Thanks for infos, Ralf. I didn't know the origin of the name and the beautiful story of that brave man, but I've always loved that little locomotive and its daily hard work; Dumbo is one of the first films seen in my childhood.
Believing that even elephants can fly - by dreaming and wanting - is perhaps essential to "think out of the box", to survive the boredom of what we are convinced to know too well.
ciao - carlo
Believing that even elephants can fly - by dreaming and wanting - is perhaps essential to "think out of the box", to survive the boredom of what we are convinced to know too well.
ciao - carlo
It seems that there is no need for air bearings, and pumps and so on, to make a good linear tracker. Just first build your own mini lathe like this one, with acceptable tolerances.
YouTube
(on air bearings, of course).
Now look at that spindle running (1 '10 "- 1' 30"): no lubrication, no air bearing ...
with great envy - carlo
YouTube
(on air bearings, of course).
Now look at that spindle running (1 '10 "- 1' 30"): no lubrication, no air bearing ...
with great envy - carlo
Lil Casey Carbon
Hi again, Carlo. Eduard has finished carbon version of the arm. This time it was listened to on the same advanced audio system, as before. This time with Koetsu cartridge. Audiophiles are completely blown away with the sound, no one feels it is possible to return to another arm and still tolerate the sound. System owner is already addicted to Lil Casey.
Actually, in my country, audiophiles are addicted to the well known foreign brands, and nobody likes domestic products, as well, as DIY components, no matter how good they are. This time they feel opposite, and it speaks for itself.
Actually, people want to know full name of Lil Casey developer, in order to be grateful to you.
Best wishes and congrats,
Walter
Hi again, Carlo. Eduard has finished carbon version of the arm. This time it was listened to on the same advanced audio system, as before. This time with Koetsu cartridge. Audiophiles are completely blown away with the sound, no one feels it is possible to return to another arm and still tolerate the sound. System owner is already addicted to Lil Casey.
Actually, in my country, audiophiles are addicted to the well known foreign brands, and nobody likes domestic products, as well, as DIY components, no matter how good they are. This time they feel opposite, and it speaks for itself.
Actually, people want to know full name of Lil Casey developer, in order to be grateful to you.
Best wishes and congrats,
Walter
dear Walter, thank you all for those compliments, also on behalf of the little Lil Casey.
Since retirement i like diying to waste time: not to make the best arm in the world (I hate too crowded clubs) but to experiment with the different types, looking for solutions to the problems they pose.
Ergo I have no desire to fool anyone, starting from myself. As says an old (retired of course) friend salesman: two very different, very exclusive, $$uper expen$$ive equipments should sound exactly the same: there are no scales claimed to weigh "better".
So for us diyers there are only two questions we have still to ask:
- does an arm with 0 offset (radial - linear - or pivoted) work better than a normal pivoted one? and if so, When, Where, and Why?
- does a radial rail arm work better than a normal linear passive (air bearing included) arm? and if so, When, Where, and Why?
I have explored almost all the types of arms (suspended arms excluded, forgive me) checking their limits: now if I were to build my last arm I would think of a simple (?) non-ideological one, which would get the right amount of side force just from the stylus drag. Easier said than done, isn't true?
carlo
full name: Carlo Ballestrero - living in Prato (near Florence), born in Rome too long ago.
Since retirement i like diying to waste time: not to make the best arm in the world (I hate too crowded clubs) but to experiment with the different types, looking for solutions to the problems they pose.
Ergo I have no desire to fool anyone, starting from myself. As says an old (retired of course) friend salesman: two very different, very exclusive, $$uper expen$$ive equipments should sound exactly the same: there are no scales claimed to weigh "better".
So for us diyers there are only two questions we have still to ask:
- does an arm with 0 offset (radial - linear - or pivoted) work better than a normal pivoted one? and if so, When, Where, and Why?
- does a radial rail arm work better than a normal linear passive (air bearing included) arm? and if so, When, Where, and Why?
I have explored almost all the types of arms (suspended arms excluded, forgive me) checking their limits: now if I were to build my last arm I would think of a simple (?) non-ideological one, which would get the right amount of side force just from the stylus drag. Easier said than done, isn't true?
carlo
full name: Carlo Ballestrero - living in Prato (near Florence), born in Rome too long ago.
