More Variac
Once more from Mark's PC thru my Mac to you (i know he really wants his own Mac and who could blame him :^)
<a href="http://p10hifi.net/tlinespeakers/sonopivot.gif"><img src="http://p10hifi.net/tlinespeakers/sonopivot-s.gif"></a>
clik on image to get bigger drawing with text
dave
Once more from Mark's PC thru my Mac to you (i know he really wants his own Mac and who could blame him :^)
<a href="http://p10hifi.net/tlinespeakers/sonopivot.gif"><img src="http://p10hifi.net/tlinespeakers/sonopivot-s.gif"></a>
clik on image to get bigger drawing with text
dave
Dave,
thanks for hassling out how to patch an image with thumbnail in the text !
(hoping to end the CAD discussion) the day an adult 3D CAD is available for the Mac, i buy one i even if i have to borrow the money.
TMK there is none. Unfortunaltely CAD left the UNIX realm and went Windoze ... too early. 🙂
Mark and Peter,
coincident engineering? 🙂 Methinks, an idea is a spiritual being oof its own and if it is around, it sometimes chooses more than one human being to be its receptacle ....holy grail talk .... ts ts ts ...🙂
Praise:
Methinks, this tilt limiting washer is a very good idea, Peterr, you should see how you integrate it. Maybe you turn your ball rest completely out of POM and have it have a smooth and rounded circular fin? What also could work fine: an O-ring just touching. Not squeezed. But, take a PTFE O-ring or Viton, in any case something not swelling from oil contact.
In fact, this has been done already and i have seen it work. But the whole setup is a yuppie design TT, a slim and flat thing and the o_ring is close to the axial bearing and the platter is thin. Not my taste, this thing. But at the platter height we are discussing here, could work gorgeous to get the tilt out.
Minor critique:
Center pin:
if the centering device is a pin sticking out, then the record is centered by pin and record center hole. I am afraid i have to remind you the record's groove pattern is not centered to the center hole and the side A's groove pattern is not centered to side B's one. Let's assume a centering pin is dia 3mm and a slotted centering tube is 7.2mm to match the record's center hole, this leaves adjustable excentricity excursion of 2.1mm max. Several records in my collection exceed that 🙁 ... and my collection is not alltoo big, 1500 records maybe.
I have written in the spec (and, for the record, nobody has objected so far) we need atleast te option of a groove-pattern-referenced centering device.
Excentricity is not that critical with a pivoted tonearm and also not with an active linear tracker like the Goldmund or Rabco. But passive linear trackers are out, mega-out with excentric records, soundstage dancing tango and µdynamix unstable. I also could say, passive linear trackers together with excentric records care to make the $$$ MC cartridge mega-out very soon.
A 7.2mm center pin eliminates the option to center the record by groove pattern.
I would not vote for a Ladegaard tonearm then or an old Dennesen ABLT albeit both are comparitively gentle in this respect, and frankly, i would have a very bad conscience to sell you one of my passive linear trackers in the future. Which makes me sit the corner and cry .... 😉
Can't you folks go with small center hole and tuck a 7.2mm pin in for most records?
Allen hex hole as centering surface for the bearing ball: if you think the hex hole is centered to the bolt, dream on. It is not.
If you want the unipivoted platter to run like a turning egg, go on, use this!
If you want to run the platter like a platter should run, you need a turned part with a shallow conical countersinking atleast on the rotor side. With the o-ring tilt eliminator, you also need it at the stator.
Mark,
please make your ball rest as big as space permits you. Like Peter did. Partial oscillations ....
/end minor critique.
Ruby ball: not expensive but not cheap either and definitely not easy to obtain (www.smallparts.com has them up to 1/8"/3.18mm, my local standardized has them up to 10mm in stock (about US$65), bigger dias can be ordered but have considerable lead time).
Yours will last for a lifetime if you do not epoxy it, because then you can rotate it if the surface should have gotten a damage.
Mark,
i would not be surprised if the old Thorens had a spherical surface "polished on" which has considerably higher qulity and smoothness than a ball-race ball. my standard textbook on Feinwerktechnik (signal engineering) describes this as well as desing detail as as method how to do it properly. And it is obvious this is meant for TTs.
Peterr,
Vacuum: was afraid i would have to elaborate (now and then i tend to understand HHs moaning 🙂 ).
The record is better be pressed on the platter surface to impede partial oscillations, particularly in proximity of the stylus, and to help the partial oscillations to find their way into the platter and leave the record. However, if this pressure is too high, the record is damaged by dirt particles not swept off the platter and now crammed into the grooves.
Imagine a self-cooked jelly preserve. If the jar is crammed full of the jelly and the lid's sealing is less than perfect, partial vacuum between jelly and lid is gone soon. Now the last jar of a batch is never full. If the same lid with imperfect sealing is used, it does not matter because the volume to be filled is soo much bigger.
Applied on TTplatter vacuum system: if the vacuum space between record and platter is increased by a connected hidden cavity (system o communicting cavities) inside the platter, then not much negative pressure / partial vacuum is needed and the sealing at the record edge can be less than perfect anyway
(My mother's mistake to accidentally use the lid marked imperfect just for the last jelly jar, together with my surprise opening it after 6 months and still finding vacuum, helped me to figure that out).
thanks for hassling out how to patch an image with thumbnail in the text !
(hoping to end the CAD discussion) the day an adult 3D CAD is available for the Mac, i buy one i even if i have to borrow the money.
