Frank,
I believe you got a good grasp of what I intend, but I like to clarify a few things nontheless.
The bearing being a unipivot is more important than the oilbath. Reasoning behind this is the same as for a unipivot arm.You may be right in saying that in such a concept the oil is unnecessary. The test will tell.
Why I think the oil will help is not so much damping of the platter but more to improve its stability. Because the bearing is a unipivot design the platter may tilt. I hope oil will at least to a degree prevent this ( together with the fact that the belt is in the same plane as the ball).
🙂 I am with you.
Would it be possible perhaps to have a sketch of this? I am afraid I dont get it without one😕
It is not that I don't believe you😀 , but I am pig-headed: I have to hear to believe😉 . So I will go on building my prototype to hear and see.
I believe you got a good grasp of what I intend, but I like to clarify a few things nontheless.
The bearing being a unipivot is more important than the oilbath. Reasoning behind this is the same as for a unipivot arm.You may be right in saying that in such a concept the oil is unnecessary. The test will tell.
Why I think the oil will help is not so much damping of the platter but more to improve its stability. Because the bearing is a unipivot design the platter may tilt. I hope oil will at least to a degree prevent this ( together with the fact that the belt is in the same plane as the ball).
All,
, written by Frank or by Havoc or by whomelse. What works: have a non-agressive, non-downtalking, non-naysaying attitude while writing. That works 
. Our communication is based on 80% body language and 20% speech, those 20% being weighted by 3/4 of how something was said and 1/4 content (Makes a total of 5% for content).
We here with written conversation are dealing with the 20% and i would say, 3/4 are outweighing 1/4 considerably. (Any idea why diyAudio provided heaps of smilies recently?)
So, if disclaimers are needed, high time to examine the own attitude, is it postive, constructive, mutually-respect-oriented enough.
Havoc, your post also had a disclaimer, it triggered what i said above.
Frank, i am adressing you particularly with what i said above.
As i sense it, Havoc is not hugging you at all and Peterr is outright angry, and i can understand them so well.
such disclaimers do not workHavoc said:
, written by Frank or by Havoc or by whomelse. What works: have a non-agressive, non-downtalking, non-naysaying attitude while writing. That works . Our communication is based on 80% body language and 20% speech, those 20% being weighted by 3/4 of how something was said and 1/4 content (Makes a total of 5% for content). We here with written conversation are dealing with the 20% and i would say, 3/4 are outweighing 1/4 considerably. (Any idea why diyAudio provided heaps of smilies recently?)
So, if disclaimers are needed, high time to examine the own attitude, is it postive, constructive, mutually-respect-oriented enough.
Havoc, your post also had a disclaimer, it triggered what i said above.
Frank, i am adressing you particularly with what i said above.
As i sense it, Havoc is not hugging you at all and Peterr is outright angry, and i can understand them so well.
TT
Bernhard,
As I see it,Peterr,Havoc and me are going along fine.
I explained before that I'll try to help them wherever I can.
This takes time and patience.
Both have totally different backgrounds and as such require different approaches.
If you want to do all the hard work than that's fine by me.
You can bully me once but not twice,so forget it.
I have better things to do with my time then taking **** from self-centered egotrippers.
Rgds.
Bernhard,
As I see it,Peterr,Havoc and me are going along fine.
I explained before that I'll try to help them wherever I can.
This takes time and patience.
Both have totally different backgrounds and as such require different approaches.
If you want to do all the hard work than that's fine by me.
You can bully me once but not twice,so forget it.
I have better things to do with my time then taking **** from self-centered egotrippers.
Rgds.
Havoc,
What might help: My TT has a 20mm thick tonearm base made from POM. The plinth is massive marine grade mahogany plywood, 60mm thick. My tonearm is an SME V. If this peak occurs, i can clearly sense the tonearm base vibrate with my fingertips. It is worse with a stiff MC cartridge, but still sensable with a high-compliant MM cartridge.
Tank: as the air consumption is constant i.e. no load step occurs after switch-on, one could use the equivalent to a CLC or CLCLC filter section in an amplifier PS: L can be simulated by a tank in series with fittings/orifices as distant as possible, C by a blind tank with one fitting connected to the line in a T-joint. L is only partially simulated as it will not build up infinited pressure increase when air flow is stopped. But the tank in series definitely strives to keep the flow constant within limits. And R could be added in the form of a control valve.
If we separate the tank volume into 5 small volumes, a pulsation-free air flow should be no problem. The total tank volume should be biggenuff to serve as a reservoir however for the case the compressor stops unexpectedly.
Checker valve before and no valve after the last tank will do fine as landing gear.
So: Frank, where is the problem?
Gas cylinders:
the pressure regulator can ecstatically oscillate.
Let's add a 20µm particle filter.
hint: Usually direct drives are avoided because properly designed DD consume excactly the space a decent platter bearing occupies.