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The arm
Well, now we know exact name, to whom to be grateful, thank you very much, Carlo. Good things should have correct names. As to the question of which component sounds better, it isn't simple. There are lots of speculations concerning, and lots of opinions. As for me, I trust my own perception, as well, as of some experienced audiophile friends. Some of them are so sensitive and well trained, as to the extent of almost being phychics. Human hearing perception is not democratic, and polit-correctness doesn't apply to it. Even ability to hear high frequencies vary a lot for different individuals, not considering more complicated aspects of sound. I would apply what I said to Lil Casey. It sounds much better, than other arms, and difference becomes even more evident, as you gradually use better and more sophisticated cartridge. And difference is really huge. It reminds me my first experience in 1982 with tube amp (made by Vladimir Lamm, who resided in my city back then, and whom I knew), after decade of listening of average hi-fi solid state amps. It was kind of revelation, and now, with Lil Casey it is revelation again.
In both cases sonical difference may be explaned by different physics.
Walter
Well, now we know exact name, to whom to be grateful, thank you very much, Carlo. Good things should have correct names. As to the question of which component sounds better, it isn't simple. There are lots of speculations concerning, and lots of opinions. As for me, I trust my own perception, as well, as of some experienced audiophile friends. Some of them are so sensitive and well trained, as to the extent of almost being phychics. Human hearing perception is not democratic, and polit-correctness doesn't apply to it. Even ability to hear high frequencies vary a lot for different individuals, not considering more complicated aspects of sound. I would apply what I said to Lil Casey. It sounds much better, than other arms, and difference becomes even more evident, as you gradually use better and more sophisticated cartridge. And difference is really huge. It reminds me my first experience in 1982 with tube amp (made by Vladimir Lamm, who resided in my city back then, and whom I knew), after decade of listening of average hi-fi solid state amps. It was kind of revelation, and now, with Lil Casey it is revelation again.
In both cases sonical difference may be explaned by different physics.
Walter
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Sorry Marik,
It's not possible passively using permanent magnets. Check out Earnshaw's theorem for the reason why. If you are thinking of something like those globe toys that suspend a sphere in mid air there are many Many problems to overcome. The globe toy works by rapidly modulating the magnetic field, basically dropping and catching the globe repeatedly. This will cause the levitated object to vibrate, not a good thing for a tonearm. Also a levitated carriage will not be held stably and would have a lot of freedom of movement in directions you don't want. You may have seen the recently introduced magnetically levitated deck. Check out the horrendous level of wobble the platter has. This is a purely gimmick product. Another problem is the strong magnetic field required. Do you want a very strong modulated magnetic field anywhere near your cartridge. And finally the arm would be completely physically disconnected from the deck leaving no possibility of mechanically grounding the arm. Good mechanical grounding is one of the most important design considerations.
Hi Walter, Carlo,
I think the most likely reason that the lil Casey sounds as it does is the elimination of the bending modes. These are present in all long tonearm designs and are the single greatest cause of colouration in most. By getting rid of the arm tube you also get rid of the colouration it introduces. Until you hear an arm without bending mode colouration you don't realise just how much most arms have.
Niffy
Modern manufacturing techniques would easily allow the construction of a magnetic array as Jim described, it could just as easily have a halbach array built into it. Regardless of how fancy you make your magnet array it will be unstable and collapse. If using permanent magnets the system HAS to have at least one axis constrained in order to achieve stability. The only magnetic levitation that works using permanent magnets is something like the levitron toy.
Levitron - Wikipedia
This system is still constrained by the gyroscopic action of the spinning top. Having your tonearm spinning around is unlikely to result in good sound quality.
The only practical way to make a tonearm magnetically levitate is to use an active system.
