Origami Idler Drive?

[Zero One]

There has been some discussion over on the vinyl engine on what makes TTs have their distinctive sound and from this and other papers I have read on the subject it seems the idler drive might actually be the best system, but as they are pretty much all old designs now they are hampered by rough motors and poor bearings that were in use in their day.

It occurred to me that maybe the floppy drive motor might be the ideal cadidate for the job, at first I thought is would be hard to set up, but thinking about it, if the speed can be varied electronically then a lot of the potential problems of the idler would go away, as you would just need a fixed straight shaft running against the idler neither the motor nor the idler would need to be raised in relation to one another to adjust speeds, so all sorts of brackets and knobs and springs are deleted.

I imagine the floppy drive would be far smoother than the original motors as well and this is probably even more important to an idler drive than it is to a belt drive.

Possibly other similar motors like video head motors might be even better, though I have no idea how you would control the speed.

Anyone tried to floppy their idler?

 

[graeme uk]

I use an idler (a lenco heavily modified).

The motor is very smooth and quiet, but getting rid of the idler movement and the conical shaft has got to be a good thing.

Idlers do need (or at least benefit) from quite alot of torque though. How strong are the floppy motors?

 

[Zero One]

Ji Graeme

Not sure how torquey floppy drives are but I imagine they are pretty reasonable. I guess since they can be speed adjusted that a smaller shaft could be used and a higher rotational speed if low speed torque is insufficient. Of course this would be a little noisier.

As I understand it the older 5 inch floppy drive motors are a bit stronger.

There are also lots of stepper motors out there some of which are amazingly powerful and smooth though I guess controlling them becomes an issue. Some of those can run at very low revs too, so a larger pinion could be used and maybe lower vibration/noise as a result.

Another possible motor could be a video head motor, though once again I think speed control is a bit tricky from what I have heard, there is also the capstan drive which from memory has a small vertical shaft as part of the package, not sure what speed they operate at though.

 

[graeme uk]

worth looking into by the sounds of it, although making a new TT just using a lenco or garard motor would be easier. I really dont think the motors are that bad. My lenco is speed stable and very quiet. The lenco drive is easier to use in a home built TT as it drives the underside of the platter rather than the inner lip meaning driving a different platter on a different bearing (what ive done) is very easy.

As you say though, having a solid mounted idler and a straight motor shaft might be beneficial.

 

[Aquarium]

Before you indulge in the obvious need to tweak I would advise some strong words of caution.The Lenco motor and drive system is advocated by the guy (Jean Nantais) who brought them back out of the dark ages as being near perfect.What you need to address is the issue of a good mass plinth and good tonearm.You will then beat the best the world has to offer.

 

[phn]

I agree. We need to put the "idler-wheel rumble" myth to rest. People would hardly pay the money they do for EMTs and Garrards if they had rumble problems.

Designing an idler-wheel deck sounds cool. But it probably won't be easy. Perhaps the best solution is a Japanese deck I saw in a hi-fi rag in the mid 1980s. I don't remember who made it. I do remember it being VERY expensive.

Maybe this is known to everybody. But I haven't seen the deck since. It had a metal platter, probably 10 cm thick. On the otside there was this drive shaft/rod, also 10 cm. The idler-wheel was magnetic. It was basically a rubber-insulated magnetic rod. But even that might not be simple. Chance is that the driving rod/wheel will have to be floating somehow.

 

[amsci99]

I agree. We need to put the "idler-wheel rumble" myth to rest. People would hardly pay the money they do for EMTs and Garrards if they had rumble problems.

Designing an idler-wheel deck sounds cool. But it probably won't be easy. Perhaps the best solution is a Japanese deck I saw in a hi-fi rag in the mid 1980s. I don't remember who made it. I do remember it being VERY expensive.

Maybe this is known to everybody. But I haven't seen the deck since. It had a metal platter, probably 10 cm thick. On the otside there was this drive shaft/rod, also 10 cm. The idler-wheel was magnetic. It was basically a rubber-insulated magnetic rod. But even that might not be simple. Chance is that the driving rod/wheel will have to be floating somehow.

phn,

I think you are referring to the Teragaki designed Seiko-Epson Sigma series turntables. The Sigma 2000 was released in 1987, followed by the Sigma 3000 and 5000 in 1994. Very limited edition models, only about 30 to 40 units were made and the Sigma 5000 costed about 32,000,000 Yen when released. I have been trying to locate magazines which reviewed this deck but unfortunately was unable to find any.