TMK there is none. Unfortunaltely CAD left the UNIX realm and went Windoze ... too early. 🙂
Mark and Peter,
coincident engineering? 🙂 Methinks, an idea is a spiritual being oof its own and if it is around, it sometimes chooses more than one human being to be its receptacle ....holy grail talk .... ts ts ts ...🙂
Praise:
Methinks, this tilt limiting washer is a very good idea, Peterr, you should see how you integrate it. Maybe you turn your ball rest completely out of POM and have it have a smooth and rounded circular fin? What also could work fine: an O-ring just touching. Not squeezed. But, take a PTFE O-ring or Viton, in any case something not swelling from oil contact.
In fact, this has been done already and i have seen it work. But the whole setup is a yuppie design TT, a slim and flat thing and the o_ring is close to the axial bearing and the platter is thin. Not my taste, this thing. But at the platter height we are discussing here, could work gorgeous to get the tilt out.
Minor critique:
Center pin:
if the centering device is a pin sticking out, then the record is centered by pin and record center hole. I am afraid i have to remind you the record's groove pattern is not centered to the center hole and the side A's groove pattern is not centered to side B's one. Let's assume a centering pin is dia 3mm and a slotted centering tube is 7.2mm to match the record's center hole, this leaves adjustable excentricity excursion of 2.1mm max. Several records in my collection exceed that 🙁 ... and my collection is not alltoo big, 1500 records maybe.
I have written in the spec (and, for the record, nobody has objected so far) we need atleast te option of a groove-pattern-referenced centering device.
Excentricity is not that critical with a pivoted tonearm and also not with an active linear tracker like the Goldmund or Rabco. But passive linear trackers are out, mega-out with excentric records, soundstage dancing tango and µdynamix unstable. I also could say, passive linear trackers together with excentric records care to make the $$$ MC cartridge mega-out very soon.
A 7.2mm center pin eliminates the option to center the record by groove pattern.
I would not vote for a Ladegaard tonearm then or an old Dennesen ABLT albeit both are comparitively gentle in this respect, and frankly, i would have a very bad conscience to sell you one of my passive linear trackers in the future. Which makes me sit the corner and cry .... 😉
Can't you folks go with small center hole and tuck a 7.2mm pin in for most records?
Allen hex hole as centering surface for the bearing ball: if you think the hex hole is centered to the bolt, dream on. It is not.
If you want the unipivoted platter to run like a turning egg, go on, use this!
If you want to run the platter like a platter should run, you need a turned part with a shallow conical countersinking atleast on the rotor side. With the o-ring tilt eliminator, you also need it at the stator.
Mark,
please make your ball rest as big as space permits you. Like Peter did. Partial oscillations ....
/end minor critique.
Ruby ball: not expensive but not cheap either and definitely not easy to obtain (www.smallparts.com has them up to 1/8"/3.18mm, my local standardized has them up to 10mm in stock (about US$65), bigger dias can be ordered but have considerable lead time).
Yours will last for a lifetime if you do not epoxy it, because then you can rotate it if the surface should have gotten a damage.
Mark,
i would not be surprised if the old Thorens had a spherical surface "polished on" which has considerably higher qulity and smoothness than a ball-race ball. my standard textbook on Feinwerktechnik (signal engineering) describes this as well as desing detail as as method how to do it properly. And it is obvious this is meant for TTs.
Peterr,
Vacuum: was afraid i would have to elaborate (now and then i tend to understand HHs moaning 🙂 ).
The record is better be pressed on the platter surface to impede partial oscillations, particularly in proximity of the stylus, and to help the partial oscillations to find their way into the platter and leave the record. However, if this pressure is too high, the record is damaged by dirt particles not swept off the platter and now crammed into the grooves.
Imagine a self-cooked jelly preserve. If the jar is crammed full of the jelly and the lid's sealing is less than perfect, partial vacuum between jelly and lid is gone soon. Now the last jar of a batch is never full. If the same lid with imperfect sealing is used, it does not matter because the volume to be filled is soo much bigger.
Applied on TTplatter vacuum system: if the vacuum space between record and platter is increased by a connected hidden cavity (system o communicting cavities) inside the platter, then not much negative pressure / partial vacuum is needed and the sealing at the record edge can be less than perfect anyway
(My mother's mistake to accidentally use the lid marked imperfect just for the last jelly jar, together with my surprise opening it after 6 months and still finding vacuum, helped me to figure that out).
Eccentricity Cure
I believe Nakamichi made a turntable 20 years ago that had a straight arm (ala linear tracking arm) that coupled to a center zero type moving coil meter via photo couplers.
The stylus was placed on the center groove (I think) and the record/platter rotated and the rcord could be then be positioned on the undersized center spindle and then clamped (locked) so as to minimize the meter deflection (grooves concentric with platter).
This would not be too hard to replicate.
Eric.
I believe Nakamichi made a turntable 20 years ago that had a straight arm (ala linear tracking arm) that coupled to a center zero type moving coil meter via photo couplers.
The stylus was placed on the center groove (I think) and the record/platter rotated and the rcord could be then be positioned on the undersized center spindle and then clamped (locked) so as to minimize the meter deflection (grooves concentric with platter).
This would not be too hard to replicate.
Eric.
Eric,
i know this Nakamich behemoth, European version used pivoted arm for excentricity measuring. You are right, the sensor could be easy to implement. However, i carefully avoided mentioning it as i am scared concerning the actor, the mechanics needed right under the platter top surface. A buried µscope crosstable adjustment.
Kills any record/platter impedance matching for sure.
BTW, German engineers have a bad reputation AFA service-friendly and simple design is concerned, (being German engineer myself, i am proud noone has yet called my engineering German engineeering, i agree with foreigner's opinion abut that) but among German engineers Nakamichi's desings are reputed as insanely complex and unserviceable.
