Your right Baggins, it sounds odd this theory.
My thinking of this: The horizontal movement is for about 18 cm, the vertical only +/- 2mm or slightly more with a bumpy record. And with an excentric record (not the best for sound) the horizontal movement has to be smooth because it is oscillating movement with still points in it.
I figured out how to grind a sleeve in a glass tube: with a diamond grinding disc on the bench grinder, running in water with a sponge on about 3000rpm. Those disc can be bought here for 5 Euro's
Now i have a vacancy: till next week
My thinking of this: The horizontal movement is for about 18 cm, the vertical only +/- 2mm or slightly more with a bumpy record. And with an excentric record (not the best for sound) the horizontal movement has to be smooth because it is oscillating movement with still points in it.
I figured out how to grind a sleeve in a glass tube: with a diamond grinding disc on the bench grinder, running in water with a sponge on about 3000rpm. Those disc can be bought here for 5 Euro's
Now i have a vacancy: till next week
After further consideration i think that vertical warping may just tip
the carriage onto the front or rear contact points of the bearings in the glass tube. But then, how does the carriage not slide into the bottom of the tube due to the drag of the stylus?
It may be that all these forces are in the correct proportions - and the arm obviously works or they wouldnt be able to sell them!
the carriage onto the front or rear contact points of the bearings in the glass tube. But then, how does the carriage not slide into the bottom of the tube due to the drag of the stylus?
It may be that all these forces are in the correct proportions - and the arm obviously works or they wouldnt be able to sell them!
Yes I think you must be right because if the cartridge pulled the
carriage into the bottom of the tube when cresting a warp I doubt if the increased resistance of the 4 contact points on the descent would allow it to climb back up the tube wall to the central position and I cant see how this wouldnt cause more distortion than simple radial tracking error.
carriage into the bottom of the tube when cresting a warp I doubt if the increased resistance of the 4 contact points on the descent would allow it to climb back up the tube wall to the central position and I cant see how this wouldnt cause more distortion than simple radial tracking error.
Hello all,
Interesting thread... just some thoughts that have run thru my head as I have been reading ... The 'bearings' should be as hard as the 'glass rod' part (rubies for watches?? on an alumina rod (rather than cylinder or C-shape?)).
For the warped records... perhaps an alternative is to restrain the tonearm to move horizontally in a horizontal slit and allow the 'glass rod' to rotate via circular bearing mounts (at both ends? extra rigidity of a 12" rail with two mounts would not hurt, can also have a longer carriage). So that, the vertical displacement of the record is taken up by rotation of the rod and arm together. Making the slit larger to allow for warped records doesn't sound that appealling.
Or, why not two rails, knife-edge in V bearings on either side of the platter. Could a nicely tensioned spring mount handle vertical displacement & VTA & load??
Check out the PiTracer, for example.
Best
wilson
Interesting thread... just some thoughts that have run thru my head as I have been reading ... The 'bearings' should be as hard as the 'glass rod' part (rubies for watches?? on an alumina rod (rather than cylinder or C-shape?)).
For the warped records... perhaps an alternative is to restrain the tonearm to move horizontally in a horizontal slit and allow the 'glass rod' to rotate via circular bearing mounts (at both ends? extra rigidity of a 12" rail with two mounts would not hurt, can also have a longer carriage). So that, the vertical displacement of the record is taken up by rotation of the rod and arm together. Making the slit larger to allow for warped records doesn't sound that appealling.
Or, why not two rails, knife-edge in V bearings on either side of the platter. Could a nicely tensioned spring mount handle vertical displacement & VTA & load??
Check out the PiTracer, for example.
Best
wilson
Had another idea (but accidently killed the browser)... and began looking around for ideas on the web, here are some. These are clearly not DIY, but might be used as other jumping-off points.
Jewel (ruby/glass sphere in carbide [drillbit] seat?) spindle rather than annular bearing mount for the 'rod' part, if it is to rotate to account for warped records (less moving parts, 1 contact point at each end rather than a whole race of ball-bearings).