The magnetic gap does not need to be large. All the toys and gadgets (like the levitating turntable) have large visible gaps so that they look impressive. By making the gap smaller you will make the carriage more dimensionality stable and less wobbly and you will not require such a strong magnetic field. In order to maintain stable levitation the magnetic field has to modulated, basically picking up and dropping the arm repeatedly. This will cause the arm to vibrate at the frequency of the modulation. The modulation frequency will have to be well into the ultrasonic region, say 100khz. Class-D amplifiers work at this sort of frequency and some of them (Hypex) sound very good so introducing a high frequency modulation doesn't need to be a problem. You may run into a problem of the coils acting like antenna and strongly transmitting at 100khz.
Maglev trains seem to work fine and are smooth in operation so it should be possible to do the same with a tonearm. The engineering challenges of building such an arm are not trivial. I can see no benefits of using Maglev over an air bearing and several disadvantages. And don't forget about the good old mechanical linear tracker with its superior mechanical grounding.
Purely passive magnetic levitation lives next door to the perpetual motion machine.
Niffy
Levitron - Wikipedia
This system is still constrained by the gyroscopic action of the spinning top. Having your tonearm spinning around is unlikely to result in good sound quality.
The only practical way to make a tonearm magnetically levitate is to use an active system.
The magnetic gap does not need to be large. All the toys and gadgets (like the levitating turntable) have large visible gaps so that they look impressive. By making the gap smaller you will make the carriage more dimensionality stable and less wobbly and you will not require such a strong magnetic field. In order to maintain stable levitation the magnetic field has to modulated, basically picking up and dropping the arm repeatedly. This will cause the arm to vibrate at the frequency of the modulation. The modulation frequency will have to be well into the ultrasonic region, say 100khz. Class-D amplifiers work at this sort of frequency and some of them (Hypex) sound very good so introducing a high frequency modulation doesn't need to be a problem. You may run into a problem of the coils acting like antenna and strongly transmitting at 100khz.
Maglev trains seem to work fine and are smooth in operation so it should be possible to do the same with a tonearm. The engineering challenges of building such an arm are not trivial. I can see no benefits of using Maglev over an air bearing and several disadvantages. And don't forget about the good old mechanical linear tracker with its superior mechanical grounding.
Purely passive magnetic levitation lives next door to the perpetual motion machine.
Niffy
Modern manufacturing techniques would easily allow the construction of a magnetic array..
Maybe, but how long would last the magnetism of arrays made in such way? in any case you have described the situation perfectly: Purely passive magnetic levitation lives next door to the perpetual motion machine.
The electromagnetic solution seems feasible, but with what advantages? the resonances could be greater than with compressed air, perhaps altering the field with a possible avalanche effect
c
Have you seen that video with that 1 micron tolerance spindle running? amazing, completely different from a lapped surface, it completely surprised me
c
Maybe, but how long would last the magnetism of arrays made in such way? in any case you have described the situation perfectly: Purely passive magnetic levitation lives next door to the perpetual motion machine.
The electromagnetic solution seems feasible, but with what advantages? the resonances could be greater than with compressed air, perhaps altering the field with a possible avalanche effect
c
Have you seen that video with that 1 micron tolerance spindle running? amazing, completely different from a lapped surface, it completely surprised me
c
I had seen that video several years ago. It required a complete overhaul and upgrade of an already very high quality lathe. Very impressive but not the type of thing that you or I could do in the garden shed. My guess on how the spindle ran so freely is that it had captured a pocket of air under it that was slowly leaking through the very small gap. This pocket will eventually loose all the air due to this leakage and would slowly sink into the outer block. It may be possible to use this for a turntable main bearing if you could maintain the air pocket but then you're back to pumps all be it with a very low flow rate. Even a small high pressure regulated tank could probably run this bearing for a very long time, depending on the mass of the platter, so the pump would not be in constant use.
As there would be no air pocket with an open ended rail for a linear arm I doubt that it would work as is in this application. If you were to build an air pocket in the middle of the bearing block it could then possibly work. You would need to supply air via a tube similar to how Jim's arm works so again you are back to tanks and pumps. It would be like a normal air bearing but with a very much smaller air gap.
The rail would have to be kept scrupulously clean for reliable operation. The very small air gap would probably make this an exceedingly stiff bearing, hopefully with a resonant frequency with the mass of the arm outside of the audio band. This should give excellent mechanical grounding across the entire audio band.
