magazine where the author was trying to prove that Idler roll is the most preferable transmission as it forms a mechanical filter of lower order. Here is the link (in Russian):

http://www.shabad.ru/aml/About%20rollers%20and%20springs.htm

Saying it, I have to note that the author of the article is well knows falsifier who have a reputation to write fraudulent articles and to conceive counterfeit to ideas into public to fulfill specific marketing campaigns. Still, the conclusions in the articles are not wrong – an Idler roll does have some transfer advantages … but for very light platters. With increase of the platter’s mass I think any theoretical advantages get equalized or completely reversed. Where is the truth? It is hard to say. It is VERY difficult methodologically honest to compare TT.  There is so many valuables involved!

The Idler Drive looks like coming back. So, a few years back it was the microprocessor controlled DD. Before it was a belt or a combination of belts…. I think it is a purely marketing circus invented by idiots of Framer- Weiss level. When SME made 3012 then if few years the pips sold very expensive bronze bearings on this arm. There were a number of highly scientific and serious articles about advantage of bronze over steel. Then the same was reversed to plastic bearings. Then it went to second round and the advantage of steel was rehabilitated. Over the years each 5-6 years the fashion on the preferable 3012 bearing was rotating…  I think the same is with Idler drives. A few companies would like to make them and they make the “market makers” to spread new set of “believes”. A dozen of so on-line cronies join the chorus and the “new” revolutionary topology is born. Isn’t it how the industry proper itself? Have you read TAS blog and alike?

What is important to understand however is that revoltingly-unserious level of industry treating the different technological aspect (Idler Drive for instance) is not necessary an indication that the given technological aspect is wrong. We just do not have any answers as the audio industry never care to ask any complex or deep questions.

Rgs, Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-21-2010 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 439
Joined on 01-07-2006

Post #: 3
Post ID: 14050
Reply to: 14043
Platter mass
fiogf49gjkf0d
 Romy the Cat wrote:

Still, the conclusions in the articles are not wrong – an Idler roll does have some transfer advantages … but for very light platters. With increase of the platter’s mass I think any theoretical advantages get equalized or completely reversed.



Romy, would you elaborate on that more? Looking at his formulas it looks like higher mass gives
lower resonance point, which is I guess desireable?

Cheers,
nset



Cheers,
Jarek
07-21-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 4
Post ID: 14052
Reply to: 14050
In my view Mass matters.
fiogf49gjkf0d

 N-set wrote:
Romy, would you elaborate on that more? Looking at his formulas it looks like higher mass gives lower resonance point, which is I guess desireable?

Yes, the resonance point go lover but also the ratio of contribution”from platter” vs. “from motor” get changed with increase the platter. If to embrace the filter analogy of the author above then the idler is closer to first order filer and belt is to a second order filter. The second filter has a cap and coil and spins phase much more than a fist order filter. However, if we begin to beef up coil (platter) for instance then we can have a second order filter to operate within Bessel Q and the phase shift will be identical to first order filter.

In more practical terms – with substantial (very substantial) increase of mass makes the system is only platter scenic and the platter’s moment of inertia get dominated. Will, the idler be benefited with increase of platter mass? I do not know. Have you seen any heavy TT with idler? I do not. My presumption is that with increase of platter mass, let say arbitrary that it will happens at 30-50 pounds, the difference between belt and idler does not exist anymore. Or let me to put in this way: the sonic consequences of suspending of the 50 pounds overtake any minute advantages or disadvantages that idler or belt drive will have.

I do feel that substantially heavy platter will make a user do not care how momentum went to this platter. Take a 100 pounds platter (like American Sound TT) and I doubt that you will distinct what kind drive it had.