Cannot second that, hearsay to me, never tore one apart. But what i can tell, my comments on Nakamichi sonics are unprintable. Ready for sin bin and lawsuit.
i know this Nakamich behemoth, European version used pivoted arm for excentricity measuring. You are right, the sensor could be easy to implement. However, i carefully avoided mentioning it as i am scared concerning the actor, the mechanics needed right under the platter top surface. A buried µscope crosstable adjustment.
Kills any record/platter impedance matching for sure.
BTW, German engineers have a bad reputation AFA service-friendly and simple design is concerned, (being German engineer myself, i am proud noone has yet called my engineering German engineeering, i agree with foreigner's opinion abut that) but among German engineers Nakamichi's desings are reputed as insanely complex and unserviceable.
Cannot second that, hearsay to me, never tore one apart. But what i can tell, my comments on Nakamichi sonics are unprintable. Ready for sin bin and lawsuit.
The Wow Factor
Hi Bernard, perhaps I'm wrong but a quick scan through through this thread mentioned thngs like an undersized center post and center weight clamping or vacuum clamping.
I reckon a useful accessory to the tt designs brewing here would be a means of easily and quickly centering the record - this would be icing on the cake imo after going to so much trouble to build non resonant platters, silent bearings, silent and speed stable platter drive etc, ..... the last thing left is to eliminate eccentricity derived wow.
My now long previous thoughts include an appropriately undersized center pin and and a hollowed center weight with a temporary vacuum connection and an air path from near the center pin to the vacuum cavity under the record.
A photocoupled arrangement attached to any old arm and a circuit with gain and offset controls would allow easy centering and confirmation before the vacuum is applied and the record position is locked.
I see this as a manual operation that takes maybe 30 seconds - I definitely did not consider mechanised operation for sonics reasons. 😉
The auxiliary sensing arm and its support system and electronics/display could be self contained and totally seperate from the turntable system - and portable even.
Some kind of vacuum pump need only be applied long enough to provide record clamping and then the vacuum line removed.
With these icings it would be a tasty cake.
I also reckon that the whole turntabe ought to enclosable (perspex lid) to keep stylus sound out of the room, and room sounds out of the stylus - I always prefer a tt with the lid down.
In Australia good engineering is breakages that can be fixed with big pliers and a piece of fence wire. 🙂
Ever tried working on a Jaguar or Aston Martin ? - English engineers are even worse. 🙄
Eric.
Hi Bernard, perhaps I'm wrong but a quick scan through through this thread mentioned thngs like an undersized center post and center weight clamping or vacuum clamping.
I reckon a useful accessory to the tt designs brewing here would be a means of easily and quickly centering the record - this would be icing on the cake imo after going to so much trouble to build non resonant platters, silent bearings, silent and speed stable platter drive etc, ..... the last thing left is to eliminate eccentricity derived wow.
My now long previous thoughts include an appropriately undersized center pin and and a hollowed center weight with a temporary vacuum connection and an air path from near the center pin to the vacuum cavity under the record.
A photocoupled arrangement attached to any old arm and a circuit with gain and offset controls would allow easy centering and confirmation before the vacuum is applied and the record position is locked.
I see this as a manual operation that takes maybe 30 seconds - I definitely did not consider mechanised operation for sonics reasons. 😉
The auxiliary sensing arm and its support system and electronics/display could be self contained and totally seperate from the turntable system - and portable even.
Some kind of vacuum pump need only be applied long enough to provide record clamping and then the vacuum line removed.
With these icings it would be a tasty cake.
I also reckon that the whole turntabe ought to enclosable (perspex lid) to keep stylus sound out of the room, and room sounds out of the stylus - I always prefer a tt with the lid down.
In Australia good engineering is breakages that can be fixed with big pliers and a piece of fence wire. 🙂
Ever tried working on a Jaguar or Aston Martin ? - English engineers are even worse. 🙄
Eric.
TT maxon motor
Eric,
your post deserves a decent answer, just too busy now.
All,
I have put an order list for TT-suited maxon and MKV caps in the Electronics and Parts forum board. Please read and then come back with email orders to me privately if you want some.
I opted for the high supply voltage as main use is 33rpm of platter and about 1000rpm for the motor. It is not that easy to build a decent voltage regulator for voltages below 1.5V. 7V looks easier to get it decent.
Eric,
your post deserves a decent answer, just too busy now.
All,
I have put an order list for TT-suited maxon and MKV caps in the Electronics and Parts forum board. Please read and then come back with email orders to me privately if you want some.
I opted for the high supply voltage as main use is 33rpm of platter and about 1000rpm for the motor. It is not that easy to build a decent voltage regulator for voltages below 1.5V. 7V looks easier to get it decent.
Hi Eric:
I can see how it will work in principle. (And no doubt has been done already). I can imagine a series of thin radial suction slots in the platter extending to just before the LP edge, and a 'cap' to seal over the label/post and a leaky or hollow centre post to transfer the vacuum beneath the disc. Clever 😎
I think that a centre weight/clamp would not be necessary as apart from that part under the cap, the whole area of the disc will experience a downforce due to vacuum. It could therefore help to have the cap as small as possible (and hence sealing onto the label not the run-out) while still allowing room for vacuum connection. This maximises the pull down effect at the centre of the disc. (The bit under the cap is not pulled down as it would has equal pressure across it at that point due to the leaking centre post).
I guess quite a soft compliant seal at the platter outer radius and the lip of the centre 'cap' is needed to prevent leakage?
