AD,
Until your design becomes 3-D, I really wouldn't worry too much about that.
I have a feeling you've got plenty of time.
TerryO
yeah tinitus, I do like where you are going with that but...
Using a feedback system with a light beam could be done pretty easily. I picked up a couple "light to frequency" sensors at radio shack. I think I'm gonna use them to sense the light, and provide a PWM signal for a motor. The output am either variable frequency, or variable pulse width. I need to check on that.
Would making the arm like three feet long be an option?
Using a feedback system with a light beam could be done pretty easily. I picked up a couple "light to frequency" sensors at radio shack. I think I'm gonna use them to sense the light, and provide a PWM signal for a motor. The output am either variable frequency, or variable pulse width. I need to check on that.
Would making the arm like three feet long be an option?
bloddy hell
I just got an idea how to make a simple and very smooth tangential motor
a weight hanging in a string is the motor
and 'speed' is controlled by a small hydraulic system with a adjustable valves
it would ofcourse be optimal if you can control the hydraulic valves with a servo/PWM system
I just got an idea how to make a simple and very smooth tangential motor
a weight hanging in a string is the motor
and 'speed' is controlled by a small hydraulic system with a adjustable valves
it would ofcourse be optimal if you can control the hydraulic valves with a servo/PWM system
lol yeah, I did actually mean three feet. rotational inertia would be huge, and LF resonances would be lurking. BUT tracking angle error and skating forces would be minimized. Why the BLOODY HELL doesn't somebody CUT records with a pivoting mechanism!?
Rant off.
I have read about a tonearm being advanced with a heated wire cutting through a block of ice. Also super smooth and analogue.
OK back on topic. Animus, I really do relish the thinking part of a project like this!
Come up with any more wild ideas we can shoot down?
>.<
Tade
Rant off.
I have read about a tonearm being advanced with a heated wire cutting through a block of ice. Also super smooth and analogue.
OK back on topic. Animus, I really do relish the thinking part of a project like this!
Come up with any more wild ideas we can shoot down?>.<
Tade
thinking out of the box?
You need to think out of the box but keep in mind that there are allot of very smart people out there that have done this all before.
Spindle bearing. My TT uses a simple oil well lubricated plain bearing with a single ball bearing in the bottom for the precision shaft to work against. Quiet and works very well. Anything based on a roller bearing is going to be noisy. Magnets will work but are tricky. Air bearings will work but require VERY, VERY tight tolerances to work well. This brings that need for very clean air.
Tone arm. Some have mentioned carbon fibre. Some of it is conductive and some isn't, it depends on the type. One problem I see is that it is VERY STIFF. This means that the internal damping is nil and it will ring when exposed to any energy source. My money would be on something like Balsa impregnated with resin or lacquered. MDF is not to bad an idea either though structurally it leaves allot to be desired. Maybe an MDF core with Balsa or spruce veneer.
Drive system. The best systems generally use belts. This provides isolation from motor noise and somewhat reduces the motor cogging from being transferred as well.
Motor and control. A standard motor will likely prove to be a poor choice. Some use simple synchronous motors locked to the AC line. 60Hz, or 50Hz if that is your local, is pretty stable and accurate. Some also have crystal locked drivers with dividers for the chosen speed. I would even look at some of the old floppy drives. Epson drives had a motor pack that drove the disk via a belt and had command and power input as well as all drive right on it. The belt pulley was around .25" wide making it ideal to the task.
Platter. So many choices, heavy, flat, stable (both thermally and dimensionally) , stiff, high internal damping are all parameters I would take into account.
Suspension. Springs are generally used. Magnets could also be employed to float the unit.
Electronics. The choice of cartridge will determine what if any is needed. Generally this is not built into the table but instead is an outboard unit. MM have a higher output and so are not in need of an additional gain stage. MC on the other hand need a bit of a bump. This is putting the cart before the horse though.
In closing. I seriously doubt that you could build a TT that would sound reasonably good for less than a hundred dollars in new parts and the rest being scrounged from surplus. There are far more ways to skin this cat and a fair search should kill allot of the more wacky ideas put up. Look at and read about what others have done. Some are insane, others are brilliant, still others are just plain stupid. By way of example, Nelsons stuff fall under the brilliant moniker.