 

[phn]

It could be Teragaki. I couldn't say. I googled Teragaki Seiko-Epson Sigma. There are quite a few of these ultra high-end decks out there. Back when I saw this deck, Thorens and Nakamichi were pretty much the only ones to make these kind of "prestige" decks. That's probably not true. But there were a lot fewer manufacturers back then.

 

[cubastreet]

I think idler wheel with a DC motor is pointless.
The advantage of idler wheel over direct drive is the synchronous or induction motors they use which don't need a feedback system and therefore don't 'hunt' for the correct speed.

 

[mosin]

Before you indulge in the obvious need to tweak I would advise some strong words of caution.The Lenco motor and drive system is advocated by the guy (Jean Nantais) who brought them back out of the dark ages as being near perfect.What you need to address is the issue of a good mass plinth and good tonearm.You will then beat the best the world has to offer.

Hello,

I have built a turntable that uses the Lenco as a starting point, and I strongly question the notion that blindly accepts the motor and drive system as being near perfect. Rather, I consider the Lenco motor to be an inferior one. First, it is a shaded pole type. The shaded pole motor itself is vastly inferior to a three-phase eddy current type, like the Papst Aussenlaufer, for example. Second, it relies on a steel pin pushed by a spring, in place of a proper thrust bearing. The thrust pin is particularly prone to sticking in place after time has past. Third, lubrication is unsure, at best. Lenco's spindle and bearing system is also troublesome, in my honest opinion. It is imprecise and leaky. It is also fairly small, considering the claims that have been made about the turntable. Last of all, the platter rings like a bell, and all the metal stampings are pedestrian in quality. Asking a heavy plinth to fix all those issues without making serious other modifications is a bit preposterous.

So, although the Lenco can be made much better, it is not what some claim it to be. What it is, however, is a turntable with a single idea that shows immense potential, and that is its implementation of a thin wheel that runs on the underside of the platter, rather than the rim. Although Lenco's idler isn't so great, this particular idler wheel concept when combined with other improvements can take the idler turntable to highs that it has never seen before. Think about it.

-mosin

 

[Mark Kelly]

I think idler wheel with a DC motor is pointless.
The advantage of idler wheel over direct drive is the synchronous or induction motors they use which don't need a feedback system and therefore don't 'hunt' for the correct speed.

You've obviously never heard a DC motor in an idler.

BTW the motors in idlers are never synchronous, they are induction motors, usually shaded pole. Despite what you have read these are low power output motors with very poor speed / torque characteristics.

It is entirely possible to build a DC drive with much better speed / torque characteristics than any induction motor and which does not display any hunting at all. Once installed into a decent idler this is something of a revelation.

You are also completely wrong about how Direct Drives work but that's another argument.

 

[graeme uk]

Hello,

I have built a turntable that uses the Lenco as a starting point, and I strongly question the notion that blindly accepts the motor and drive system as being near perfect. Rather, I consider the Lenco motor to be an inferior one. First, it is a shaded pole type. The shaded pole motor itself is vastly inferior to a three-phase eddy current type, like the Papst Aussenlaufer, for example. Second, it relies on a steel pin pushed by a spring, in place of a proper thrust bearing. The thrust pin is particularly prone to sticking in place after time has past. Third, lubrication is unsure, at best. Lenco's spindle and bearing system is also troublesome, in my honest opinion. It is imprecise and leaky. It is also fairly small, considering the claims that have been made about the turntable. Last of all, the platter rings like a bell, and all the metal stampings are pedestrian in quality. Asking a heavy plinth to fix all those issues without making serious other modifications is a bit preposterous.

So, although the Lenco can be made much better, it is not what some claim it to be. What it is, however, is a turntable with a single idea that shows immense potential, and that is its implementation of a thin wheel that runs on the underside of the platter, rather than the rim. Although Lenco's idler isn't so great, this particular idler wheel concept when combined with other improvements can take the idler turntable to highs that it has never seen before. Think about it.

