from a few simple experiments I found that a glass base with a nylon platter might be optimal
but with air assisted bearing I think you need to consider sideways forces from motor pulley and drive rim very carefully
I would suggest a passive pulley wheel at opposite side of motor pulley
i think i like the idea of magnets over air pressure for the platter though.. since it doesnt require any extra components.. seems running an air compressor and hoses into it would be more stuff that could go wrong, and maybe even add noise, or am i missing something?.. i wonder if those 12 inch magnetic sheets would provide enough opposing forces cut into 12 inch discs and mounted to the table and under the platter
im still thinking of just using a bearing for the platter, glued inside with some flexible rubber silicone glue... it would provide suspension as well and i already have bearings left over from a cnc project... if i was going to use something else id have a central shaft to keep things centered and use magnetic levitation to hold the platter off of the table
has anyone thought of other ways to actually move the table besides an electric motor with a belt?.. maybe you could turn it with some sort of air pressure, or using magnets on the platter, coils on the table below it to turn the platter itself into the motor?
im certain the tonearm ive selected will work.. if not, my fall back idea is a simple wooden unipivot design using balsa wrapped in resin soaked canvas..
should i go with the unipivot, does anyone have a recommendation as to what i should use for a pin and hole setup?... im not sure metal on wood friction would be the best idea.. but maybe i could drill out the wood and glue in a bushing of some sort for the pin to sit in, friction reduced with bearing grease
im still thinking of just using a bearing for the platter, glued inside with some flexible rubber silicone glue... it would provide suspension as well and i already have bearings left over from a cnc project... if i was going to use something else id have a central shaft to keep things centered and use magnetic levitation to hold the platter off of the table
has anyone thought of other ways to actually move the table besides an electric motor with a belt?.. maybe you could turn it with some sort of air pressure, or using magnets on the platter, coils on the table below it to turn the platter itself into the motor?
im certain the tonearm ive selected will work.. if not, my fall back idea is a simple wooden unipivot design using balsa wrapped in resin soaked canvas..
should i go with the unipivot, does anyone have a recommendation as to what i should use for a pin and hole setup?... im not sure metal on wood friction would be the best idea.. but maybe i could drill out the wood and glue in a bushing of some sort for the pin to sit in, friction reduced with bearing grease
Please correct me if I'm wrong but isn't that how the Technics SL1210 'Direct Drive' turntables operate?
I suspect air motors are not smooth enough to do the job and there is no convenient mechanism for closely regulating speed..
Direct drive tables locate the motor assembly in the center of the platter as far away from the area where the cartridge will be navigating grooves in order to minimize magnetic coupling from the motor into the cartridge. I actually got ride of my belt driven TD-125 because I could hear the motor noise in the output of my cartridge (various) during quiet passages when the cartridge approached within a couple of inches of the motor on the last couple of cuts. The controller was completely overhauled and the motor shielded, still there was enough pick up to bother me.. (The noise was in the same amplitude range as the rumble, but had a distinct flutter tone and was very annoying) My quest for ever increasing resolution let me hear more of everything on the disk as well as every nearby source of electrical or mechanical disturbance..
Direct drive tables locate the motor assembly in the center of the platter as far away from the area where the cartridge will be navigating grooves in order to minimize magnetic coupling from the motor into the cartridge. I actually got ride of my belt driven TD-125 because I could hear the motor noise in the output of my cartridge (various) during quiet passages when the cartridge approached within a couple of inches of the motor on the last couple of cuts. The controller was completely overhauled and the motor shielded, still there was enough pick up to bother me.. (The noise was in the same amplitude range as the rumble, but had a distinct flutter tone and was very annoying) My quest for ever increasing resolution let me hear more of everything on the disk as well as every nearby source of electrical or mechanical disturbance..
all you need is a needle and small cup/bushing
Hadcock was a very clever thing
another option would be using a thread arrangement
that has been done too
you don't need more than that to make a nice and well functioning arm
one major advantage is that you can relatively easy experiment with all sort of arm designs
i didnt think using some kind of air pressure would work well because it seems like the torque would be very low unless it was some kind of air motor.. in which case youd have all the negative effects of a negative effects while using more parts... and i do believe ive seen some tables that used magnets on the platter and coils underneath.. i think thats where i got the idea from... it would be cool if you could put the magnets on the edges of the platter and drive it like that, while having a magnetic suspension underneath, but thats more work than i care to get into right now.. keeping it simple for a first build
I made a unipivot with the point from a scribe I bought at a hardware store. It was glued into the arm and rested upon an indentation drilled in a lag bolt. lol easy peasy VTA adjustment. The more important goal was to position the pivot as co linearly to the surface of the record as possible. most unipivots have the pivot way higher. Makes for better stability and a more traditional look.
weight, placed below balance centre
and unipivot bearing point is at top of arm
many many ways to balance such a system
Kind of surprised about you still wanting to try and integrate the motor into the platter. EM coupling is the first issue I can see and the second is getting smooth power delivery. Me like belts and allot of other do too!