You need to think out of the box but keep in mind that there are allot of very smart people out there that have done this all before.
Spindle bearing. My TT uses a simple oil well lubricated plain bearing with a single ball bearing in the bottom for the precision shaft to work against. Quiet and works very well. Anything based on a roller bearing is going to be noisy. Magnets will work but are tricky. Air bearings will work but require VERY, VERY tight tolerances to work well. This brings that need for very clean air.
Tone arm. Some have mentioned carbon fibre. Some of it is conductive and some isn't, it depends on the type. One problem I see is that it is VERY STIFF. This means that the internal damping is nil and it will ring when exposed to any energy source. My money would be on something like Balsa impregnated with resin or lacquered. MDF is not to bad an idea either though structurally it leaves allot to be desired. Maybe an MDF core with Balsa or spruce veneer.
Drive system. The best systems generally use belts. This provides isolation from motor noise and somewhat reduces the motor cogging from being transferred as well.
Motor and control. A standard motor will likely prove to be a poor choice. Some use simple synchronous motors locked to the AC line. 60Hz, or 50Hz if that is your local, is pretty stable and accurate. Some also have crystal locked drivers with dividers for the chosen speed. I would even look at some of the old floppy drives. Epson drives had a motor pack that drove the disk via a belt and had command and power input as well as all drive right on it. The belt pulley was around .25" wide making it ideal to the task.
Platter. So many choices, heavy, flat, stable (both thermally and dimensionally) , stiff, high internal damping are all parameters I would take into account.
Suspension. Springs are generally used. Magnets could also be employed to float the unit.
Electronics. The choice of cartridge will determine what if any is needed. Generally this is not built into the table but instead is an outboard unit. MM have a higher output and so are not in need of an additional gain stage. MC on the other hand need a bit of a bump. This is putting the cart before the horse though.
In closing. I seriously doubt that you could build a TT that would sound reasonably good for less than a hundred dollars in new parts and the rest being scrounged from surplus. There are far more ways to skin this cat and a fair search should kill allot of the more wacky ideas put up. Look at and read about what others have done. Some are insane, others are brilliant, still others are just plain stupid. By way of example, Nelsons stuff fall under the brilliant moniker.
this is just a first build for now, eventually ill upgrade and try different ideas, like making the platter itself a motor by mounting magnets to the bottom or sides and copper coils around it... if someone could do that AND float the platter on a magnetic field i dont think there would be much noise at all and you wouldnt have the worry about a belt causing a mag-lev platter to destabilize... but for now i think im going to try greased bronze bushings as opposed to ball bearings... theyll require the occassional cleaning and regreasing but should do the trick...
what exactly is the optimal properties of a tonearm?.. great thing about a linear tonearm is i can literally make it as short as i want by moving the shaft the tonearm moves on close to the center of the record if i had a reliable way to pivot it out of the way while changing records... but im just curious if its rigidity, flexibility, or the ability to absorb vibrations i should be focusing on
what exactly is the optimal properties of a tonearm?.. great thing about a linear tonearm is i can literally make it as short as i want by moving the shaft the tonearm moves on close to the center of the record if i had a reliable way to pivot it out of the way while changing records... but im just curious if its rigidity, flexibility, or the ability to absorb vibrations i should be focusing on
just a ring neo will float the platter....problem is that they are not flat and even thickness...so they will need mounting and then grinding before mangnetizing...making good magnetic bearing for the few....
The magnetic float could make radial bearing forces considerable.. and you may loose more in terms of friction and noise than you gain compares to a centered ceramic ball and platter..
better is to float the platter on a cushion off air...two plates of glass and a simple air pump can make a very nice air-bearing...
