Let's remember this thread started about 9 years ago. At the time I did not learn much about skating force and its effect on tracking. But I have always welcome anyone to share insights here. The answer is no it was not a target of this thread at the time but it can be if you want to focus on that too.
I am not against other types of tangential tonearm. (I do not like using the word "linear" in this thread since most pivot arms do not use linear bearings and are not parallel trackers, a term I prefer in describing air-bearing arms and mechanical gliding arms.) As a user and a consumer, one has to make choices in acquiring audio equipment and I just do not want to use an air pump or hoses in my listening environment so I have to preclude that. But I enjoy reading and learning about them so I peruse other threads like Jim's excellent thread so I don't want to be perceived as an air-bearing hater. Since this thread was created, it has covered many options too so it's not as restricting as one might imagine. I started the thread simply thinking about something I would use myself one day. That's all.
There's theoretical ideal and there's the real world. I am not here chasing perfection. I like things simple and elegant in its solution and I do not mind some compromise. I am also not a "neutral" fiend as I enjoy some coloration in audio reproduction. After decades of beating over my head by the Harry Pearsons of the world, I'm ready to flip the birds on them. I just don't bang my head over these things. I'm a hobbyist and any hobby should be fun. I also understand all hobbies involve some neurosis and, at times, supreme single-mindedness in order to be good at something. I have my own obsessions but I just don't like imposing it on other people.
In short, anybody with any insight is welcome to chime in here. I'm not a moderator but I can welcome you like a doorman. Although at times I interrupt to remind members to stay on topic when the discussion goes off rail when someone can go into an over long mathematical dissertation or wasting time arguing over semantics when we all know we are talking about the same damn thing or personal stories or anecdotes that interest only to the tellers and no one else.
All I ask is to stay on topic of few things that relates to pivot arms that can achieve (almost) perfect tangency. Obviously by now we all know almost all pivot arms have skating force so if there are ideas and devices that can "compensate" or "cancel" skating force feel free to discuss here. I do like servo arms and they are really also a form of pivot arms with a moving base but not every diyer can handle or understand electronics so it is best to have its own much deserving thread for those who want to dive in deeper. After all this thread is called "Angling for 90°" not "Angling for 90° without skating force" so don't let the skating force part to discourage you to come up with any clever angling ideas!
Have fun!
Completely compensating for the torque created by the skating phenomenon is not a trivial task. I've been playing with the geometry used by Marc Gomez on the SAT arms for a bit of fun. He manages to keep the variation in skating torque to +/-3% due to geometry. He largely achieves this by assuming the innermost groove is at 75mm. Any grooves closer to the spindle than this will increase this variation. An arm set to the bearwald alignment with an inner groove at 62mm will have a variation in skating torque of +/- 5.5%. Using the same type of bias system as the SAT but making the pulley at the base of the arm highly eccentric and slightly offset can reduce this to about +/- 0.3%. With a little more effort a profile that completely compensates for the geometry can be determined.
With most pivoted tangential arms the task of compensating for the variation in skating torque due to geometry should be easier as the torque will decline across the whole record rather than decline then increase as it does with a fixed geometry arm.
If the variation in stylus drag from shure are accurate at +/-10% then the variation in skating torque at the beginning, middle and end of a record could be about +/-15% with a fixed geometry arm. Removing the geometric component of this variation would reduce the overall average error by about 35% which could be significant. If the variation in stylus drag is greater than shure claims (which I suspect it is) then correcting the geometry will have less of an overall effect.
The difficult task is to compensate for the variation in skating torque due to varying stylus drag. This will require a mechanism that senses the pull on the stylus and convert this to a torque. This is what the arm shown in the patient appears to do. In order for this to work there has to be a certain amount of movement of the headshell, armtube or entire arm in direction of the pull of the stylus. This will result in a tracking error all of its own. As long as the net tracking error is reduced the system could be considered successful. The arm from the patient appears to supply the torque by tilting the arm. This will impart an azimuth error. As azimuth errors are much more audible than a similar LTA error this is probably a bad idea.
Of course any such mechanism cannot compromise the arm in any way or the impact on sound quality will likely negate any benefits.
Niffy
With most pivoted tangential arms the task of compensating for the variation in skating torque due to geometry should be easier as the torque will decline across the whole record rather than decline then increase as it does with a fixed geometry arm.
If the variation in stylus drag from shure are accurate at +/-10% then the variation in skating torque at the beginning, middle and end of a record could be about +/-15% with a fixed geometry arm. Removing the geometric component of this variation would reduce the overall average error by about 35% which could be significant. If the variation in stylus drag is greater than shure claims (which I suspect it is) then correcting the geometry will have less of an overall effect.