-mosin

Interesting points about the lenco motor. I know nothing about TT motors.

You are totally correct about the pressed steel chassis and the platter. I dont really rate the bearing either. Ive modded mine to overcome all these problems and it sounds much better.

 

[cubastreet]

You've obviously never heard a DC motor in an idler.

BTW the motors in idlers are never synchronous, they are induction motors, usually shaded pole. Despite what you have read these are low power output motors with very poor speed / torque characteristics.

It is entirely possible to build a DC drive with much better speed / torque characteristics than any induction motor and which does not display any hunting at all. Once installed into a decent idler this is something of a revelation.

You are also completely wrong about how Direct Drives work but that's another argument.

1 correct

2 incorrect

3 perhaps

4 don`t remember explaining the workings of a direct drive motor

 

[mosin]

Hello again,

You've obviously never heard a DC motor in an idler.

1 correct

Yet...

I think idler wheel with a DC motor is pointless.

Then...

BTW the motors in idlers are never synchronous, they are induction motors, usually shaded pole. Despite what you have read these are low power output motors with very poor speed / torque characteristics.

2 incorrect

Could you elaborate?

It is entirely possible to build a DC drive with much better speed / torque characteristics than any induction motor and which does not display any hunting at all. Once installed into a decent idler this is something of a revelation.

3 perhaps

It has been done by the very Mark Kelly that you responded to.

You are also completely wrong about how Direct Drives work but that's another argument.

4 don`t remember explaining the workings of a direct drive motor

The following statement leads us to believe that you know about both systems intimately, so why not tell us?

The advantage of idler wheel over direct drive is the synchronous or induction motors they use which don't need a feedback system and therefore don't 'hunt' for the correct speed.

Regards,
-mosin


Edited for flow.

 

[Mark Kelly]

1 correct

2 incorrect

3 perhaps

4 don`t remember explaining the workings of a direct drive motor

Re 2: Maybe I should have said "I have never seen an idler with a synchronous motor", I've checked out the motors in every idler I know of inc. Garrard, Thorens, Lenco, EMT, Commonwealth, ROK, Delphon and they are all induction motors.

The measured power output from the motor in my 301, often quoted as an example of a high power idler motor is actually less than 2 watts and the measured speed torque characteristic is quite poor - it's about 20% down in speed at the torque level that gives this power output.

Re: 4. My error, I reacted to your statement about avoiding hunting. I was shooting a paper tiger.

 

[mosin]

Mark,

Isn't the Rek-O-Kut B12 one? It uses the Papst Aussenlaufer motor. It isn't native to Australia, however.

-mosin

 

[Mark Kelly]

Mark,

Isn't the Rek-O-Kut B12 one? It uses the Papst Aussenlaufer motor. It isn't native to Australia, however.

-mosin

The Papst motor is technically an induction motor in that it works by inducing eddy currents in the outer shell which then accelerates until it is nearly synchronous with the stator field.

My measurements on the Papst Aussenlaufer motor indicated that it runs at about 98% of synchronous speed and has a much better speed / torque curve than does the 301 motor (-200mNm vs -50 to -100mNm). It's still not a high power device, 2 watts output if I remember correctly, making it even less efficient than a shaded pole.

* the nominal torque constant is not the output torque, it is the ratio between the output torque and the percentage change of speed that torque creates, thus the negative sign. The Garrard motor has a range of values because its torque constant depends on its supply voltage.

 

[EC8010]

I have to say I've never understood the enthusiasm for Lenco turntables. Various mechanical problems have already been mentioned, but the narrow tyre on the idler seems a recipe for disaster. Because the tyre is narrow it has to be made of harder rubber, reducing its filtering effect and transferring more noise from the motor. Further, the way that the idler is supported seems to be highly likely to allow the idler axis to rotate out of alignment with the motor shaft axis and create a scrubbing instability with attendant noise. Lastly, idler drive means an additional bearing to generate noise...

