Why three motors?

Sorry, I should have asked the question differently. With three motors, why have ONE side of the belt touching the platter? It's the belt arrangement that I question. What is the point of that? With two motors, side torque is eliminated or equalized so the platter bearing is not pressured towards one side. In the TW Acustic, it appears at least to me, the whole thing is an afterthought on cashing in on selling more motors and the original plinth design was not intended to have three motors to arrange the belt in an equilateral triangle so all three sides of the belt can touch the platter. Instead, the arrangement end up having only one side touching the belt. Wouldn't two motors be better in this case? What I see in the picture is bewildering to me. Am I missing something here? Please illuminate me.

The latest Raven turntable abandoned such scheme and opted for three motors in a single housing, which is also questionable in itself.
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T_bone: "Any idea what the tonearm with the wooden armpipe is?"

It's a German tonearm made of ebony.
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One of the explanations about the belt arrangement I read is that it simulates an idler wheel with low contact area. If that's the design intention I found that unconvincing. The three motor set up with such belt arrangement has been discontinued by the manufacturer so I have to assume the designer no longer endorse such approach.

Here's a lively discussion about the design.

Again, I found the belt arrangement to be half-baked until someone can explain it to me otherwise.

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Various three motor turntables in different belt arrangement, either single belt or triple belts and all of them have the platter touching THREE sides of the belts.

Audionote

Transrotor

Clearaudio

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I really should have changed the titled question from "Why three motors?" to "Why such belt arrangement?"

I am less interested in why using three motors but in why they arrange the belt in a 3-motor design that only one side of the belt is touching the platter.

If they use four motors, the belt would not touch the platter at all! Perhaps that's the best sound in having the blackest background.

Syntax: "Simple answer: That's Higher End"

So far that's the best answer.

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Thanks for your idea about the belt arrangement. But I seriously doubt the designer intended that way and if he did, that's a rather belabored effort to achieve small contact area by using THREE motors and not to mention belt slip. Oy! Why not just use an idler wheel? The manufacturer no longer has that model so I have to assume they have changed course.

There are formal reviews of the turntable and yet not one reviewer questioned the wisdom of the belt arrangement; they are the usual couple paragraphs describing the mechanics and they go straight to the epic flowery prose about the soundstage blah blah blah.

Your examples of combating belt creep is very interesting though. Thanks.

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"Thomas did something that was amazing. He listened to one motor, two motors, 3 motors, multiple belts and came up to the conclusion that 3 motors with one belt sounded better."

You skipped the process of him listening to THREE side of the belt touching the platter, and then TWO sides, and the finally ONE side to reach nirvana.

I have nothing against TW, it could be a different brand and all I saw was a turntable with a rather curious belt arrangement that I never saw before so I asked a simple question. Why? So far no convincing answer. Even more curious, is that the manufacturer no longer have such configuration. And I have to ask why again. Was it a flop and had to change course again? Are those 3-motor turntable owners still sticking to that belt arrangement? If change, what do you do with the extra motors?

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FYI, I posted two images of the Raven turntable, each with two different tonearms.

1st image with Analog-Tools 12" tonearm and Audiocraft AC-4000 12" tonearm

2nd image with Schroeder DSP 9" tonearm and Dynavector DV-507 9" tonearm

Both turntables have three motors with only one side of the belt touching the platter.

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Donwunder: "Where did you get that information from?? Exactly where has TW changed course??"

I have seen the 3-motors version on their website before and now it's NOT listed on their website - http://www.tw-acustic.de/engl/turntables - so I made an assumption that they are not offering that anymore. I apologize for not making that clear earlier. But why is that option not on the website anymore, just curious? Let's say they didn't change course, the question remains what is the engineering reason behind such unconventional approach. Any suggestions for the discussion?

Speaking of 3 motors, their flagship Raven Black Night uses 3 motors in a single housing with THREE pulleys, which in itself a curious design. Is it to increase triple the torque and/or to combat belt slip or belt creep, etc?

Lewm: "the configuration shown, where the belt contacts the platter on only one side of the "triangle" would seem to be a worst-case set-up for "belt creep"...... 3 motors makes no sense to me."

Lewm, perhaps you can get some hint from their writing about the Black Night, if not the AC3:

"Thanks to the three-motor drive and the battery power supply, the Raven Black Night does its job with poise, serenity and composure, yet just like the other TW-Acustic turntables, it is highly dynamic, involving and rich in timbre. The Raven Black Night is incredibly musical, its spatial presentation is so three-dimensional and tangible that the music is always reproduced with the utmost authenticity."

You see, it just does its job.

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About the TW website, what I meant is that I didn't see the listing or any prompt button for the AC3. As seen in the picture, obviously they still offer the three motor option. Once again, I apologize for the confusion and my carelessness. Yes, TW STILL makes a 3-motor turntable with only one side of the belt touching the platter. Below is description of the system:

Three-motor drive for Raven and Raven AC turntables / Technical details:

Our three motors run absolutely syncronous thanks to a sophisticated motor control
The diameters of the drive pulleys are accurate to within half a hundredth of a millimetre
The drive belt thickness is ground to a tolerance of one hundredth of a millimetre

We have taken the advantages of our unique drive system to the limit and have developed a three-motor drive for the Raven One and Raven AC. We have achieved perfect syncronicity between all three motors with our new, highly developed motor control system.

The extremely precisely machined drive belt, coupled with finely toleranced and matched pulleys give the concept the optimal basis for the precision we demand. If you were of the opinion that the Raven's drive system was unique, then of course you were right! But the new three-motor drive picks up where our unique single motor drive leaves off. The Raven or Raven AC is now available as a three-motor version. Of course, any existing Raven One or Raven AC can also be upgraded.

There's no mention of the belt configuration. Can we get back to the why now? Anyone?

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Do not try to find a reason

"TW-Acustic Raven AC – setting new trends" by Holger Barske, Editor in chief, LP magazine (Issue 6/06)

I gave up before even reading the above. I will just join the cult of voodoo science. Thanks for alerting me the review.

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