Passive magnetic bearings for the tone-arm carriage, if it is to rotate (magnet = horror on a TT? The cart is at least 6" away and cables can be routed anywhere). These must be used in motor assemblies. Would imply ferrous 'rod' = soft or steel (not stainless) or one made of tungsten carbide, which is hard and can be polished to very high tolerance (both good properties I would imagine). Where to get some? Goodfellow.com perhaps?
FAG bearings also do a nice minture linear system ... FAG bearings and at work we use Newport and other translation stages, again these are hardly DIY, but are nonetheless similar in design to curtain rails/filing cabinet rails but with much higher precision etc, using either dovetails or ball-bearings, Newport . These may be some close-ups for exploring, if anybody still wants to try that direction.
wilson
Jewel (ruby/glass sphere in carbide [drillbit] seat?) spindle rather than annular bearing mount for the 'rod' part, if it is to rotate to account for warped records (less moving parts, 1 contact point at each end rather than a whole race of ball-bearings).
Passive magnetic bearings for the tone-arm carriage, if it is to rotate (magnet = horror on a TT? The cart is at least 6" away and cables can be routed anywhere). These must be used in motor assemblies. Would imply ferrous 'rod' = soft or steel (not stainless) or one made of tungsten carbide, which is hard and can be polished to very high tolerance (both good properties I would imagine). Where to get some? Goodfellow.com perhaps?
FAG bearings also do a nice minture linear system ... FAG bearings and at work we use Newport and other translation stages, again these are hardly DIY, but are nonetheless similar in design to curtain rails/filing cabinet rails but with much higher precision etc, using either dovetails or ball-bearings, Newport . These may be some close-ups for exploring, if anybody still wants to try that direction.
wilson
Just a few thoughts about this...
Firstly, we could turn this inside out - so the rollers run on a glass/ceramic rod, or a tensioned thread.
The V guide rollers are commercially available, and the leverage at the points of contact during a warp should be plenty to overcome stiction.
For the tensioned thread, we could use Kevlar under high tension to minimise vertical deflection.
Either of these could be so compact as to enable a tangential tracking arm with minimal arm tube...
Just some more thoughts
Owen
Firstly, we could turn this inside out - so the rollers run on a glass/ceramic rod, or a tensioned thread.
The V guide rollers are commercially available, and the leverage at the points of contact during a warp should be plenty to overcome stiction.
For the tensioned thread, we could use Kevlar under high tension to minimise vertical deflection.
Either of these could be so compact as to enable a tangential tracking arm with minimal arm tube...
Just some more thoughts
Owen
Ive actually envisaged using small 1/4" dia diabolo shaped rollers
running on a tensioned stainless steel or plated wire of about
30 to 40 thous. diam . the friction in the system would only be rolling resistance plus the friction of the ptfe rollers turning on small dia shafts
bonded to the 1/4 " thick plywood arm.I think this might work and the addition of the third "keeper" roller under the wire should not add to the friction.the system will obviously cope with vertical warping -
( to my mind , that is!) what do you think ?
running on a tensioned stainless steel or plated wire of about
30 to 40 thous. diam . the friction in the system would only be rolling resistance plus the friction of the ptfe rollers turning on small dia shafts
bonded to the 1/4 " thick plywood arm.I think this might work and the addition of the third "keeper" roller under the wire should not add to the friction.the system will obviously cope with vertical warping -
( to my mind , that is!) what do you think ?
Ok,
firstly, I would use a simple loop over hook to act as the keeper - but it doesnt need to contact the thread (keep that rolling resistance low)..
Secondly, I'd not go with PTFE rollers - the stiction will be higher due to the deformation of the PTFE at the point of the roller/thread interface, I'd go with Delrin as a minimum, ideally steel or harder ceramic (not sure if you can get V roller guides in ceramic, but it is possible).
Finally I wouldnt use wire - the helix that it is wound in will affect the VTF in a minute way when the arm moves left and right, and could induce 'interesting' noises in the pickup.