Considering the materials that the bearing would need to be made from I fear that the mass would be prohibitively high.
Nice thought though.
Niffy
As there would be no air pocket with an open ended rail for a linear arm I doubt that it would work as is in this application. If you were to build an air pocket in the middle of the bearing block it could then possibly work. You would need to supply air via a tube similar to how Jim's arm works so again you are back to tanks and pumps. It would be like a normal air bearing but with a very much smaller air gap.
The rail would have to be kept scrupulously clean for reliable operation. The very small air gap would probably make this an exceedingly stiff bearing, hopefully with a resonant frequency with the mass of the arm outside of the audio band. This should give excellent mechanical grounding across the entire audio band.
Considering the materials that the bearing would need to be made from I fear that the mass would be prohibitively high.
Nice thought though.
Niffy
If I don't remember badly at some point he talks about hard disks, known to work on the laminar flow generated by high speed. I wonder how a slow rotation like that in the video could generate a similar effect, or if such a small roughness could cause what in chemistry is called gas adsorption, a superficial gaseous thin film.
As for the air bearings I confess all my prejudices: my son as teen played transverse flute all day long, so for me it's difficult to think that air may not vibrate when entering or leaving a tube ...
c
However my admiration was all for that lathe, absolute science fiction compared to mine.
As for the air bearings I confess all my prejudices: my son as teen played transverse flute all day long, so for me it's difficult to think that air may not vibrate when entering or leaving a tube ...
c
However my admiration was all for that lathe, absolute science fiction compared to mine.
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On the scale of a 1 micron air gap even a very slow rotation would have the different parts of the bearing moving at high speed relative to each other. In such a narrow gap the movement of the air would certainly be laminar. Even when the centre part was stopped the two parts didn't bind and easily started rotating again. I don't think rotational speed can have anything to do with the way this bearing behaves.
Niffy
Niffy
I don't know if it works in reality, but it is just an idea. In reality, it may be just better to use air bearing the same construction as mine with low air pressure and almost noiseless air pump which can be placed in the same room as your listening room. Air force one table has an air pump which can be placed in the same room.
The strong magnetic field may be another problem.
Jim
Excuse me Super10018, I just meant to say that the scheme looks smart - simple as an air bearing, as you point out - but that it seems to me really difficult to build permanent magnets with a field distribution (which should also be uniform) like those shown. If I remember correctly, in a cylinder the two poles are above-under, more than inside-outside.
Niffy says that today's technology makes them perfectly feasible (using Halbach arrays?), so I don't ask for anything better than to see such an arm in action.
carlo
Niffy says that today's technology makes them perfectly feasible (using Halbach arrays?), so I don't ask for anything better than to see such an arm in action.
carlo
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Hi Niffy,
Yes, I worked with passive maglev for another application and aware that to make the passive system to be stable and not collapse we do need to have one axis support (even with Hallbach array). But we do have it--isn't the 'stylus/grove' system here is exactly the axis we are looking for?
Best, M
Hi Marik,
In order to make the passive system work and not collapse you have to constrain the system. You design the system so that it has a preferred direction in which it wishes to collapse then constrain the axis that aligns with this direction. This will result in a force being applied along/about this axis. The stylus/cantilever is attached via a compliant mounting. If the constraining force is applied laterally or downwards via the stylus will result in an undesirable defection of the cantilever. The magnitude of the constraining force required when levitating even a super lightweight carriage would almost certainly be so high as to cause instantaneous misstracking. Even if it didn't as soon as the stylus was raised from the groove the constraint would disappear and the system would immediately collapse making queuing impossible.
With a linear bearing the natural axis for collapse would be at 90° to the direction the bearing moves in. This would be forwards/backwards, up/down or an angle in between and not left/right. As the stylus is sliding in the groove it can offer no constraint forward/backwards. You cannot balance the constraint using stylus drag as drag constantly changes. Even if drag didn't change you would have to balance the magnetic field to the drag to an impossibly fine degree, even thermal noise would collapse the system. You cannot constrain vertically as the arm has to be able to move vertically to track warps.