Developing the idea... So maybe radial slots are -not- necessary as the vacuum would just 'leak' across under the disc as long as the outer seal was present and the platter surface were either hard or effectively porous (e.g. felt). It's only necessary to make sure there is an air path from cap through to under the label. A cunning plan!
Any ideas on vacuum fittings? Something like a backwards bike valve? I wonder about a simple 'pinch' type rubber thing - pinch to release vacuum... Simple plastic syringe would effectively evacuate it.
Pete
Hmm, another good call I reckon!!
I can see how it will work in principle. (And no doubt has been done already). I can imagine a series of thin radial suction slots in the platter extending to just before the LP edge, and a 'cap' to seal over the label/post and a leaky or hollow centre post to transfer the vacuum beneath the disc. Clever 😎
I think that a centre weight/clamp would not be necessary as apart from that part under the cap, the whole area of the disc will experience a downforce due to vacuum. It could therefore help to have the cap as small as possible (and hence sealing onto the label not the run-out) while still allowing room for vacuum connection. This maximises the pull down effect at the centre of the disc. (The bit under the cap is not pulled down as it would has equal pressure across it at that point due to the leaking centre post).
I guess quite a soft compliant seal at the platter outer radius and the lip of the centre 'cap' is needed to prevent leakage?
Developing the idea... So maybe radial slots are -not- necessary as the vacuum would just 'leak' across under the disc as long as the outer seal was present and the platter surface were either hard or effectively porous (e.g. felt). It's only necessary to make sure there is an air path from cap through to under the label. A cunning plan!
Any ideas on vacuum fittings? Something like a backwards bike valve? I wonder about a simple 'pinch' type rubber thing - pinch to release vacuum... Simple plastic syringe would effectively evacuate it.
Well we all know what the answer to this is don't we ?? 😉 Mind you, the one vacuum may upset the other 🙁
Pete
Big hole small bolt theory- not related to my social life!!
Responce to Dice 45:
--Unfortunaltely CAD left the UNIX realm and went Windoze ... too early. 🙂
Does this confirm the rumor that $%%&& Autocad is now only available on Windoz now??? I had heard that converting other unix to OSX unix was a about an hour's work. Even though we know thats not true, I figgured it would happen.
Now You are saying it can't!! I hate those guys!!!!
I own a Mac still, but gave it up for work- being an architect, I needed ACAD - I don't want to learn another!
--Praise:
Methinks, this tilt limiting washer is a very good idea, Peterr, you should see how you integrate it.
I think the washer would be best as some kind of plastic also.
If so, and with oil lube, if probably wouldn't have to turn
Note that you can adjust the amount of tilt by raising or lowering it on the threaded bolt. Idon't like the rim of the platter touching the bottom of the well, even with a fin, because the forces are very powerful out at the rim the speed is high. I think touching will cause a big upset to the platter.
---Minor critique: Center pin:
I heard your initial request, but Peters idea was too cool not to incorporate on one of the drawings! One solution: make a countersink on the top of the platter around the center bolt. Add a nut. cut off the bolt lower than the top of the platter. Further on you will see that this helps in other ways. Of course the pin isn't necessary, so maybe my first drawing is better?
--if you think the hex hole is centered to the bolt, dream on. It is not.If you want the unipivoted platter to run like a turning egg, go on, use this!
Well, lets not be too dramatic!!
You gotta have faith and consider the options!
I don't hate machining as it appears but on this project I do indeed. Too much machining is very expensive. It is always an option and very pretty, but I like to cleverly figure out how to avoid it. Don't get me wrong- I love a Bimota motorcycle as much as the next techhead, but lets keep it as simple as possible-as long as the price is fiddling time, not performance!
I think most people here are willing to adjust something rather then spend money!
OK... on my Thorens, the platter was visably eccentric. I looked at the platter below and noticed that the shaft extending below was attached with a flange with 3 bolts into the platter
I loosened the bolts and disovered they were not countersunk!
because the heads were flat underneath, I could move the shaft flange a small amount because the bolt holes were larger than the bolts. I left it lightly tightened, put the shaft and platter back in the base, rotated it, and tapped it back and forth, and after half an hour, and useing a pencil lead touching the side to show the high point, had it VERY concentric. Then tightened the screws. A dial indicator could be used also of course.
So heres what I suggest: The big bolt has a hole a few millimeters bigger than it's diameter through the plinth.
There are washers between the pinch nuts above and below the plinth. To get the platter concentric, slighty loosen a nut and tap the pivot around until it is right. Yes this requires removing the platter each time because it is a unipivot, but one TV show should do it!
Remember, the distance to the tonearm or motor won't vary if this adjustment isn't perfect, Basically the precision is required only to keep the distance to the edge of the well the same on all sides.
---If you want to run the platter like a platter should run, you need a turned part with a shallow conical countersinking atleast on the rotor side. With the o-ring tilt eliminator, you also need it at the stator.
Not necessarily - see above
The washer tilt eliminator is better in this case because it also has a bigger hole than the shaft and can be pinched between two nuts to keep in in place once adjusted.
Now, the platter bearing locator might as well be machined in, I agree, but if we make the hole for the small bolt bigger, and put the nut on the top surface recess as mentioned above, we could make this also adjustable. This might be useful if anyone thinks of a 12" disk that is perfectly machined that is available in any store!
Wishful thinking
---Mark,please make your ball rest as big as space permits you
No problem, just get a bigger diameter bolt!
--i would not be surprised if the old Thorens had a spherical surface "polished on"
Ok I believe you 😉 will the 1/8" ruby work?