The magnetic float could make radial bearing forces considerable.. and you may loose more in terms of friction and noise than you gain compares to a centered ceramic ball and platter..
better is to float the platter on a cushion off air...two plates of glass and a simple air pump can make a very nice air-bearing...
i think the bronze bearing setup i posted would work well for a tonearm, and its ultimate simplicity too.. easy to maintain as well if theres an open ended rod like that since the tonearm could be slid off to clean the rod/bearing..
also, in the end of the tube for the tonearm, my idea was to glue a metal threaded bushing into it so that a threaded headshell could be fitted to hold the cartridge
i modeled the backside of it as a weight.. but im not sure if that will actually be a weight, a hollow compartment to place lead weights, or if there will just be a couple inches of shaft there that i could slide wooden rings onto, and hold on with a rubber o-ring so they dont slip off the back side
also, in the end of the tube for the tonearm, my idea was to glue a metal threaded bushing into it so that a threaded headshell could be fitted to hold the cartridge
i modeled the backside of it as a weight.. but im not sure if that will actually be a weight, a hollow compartment to place lead weights, or if there will just be a couple inches of shaft there that i could slide wooden rings onto, and hold on with a rubber o-ring so they dont slip off the back side
i guarantee that the above design with a bushing will fail. The side load on the cantilever of a cartridge is far far too feeble. I am extremely surprised that the gentleman who used a linear roller bearing achieved success. In fact, I am surprised that a passive linear tonearm, even one in which in which an air bearing is used, can function due to the mass of the tonearm/sled. I would be afraid that when the arm accelerates into the lead out groove it doesn't just tear of the cantilever. An arm like the Kuzma air bearing is a beautiful piece of work but still...
i would honestly love to see a record produce enough forces to tear a carbon fiber cantilever apart before the low friction bearing moves, there just isnt enough friction in the bearing, nor is there enough sudden force in the record to tear it off... and how can your guarantee that it will fail be valid when you would have guaranteed the other listed linear systems would fail, when they in fact work?.. i bet it works just fine... even if i do in fact decide to use balsa wrapped in resin soaked fabric
with air pressure supported, it is indeed very strange to see how easily it moves from side to side, accurately following any groove
but true, its also easily disturbed
just very very little dust, and its completely stuck
needs to be kept highly polished and shiny, always
sadly, airpumps are noisy and very annoying
too much trouble to my liking
but hearing one is a whole different thing
Take a look at the Souther linear tracking arms, as well as the OPUS 3 - these should give you a very good idea of the bearing designs that work in passive linear trackers - and they work well.
The cantilever will probably not snap off if the side forces are excessive but you will get lots of skipping. My limited experimenting indicates that everything you can do to keep drag and mass to a minimum will help - sadly this does preclude the use of a lot of cartridges. The Souther from direct experience is very fussy and likes low mass, high compliance cartridges best, also things like the dress of the cartridge leads can result in major mis-tracking if not handled correctly..
My solution to these sorts problems is the use a 16" transcription arm.. (Effective length is 12") Long arm tubes usually result in high mass which means low compliance, high mass cartridges must be used - which are my preference anyway.. Have a look at Nanooks 212 arm thread for an alternative approach.. (It's a long diy arm that can be designed to have medium mass)
The cantilever will probably not snap off if the side forces are excessive but you will get lots of skipping. My limited experimenting indicates that everything you can do to keep drag and mass to a minimum will help - sadly this does preclude the use of a lot of cartridges. The Souther from direct experience is very fussy and likes low mass, high compliance cartridges best, also things like the dress of the cartridge leads can result in major mis-tracking if not handled correctly..
My solution to these sorts problems is the use a 16" transcription arm.. (Effective length is 12") Long arm tubes usually result in high mass which means low compliance, high mass cartridges must be used - which are my preference anyway.. Have a look at Nanooks 212 arm thread for an alternative approach.. (It's a long diy arm that can be designed to have medium mass)
Miib,
I forgot to add, I think your air bearing platter idea with glass plates is brilliant. a thin air film will have an extremely high resonant frequency and thus practically "stick" the platter to the plinth. Then you can make your plinth massive and have an incredibly good sink for the energy.
I love it!
I forgot to add, I think your air bearing platter idea with glass plates is brilliant. a thin air film will have an extremely high resonant frequency and thus practically "stick" the platter to the plinth. Then you can make your plinth massive and have an incredibly good sink for the energy.
I love it!
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