Kevlar thread is very fine, extremely strong, and available from model stores for around $4 for 50 meters. At 20* the tensile strength of steel, you could really crank up the tension to make deflection a distant memory, and the extreme thinness would minimise rolling resistance.
Just my thoughts
Owen
firstly, I would use a simple loop over hook to act as the keeper - but it doesnt need to contact the thread (keep that rolling resistance low)..
Secondly, I'd not go with PTFE rollers - the stiction will be higher due to the deformation of the PTFE at the point of the roller/thread interface, I'd go with Delrin as a minimum, ideally steel or harder ceramic (not sure if you can get V roller guides in ceramic, but it is possible).
Finally I wouldnt use wire - the helix that it is wound in will affect the VTF in a minute way when the arm moves left and right, and could induce 'interesting' noises in the pickup.
Kevlar thread is very fine, extremely strong, and available from model stores for around $4 for 50 meters. At 20* the tensile strength of steel, you could really crank up the tension to make deflection a distant memory, and the extreme thinness would minimise rolling resistance.
Just my thoughts
Owen
I was contemplating solid drawn wire ,the tensioning being a belt and braces idea for loading and unloading.But we seem to be getting down to an agreement on what might work, dont you think.?What do you think of the birch ply arm Idea?
I have a small Myford so i can turn different rollers and try them. its just finding the time!
I have a small Myford so i can turn different rollers and try them. its just finding the time!
To be frank pixpop , I havn't got a clue.
But then again glass tubes can resonate ,in fact anything (almost)
can resonate - so unless youve got the facilities of the materials laboratory of a university at hand - youve just got to see if it works .
thats one reason why I,m advocating such a simple design .It wont
break anyones heart or pocket if it doesn't work.
But then again glass tubes can resonate ,in fact anything (almost)
can resonate - so unless youve got the facilities of the materials laboratory of a university at hand - youve just got to see if it works .
thats one reason why I,m advocating such a simple design .It wont
break anyones heart or pocket if it doesn't work.
Is de vertical movement of cart suspended on the elasticty of the stings? If so, the compliance of it will be much lower on the both ends of string-suspension.
I think also the solid string combined with a "hard" V shaped wheel works best with a string-suspended arm. I suggest steel strings from a guitar. But this might resonate like a guitar??
The higher the tension is of the string, the harder the wheel has to be. Fit a small ball bearing in the wheel with a press-fit, lesser rolling resistance compared to a gliding contact imo.
I am very curious for the results of you two, Baggins and Owen.
I think also the solid string combined with a "hard" V shaped wheel works best with a string-suspended arm. I suggest steel strings from a guitar. But this might resonate like a guitar??
The higher the tension is of the string, the harder the wheel has to be. Fit a small ball bearing in the wheel with a press-fit, lesser rolling resistance compared to a gliding contact imo.
I am very curious for the results of you two, Baggins and Owen.
Ok,
I'll jump in here.
The intention is to model V guide roller blocks which include a roller bearing instead of a bush, and will be high grade steel (commercially available, or Baggins' home made variation).
The 'filament' is intended to be as small a profile as possible, to create a point of rotation at the point where the V rollers sit on it.
The filament needs to be tensioned to minimise the effect of the transit of the carriage, and to minimise the compliance of the system. It WILL resonate, but that can be controlled (or not as the case may be). The resonance will be less of an issue with a solid rail, but then you have to grind a suitable rail, and manage the smoothness of the rail itself to minimise rolling resistance and self noise.
The vertical compliance will be that of the cartridge.
The choise (in my case) of Kevlar thread is to enable very high tensions to be used (pushing the resonances up), with a small cross section to reduce the effect of stiction in the vertical plane - both beneficial.
Steel strings could be used, but the tension would have to be reduced to avoid permenant stretchng as the yeild point could be exceeded.
As the filament would be low mass, the excited resonances are likely to be low amplitude, and if sufficiently high in frequency of little consequence in comparison to the mass of the carriage - and the only location where there wouldnt be differential resonances are when the carriage is in the centre of the filament (i.e. the resonance of both sides would be the same) .
Does that clarify things..?
Owen
I'll jump in here.