But and airbearing does not consume the same space as a conventional bearing. If you think about it, you may find a way to couple a motor to your platter without messing with the bearing, maybe you even couple to the rotor of the bearing.
Belt drive:
A heavy platter stores rotational energy, you posted the correct formula. It behaves way similar compared to a big inductivity than the tank mentioned above. You try to accelerate it suddenly, you break your arm. Same with negative acceleration. Changes in rotational speed must be minute ones. Due to I*w^2.
Any ripple in torque or speed cannot cause audible change of the platter speed once it is heavy enough. Even with a hard-locked DD and a PLL you will have to reduce the regulator amplification, the P component, until slow oscillation of speed stops and then you arrived at the same weak coupling as with the belt drive. Just it is caused electrically now. Belt drive does achieve the same thing, just simpler and cheaper.
Now the belt can be made tension-stiff. Unelastic. A kevlar string will do fine, just the knot will drive you nuts. Is the force a kevlar string can transmit needed? methinks no. A magnetic tape will do, it is pre-stressed mylar and about as tension-stiff as the kevlar string. Just its geometric properties are way better defined; it can be used as a flat belt.
Moreover, tape is slippery, it won't transmit speed changes beyond an upper limit. It lets high frequency changes drown in its slipperyness. Good. So, such a belt cannot store energy, it cannot make the system a 2nd order system itself, able to oscillate. For oscillation, the necessary springs must be hidden with the motor now.
Motor:
no objection from me against any form of asynchonous motors. Be they DC or AC. asynchonous motors provide a constant torque (well, almost), they are not locked to the rotating field.
A synchronous motor like used in many lightweight suspended TTs like Linn, PinkTrianlge, Thorens, ... , tries to lock the rotor to its rotating electric field. But the forces doing that behave like virtual springs. Either the maximum torque is within limits, then the springs extend and contract, or torques exceeds limits, then the springs break.
A belt drive with a syncronous motor is a 2nd order system, able to oscillate; if then the belt is elastic too, it becomes a 3rd order system.
A belt drive with an asyncronous motor and unelastic belt is a 1st order system, unable to oscillate.
The motor i am suggesting is an asyncronous DC voice coil motor with 13 overlapping windings and i was not able to measure torque ripple with my means.
When i feed something between 0.3-0.5 Volt to the motor, the shaft begins to creep smoothly into rotation without any cogging.
Of course, for badly warped records a velveted plate is needed to press the rocord flat during application of vacuum, but once the seal lip carresses the record edge, the vacuum will keep the record flat. I tried that out.
Not agreed. For the unipivot, something must keep the platter levelled and i prefer gravity to do that job, not a washer grinding inside a hole all the time.
If the unipivot is to work, the mass ad gyroscope effect of the platter must be biggenuff to ignore tracking force.
If i decide to go for an airbearing, air supension, maybe even active one, is within short reach because of pressurized air available.
I wish i could. Loudest peak on record i know is Mercury SR90316, Schoenberg op.16 Five pieces for Orchestra, 1st mvmnt. Massive brass at +17dB, i measured it. now one would have to know frequency of the peak, guess groove excursion and velocity (consult RIAA curve), consider stylus and cantilever mass (let's ignore cantilever damping and tonearm mass for simplicity). One then would get a figure of the worst case. A figure not telling much or helping imagination.
What might help: My TT has a 20mm thick tonearm base made from POM. The plinth is massive marine grade mahogany plywood, 60mm thick. My tonearm is an SME V. If this peak occurs, i can clearly sense the tonearm base vibrate with my fingertips. It is worse with a stiff MC cartridge, but still sensable with a high-compliant MM cartridge.
i agree with you partially. 1st the energy, or a percentage of it as bg as possible, must leave the record. For this an impedance match between record and platter surface helps. Vinyl is best impeadnce match. And it happens to have the properties you claim to a sufficient extent, so i would presume.
Agreed. I may repeat myself: the Melco engineers found out that at abot 40kg of mass, the motor/drive issue ceased to matter at all.
Well, an airbrush compressor is the Rolls Royce solution, it is not as loud as a fridge (refrigerator). I did not manage to salvage a fridge compressor on my only attempt, but i have heard from others it can be done. And a fridge is not too loud, right?
Tank: as the air consumption is constant i.e. no load step occurs after switch-on, one could use the equivalent to a CLC or CLCLC filter section in an amplifier PS: L can be simulated by a tank in series with fittings/orifices as distant as possible, C by a blind tank with one fitting connected to the line in a T-joint. L is only partially simulated as it will not build up infinited pressure increase when air flow is stopped. But the tank in series definitely strives to keep the flow constant within limits. And R could be added in the form of a control valve.
If we separate the tank volume into 5 small volumes, a pulsation-free air flow should be no problem. The total tank volume should be biggenuff to serve as a reservoir however for the case the compressor stops unexpectedly.