I think the design is coming together! What do others think?
Are we getting close?
Remember the advantage of oil: -many viscosities to try
to get best damping, also lubes and damps pivot!
Responce to Dice 45:
--Unfortunaltely CAD left the UNIX realm and went Windoze ... too early. 🙂
Does this confirm the rumor that $%%&& Autocad is now only available on Windoz now??? I had heard that converting other unix to OSX unix was a about an hour's work. Even though we know thats not true, I figgured it would happen.
Now You are saying it can't!! I hate those guys!!!!
I own a Mac still, but gave it up for work- being an architect, I needed ACAD - I don't want to learn another!
--Praise:
Methinks, this tilt limiting washer is a very good idea, Peterr, you should see how you integrate it.
I think the washer would be best as some kind of plastic also.
If so, and with oil lube, if probably wouldn't have to turn
Note that you can adjust the amount of tilt by raising or lowering it on the threaded bolt. Idon't like the rim of the platter touching the bottom of the well, even with a fin, because the forces are very powerful out at the rim the speed is high. I think touching will cause a big upset to the platter.
---Minor critique: Center pin:
I heard your initial request, but Peters idea was too cool not to incorporate on one of the drawings! One solution: make a countersink on the top of the platter around the center bolt. Add a nut. cut off the bolt lower than the top of the platter. Further on you will see that this helps in other ways. Of course the pin isn't necessary, so maybe my first drawing is better?
--if you think the hex hole is centered to the bolt, dream on. It is not.If you want the unipivoted platter to run like a turning egg, go on, use this!
Well, lets not be too dramatic!!
You gotta have faith and consider the options!
I don't hate machining as it appears but on this project I do indeed. Too much machining is very expensive. It is always an option and very pretty, but I like to cleverly figure out how to avoid it. Don't get me wrong- I love a Bimota motorcycle as much as the next techhead, but lets keep it as simple as possible-as long as the price is fiddling time, not performance!
I think most people here are willing to adjust something rather then spend money!
OK... on my Thorens, the platter was visably eccentric. I looked at the platter below and noticed that the shaft extending below was attached with a flange with 3 bolts into the platter
I loosened the bolts and disovered they were not countersunk!
because the heads were flat underneath, I could move the shaft flange a small amount because the bolt holes were larger than the bolts. I left it lightly tightened, put the shaft and platter back in the base, rotated it, and tapped it back and forth, and after half an hour, and useing a pencil lead touching the side to show the high point, had it VERY concentric. Then tightened the screws. A dial indicator could be used also of course.
So heres what I suggest: The big bolt has a hole a few millimeters bigger than it's diameter through the plinth.
There are washers between the pinch nuts above and below the plinth. To get the platter concentric, slighty loosen a nut and tap the pivot around until it is right. Yes this requires removing the platter each time because it is a unipivot, but one TV show should do it!
Remember, the distance to the tonearm or motor won't vary if this adjustment isn't perfect, Basically the precision is required only to keep the distance to the edge of the well the same on all sides.
---If you want to run the platter like a platter should run, you need a turned part with a shallow conical countersinking atleast on the rotor side. With the o-ring tilt eliminator, you also need it at the stator.
Not necessarily - see above
The washer tilt eliminator is better in this case because it also has a bigger hole than the shaft and can be pinched between two nuts to keep in in place once adjusted.
Now, the platter bearing locator might as well be machined in, I agree, but if we make the hole for the small bolt bigger, and put the nut on the top surface recess as mentioned above, we could make this also adjustable. This might be useful if anyone thinks of a 12" disk that is perfectly machined that is available in any store!
Wishful thinking
---Mark,please make your ball rest as big as space permits you
No problem, just get a bigger diameter bolt!
--i would not be surprised if the old Thorens had a spherical surface "polished on"
Ok I believe you 😉 will the 1/8" ruby work?
I think the design is coming together! What do others think?
Are we getting close?
Remember the advantage of oil: -many viscosities to try
to get best damping, also lubes and damps pivot!
Hifi Cognoscensus
Hi Pete,
It sounds like some of my vacuum ideas have hit a chord.
I had envisioned a sheet of 1mm or 2mm or so thickness rubber sheet glued or placed centrally on the platter, and a number (4 ?)of thin strips radiating from the center to near the primeter of a 12" of this rubber removed to provide a vacuum path to the vacuum resevoir in the underside of the center puck.
I figured a carburettor float valve could cheaply and reliably provide a perfect air non return valve and without preload like a car/bike valve has.
Lifting the outside edge of the record would easily break the vacuum seal.
For vacuum generation, a camping air mattress rubber dome type footpump with the valves reversed might be suitable, or an electronics workbench solder sucker desolder tool (spring loaded syringe really).
I believe that the compressor from a discarded bar refrigerator can be made into a very quiet vacuum pump - an occasional squirt of oil is required I think.
These thoughts of mine extend to a hollow center spindle and a permanent tube connection to a reasonably large vacuum resevoir such as an out of date camping gas cylinder (cheap) intermittently evacuated by a fridge compressor vacuum pump and connected to the turntable via a vacuum solenoid valve.
The record clamp/puck providing the top vacuum seal and resevoir would benefit by being flat across the underside to allow choice of loosley placed o-rings of differing sizes to allow choice of contact point diameters.
The right soft compliance (silicone probably) o-ring for the puck and sheet for the platter would provide effective and easlly cleanable/maintainable dealing surfaces, and IMO provide a nice sounding vinyl record damping/loading characteristic.
This is one of my 'I'll try it one day' thought experiments - maybe it can be done cheaply and effectively.