The intention is to model V guide roller blocks which include a roller bearing instead of a bush, and will be high grade steel (commercially available, or Baggins' home made variation).
The 'filament' is intended to be as small a profile as possible, to create a point of rotation at the point where the V rollers sit on it.
The filament needs to be tensioned to minimise the effect of the transit of the carriage, and to minimise the compliance of the system. It WILL resonate, but that can be controlled (or not as the case may be). The resonance will be less of an issue with a solid rail, but then you have to grind a suitable rail, and manage the smoothness of the rail itself to minimise rolling resistance and self noise.
The vertical compliance will be that of the cartridge.
The choise (in my case) of Kevlar thread is to enable very high tensions to be used (pushing the resonances up), with a small cross section to reduce the effect of stiction in the vertical plane - both beneficial.
Steel strings could be used, but the tension would have to be reduced to avoid permenant stretchng as the yeild point could be exceeded.
As the filament would be low mass, the excited resonances are likely to be low amplitude, and if sufficiently high in frequency of little consequence in comparison to the mass of the carriage - and the only location where there wouldnt be differential resonances are when the carriage is in the centre of the filament (i.e. the resonance of both sides would be the same) .
Does that clarify things..?
Owen
Yes Owen its more obvious now for me.
Sometimes its better to choose low mass parts(as the light Keflar string) they resonate only shortly in time. High mass parts resonates also, but keep resonating longer.
I once had speakers with a wall thickness of only 5 mm, made of 25cm diameter PVC tubes. Same story with this.
Sometimes its better to choose low mass parts(as the light Keflar string) they resonate only shortly in time. High mass parts resonates also, but keep resonating longer.
I once had speakers with a wall thickness of only 5 mm, made of 25cm diameter PVC tubes. Same story with this.
Today I made a slightly different design of air bearing. well, I have not seen it in a diy tonearm before.
I Have used the v channel made out of extruded aluminium design, but instead of feeding the air from the slide (havent seen that on a diy tonearm but have on a professional one), or from a bottom chamber with many holes in it, It contains only a single hole on each side in the center. This whole feeds into a channel machined onto a matching piece of the extruded aluminum. Almost exactly like an air hockey puck. Ill post some pics later i promise.
Also, I dont see the point of using a taught string or wire in you plans. I can hone a much sharper edge onto a piece of nice steel than any string pulled taught enough to give a similar amount of deflection. However, I have a radical idea:
How about let the arm use some small smooth ceramic rings riding on a taught wire, which is rotating! spin the wire and the friction in either plane should become very very low. Damp the wire from motor vibration with some sort of guide resting on the wire. Maybe felt soaked in grease or something. I think i will build one of these.
I Have used the v channel made out of extruded aluminium design, but instead of feeding the air from the slide (havent seen that on a diy tonearm but have on a professional one), or from a bottom chamber with many holes in it, It contains only a single hole on each side in the center. This whole feeds into a channel machined onto a matching piece of the extruded aluminum. Almost exactly like an air hockey puck. Ill post some pics later i promise.
Also, I dont see the point of using a taught string or wire in you plans. I can hone a much sharper edge onto a piece of nice steel than any string pulled taught enough to give a similar amount of deflection. However, I have a radical idea:
How about let the arm use some small smooth ceramic rings riding on a taught wire, which is rotating! spin the wire and the friction in either plane should become very very low. Damp the wire from motor vibration with some sort of guide resting on the wire. Maybe felt soaked in grease or something. I think i will build one of these.
Hi Owen ,
I think were 95% agreed on the way forward with this project
it will be interesting to see if it works ,though God knows when I'll
have the time to make one (Ive just bought another car and it needs some work) .
Ive really enjoyed the mental excercise of trying to design out all the snags though .If you can make one before me please post you findings.
Baggins.
I think were 95% agreed on the way forward with this project
it will be interesting to see if it works ,though God knows when I'll
have the time to make one (Ive just bought another car and it needs some work) .
Ive really enjoyed the mental excercise of trying to design out all the snags though .If you can make one before me please post you findings.
Baggins.
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