Checker valve before and no valve after the last tank will do fine as landing gear.
So: Frank, where is the problem?
A medium size airbrush compressor carried the 50kg platter of the Apolyth TT.
Gas cylinders:
the pressure regulator can ecstatically oscillate.standard parts in pneumatics. Inexpensive.
Let's add a 20µm particle filter.
hint: Usually direct drives are avoided because properly designed DD consume excactly the space a decent platter bearing occupies.
But and airbearing does not consume the same space as a conventional bearing. If you think about it, you may find a way to couple a motor to your platter without messing with the bearing, maybe you even couple to the rotor of the bearing.
Belt drive:
A heavy platter stores rotational energy, you posted the correct formula. It behaves way similar compared to a big inductivity than the tank mentioned above. You try to accelerate it suddenly, you break your arm. Same with negative acceleration. Changes in rotational speed must be minute ones. Due to I*w^2.
Any ripple in torque or speed cannot cause audible change of the platter speed once it is heavy enough. Even with a hard-locked DD and a PLL you will have to reduce the regulator amplification, the P component, until slow oscillation of speed stops and then you arrived at the same weak coupling as with the belt drive. Just it is caused electrically now. Belt drive does achieve the same thing, just simpler and cheaper.
Now the belt can be made tension-stiff. Unelastic. A kevlar string will do fine, just the knot will drive you nuts. Is the force a kevlar string can transmit needed? methinks no. A magnetic tape will do, it is pre-stressed mylar and about as tension-stiff as the kevlar string. Just its geometric properties are way better defined; it can be used as a flat belt.
Moreover, tape is slippery, it won't transmit speed changes beyond an upper limit. It lets high frequency changes drown in its slipperyness. Good. So, such a belt cannot store energy, it cannot make the system a 2nd order system itself, able to oscillate. For oscillation, the necessary springs must be hidden with the motor now.
Motor:
no objection from me against any form of asynchonous motors. Be they DC or AC. asynchonous motors provide a constant torque (well, almost), they are not locked to the rotating field.
A synchronous motor like used in many lightweight suspended TTs like Linn, PinkTrianlge, Thorens, ... , tries to lock the rotor to its rotating electric field. But the forces doing that behave like virtual springs. Either the maximum torque is within limits, then the springs extend and contract, or torques exceeds limits, then the springs break.
A belt drive with a syncronous motor is a 2nd order system, able to oscillate; if then the belt is elastic too, it becomes a 3rd order system.
A belt drive with an asyncronous motor and unelastic belt is a 1st order system, unable to oscillate.
The motor i am suggesting is an asyncronous DC voice coil motor with 13 overlapping windings and i was not able to measure torque ripple with my means.
When i feed something between 0.3-0.5 Volt to the motor, the shaft begins to creep smoothly into rotation without any cogging.
a 20kHz wavelength in PVC is about 15 cm long. Moreover, we have wideband signal, i do not think this is critical. Nevertheless the cavity system on the platter's bottoms side is designed as to act as a wideband diffractor for wavefronts.
As you wish 🙂 but the key thought for the vacuum system is not pulling the record flat alone, it is ensuring a tight (but not overtightened) contact between record and platter in order to get the energy out of the record.
Of course, for badly warped records a velveted plate is needed to press the rocord flat during application of vacuum, but once the seal lip carresses the record edge, the vacuum will keep the record flat. I tried that out.
Not agreed. For the unipivot, something must keep the platter levelled and i prefer gravity to do that job, not a washer grinding inside a hole all the time.
If the unipivot is to work, the mass ad gyroscope effect of the platter must be biggenuff to ignore tracking force.
Agreed, this depends on the design of each of you all. I prefer to design integrated because then i can have elements serve more than one purpose. You may prefer to design modular because you want to separate functions and maybe exchange them after exploring.
If i decide to go for an airbearing, air supension, maybe even active one, is within short reach because of pressurized air available.
Agreed.
You got 13 points 😀 ... well, i share your concern about the oil and i probaly wold not like to mess with it either, but with some more thinking it could made work safely and cleanly; the setup could be made wife-proof
Michael,
if you think you can handle it, ok 🙂 but i want to remind you that in technical specifications of materials, exposure limit to chemical substances is limited to 90 days, noone would dare to guarantee anything if you drown a material in oil for a year.
For the case you stick with the PU floats, a jig with a disc knife, a rolling cutter may help.
if you think you can handle it, ok 🙂 but i want to remind you that in technical specifications of materials, exposure limit to chemical substances is limited to 90 days, noone would dare to guarantee anything if you drown a material in oil for a year.
You will find that challenging. Maybe you reconsider turned parts with cavities in it? they will not float as eagerly as PU foam admitted.