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-21-2010 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,074
Joined on 10-12-2006

Post #: 5
Post ID: 14054
Reply to: 14052
The Driver and the Driven: Is Bigger Aways Better?
fiogf49gjkf0d

I have owned and played with a couple of "classic" idler-driven TTs, but I was very young at the time, and incapable of pushing the design then, even if I'd wanted to.  As it happened, I abandoned the idler TTs for a belt-driven Rek-O-Kut "broadcast" model (!), for reasons of sonics.  Even though the stock Rek-O-Kut was no better in some areas (sonic break-through and "microphonic" self-noise), it was audibly better in terms of speed control (pitch, rhythm and dynamics).

With the almost hysterical "revival" of interest in the idler-driven designs, perhaps someone has finally figured out how to eliminate the sense that the music is being "dictated" by the motor.  I would not post this at AA (for the same reasons I would not kick a hornets' nest...), but I also got to this point with my Technics DDs, and I see the problem as not only related sonically, but similarly sourced, namely too great a reliance on the motor, itself.

We've beaten this one up pretty good in the past, but I have never gotten a satisfying response to the question, how does one physically isolate the (idler) motor, itself, from the platter, since the heavier the platter, the more powerful and "connected" the idler has to be, because of its operating principle?  I can see (and hear...) how a +/- pliable belt from a "barely big-enough" motor can provide "enough" drive to a massive platter to average out nicely, once the platter is up to speed.  But I still do not understand how the "Big Motor" approach makes things better than worse in the end, based on my own experience.

Paul S

07-21-2010 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 439
Joined on 01-07-2006

Post #: 6
Post ID: 14056
Reply to: 14054
A middle path
fiogf49gjkf0d
My EMT930 has a moderate platter. 3kg I guess.
I guess the only isolation of the idler/motor vs. platter is the
idler's rubber (and to small extent motor's rubber suspension too).
It's quality is crucial and it has to be changed from time to time.
EMT prohibits touching the idler with bare hands,
not to leave even smallest traces of grease.
Not being an advertiser of any topology, may I point that broadcasters got rid
of idlers for DDs most probably  for the convenience
of an instantenous start. EMT930 starts from zero in 1s, EMT950 in 0.2s...



Cheers,
Jarek
07-21-2010 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,074
Joined on 10-12-2006

Post #: 7
Post ID: 14057
Reply to: 14056
DJs
fiogf49gjkf0d
N-set, certainly no appologies are necessary from any quarter, since what "works", works, but I am not encouraged that the idler interface is so critical, since I regard as key to the massive-ish belt drive system's "success" its built-in slop factors.  It has been my amused observation that the more one relies on any "critical" or "proprietary" component(s), the more likely one is to encounter real world problems with playback. 

As for why DJs chose/choose DD, sonics is not the main reason, rather it is reliable "acceptable" playback to serve as a backdrop while they bellow their own names over the airwaves.

Best regards,
Paul S
07-22-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 8
Post ID: 14063
Reply to: 14056
Idler transition and distance of bearing anchoring.
fiogf49gjkf0d
I did not think about it unit how, unit N-set mention his EMT930. I am not a big fan of EMT tabbies but I have a huge respect to EMT927 . What I very much like in EMT927, among other things, is the very long platter bearing.  The Idler roll runs across the platter, not across the end of platter like on the cheap TT but at ¾- very smart. Then is the most important – the EMT927 has a LONG bearing shaft and the point of Idler force and verticals suspension force are well separated in space. I think it shall be a very good as it further improves the whole picture.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-22-2010 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 9
Post ID: 14065
Reply to: 14063
EMT 948 & 950
fiogf49gjkf0d
Romy, besides via the radio, did you ever have the opportunity to hear either the 948 or 950 in a domestic installation?
07-22-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 10
Post ID: 14067
Reply to: 14065
…and the different EMT turntables.
fiogf49gjkf0d
 guy sergeant wrote:
Romy, besides via the radio, did you ever have the opportunity to hear either the 948 or 950 in a domestic installation?