Eric.
Hi Pete,
It sounds like some of my vacuum ideas have hit a chord.
I had envisioned a sheet of 1mm or 2mm or so thickness rubber sheet glued or placed centrally on the platter, and a number (4 ?)of thin strips radiating from the center to near the primeter of a 12" of this rubber removed to provide a vacuum path to the vacuum resevoir in the underside of the center puck.
I figured a carburettor float valve could cheaply and reliably provide a perfect air non return valve and without preload like a car/bike valve has.
Lifting the outside edge of the record would easily break the vacuum seal.
For vacuum generation, a camping air mattress rubber dome type footpump with the valves reversed might be suitable, or an electronics workbench solder sucker desolder tool (spring loaded syringe really).
I believe that the compressor from a discarded bar refrigerator can be made into a very quiet vacuum pump - an occasional squirt of oil is required I think.
These thoughts of mine extend to a hollow center spindle and a permanent tube connection to a reasonably large vacuum resevoir such as an out of date camping gas cylinder (cheap) intermittently evacuated by a fridge compressor vacuum pump and connected to the turntable via a vacuum solenoid valve.
The record clamp/puck providing the top vacuum seal and resevoir would benefit by being flat across the underside to allow choice of loosley placed o-rings of differing sizes to allow choice of contact point diameters.
The right soft compliance (silicone probably) o-ring for the puck and sheet for the platter would provide effective and easlly cleanable/maintainable dealing surfaces, and IMO provide a nice sounding vinyl record damping/loading characteristic.
This is one of my 'I'll try it one day' thought experiments - maybe it can be done cheaply and effectively.
No comprehendo - what is the hifi cognoscenti concensus on turntable acoustic covers ?.
Eric.
Hi Eric,
"Lifting the edge would easily break the seal"
If this is true, it is a good, simple solution. The vacuum clamping can actually be very strong (over 100 pounds) While you are trying to lift the edge, keep in mind that the unipivot is tilting!! As Dice says, vacuum shouldn't be this strong and can be varied, of course, but I think a pressure release valve would be a good thing. Anyone here who rides a quality bicycle can tell you about a "Presta valve" It is for bike tires, and is: much smaller diameter than a car type (schrader) valve, not spring loaded, usually comes as a cylinder threaded all along the outside, with a flange and clamping nut at the end. It is also made for containing air. If the valve ends up as the center pin, it is small enough diameter to allow several millimeters of concentricity adjustment.
I'm not sure, but I think Bernhard is suggesting that the vacuum chamber be INSIDE the platter. This raises issues of resonance, he was concered about the fin rim for this reason I think, BUT if the platter is really 100mm thick or more, his idea has a lot of appeal to me. It would be very simple: slots or holes (or the mat idea of yours) to the surface, the pipe to evacuate comes out where the center pin normally is, but small diameter to allow adjustment.
I would be interested in opinions on the rubber mat. I got the impression that the record might sit directly on the platter.
Another seal arangement would be to have silicone o rings in a groove at the inner and outer edge of the platter, with holes or slots coming thrrough the top of the platter to give an air path.
I suspect that the air will find it's way under the record pretty well with only a few holes.
OK, with the internal platter tank scheme you have to push on a hose, pump a couple times, then remove the hose. Not as elegant as flipbing a switch. BUT I have a solution: Car mechanics use a hand vacuum pump to check car vacuum systems.
It is plastic, has a guage!!, and you operate it like a gun, pulling a big trigger. It is exactly right for our job, being made for a similar job. You push the hose onto the pin with one hand, and pump with the other. The cost? about $40 or less!!! Edmund Scientific has them:
http://www.scientificsonline.com/Products/DisplayProduct.cfm?productid=644
Waddayouguyys think?
"Lifting the edge would easily break the seal"
If this is true, it is a good, simple solution. The vacuum clamping can actually be very strong (over 100 pounds) While you are trying to lift the edge, keep in mind that the unipivot is tilting!! As Dice says, vacuum shouldn't be this strong and can be varied, of course, but I think a pressure release valve would be a good thing. Anyone here who rides a quality bicycle can tell you about a "Presta valve" It is for bike tires, and is: much smaller diameter than a car type (schrader) valve, not spring loaded, usually comes as a cylinder threaded all along the outside, with a flange and clamping nut at the end. It is also made for containing air. If the valve ends up as the center pin, it is small enough diameter to allow several millimeters of concentricity adjustment.
I'm not sure, but I think Bernhard is suggesting that the vacuum chamber be INSIDE the platter. This raises issues of resonance, he was concered about the fin rim for this reason I think, BUT if the platter is really 100mm thick or more, his idea has a lot of appeal to me. It would be very simple: slots or holes (or the mat idea of yours) to the surface, the pipe to evacuate comes out where the center pin normally is, but small diameter to allow adjustment.
I would be interested in opinions on the rubber mat. I got the impression that the record might sit directly on the platter.
Another seal arangement would be to have silicone o rings in a groove at the inner and outer edge of the platter, with holes or slots coming thrrough the top of the platter to give an air path.
I suspect that the air will find it's way under the record pretty well with only a few holes.
OK, with the internal platter tank scheme you have to push on a hose, pump a couple times, then remove the hose. Not as elegant as flipbing a switch. BUT I have a solution: Car mechanics use a hand vacuum pump to check car vacuum systems.
It is plastic, has a guage!!, and you operate it like a gun, pulling a big trigger. It is exactly right for our job, being made for a similar job. You push the hose onto the pin with one hand, and pump with the other. The cost? about $40 or less!!! Edmund Scientific has them:
http://www.scientificsonline.com/Products/DisplayProduct.cfm?productid=644
Waddayouguyys think?