For the case you stick with the PU floats, a jig with a disc knife, a rolling cutter may help.
this is what i am meaning 🙂
old fridge, get the compressor.
For an air bearing we are talking µm. If the snooker ball is coated with a MRA release wax or lacquer, and after epoxing, this MLA layer is polished off, you have your airgap. Provided the snooker ball is round enough.
Dice: agreed, disclaimers are no solution, but please remember that some people do not think in english and consequently have problems explaining ideas they feel strongly about in a "proper" way.
My compressor comes from the display of a butcher shop, it is quite large and heavy. The noise is because fridge compressors derive part of their lubrication from the freon, and this gets lost when you use them as an air compressor so they become noisier.
Fdegrove: way don't you give a neat explication of your ideas, with a few drawings if possible? This would be helpfull to understand your reactions.
My compressor comes from the display of a butcher shop, it is quite large and heavy. The noise is because fridge compressors derive part of their lubrication from the freon, and this gets lost when you use them as an air compressor so they become noisier.
Fdegrove: way don't you give a neat explication of your ideas, with a few drawings if possible? This would be helpfull to understand your reactions.
Havoc,
..yes and as we from diyAudio know this, diyAudio provided heaps of smilies 🙂 ...if you all use them to indicate how you yourself feel, English should be the minor problem 
.. Havoc, for you it should be no problem at all.
Frank,
yes, specific drawings and descripitive descriptions, please! Must admit, reading your descriptions, 1st i got
and 
, then 
..yes and as we from diyAudio know this, diyAudio provided heaps of smilies 🙂 ...if you all use them to indicate how you yourself feel, English should be the minor problem .. Havoc, for you it should be no problem at all.Frank,
yes, specific drawings and descripitive descriptions, please! Must admit, reading your descriptions, 1st i got
and , then Dice, I don't know where you got the idea that it is no problem for me! Half of the smilies you use I do not understand and I haven't the faintest idea how to put them in the text. I use my mouse as little as possible while typing, so the only ones I get into it are the simple ones that can be typed. Honest!
Serious again: the compressor noise can be solved. It cannot be worse than my pc.
An active air suspension would be nice. In the lab we used to have one on the tables to isolate the interferometer from the vacuum pumps in the basement that an idiot of an architect had fastened to the foundation. It is a pain to set up and adjust but a great thing to have. Personally I will not go that far.
I must admit I have abandoned the magnetic idea almost completely. Centering different parts is next to impossible. You cannot make it and then machine it. And most of all, a magnetic bearing based on repulsion is fundamently unstable and can thus never be made self-centering unless you add friction based elements and that make the whole excersise pointless.
The problem with the air bearing (apart from the compressor) is the machining. Glass is a far more difficult material to process than metals. You cannot put it on a lathe and turn it. This is certainly not DIY. I turning lapped metal for this bearing surface. In metal you can drill 0.3mm hole and turn a 50mm center hole that is well concentric with the outer rim. Lapping is not exactly difficult, it only takes time.
You guys seem to have misunderstood the "landing gear" remark. My point is that I do not want the air bearing to "collapse". Suppose the compressor fails and you do not notice it. If the drive stays on, both surfaces will grind to a halt. Maybe the little balls all around are a solution to that as proposed by Livemusic.
At the moment I'm doing some work on an air bearing as discussed here (inclusive pool ball). The motor however would be integrated in the platter. It will be an asynchonous AC motor, needing a multi-phase drive. We'll see. Don't hold your breath, it may take a while and may even never see the daylight.
Serious again: the compressor noise can be solved. It cannot be worse than my pc.
An active air suspension would be nice. In the lab we used to have one on the tables to isolate the interferometer from the vacuum pumps in the basement that an idiot of an architect had fastened to the foundation. It is a pain to set up and adjust but a great thing to have. Personally I will not go that far.
I must admit I have abandoned the magnetic idea almost completely. Centering different parts is next to impossible. You cannot make it and then machine it. And most of all, a magnetic bearing based on repulsion is fundamently unstable and can thus never be made self-centering unless you add friction based elements and that make the whole excersise pointless.
The problem with the air bearing (apart from the compressor) is the machining. Glass is a far more difficult material to process than metals. You cannot put it on a lathe and turn it. This is certainly not DIY. I turning lapped metal for this bearing surface. In metal you can drill 0.3mm hole and turn a 50mm center hole that is well concentric with the outer rim. Lapping is not exactly difficult, it only takes time.
You guys seem to have misunderstood the "landing gear" remark. My point is that I do not want the air bearing to "collapse". Suppose the compressor fails and you do not notice it. If the drive stays on, both surfaces will grind to a halt. Maybe the little balls all around are a solution to that as proposed by Livemusic.
At the moment I'm doing some work on an air bearing as discussed here (inclusive pool ball). The motor however would be integrated in the platter. It will be an asynchonous AC motor, needing a multi-phase drive. We'll see. Don't hold your breath, it may take a while and may even never see the daylight.