I do not think that “via radio” would be very sane way to judge TT, would it be?  I do not remember the EMT numbers. I did hear a few EMT in various settings; still I do not think that in those cases I was comfortable to recognize sound that is specifically derivative of the TT. My familiarity with EMT mostly derives from a friend of mine who owners a few EMTs. With his TT I play in attendance for some time. The 927 impressed a lot, primary by the fact that it had longer bearing rod.  I know that he had also a few other EMT, there was EMT 930 among them, were there specifically 948 or 950 I do not know/remember. I do remember that any smaller EMT had much shorter bearing cylinder. I feel that extended length of bearing cylinder is very-very cool thing as it minimize the micro-beating of the platter in case of side momentum is applied. I am not well familiar with EMT in order to make comparative judgment between sounds of their models.

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-22-2010 Post does not mapped to Knowledge Tree
Stitch


Behind The Sun
Posts 222
Joined on 01-15-2009

Post #: 11
Post ID: 14068
Reply to: 14056
Let's deny Physic and Science
fiogf49gjkf0d
 N-set wrote:
 EMT930 starts from zero in 1s, EMT950 in 0.2s...
That was the only goal for it. These units were made for only 1 reason, to start as fast as possible (Radio Stations used vinyl and when the talk stopped, the music had to start). Next was the reliability, it had to run 23h per day, all day long. Btw. same with EMT carts, they were never made to last a longer period, they started fast and died fast. They were thrown away, the Stations had a boatload from them, no one made a retip, adjustments, VTA, VTF...
Nothing from this has anything in common with sound quality. It is indeed nothing special. EMT's are collected from those who think, what was used in Broadcast has to be superior. Even 40 years later. To deny Physics is common in the audiophile community. God, please, send brain.
The Radio signal was limited anyway, for what should they need lower Bass or high frequencies? The EMT's (and similar ones) made a job, not more. Full range was never a goal.And they can't.
The Broadcast Stations were the first who replaced them as fast as possible with DD's. But even that had nothing to do with sound quality. Same is today with Harddisc. The only real serous equipment from Broadcast Stations was their technical sending equipment from Rhode & Schwarz (Tuner, Transmission....)
Like Romy wrote, everything in "High End" comes back, today this, tomorrow that...


Kind Regards
Stitch
07-22-2010 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 439
Joined on 01-07-2006

Post #: 12
Post ID: 14081
Reply to: 14068
EMT
fiogf49gjkf0d
I'm a physicist actually :-) I'm denying modern physics every day. Not to deny the string theory one must be a complete idiot: 1+2+3+4+....=-1/12!!!
I've made a stupid mistake and decomposed my EMT for cleaning and now, in big pains
and with a help of some German EMT angel, I'm slowly bringing it back to the shape. The good point
about all that thoroughly anal process is that I "learn" the machine. I must say I still have
no experience with the sound as I decomposed the deck before I started listening...
But just learning the mechanics of the deck, I'd not take your criticism Stich too seriously.
Have you had some more-than-momentary experience with 930 or 927?
There are some obvious limitations (anal joke "3 phase"power supply of the motor with drifting caps),
but there are some things very-very well thought over,
like the long shaft Romy mentioned.
I don't know if 927 or my neighbour has longer than me, I'm fine with what I have.
And reliability under harsh conditions I'd rather take as a good indication.
As for the carts, they do seem to last some years, then EMT offers a rebuilt (and vdH offers a rettip if you wish)
and you can use it again and again. The weak point is the rubber suspension which hardens.
TSD15 is I think has been around for 40 or so years in continous production.
VTA, VTF....
All that adjustments are usually incorporated to make the arm sort of universal, which at the end is impossible.
EMT is a complete system, so they've optimised the geometry for their own stuff.

I'm not a fan of any topology. Like Paul says, the topology is just a mean not an end in itself.
EMT930 was probably the best I could afford with my budget at the moment so I decided to try.
If I hate it, will sell it to some stupid collector for $$$$$. You are continously mentioning introduction of DD's instead of
idlers by broadcasters. Why? As I've try to point out the reason for that could have been
not because of limitations of idlers but because of more convenienet operation (ultra fast start, no need to
change idlers, search options, etc).