The only way that magnetic levitation can be used in a passive way is to build a normal mechanical linear arm running on wheels with bearings and then use magnetic levitation to relieve some of the weight of the carriage. The friction of the bearings is directly related to the load applied. If you reduce the load you reduce the friction. So if you support half the weight with magnets only half the weight will be applied to the bearings and the friction of the bearings will be reduced to about half. The contact of the wheels on the rail will act as the constraint making the system stable.
I did quite a lot of work on this idea at one time. You do still have the same problems that you would with a normal mechanical linear arm such as bearing chatter if using ballrace bearings. It only works using magnetic repulsion. (I tried using attraction but this massively overdamped the system and resulted in worse overall friction than without it.) As the magnetic field is only working vertically, it doesn't have to deal with stylus drag, the gap between the magnets can be very small so only very small magnets are required. I had a row of neodymium magnets that were about 1mm wide and 1mm deep and about 5mm long. These have to run the full length of the rail. The carriage had two small 2mm diameter 1mm thick magnets attached in adjustable mounts. It definitely reduced friction. I abandoned this line of experimentation in favour of the pin bearings I now use as these gave a better reduction in friction, greater consistency, eliminated chatter and offered much better mechanical grounding. It is probably possible to combine the magnetic and pin bearings but with the design of my current rail the gap between the magnets would be too great. One probable downside of reducing the load using magnets and pin bearings is that the efficiency of the mechanical ground may be compromised. I feel that improving mechanical grounding made much more difference than reducing friction.
Niffy
In order to make the passive system work and not collapse you have to constrain the system. You design the system so that it has a preferred direction in which it wishes to collapse then constrain the axis that aligns with this direction. This will result in a force being applied along/about this axis. The stylus/cantilever is attached via a compliant mounting. If the constraining force is applied laterally or downwards via the stylus will result in an undesirable defection of the cantilever. The magnitude of the constraining force required when levitating even a super lightweight carriage would almost certainly be so high as to cause instantaneous misstracking. Even if it didn't as soon as the stylus was raised from the groove the constraint would disappear and the system would immediately collapse making queuing impossible.
With a linear bearing the natural axis for collapse would be at 90° to the direction the bearing moves in. This would be forwards/backwards, up/down or an angle in between and not left/right. As the stylus is sliding in the groove it can offer no constraint forward/backwards. You cannot balance the constraint using stylus drag as drag constantly changes. Even if drag didn't change you would have to balance the magnetic field to the drag to an impossibly fine degree, even thermal noise would collapse the system. You cannot constrain vertically as the arm has to be able to move vertically to track warps.
The only way that magnetic levitation can be used in a passive way is to build a normal mechanical linear arm running on wheels with bearings and then use magnetic levitation to relieve some of the weight of the carriage. The friction of the bearings is directly related to the load applied. If you reduce the load you reduce the friction. So if you support half the weight with magnets only half the weight will be applied to the bearings and the friction of the bearings will be reduced to about half. The contact of the wheels on the rail will act as the constraint making the system stable.
I did quite a lot of work on this idea at one time. You do still have the same problems that you would with a normal mechanical linear arm such as bearing chatter if using ballrace bearings. It only works using magnetic repulsion. (I tried using attraction but this massively overdamped the system and resulted in worse overall friction than without it.) As the magnetic field is only working vertically, it doesn't have to deal with stylus drag, the gap between the magnets can be very small so only very small magnets are required. I had a row of neodymium magnets that were about 1mm wide and 1mm deep and about 5mm long. These have to run the full length of the rail. The carriage had two small 2mm diameter 1mm thick magnets attached in adjustable mounts. It definitely reduced friction. I abandoned this line of experimentation in favour of the pin bearings I now use as these gave a better reduction in friction, greater consistency, eliminated chatter and offered much better mechanical grounding. It is probably possible to combine the magnetic and pin bearings but with the design of my current rail the gap between the magnets would be too great. One probable downside of reducing the load using magnets and pin bearings is that the efficiency of the mechanical ground may be compromised. I feel that improving mechanical grounding made much more difference than reducing friction.
Niffy