Havoc,
the smilies can be chosen by clicking on the "get more" link in the smilies window, you also can load the smilies in a separate browser window if you save the smilie URL or you can print this page out. I have taken care that all smilies have names easily rememorable. If you are not familiar with the terms used, it does not hurt to look them up in the dictionary.
tell you a secret, had to look up about a third of them mayself. 🙂
You can type the text/colons and this works as well as clicking on them (i always type)
You switch diagonals a few times to iterate to perfect leveling. I hae done this on a test slab and it worked good, good beyond any expectation. it was possible to level the stone so good you could place a snooker ball anywhere and it would not roll away. Our level gauge (fluid/bubble) had a resolution of 0.01mm/m and bubble was exactly centered.
Before i forget it, i can get the glass peice with bubble and fluid in ot and a scale etched on the glass if someone of you needs it to embed it into the plinth. Coast about Euro40 per piece. Available resolutions: 0.1, 0.05, 0.02, 0.01 mm/m
Magnetic bearing: you got it.
.. 🙂 ... my initial concern form the start.
Flat air bearing: i consider to order granite slabs used for measuring purposes and ground flat to 3µm.
The do not need further lapping.
They usually have 5cm thickness; you can have it thicker but they refuse to make it thinner as then they cannot guarantee flatness.
Landing gear: i got you. The balls suggested by livemusic are indeed a good idea to protect the bearing surface. Maybe my differntial screws come into the game here. They can be adjusted to 0.05mm per revolution i.e. they can brought to slight contact when air is on and then recessed by a demanded count of µm in a controlled way.
You are going the direct drive way? I am impressed! 🙂
the smilies can be chosen by clicking on the "get more" link in the smilies window, you also can load the smilies in a separate browser window if you save the smilie URL or you can print this page out. I have taken care that all smilies have names easily rememorable. If you are not familiar with the terms used, it does not hurt to look them up in the dictionary.
tell you a secret, had to look up about a third of them mayself. 🙂You can type the text/colons and this works as well as clicking on them (i always type)
Yes indeed, but a passive air supsension does the same job acoustically, it just is not as easy to level. But the µcontroller solution i hassled out for my diploma thesis also is fine for leveling by hand. You have 4 separate air springs, loceted in the 4 corners of your plinth, and you bring them to same pressure, say, 6 bar. Then you lock the valves of 2 diagonally located air springs and let them act as hinge. Now you release air from one while you pump air into the other until the plinth is level rectangularly to the "hinge" diagonal straight. Then you switch to the other diagonal: you lock the valves of the ones you were pumping releasing and do the pumping/releasing job on the two you had locked before.
You switch diagonals a few times to iterate to perfect leveling. I hae done this on a test slab and it worked good, good beyond any expectation. it was possible to level the stone so good you could place a snooker ball anywhere and it would not roll away. Our level gauge (fluid/bubble) had a resolution of 0.01mm/m and bubble was exactly centered.
Before i forget it, i can get the glass peice with bubble and fluid in ot and a scale etched on the glass if someone of you needs it to embed it into the plinth. Coast about Euro40 per piece. Available resolutions: 0.1, 0.05, 0.02, 0.01 mm/m
Magnetic bearing: you got it.
.. 🙂 ... my initial concern form the start.Flat air bearing: i consider to order granite slabs used for measuring purposes and ground flat to 3µm.
The do not need further lapping.
They usually have 5cm thickness; you can have it thicker but they refuse to make it thinner as then they cannot guarantee flatness.
Landing gear: i got you. The balls suggested by livemusic are indeed a good idea to protect the bearing surface. Maybe my differntial screws come into the game here. They can be adjusted to 0.05mm per revolution i.e. they can brought to slight contact when air is on and then recessed by a demanded count of µm in a controlled way.
You are going the direct drive way? I am impressed!
🙂1. Important message for everyone dealing with unipivot bearing platter:
Keep your platter CG as close to the pivot point as possible.
Seems like low CG can help to stabilize the platter – true for the static case only. When your platter starts to spin, centrifugal force comes in to the picture. Example: if CG is 10 mm below the pivot, and platter rim goes down 1 mm from any reason (the needle drops on to LP) then the tilt moment due to centrifugal force is 3 times bigger than the stabilizing moment due to CG shift. Here a gyroscopic force reveals his tricky nature: any stabilizing force (buoyant force, air pressure) trying to return the platter to its nominal position, actually causes the platter to tilt in the other plane, perpendicular to the force – axis plane, and so on – the wobble party started. This means additional sort of vibrations is induced (precession - like) – the last thing I wanted to have. Just plain physic again.