The difficult task is to compensate for the variation in skating torque due to varying stylus drag. This will require a mechanism that senses the pull on the stylus and convert this to a torque. This is what the arm shown in the patient appears to do. In order for this to work there has to be a certain amount of movement of the headshell, armtube or entire arm in direction of the pull of the stylus. This will result in a tracking error all of its own. As long as the net tracking error is reduced the system could be considered successful. The arm from the patient appears to supply the torque by tilting the arm. This will impart an azimuth error. As azimuth errors are much more audible than a similar LTA error this is probably a bad idea.
Of course any such mechanism cannot compromise the arm in any way or the impact on sound quality will likely negate any benefits.
Niffy
At the risk of sounding pedantic, the side forces [skating] in Frank's PLT arm are compensated for, not cancelled.
See posts #1809, 1813, and 1814:
Angling for 90° - tangential pivot tonearms
Note his comment in post #1809 "My LT arm will pass the thread test if one pulls with about the same force that the stylus/record interface generates." To me, this says that the arm has built-in anti-skating. Also, look at the paragraph at the bottom of column 5 and the top of column 6 in Frank's patent, wherein he describes various forces including specifically 'skating force'. I attached a copy of Frank's US patent, and I urge all of you to carefully read through it and understand it as best you can. I have studied it carefully, highlighting and color-coding the various parts to help me visualize how they all work together but, of course, the patent drawings won't reveal the various magnetic forces at play. I am very confident that there is a formidable amount of proprietary knowledge that goes into making that arm work, important details way above and beyond what is described literally in the patent. I suspect that much of that information has the definitive answer to the questions we are debating, but we will never find out because, well, it's proprietary. Please, don't anyone misconstrue that I am bashing Frank's PLT in any way. On the contrary, I admire it as an elegant looking and exquisitely well engineered product that satisfies all the design criteria discussed since the inception of this thread. Unfortunately, it is beyond the capabilities of even the most well-equipped diy'er.
Carlo: I am, too, a 'must touch it to believe' person. I don't believe it is possible to make a PLT for which skating is nonexistent or 'cancelled'. I have resolved in my mind that making a PLT is making a pact with the devil, and the inescapable side-effect is some residual skating force that has to be compensated in one form or another. I once owned a Decca International unipivot that had magnetic bearing cushioning and magnetic anti-skate, and it worked well. Frank has taken the application of magnetics for tonearms and pushed that engineering asymptotically to the max.
directdriver: I think you are in a bit of a pickle here. As a consumer, you are looking for something that's simple and easy to use, is passive in that it needs no air pumps or servos, and tracks with no angular error. Frank's PLT meets all your stated criteria, and is available commercially. It will never be copied successfuly as a diy project. You really have no choice other than to buy one of Frank's arms, set it up, and then report back to us how much you like it.
Ray K
no moolah
Haha! Ray, you're talking about money I simply don't have. The newest version with magnesium arm tube retails for $12,500. If I can afford one, I probably wouldn't be here at a diy forum. But I promise to report back when I hit the jackpot. There is a rave review here about its positive sonic impression on the reviewer. You do have a good point though that it fits most of my criteria,... except the price!
Here's a story on the development of the tonearm by the manufacturer. There's even a paragraph that might interest Ray. It's an account of Frank wanting to build a servo arm or a "motorized carriage system":
A motorized carriage system is very intriguing for me. It would be the ultimate accessory. This would be similar to something Conrad Hoffman once suggested in post#5 that since traditional pivot arms have been a matured technology that placing it on a servo carriage system or a motorized armpod or arm base carries tremendous appeal and audiophiles get to keep their favorite pivot arm, provided the headshell offset can be undone and with no offset angle on the vertical bearings.
You really have no choice other than to buy one of Frank's arms, set it up, and then report back to us how much you like it.
Haha! Ray, you're talking about money I simply don't have. The newest version with magnesium arm tube retails for $12,500. If I can afford one, I probably wouldn't be here at a diy forum. But I promise to report back when I hit the jackpot. There is a rave review here about its positive sonic impression on the reviewer. You do have a good point though that it fits most of my criteria,... except the price!
Here's a story on the development of the tonearm by the manufacturer. There's even a paragraph that might interest Ray. It's an account of Frank wanting to build a servo arm or a "motorized carriage system":
A motorized carriage system is very intriguing for me. It would be the ultimate accessory. This would be similar to something Conrad Hoffman once suggested in post#5 that since traditional pivot arms have been a matured technology that placing it on a servo carriage system or a motorized armpod or arm base carries tremendous appeal and audiophiles get to keep their favorite pivot arm, provided the headshell offset can be undone and with no offset angle on the vertical bearings.