Before I'm accused of never having heard an idler drive turntable on a decent plinth, I've used my Garrard 301 for 33 years. First on a 20lb concrete/wood plinth, now on a 40lb lead/MDF sandwich. But the 301 will soon be relegated in favour of a belt drive.

 

[mosin]

I have to say I've never understood the enthusiasm for Lenco turntables. Various mechanical problems have already been mentioned, but the narrow tyre on the idler seems a recipe for disaster. Because the tyre is narrow it has to be made of harder rubber, reducing its filtering effect and transferring more noise from the motor. Further, the way that the idler is supported seems to be highly likely to allow the idler axis to rotate out of alignment with the motor shaft axis and create a scrubbing instability with attendant noise. Lastly, idler drive means an additional bearing to generate noise...

Before I'm accused of never having heard an idler drive turntable on a decent plinth, I've used my Garrard 301 for 33 years. First on a 20lb concrete/wood plinth, now on a 40lb lead/MDF sandwich. But the 301 will soon be relegated in favour of a belt drive.

EC8010,

This is an area where we disagree. I see the narrow tire as Lenco's greatest asset because less contact means less noise transmitted to the platter. I also disagree that the rubber formulation has to be harder to work properly. In fact, I believe the opposite. A softer rubber will have less slippage than a hard one, and bearing noise can be avoided entirely. The orientation of the Lenco idler is also an asset because it is essentially wedged into position, and the result is that very little spring assistance is required for it to work. If properly aligned, the mechanism is, in my opinion, the superior method of all idler turntables. The caveat, and there is one, is the conventional way the idler wheel is attached to its engagement lever, but that can be overcome. If executed properly, noise can be reduced to a level that is practically nonexistent, and accuracy of alignment can be enhanced. This I know for certain because my turntable has such a design thanks to high tech materials that were not available during the height of idler drive turntable production.

-mosin

 

[mosin]

and again...

I waited too long to edit my last post, but I thought of some things that may help you to understand my position regarding the idler wheel. One has to do with the Lenco tapered motor shaft. (I am using a modified Lenco motor until a suitable replacement can be found.) The taper requires a thin idler, in order that the speed can be set precisely. Anyway, I am sure you have noticed new cars that have large wheels with tires that have narrow sidewalls, right? In serious autos, like the Ferrari F40, they are purposefully designed, so that they have less flex in turns, but you know that already. It occurred to me that such an implementation could be used in an idler wheel with success, and it would be especially useful with a design, like the Lenco's, which has a configuration that runs on the underside of the platter, although it might be helpful for rim driven models, too. I have always assumed that the extra width on typical idler wheels was to compensate for the extra height of them, so they would not flex. The good part of those designs is that much of the noise is soaked up by the rubber, but the downside has always been shrinking and hardening which left flat spots and slick places. Adequate lubrication is also a problem with them. The result of this inevitable wear of the rubber is rumble, uneven speed and accelerated wear to the idler bushing and shaft. Also, the heavier weight requires a heavier spring to actuate the assembly. Then there is the need to have the wheel resurfaced from time to time by someone who is equipped for such a service.

So, I have an idea, but one that allows more noise to be transmitted from the idler linkage and bushing/shaft arrangement, right? Initially, that was right, but I changed the entire assembly, and it works. I have applied for a provisional patent on a design that entirely dispenses with the bushing and shaft. It implements a yoke made from a heat treated stainless steel specialty alloy around a new wheel which is made from a particularly stiff aluminum alloy. There is a very small, but precise, captive silicon nitride ball on each of the inside arms of the yoke that runs in a divot which has been milled into a piece of Torlon that replaces the age-old bronze bushing. Torlon is a structural engineering plastic that will operate in abrasive conditions with little, or no, lubricant. It is virtually impossible to wear out in such an application, and best of all, the arrangement is completely silent. Further, it is not a good conductor of resonances from the linkage (which has also been modified). The design also allows the rubber to be fairly soft and user replaceable. Currently, I am using selected, but reasonably commonplace, 70 durometer nitrile o-rings, and I plan to experiment with o-rings of an even softer material, but so far, the performance of the new idler type exceeds my expectations. Combined with other changes, I feel that it has helped bring the idler up a step, or two.

-mosin