Let’s say some small CG-pivot shift is unavoidable (due to different LP weight, for instance). So the importance of dumping means to keep precession frequency lower cannot be overstressed: heavy weight platter, viscous fluids… I guess the idler pulley, symmetrical to the main motor pulley can work here. In the same time, it cancels the belt side force – one more advantage.
2. What a hell is overdumping (mentioned by fdegrove)? All kind of vibration down the lower LP side ideally should be sunken and not reflected back to stylus, this is our main goal – am I wrong? Of course, the LP surface should be kept firmly on place not allowed moving due to stylus force, even microscopically. That’s why the compliant platter mats of any kind are out of discussion, I guess. OK, if you are speaking about particular frequency band to be dumped and the others have to be reflected, it make sence. But how can one predict the certain frequency vibration behaviour in the particular platter design?
Regards
Michael
Keep your platter CG as close to the pivot point as possible.
Seems like low CG can help to stabilize the platter – true for the static case only. When your platter starts to spin, centrifugal force comes in to the picture. Example: if CG is 10 mm below the pivot, and platter rim goes down 1 mm from any reason (the needle drops on to LP) then the tilt moment due to centrifugal force is 3 times bigger than the stabilizing moment due to CG shift. Here a gyroscopic force reveals his tricky nature: any stabilizing force (buoyant force, air pressure) trying to return the platter to its nominal position, actually causes the platter to tilt in the other plane, perpendicular to the force – axis plane, and so on – the wobble party started. This means additional sort of vibrations is induced (precession - like) – the last thing I wanted to have. Just plain physic again.
Let’s say some small CG-pivot shift is unavoidable (due to different LP weight, for instance). So the importance of dumping means to keep precession frequency lower cannot be overstressed: heavy weight platter, viscous fluids… I guess the idler pulley, symmetrical to the main motor pulley can work here. In the same time, it cancels the belt side force – one more advantage.
2. What a hell is overdumping (mentioned by fdegrove)? All kind of vibration down the lower LP side ideally should be sunken and not reflected back to stylus, this is our main goal – am I wrong? Of course, the LP surface should be kept firmly on place not allowed moving due to stylus force, even microscopically. That’s why the compliant platter mats of any kind are out of discussion, I guess. OK, if you are speaking about particular frequency band to be dumped and the others have to be reflected, it make sence. But how can one predict the certain frequency vibration behaviour in the particular platter design?
Regards
Michael
Michael,
you are right with your remarks about the wobble party.
Michael and Havoc,
I stand corrected, CoG has to be as close to the pivot as even possible. This calls for a heavy platter as record weight can vary beteween 95gr and 260gr,, no i am not kidding. record weight variation has to made drown in the platter weight.
Looks like the unipivot is not as simple as it looks.
you are right with your remarks about the wobble party.
Michael and Havoc,
I stand corrected, CoG has to be as close to the pivot as even possible. This calls for a heavy platter as record weight can vary beteween 95gr and 260gr,
, no i am not kidding. record weight variation has to made drown in the platter weight.Looks like the unipivot is not as simple as it looks.
TT
Michael,Dice and Peterr,
"you are right with your remarks about the wobble party. "
This is what I expressed before in previous post.
I realise my English isn't the best around but still...
I think introducing a POM or Delrin washer into the bearing sleeve to counteract any tendency to wobble wouldn't be too detrimental
to the unipivot's behaviour.After all once the TT has achieved rotational speed the washer is basically out of play if not fitted too tightly ?
And here I would play with adding the right amount of oil to stabilize and dampen to pivot's tendency to wobble.
Looking at the WTT design may spark inspiration as well.
Rgds,
Michael,Dice and Peterr,
"you are right with your remarks about the wobble party. "
This is what I expressed before in previous post.
I realise my English isn't the best around but still...
I think introducing a POM or Delrin washer into the bearing sleeve to counteract any tendency to wobble wouldn't be too detrimental
to the unipivot's behaviour.After all once the TT has achieved rotational speed the washer is basically out of play if not fitted too tightly ?
And here I would play with adding the right amount of oil to stabilize and dampen to pivot's tendency to wobble.
Looking at the WTT design may spark inspiration as well.
Rgds,
Pedro,
WTT design for you? Apart from the platter and the shaft, it is eeeezy to manufacture. 5 assymmetric teflon pads to support the shaft, that is all.
WTT sonics are very good, just a bit boring. But with another platter, this could become another issue.
WTT design for you? Apart from the platter and the shaft, it is eeeezy to manufacture. 5 assymmetric teflon pads to support the shaft, that is all.
WTT sonics are very good, just a bit boring. But with another platter, this could become another issue.
TT
Bernhard,Pedro an Peterr:
Dice:
You're spot on.
The sound of the WTT actually exemplifies perfectly my expressions and caveat about overdamping a design.
I wouldn't go for the arm either (more of the same sonic footprint ) no matter how spectacular its design,for the same reason.
The pivot is the thing to study in this TT.