Cheers,
Jarek
07-23-2010 Post does not mapped to Knowledge Tree
Stitch


Behind The Sun
Posts 222
Joined on 01-15-2009

Post #: 13
Post ID: 14086
Reply to: 14081
The Volkwagen "Beetle" is a technical wonder
fiogf49gjkf0d
Even today. For some. When those Believers are Audiophiles.I know a lot of intelligent people who think, that their LP12 is easily among the top performers of today. Or Transrotor, Clearaudio, Schroder Arm or whatever. When they don't understand what they hear, everything is great.  Or when they don't know what is possible. The Audiophile world is full of them.
I don't care what one loves or not.
Some designs are simply better than others, based on technical reasons and knowledge. 
Idler Drive is not among that. It never was. It is a result from an era where no other solutions were available. And solidity is not a part of good sound which more modern and better designed units can offer.
After all, the desperate Audiophile can - and will - still say "... but I like it."
That is normally the final comment for everything.



Kind Regards
Stitch
07-23-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 14
Post ID: 14087
Reply to: 14086
To EMT or not EMT - who cares?
fiogf49gjkf0d

It is interesting that any conversation about a specific technology in TT instantly get converted into conversation about brands.  We were talking about idler roles and then we get embraced into thinking of Garrard vs. EMT. Perhaps it needs to be this way even though we all understand that quality of sound (positive or negative) from Garrard, Thorens, EMT, Lenco or from whoever is NOT only the result of idler drive.

I personally have no problems with idler drive if it make properly. What does it mean properly? It means that idler connection does not exhibit any negative impact to the performance of entire TT. I would not argue what is better: idler, belt, different versions of DD or some idiotically-exotic drive methods (like magnetic or jet). The whole point is that if a given drive was made good-enough in respect to own topology then the comparative predominance of individual drives shall be absolutely identical.

I think the only subject that might be under desiccation is not which drive is better but in what TT the given drive is implemented to its optimum best. I think in term of idler drive the EMT tables went further than anybody else. But again, it was not best idler drives but it was best environment for idler drives. The EMT 927 has a huge 16” platter and idler roll is grabbing in the middle. Only the gyroscopic effect of the platter shall make this configuration way beyond what flimsy Garrards or Thorens would do.

Would it mean that EMT tables have some kind of ultimate idler drives? Absolutely not. In fact there is no such a thing as ultimate solution for TT as all TT are made to fit very narrow and very specific requirements.  In the past EMT were made for very limited and irrelevant today need of broadcast industry. Stitch is right – they did not even dream to get of TT the sound that we are trying to push out of it today. If the EMT tables perform today good then it is an accident – nothing more or less. It is like Germans, Italians of Brits made some tube in end of 30s and they have the objective that today would make us to laugh.  How the hell they know that in 70 years their tubes will be considered as some kind of reference in the sonic condition that did not even exist at that time?

I disagree with Stitch view that science today has anything to do with sound of TT. The problem is that we do not have in today’s world serious sciences who work on design and assessment of turntables.  Sure, we have a number of talented people who with best objective come to audio and try to use what they have to make an interesting TT. The problem is that if they succeed then it take unavoidable 2 years of industry involvement that will convert any talented and wiling individual into a another industry deadbeat. As the result all contemporary TTs are not made not to serve the sonic demands but to satisfy the demands of marketing campaign that were redeveloped to publicize worthless BS around the TT. 

Anyhow, the side-subject of this topic is a very sad fact that we do not a true knowledge how our top of the line TTs sound in reality and how this or that technology work in them. If you take 20 top-flying of TT today then do we really know how they sound? I do not think so. Those turntables temporary owned by a small group of industry pimps who customary have very bad sound in their listening rooms and who pay mortgages and put kids though colleges by talking about turntables. Also, those turntables owned by a small army of the industry followers – the Robb Reports junkies – who suck in the publicity waves and buy in what they were told. They might be fine people but in term of independent sane audio judgment then are no different than the shit that flow in sewers in accordance with the rules of simplistic gravity. As, the result 95% of top flying TT in the hands of the people who are not able to give evaluation to the technologies  that were used to make those turntables.