The only linear tracking bearing that will work is one based on an air bearing. Anything else and the stiction will overwhelm that cartridge. The linear tracking tone arms are a hell of a thing. Having worked to the required tolerances I would not want to have to make one. There is a hell of allot of fine tuning to get it just right, not to tight or to loose.
Air supply is the simple part and demand is minimal. An aquarium pump is more than adequate for the job.
I do like the idea of the platter being supported on an air bearing. I would look at lapping a plate of tempered glass with a precision spindle bonded in the middle. It would reside in an air bearing that was bonded into a surface table of granite. Feed the air into the bottom of the spindle bearing and have a couple of small holes to feed the interface between the platter and the granite and you are there. Suspend it on three of four appropriate springs as feet and you are 75% of the way there. VERY rigid and the great mass will isolate it from any minor disturbances it might be exposed to.
The only linear tracking bearing that will work is one based on an air bearing. Anything else and the stiction will overwhelm that cartridge. The linear tracking tone arms are a hell of a thing. Having worked to the required tolerances I would not want to have to make one. There is a hell of allot of fine tuning to get it just right, not to tight or to loose.
Air supply is the simple part and demand is minimal. An aquarium pump is more than adequate for the job.
I do like the idea of the platter being supported on an air bearing. I would look at lapping a plate of tempered glass with a precision spindle bonded in the middle. It would reside in an air bearing that was bonded into a surface table of granite. Feed the air into the bottom of the spindle bearing and have a couple of small holes to feed the interface between the platter and the granite and you are there. Suspend it on three of four appropriate springs as feet and you are 75% of the way there. VERY rigid and the great mass will isolate it from any minor disturbances it might be exposed to.
mike, its something i would experiment with, but for this build i long decided to route a groove around the edge of the platter to loop a belt around and around the motor, and at this point, until i find a better, more simpler idea i intend to just use an abec-7 bearing to suspend and allow the platter to move
on another note.. anyone have any good rule as to what the unipivot joint needs to be? surely the cup would have to be a bit larger than the pin to allow it to pivot up and down.. but how much bigger? and is there anything i can buy to glue into a hole drilled in the wood to use as a cup?... something like the vee-bearings i seen for example, but of course, larger
on another note.. anyone have any good rule as to what the unipivot joint needs to be? surely the cup would have to be a bit larger than the pin to allow it to pivot up and down.. but how much bigger? and is there anything i can buy to glue into a hole drilled in the wood to use as a cup?... something like the vee-bearings i seen for example, but of course, larger
from "diy tt project"...to:.."advice needed"
I hadn't followed this thread at all, but have gone back and read all the posts. But I have some serious concerns regarding this whole thread and what's happening within it. Sorry if this appears to be finger wagging. turntable only:
The tonearm:
I hadn't followed this thread at all, but have gone back and read all the posts. But I have some serious concerns regarding this whole thread and what's happening within it. Sorry if this appears to be finger wagging. turntable only:
- -the simplest idea is as TerryO and kevinkr mentioned. Get an existing table and start rebuilding or modifying. I've done this with an old Sugden BD1 "kit" table from the UK. I've also modified a Dual 1214 and a Garrard Lab80, both idlers with incredible soundstaging and huge bass and PRAT
- -once you get some experience with a few drive types (direct drive, belt, idler), find out which one has most of the characteristics that you are after. Each has their own sound, strengths and weaknesses
- - purchase a respectable turntable of that type, or use one of the originals (from the previous step).Before doing anything else, take the selected table down to nothing but nuts, bolts and raw parts. Clean everything, lubticate and reassemble.
- -Listen to it and enjoy some music with a new, but inexpensive cartridge (a Grado, or Shure, etc.)
- -Build the best plinth and motor control system you can afford. Some like multi-layered construction (plywood is often used), constrined layer (2 or more materials glued together), stone (granite, slate, etc.), solid surface (Corian, etc), wood (both solid and laminated plinths). If the motor/platter system has high Inertia, a motor control system may not even be required if using an AC motor. If using a DC motor, some kind of system may have to be purchased or developed.
The tonearm:
- -the simplest is a DIY uni-pivot. These are the easiest to get right if the use of good materials are used. I like aluminium ones. Next is wood construction. Avoid carbon fibre: I've yet to hear one that is better than good aluminium or wooden ones. I'm sure there are some out there, just that I haven't personally heard any.