Top it of with a well designed,undamped (to my taste) unipivot arm (12") and you have a TT with promising dynamic range.
And as you said :easy to build in a workshop.
Cheers,
Bernhard,Pedro an Peterr:
Dice:
You're spot on.
The sound of the WTT actually exemplifies perfectly my expressions and caveat about overdamping a design.
I wouldn't go for the arm either (more of the same sonic footprint ) no matter how spectacular its design,for the same reason.
The pivot is the thing to study in this TT.
Top it of with a well designed,undamped (to my taste) unipivot arm (12") and you have a TT with promising dynamic range.
And as you said :easy to build in a workshop.
Cheers,
TT
Havoc,
Further to your post requesting some drawings explaining the ideas I so badly express in my previous posts:
Unfortunately all my drawing software and audio related docs are still at my residence in Munich waiting to get picked up .(holiday season forcing me to wait).
This is not something I want to draw in MS Paint...🙁
**Regarding your concern towards the sudden loss of air supply to the bearing assembly of the TT:
Other than inserting some simple blocking valves ( a simple hinged door system or sealed cork system ) put strategically at the buffer tank's air outlet or just behind the air inlets of the TT ,allowing airflow in one direction only and having underpressure closing it automatically, the provision of some cushioning (Delrin,PTFE,POM ring or strips,or combination of materials with the right properties for the job would do) between rotor and stator,I can't come up with anything more elegant for now.
I think the lift of the platter needs only to be minimal, (just not to touch any surface)so the sudden loss of air will not be that dramatic.
Applying Tesla principles here seems over the top ,right ?
One could also use a fail over system but that too seems over the top,well experience will tell.
BTW,I agree that magnets are bitches to fix in such a system.
If I'm not mistaken Jean-Claude Verdier has implemented this North-South magnet principle in his TT to give the platter some initial lift ?
Has anyone any idea how the big players solve this (if at all)?
I'm thinking of Lloyd Walker,Rockport and so on.
**Anyone willing to do some colateral thinking on implementing air propelled turbine principles ? (avionics)
I have some vague idea that tells me we can actually do away with any electrical motor if we use an air supply to both lift and rotate the rotor simultaneously.
The actual rpm can than be measured and an electronically controlled valve can then minutely adjust pressure to the system for instance.
At the same time this will also do away with any belt and pulley sideways pull to the platter...
It may seem tricky but I think it is feasable.
Solving the 45 Rpm rotation is an other issue,here I have no ideas as yet.
I actually mentioned it already (admittedly briefly)in a previous post,no one seems to have noticed ?
Bernhard,
Whip up your calc pls.
Greetz,
For sale:One used Rolls Royce Jetengine for Boeing 747 in mint condition.Offers welcomed.🙂 🙂
Havoc,
Further to your post requesting some drawings explaining the ideas I so badly express in my previous posts:
Unfortunately all my drawing software and audio related docs are still at my residence in Munich waiting to get picked up .(holiday season forcing me to wait).
This is not something I want to draw in MS Paint...🙁
**Regarding your concern towards the sudden loss of air supply to the bearing assembly of the TT:
Other than inserting some simple blocking valves ( a simple hinged door system or sealed cork system ) put strategically at the buffer tank's air outlet or just behind the air inlets of the TT ,allowing airflow in one direction only and having underpressure closing it automatically, the provision of some cushioning (Delrin,PTFE,POM ring or strips,or combination of materials with the right properties for the job would do) between rotor and stator,I can't come up with anything more elegant for now.
I think the lift of the platter needs only to be minimal, (just not to touch any surface)so the sudden loss of air will not be that dramatic.
Applying Tesla principles here seems over the top ,right ?
One could also use a fail over system but that too seems over the top,well experience will tell.
BTW,I agree that magnets are bitches to fix in such a system.
If I'm not mistaken Jean-Claude Verdier has implemented this North-South magnet principle in his TT to give the platter some initial lift ?
Has anyone any idea how the big players solve this (if at all)?
I'm thinking of Lloyd Walker,Rockport and so on.
**Anyone willing to do some colateral thinking on implementing air propelled turbine principles ? (avionics)
I have some vague idea that tells me we can actually do away with any electrical motor if we use an air supply to both lift and rotate the rotor simultaneously.
The actual rpm can than be measured and an electronically controlled valve can then minutely adjust pressure to the system for instance.
At the same time this will also do away with any belt and pulley sideways pull to the platter...
It may seem tricky but I think it is feasable.
Solving the 45 Rpm rotation is an other issue,here I have no ideas as yet.
I actually mentioned it already (admittedly briefly)in a previous post,no one seems to have noticed ?
Bernhard,
Whip up your calc pls.
Greetz,
For sale:One used Rolls Royce Jetengine for Boeing 747 in mint condition.Offers welcomed.🙂 🙂
Come on, use the MS word picture editor.......