I think (experiment required again - I'm off line for a week anyway from tonight) that you are over-complicating the vacuum thing - let's see if it just leaks across under the record and all we need is a simple circular soft rubber seal at the outer edge of the record/platter and another to seal the cap to the top of the label over the centre post (and no holes in the platter!!). I'm also thinking what a reservoir would do for us - only make any leakage less of a problem, so if we can eliminate leakage then we can lose the reservoir (apart from that provided by the 'cap' over the centre post). I like the idea of the post also being the valve - but this may make it too specialist for our simple TT kitchen. Others ideas please...
A first proof of proof of concept experiment should be reasonably easy - I've no time before going offline - but I'd try a simple plastic syringe (plastic ended, not needle - dunno what they are called) pulled out to create enuf vacuum and maybe a cut in half ping-pong ball and a sheet of soft rubber - the seal - (from a surgical glove?) for the centre cap with an LP just lying on a flat surface.
The only problem I can see if with a warped record - it would be difficult to get the edges down all the way around to get seal. I'll ponder on it.... Going back to previous rantings on gelletanous platter surfaces I was mulling over some sort of edge clamp arrangement that just nips down onto the very edge of the LP without fouling the run-in. Dunno - needs more thought. Something like a small bore plastic/rubber pipe slitted all along and wrapped round the record to clamp it to a small lip on the platter - with a seal between? Some sort of O ring - available at right size?? I'm wondering if such a cleanly slitted soft rubber pipe may be all that's needed? Glued to underneath of platter rim?
Someone mentioned a rubber mat for this whole thing to work. Thinking about this, an -all- rubber mat right across the platter may be self defeating as it could just seal up and the vacuum wouldn't get where we need it - that is - all over-. It would need channels, but you'd only get suction at these channels. Instead pulling it down onto a -hard- platter and relying on leakage I think would work - the -whole- record area would be sucked down - this is what we want.
Hope someone can do some experiments... Have fun...
Pete
A first proof of proof of concept experiment should be reasonably easy - I've no time before going offline - but I'd try a simple plastic syringe (plastic ended, not needle - dunno what they are called) pulled out to create enuf vacuum and maybe a cut in half ping-pong ball and a sheet of soft rubber - the seal - (from a surgical glove?) for the centre cap with an LP just lying on a flat surface.
The only problem I can see if with a warped record - it would be difficult to get the edges down all the way around to get seal. I'll ponder on it.... Going back to previous rantings on gelletanous platter surfaces I was mulling over some sort of edge clamp arrangement that just nips down onto the very edge of the LP without fouling the run-in. Dunno - needs more thought. Something like a small bore plastic/rubber pipe slitted all along and wrapped round the record to clamp it to a small lip on the platter - with a seal between? Some sort of O ring - available at right size?? I'm wondering if such a cleanly slitted soft rubber pipe may be all that's needed? Glued to underneath of platter rim?
Someone mentioned a rubber mat for this whole thing to work. Thinking about this, an -all- rubber mat right across the platter may be self defeating as it could just seal up and the vacuum wouldn't get where we need it - that is - all over-. It would need channels, but you'd only get suction at these channels. Instead pulling it down onto a -hard- platter and relying on leakage I think would work - the -whole- record area would be sucked down - this is what we want.
Hope someone can do some experiments... Have fun...
Pete
Folks,
had a very simple idea how design a vacuum system this afternoon. Does not need a record clamp at all. Works with inner and outer seal lip, the inner seal lip also serving as the check valve allowing the air to be sucked out and then keeping the vacuum. Release valve is a dog ear of the outer seal lip which is pulled don to release the vacuum.
Oh yes , and i figured out how to build an excentricity-correcting center pin, dia 7.2mm.
Give me some time, i 1st have to to draw it and then i post it.
Compatible with both, air bearing and unipivot.
Vacuum chamber: of course inside the platter, where else? I intend to use a system of communicating cavites to avoid resonance problems. I place the at the bottom of the platter, to let them act as diffusor to arriving wavefronts and close them with the axial airbearing surface plate.
Before i forget it, if you intend to stay with mechanical impedance matching, stay away from a rubber mat. Rubber is only allowed in the range of record edge and label.
had a very simple idea how design a vacuum system this afternoon. Does not need a record clamp at all. Works with inner and outer seal lip, the inner seal lip also serving as the check valve allowing the air to be sucked out and then keeping the vacuum. Release valve is a dog ear of the outer seal lip which is pulled don to release the vacuum.
Oh yes , and i figured out how to build an excentricity-correcting center pin, dia 7.2mm.
Give me some time, i 1st have to to draw it and then i post it.
Compatible with both, air bearing and unipivot.
Vacuum chamber: of course inside the platter, where else? I intend to use a system of communicating cavites to avoid resonance problems. I place the at the bottom of the platter, to let them act as diffusor to arriving wavefronts and close them with the axial airbearing surface plate.
Before i forget it, if you intend to stay with mechanical impedance matching, stay away from a rubber mat. Rubber is only allowed in the range of record edge and label.
Wood for bearings
Mr Feedback mentioned a few posts back about ebony for bearings.
This is probably what was used, lignum vitae:
http://www.lignum-vitae.com/page3.html
Very interesting stuff. Its self lubricating, extremely dense, and machinable and geometrically stable.
It was used for propeller shaft bearings for years.
We made it for rotating shaft bearings in a wetted solvent, printing press environment. It lasted longer than anything else. Really nice stuff.
Just my $0.02.