A good case to point.  My EMT guy that I told above has also a tope of the line Micro. Over the year we have a number of desiccations: what TT has better bass 927 or Micro. Here is an interesting twist: we did this thinking not to convince anybody else but for ourselves and over the years (!!!) he using both of the TTs realized that he can’t answer this question. Interesting is that I do not agree with my friend’s playback and particularly with bass that he is getting but I very much understand how he feel about hit TT comparing. If criteria of interest is not the superficial BS that need to be delivered to somebody with objective “to convince” but own deep interest on the subject then it is very difficult to find satisfactory answers.  We do not know how our “best” TT performer as we do not have a framework where a nature interest in TT Sound will be exposed to public without any agenda. With TT we are in managed environment where opinions are passed as tools of same not the properly of actual performance.

Therefore, looking at all of it I do not believe in any conversations about TT. I think a TT much be comfortable for a person to use - nothing more.  Everything else is included into the person private thinking about his TT, his sound and how to convert from one into another….

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-31-2010 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 439
Joined on 01-07-2006

Post #: 15
Post ID: 14149
Reply to: 14087
One idler is bad? Three idlers anyone?
fiogf49gjkf0d
Leaving all that unnecessary bitchings and emotions aside
 (btw, talking about TT resembles talking abut foundations
of quantum mechanics, emotions and flames appear within seconds!),
I've been,purely theoretically, thinking if employing 3 idlers or even 4 to drive the platter into that magical
floating rotation would be beneficial.
Just like it is attempted in some belt drive designs.
Garrad 1001, EMT 5027,...Stick out tongue?



Cheers,
Jarek
07-31-2010 Post does not mapped to Knowledge Tree
Stitch


Behind The Sun
Posts 222
Joined on 01-15-2009

Post #: 16
Post ID: 14150
Reply to: 14149
No way out
fiogf49gjkf0d
Great idea. :-)


Kind Regards
Stitch
07-31-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 17
Post ID: 14151
Reply to: 14149
I never agreed with it.
fiogf49gjkf0d

 N-set wrote:
Leaving all that unnecessary bitchings and emotions aside
 (btw, talking about TT resembles talking abut foundations
of quantum mechanics, emotions and flames appear within seconds!),
I've been,purely theoretically, thinking if employing 3 idlers or even 4 to drive the platter into that magical
floating rotation would be beneficial.
Just like it is attempted in some belt drive designs.
Garrad 1001, EMT 5027,...?
N-set,

I do not where you see emotions and flames. I think you are confusing emotions and flames with a well-mature and very healthy hate. Anyhow, any online conversations are subordinate of the Godwin's Law. I prefer do not use the "reductio ad Hitlerum" as a final argument but to open my argument with this. :-)

Anyhow, regarding you idea of multiple idlers rolls. I do not now like it as much as I do not like the idea of multiple direct driver or multiple belts. I have expressed my arguments on the very same subject somehow in the site before, unfortunately the site is becoming large and I do not remember where. I do feel that the idea of the multiple drives is use explicitly for building up more expensive products – there is absolutely no theoretical justification for this with which I would  know and agree.  Suing it I am under presumption that there are no other then theoretical justifications of the multiple drive’s advantages or disadvantages. I do not feel that anyone anywhere conducted any methodologically-properly practical tests to assess the tangible results.

Rgs, Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-31-2010 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 439
Joined on 01-07-2006

Post #: 18
Post ID: 14152
Reply to: 14150
Multiple Nazi idlers and their belts
fiogf49gjkf0d
 Stitch wrote:
Great idea. :-)


3x the rumble for you Stitch Wink

What is hate then if not one of the emotions inducing flames? Big Smile

The only purely theoretical point which is intriguing for me
in the whole multiple drive idea is whether one can achieve a uniform "floating" rotation:
the forces perpendicular to the spindle balance out
and the spindle rotates without (too much) intercation with bearing's walls.
Is it reliably, repeatedly and proveably achieveable
under dynamical condictions in practice? No idea.
Not that I'm in any sense attached to
the idea, but with idlers one can in principle easy controll the
force perpendicular to the platter's axis, so might be that the balancing
is easier...or a BS as synchronizing 3 motors must be a hell.