Yes, I have noticed your post about air-drive, and I did already before that some thinking on it, in other words: you are to late with your patent 🙂. The problem with all turbines is they are working well in one direction only. It is almost impossible to brake on the motor, what happens when the platter turns faster as the moter to smooth the speed. Only solution there is to use dual turbines, turning in opposing directions and control the speed by working on the ratio between them. Most likely any imperfection in the bearing surface will already make the platter spin (but not in a controlled way).
A way to implement could be like this: The platter consistes of 2 bearing surfaces, joined by a short thick axis. Air is pumped at the joining axis. The lower bearing surface has groves giving it a counter-clockwise spin opposing normal turning of the platter. The upper bearing has groves giving it a clockwise spin, providing normal drive. By varying the amount of air to the lower bearing, you can vary the brakeing on the platter regulating the speed.
Other way, disposing of controlled valves: use an eddy-current brake instead of the brakeing turbine. This will also damp out anything else.
As it is electronically controlled, speed can be chosen freely.
No, not impossible.
Dice, nothing is simple. 😉
Yes, I have noticed your post about air-drive, and I did already before that some thinking on it, in other words: you are to late with your patent 🙂. The problem with all turbines is they are working well in one direction only. It is almost impossible to brake on the motor, what happens when the platter turns faster as the moter to smooth the speed. Only solution there is to use dual turbines, turning in opposing directions and control the speed by working on the ratio between them. Most likely any imperfection in the bearing surface will already make the platter spin (but not in a controlled way).
A way to implement could be like this: The platter consistes of 2 bearing surfaces, joined by a short thick axis. Air is pumped at the joining axis. The lower bearing surface has groves giving it a counter-clockwise spin opposing normal turning of the platter. The upper bearing has groves giving it a clockwise spin, providing normal drive. By varying the amount of air to the lower bearing, you can vary the brakeing on the platter regulating the speed.
Other way, disposing of controlled valves: use an eddy-current brake instead of the brakeing turbine. This will also damp out anything else.
As it is electronically controlled, speed can be chosen freely.
No, not impossible.
Dice, nothing is simple. 😉
TT
Fellows,
Here is some interesting reading from the mouth of a designer I regard very highly.
http://www.cris.com/~tnv2001/WHITPAPR.HTML
Greetz,
Fellows,
Here is some interesting reading from the mouth of a designer I regard very highly.
http://www.cris.com/~tnv2001/WHITPAPR.HTML
Greetz,
TT
Havoc,
Do you have telepathetic gifts of any kind?
These are the same things I've been tinkering with on and off years ago.
Then along came CD,a change of occupation and well, the rest is as they say history.
I couldn't have put it into words like that though.😉
So nothing left to patent,right?
Another problem may be turbulence noise ?
Have you considered a simpleton like Archimedes screw?
MS Word Picture editor ? I'll try to shoot myself in the foot with it.
Anyway I think by now everyone has caught up on the ideas I struggled to express ?
Greetz,
Havoc,
Do you have telepathetic gifts of any kind?
These are the same things I've been tinkering with on and off years ago.
Then along came CD,a change of occupation and well, the rest is as they say history.
I couldn't have put it into words like that though.😉
So nothing left to patent,right?
Another problem may be turbulence noise ?
Have you considered a simpleton like Archimedes screw?
MS Word Picture editor ? I'll try to shoot myself in the foot with it.
Anyway I think by now everyone has caught up on the ideas I struggled to express ?
Greetz,
Preliminary motor/pulley
All,
i know that some of you are quick in setting up a prototype. For that i have stumbled into a preliminary motor/pulley solution.
OUr local surplus shop has voice coil motors made by VEM (Volkseigener Betrieb Elektrische Maschinen, former German Democratic Republic). Not as good as maxon and not as silent but else just about the same. And best of all, this motor has already a pulley usable for flat belts like magnetic tape on its shaft.
I suggest this motor for all who fervently want to try out their setup and who do not wnat ot wait until the maxon motor with CNC pulley is avaiable.
I could pick up this motor from the shop, put it into a bubble bag and amil it to you.
Tell me, who wants such a VEM motor with pulley right now?
All,
i know that some of you are quick in setting up a prototype. For that i have stumbled into a preliminary motor/pulley solution.
OUr local surplus shop has voice coil motors made by VEM (Volkseigener Betrieb Elektrische Maschinen, former German Democratic Republic). Not as good as maxon and not as silent but else just about the same. And best of all, this motor has already a pulley usable for flat belts like magnetic tape on its shaft.
I suggest this motor for all who fervently want to try out their setup and who do not wnat ot wait until the maxon motor with CNC pulley is avaiable.
I could pick up this motor from the shop, put it into a bubble bag and amil it to you.
Tell me, who wants such a VEM motor with pulley right now?
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