I know of air bearings etc however it's occurred to me that:
a) the sides of a large platter are smooth to minimise variations in speed.
b) motors or any pulse of energy causes variations in speed.
c) that multiple air jets using the friction of the air against the edge of the platter can rotate - a case of 'contactless' air propulsion where the air is regulated to prevent any variation in velocity.
This would then have a constant speed, with low variability. Multiple jets are likely to be needed to provide enough force to overcome the needle-record and bearing friction.
Just wondered if this has been attempted previously?
a) the sides of a large platter are smooth to minimise variations in speed.
b) motors or any pulse of energy causes variations in speed.
c) that multiple air jets using the friction of the air against the edge of the platter can rotate - a case of 'contactless' air propulsion where the air is regulated to prevent any variation in velocity.
This would then have a constant speed, with low variability. Multiple jets are likely to be needed to provide enough force to overcome the needle-record and bearing friction.
Just wondered if this has been attempted previously?
When the application is high end audio, the problem with air bearings and air jets is the noise that they generate. Think of a leaky impact wrench air hose at your local mechanic shop. Otherwise, it's a perfect application for contactless bearings, just one that is not all that useful for audio purposes.
You describe a Tesla turbine.
It can be done whitout any jet or compressed air. Imagine the two discs of the turbine being separated (the shaft between them is cut). One, the platter, is plain, whitout any holes and the other, driven by the motor, has holes close tho its shaft to allow for fresh air intake. Distance between platter and driver disc have to be kept small and constant.
The system works (I have buid one) but needs a speed regulation loop sensing the speed of the platter. And speed is ramping up slowly.
Hello NickKUK,
The idea occurred to me many years ago, but I didn't know much and it remained just a thought. I collected a lot of literature at the time concerning the science of "Fluidics" which I still have. If you have the necessary knowledge, by all means pursue the idea. And don't let anyone discourage you.
To get a turn table up to speed quickly, there could be a solenoid under the platter whose plunger impacts a surface on the underside of the platter and quickly retracts.
You could conduct a patent search as I think there exist patents.
Ralf
The idea of revolving a platter with air occurred to me many years ago, but at the same time I figured it would require some sort of a “brake” , such as the tensioning band of a stationary bicycle, in order to maintain speed accurately. And would such a brake band build up static electricity or other problems ?.
An acrylic medium weight platter with ~13 inch diameter with lowest friction center bearing which is lifted by repulsion magnets at bottom of spindle, adjusted so as the bearing spindle never looses contact with base just reduces platter weight force which reducese friction and a single airflow system bifurcated in to three parts which blows air by three vent on three equidistance places of circumferance of platter which also has cavities or small fins on bottom side so as air pushes in to cavities will work somewhat ?
Maybe the brake could be a stream of air in the opposite direction, with the control system balancing the two streams to maintain set speed?
Jan
Hello Hiten,
I don't know if there is such a word as "trifurcated" I was trying to be funny.
Ralf
An alternative could be some kind of eddy current drive. On the principle of electricity power meters. Perhaps not a new idea.
Noise both from air jets and source pump, speed control, startup time. People complain about noise from air bearing arms, and use bottle air, but the volumes needed to rotate a platter are going to be higher.
Perhaps you could engineer something using the coanda effect?
Perhaps you could engineer something using the coanda effect?
Thinking about this more over the last few days. The source of air would be an issue - possibly a fast moving Archimedean screw drive to reduce the pulsing from a compressor valve.
Or a scroll compressor - basically the same but in a condensed spiral format.
Or a scroll compressor - basically the same but in a condensed spiral format.
These air experiments are just probe in to what can be achieved. Something new to the hobby. I am almost sure source of air jet will be noisier than a belt drive motor.
If anyone has opened a music box mechanism it has finned governor to stabilize the speed. If such finned shaft can drive a rubber pully (Small diameter to large for torque) it can work somewhat. Advantage would be less air pressure required resulting in less noise.
(Image taken from internet)
If anyone has opened a music box mechanism it has finned governor to stabilize the speed. If such finned shaft can drive a rubber pully (Small diameter to large for torque) it can work somewhat. Advantage would be less air pressure required resulting in less noise.
(Image taken from internet)
Tom Fletcher's barely enough powered Nottingham gets up to speed with a little help from the listener's hand.
(It makes you feel a part of the process: )
That could be solved by putting the jets under the platter.
You could then have vanes on the bottom of the platter for better drive.
Any sort of thing I can think of to prevent runaway platter speeds on ultra low friction bearings seems problematic. We have to regulate the speed within 1-2 tenths of one rpm for speed irregularities to not be audible. Your proposal just might work, but it would require an investment in time, machining,and materials to find out 🤷♂️. A remotely hidden 5 -10 gallon air tank would take care of the worry of air noise I would think. That’s Another thing that would have to be built and tested to find out. It does nicely remove the necessity for very expensive motors with elaborate power supplies and electronics though. You could play recordings at virtually any speed you wanted.
The amount of air required to turn a platter on a very low friction bearing would be minimal I think. Regulating that speed is where I think the big problem would be. A super small difference in air flow might result in a 35 or 31 rpm speed. It might need adjusting all the time due to temperature and humidity changes.