Cheers,
N



Cheers,
Jarek
07-31-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 19
Post ID: 14153
Reply to: 14152
N-set number of idlers or belts
fiogf49gjkf0d
 N-set wrote:
The only purely theoretical point which is intriguing for me
in the whole multiple drive idea is whether one can achieve a uniform "floating" rotation:
the forces perpendicular to the spindle balance out
and the spindle rotates without (too much) intercation with bearing's walls.
Is it reliably, repeatedly and proveably achieveable
under dynamical condictions in practice?

 
I have no answers but I have a theoretical contra-argument. Why do you feel that uniform "floating" rotation is possible only with N amount of drives?  Let look in this deeper. A single drive would it be idlers of belt transmitting moment to platter has errors (slips, bends, elasticity…  etc). Those errors make a platter to reset microscopic backlash in bearing. The minute deviation of speed is not truly a problem but the platter rocking back in force while it clears the micro freedoms between mating element of bearing is a problem.
 
Now we presume that let say 3 idlers or belts driver the platter at 120 degree and they create more uniform rotation. Yes, the errors of each idler or belt is less critical and now it transmits 1/3 of moment. However, why we are under a presumption that idlers or belts errors have random character. What will happen if idlers or belts errors took place in near same time? We just have no control over it as the idlers and belts are not synchronized.  Now, let see how a single idler or belt work. The force of the moment from ONLY side permanently offset the backlash of the bearing, creating a mechanical biasing of the bearing errors. So, the theoretical conclusion is that a single drive is better.
 
In reality there is only two known to me ways to address the problem that agree with my theory. First is to make the bearing longer. The longer bearing shaft is less left-right backlash. The EMT 927 is way ahead in it that any other turntable. Second is increase the platter mass in order to make the platter do not sense the idlers or belts errors.  A large platter weigh has own issues with bearing but this is a whole other subject…
 
The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-13-2010 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 439
Joined on 01-07-2006

Post #: 20
Post ID: 14235
Reply to: 14153
"Hearing" backlash?
fiogf49gjkf0d
 Romy the Cat wrote:

 
Why do you feel that uniform "floating" rotation is possible only with N amount of drives? 


I don't feel it's the only way :-)

 Romy the Cat wrote:

Let look in this deeper. A single drive would it be idlers of belt transmitting moment to platter has errors (slips, bends, elasticity…  etc). Those errors make a platter to reset microscopic backlash in bearing. The minute deviation of speed is not truly a problem but the platter rocking back in force while it clears the micro freedoms between mating element of bearing is a problem.
 
Now we presume that let say 3 idlers or belts driver the platter at 120 degree and they create more uniform rotation. Yes, the errors of each idler or belt is less critical and now it transmits 1/3 of moment. However, why we are under a presumption that idlers or belts errors have random character. What will happen if idlers or belts errors took place in near same time? We just have no control over it as the idlers and belts are not synchronized.  Now, let see how a single idler or belt work. The force of the moment from ONLY side permanently offset the backlash of the bearing, creating a mechanical biasing of the bearing errors. So, the theoretical conclusion is that a single drive is better.


Actually I've been wondering if one can reliably detect this backlash by some means.
The spindle preforms a micro-wobbling, interacting with the bearing's walls.
Perhaps the last can be heard by e.g. a stethoscope (if one learns how to recognize how it sounds)
attached to the bearing.
I'm thinking if something like this:
http://www.radiolocman.com/shem/schematics.html?di=64243
connected to good phones (I have stax lambda system somewhere, which was nota bene designed for
vibration examination in mercedesses)
would help?
Does it make any sense or am I totally off the track?

Cheers,
N-set



Cheers,
Jarek
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