Steve
Mr Feedback mentioned a few posts back about ebony for bearings.
This is probably what was used, lignum vitae:
http://www.lignum-vitae.com/page3.html
Very interesting stuff. Its self lubricating, extremely dense, and machinable and geometrically stable.
It was used for propeller shaft bearings for years.
We made it for rotating shaft bearings in a wetted solvent, printing press environment. It lasted longer than anything else. Really nice stuff.
Just my $0.02.
Steve
It has been a busy weekend I read.
I have been working on the proto this weekend. The plinth is almost done and I hope to get the other parts this week. I am going to built it just as my drawing shows. Different centerpins, anti-tilt rings, hexbolt replacements and even vacuums may be added later. For now I consider this thing a first prototype not a final design. Just want to see it work asap.
Peter
I have been working on the proto this weekend. The plinth is almost done and I hope to get the other parts this week. I am going to built it just as my drawing shows. Different centerpins, anti-tilt rings, hexbolt replacements and even vacuums may be added later. For now I consider this thing a first prototype not a final design. Just want to see it work asap.
Peter
😡 Alas this is not going to be the case. It will take at least a few more weeks. I have them made at my work, but they are very very busy right now. I will have to practice some patience right now.
Just curious:
Is there anybody out there working on an airbearing prototype?
Peter
Peterr,
yes me, or should i say, i pushing my design work forward, planning the project to as usual 🙂
As i may have mentioned elsewhere, i have two linear tracking tonearms designed ready and intend to try them out on this new turntable. I need a top-notch TT supporting tonearmbases for 2 linear trackers, i want to be able to demo my mechanical and my airborne LT for sonic comparison.
top-notch means: Same league as Walker Proscenium or Rockport Sirius. I want the tonearms to show where their limits are and not the TT's limit.
So i am heading in a cost-no-object direction (not meaning i am not thinking my head off how to get that as affordable as possible) and this if for me the airbearing variant i initially posted as pix..
This means: vacuum clamping for the record without record clamp or weightpiece.
Eric and peted,
thanxalot for kicking that wedge away, that mental block i had. I mean the necessity of a vacuum record clamp.
For years, i had the strong opinion a vacuum system will not work w/o a puck or clamp. Now i had an idea how to get along without. And this §$%&§$%§!! excentricity correcting center pin can have back his original 7.2mm dia and centerpin and record clamp do not fight each other ... because there is no record clamp.
Eric,
i am not with you AFA the TT lid is concerned: i am undecided if the TT sounds better with lid pen or closed. Depends on the TT.
I am firmly decided that the TT sounds better with the lid removed completely from the plinth and i use a lightweight construction covered with transparent silk as dust cover if need one. I was able to convince many people to unmount the hinges from their TT lids and use the lid as dust cover the same way: remove/stash it away when spinning records.
yes me, or should i say, i pushing my design work forward, planning the project to
as usual 🙂As i may have mentioned elsewhere, i have two linear tracking tonearms designed ready and intend to try them out on this new turntable. I need a top-notch TT supporting tonearmbases for 2 linear trackers, i want to be able to demo my mechanical and my airborne LT for sonic comparison.
top-notch means: Same league as Walker Proscenium or Rockport Sirius. I want the tonearms to show where their limits are and not the TT's limit.
So i am heading in a cost-no-object direction (not meaning i am not thinking my head off how to get that as affordable as possible) and this if for me the airbearing variant i initially posted as pix..
This means: vacuum clamping for the record without record clamp or weightpiece.
Eric and peted,
thanxalot for kicking that wedge away, that mental block i had. I mean the necessity of a vacuum record clamp.
For years, i had the strong opinion a vacuum system will not work w/o a puck or clamp. Now i had an idea how to get along without. And this §$%&§$%§!! excentricity correcting center pin can have back his original 7.2mm dia and centerpin and record clamp do not fight each other ... because there is no record clamp.
Eric,
i am not with you AFA the TT lid is concerned: i am undecided if the TT sounds better with lid pen or closed. Depends on the TT.
I am firmly decided that the TT sounds better with the lid removed completely from the plinth and i use a lightweight construction covered with transparent silk as dust cover if need one. I was able to convince many people to unmount the hinges from their TT lids and use the lid as dust cover the same way: remove/stash it away when spinning records.
Just a thought.
Do you know the vacuvin http://www.vacuvin.nl/
It is a very simple product to keep your bottle of wine vacuum after opening (as if you didn't drink it all...😛 )
I think it could be easily used to suck the air out of you TT.
Do you know the vacuvin http://www.vacuvin.nl/
It is a very simple product to keep your bottle of wine vacuum after opening (as if you didn't drink it all...😛 )
I think it could be easily used to suck the air out of you TT.
The wine saver is a good suggestion Peterr.
My thoughts were a solder sucker for single handled operation.
With suitable lubricant these can pull a decent vacuum.
Bernard, I don't like the extra sound source coming from the stylus tip - sure it does add air to the listening room but it is still an extra acoustic sound source.
I agree that any cover has to be seperate from the tt system proper, and that an acoustically absorbtive material would likely be better than the standard perspex lid on hinges arrangement.
Eric.
My thoughts were a solder sucker for single handled operation.
With suitable lubricant these can pull a decent vacuum.
Bernard, I don't like the extra sound source coming from the stylus tip - sure it does add air to the listening room but it is still an extra acoustic sound source.
I agree that any cover has to be seperate from the tt system proper, and that an acoustically absorbtive material would likely be better than the standard perspex lid on hinges arrangement.
Eric.
- Status
- Not open for further replies.