- -for linear trackers, look at the Ladegaard's Air Bearing Tangential Tonearm and the Rauna/Opus3 mechanical tracker.
- -unless you have access to high precision tooling (and this can be hand tooling, but must be accurate), avoid the use of any Gimbal bearing design. Hard enough for manufacturers to get right with high precision machine tools and measuring[/P]equipment.
- -at this point, do whatever you desire. Simpler is always better than complex. An engineered solution usually sucks. Better to start with good, basic design and excellent implementation, thatn to start with a complicated design. Engineered solutions are not the answer. The answer is not having to engineer a solution.
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a standard drill bit makes a point at 118 degree angles... now would this be suitable for a unipivot? drill a pointed hole into something for the pin to mount into?.. that pin could be a small screw with the head cut off and the top grinded to an angle which could be threaded into a bushing on the table so that the height can be adjusted by simply turning the screw one direction or another... would this work? or would i be better off with a plumb bob and saffire vee bearing?
Hello AnimusDivinus
A standard twist drill with a point angle of 118 or 135 Degrees will NOT
make a hole with a sharp point! Take a close look at a drill and you will see a small flat at its tip.
I have never looked inside of a unipivot tone arm and so do not know how they actually assure a precision point to point fit. My inclination would be to drill and ream an accurate hole into the underside of the tone arm and insert three precision 1/16" bearing balls with a light press fit and then set that assembly on top of a heat treated needle.
I'll make a drawing in AutoCad and submit that in a next post.
As others have written in this thread, the center of gravity of the tone arm must lie below the point of contact between the balls and the needle.
Think of a man on a rope in a high wire act.
Sincerely,
Ralf
A standard twist drill with a point angle of 118 or 135 Degrees will NOT
make a hole with a sharp point! Take a close look at a drill and you will see a small flat at its tip.
I have never looked inside of a unipivot tone arm and so do not know how they actually assure a precision point to point fit. My inclination would be to drill and ream an accurate hole into the underside of the tone arm and insert three precision 1/16" bearing balls with a light press fit and then set that assembly on top of a heat treated needle.
I'll make a drawing in AutoCad and submit that in a next post.
As others have written in this thread, the center of gravity of the tone arm must lie below the point of contact between the balls and the needle.
Think of a man on a rope in a high wire act.
Sincerely,
Ralf
Hello Animus Divinus
As promised, here is my unipivot suggestion.
For all I know, that may be how everyone is doing it. But as I said, I've never looked at the underside of a unipivot tone arm.
I used 1/8" balls because they are easier to find if you drop one on the floor. The balls could be carbide or some semi-precious stone.
Sincerely,
Ralf
As promised, here is my unipivot suggestion.
For all I know, that may be how everyone is doing it. But as I said, I've never looked at the underside of a unipivot tone arm.
I used 1/8" balls because they are easier to find if you drop one on the floor. The balls could be carbide or some semi-precious stone.
Sincerely,
Ralf
Hello AnimusDivinus
Reading one of your previous posts, you suggest sliding a tone arm on a shaft, utilizing a greased bronze bushing. I am not a naysayer and I am the first one to support an "off the wall idea" but this one will not work! The viscosity of the grease will kill that idea. Even if you use an oil impregnated bronze bushing, the friction will still be too high. The only way the above would not be true is, if you used a servo motor to move the carriage.
Sincerely,
Ralf
Reading one of your previous posts, you suggest sliding a tone arm on a shaft, utilizing a greased bronze bushing. I am not a naysayer and I am the first one to support an "off the wall idea" but this one will not work! The viscosity of the grease will kill that idea. Even if you use an oil impregnated bronze bushing, the friction will still be too high. The only way the above would not be true is, if you used a servo motor to move the carriage.
Sincerely,
Ralf
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so youre saying the balls are pressed in with tension?... doesnt seem like it would be a very reliable fit.. seems if you had to remove the tonearm for any reason they could fall out... for the pin i guess i could still use a screw with the head cut off.. put the screw into my drill press chuck to spin it as i grind a point onto it
could probably put a tad amount of glue inside the hole in the tonearm before dropping the balls in... also, it seems the pin should have a sharper angle than the hole does so it rests on the tip of the pin, and gives room for it to be tilted up and down when moving the tonearm, or playing a warped record, if the angled matched then it would resist being moved
could probably put a tad amount of glue inside the hole in the tonearm before dropping the balls in... also, it seems the pin should have a sharper angle than the hole does so it rests on the tip of the pin, and gives room for it to be tilted up and down when moving the tonearm, or playing a warped record, if the angled matched then it would resist being moved
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