Thanks for your kind and comprehensive reply, Directdriver; now I'm sure to be offtopic.
I tried to explore the PLTs and the Linears by building some TAs somehow different from the existing ones, arms that could easily be defined as good sounding; but I try to observe my experiments carefully, not to fool myself. Replacing a distortion on the left channel with one on the right didn't seem a great result.
So why to make a PLT, angling for 90°, or even an LT? What are the problems to be solved, and is tangency really essential, or is it a problem itself?
In my provocation - long life to the offset - I was looking for just that: after years of attempts and discussions maybe we need to reconsider a little the premises.
So what remains to be explored in this thread? From the geometric point of view, maybe just an extensible true Thales, the only pivoted that could overcome the famous string test: but i've already paid my price with the Syrinx, and trying till now without result .
I continue to hope that someone more clever will someday want to take up that baton.
hi to all - carlo
last offtopic - I agree (almost) completely with Niffy about the practical impossibility of obtaining skating cancellation from SD without a headshell movement (so convinced that suspended arms are the only type that I never wanted to experiment). What he says anticipates even my analysis on Percy Wilson TA, which is a brilliant device probably able to convert the stylus drag into an ideal antiskating, but at the price of a certain rolling: ie an azimuth error, which I consider among the worst defects that an arm can have
Attached a Freecad 3d mockup, for those who want play with.
I tried to explore the PLTs and the Linears by building some TAs somehow different from the existing ones, arms that could easily be defined as good sounding; but I try to observe my experiments carefully, not to fool myself. Replacing a distortion on the left channel with one on the right didn't seem a great result.
So why to make a PLT, angling for 90°, or even an LT? What are the problems to be solved, and is tangency really essential, or is it a problem itself?
In my provocation - long life to the offset - I was looking for just that: after years of attempts and discussions maybe we need to reconsider a little the premises.
So what remains to be explored in this thread? From the geometric point of view, maybe just an extensible true Thales, the only pivoted that could overcome the famous string test: but i've already paid my price with the Syrinx, and trying till now without result .
I continue to hope that someone more clever will someday want to take up that baton.
hi to all - carlo
last offtopic - I agree (almost) completely with Niffy about the practical impossibility of obtaining skating cancellation from SD without a headshell movement (so convinced that suspended arms are the only type that I never wanted to experiment). What he says anticipates even my analysis on Percy Wilson TA, which is a brilliant device probably able to convert the stylus drag into an ideal antiskating, but at the price of a certain rolling: ie an azimuth error, which I consider among the worst defects that an arm can have
Attached a Freecad 3d mockup, for those who want play with.
magnetic anti-skating
There's a commercial product made by Morsiani in Italy using similar concept to the Decca with magnets for anti-skating. There's even a DIY project using Morsiani's published paper.
There's a commercial product made by Morsiani in Italy using similar concept to the Decca with magnets for anti-skating. There's even a DIY project using Morsiani's published paper.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
As I understand, there where some misunderstanding in the forum about this arm. Some looking at a convergence somewhere in the prolongation of the arm.
The convergence point is the Z point on his picture. That could allow to make a full mechanical version of it.
I have edited his image.
To resume, 3 lines articulated (free to rotate on each others), AB, BC, CZ.
The BC always parallel to the arm if we look from the top, attached to it on its vertical axe B IE turning in the same time. The only fixed axe is at A.
I have no idea of the practical forces needed to move this assembly, reason why he had chose to use a motor to move the system with an error detection ?, but, indeed, the cantilever will always stay tangential to the groove and it is a strait arm, that means no lateral forces on the cantilever due to centipede effects of non tangential angle.
It should be easy for a DIY to make a quick prototype in the air to figure out if this mechanical assembly move freely enough at the end of the record or or if it gets stuck.
On the contrary, at he beginning of the record, the friction forces on the diamond tip will push the system towards the inside of the disc, which is equivalent to a classic angled arm on this point. We could imagine a nylon wire with a counter weight attached to the point B axe and which would hang at point X to compensate. With the benefit that it don't act on the arm itself. The motorized version solved this problem, the axis AB being no longer free to turn.
Attachments
Here in Italy Morsiani tonearms (and more the TTs) are well known and appreciated handycrafted unipivots. The magnetic antiskating is cleverly conceived but, as usual, is variable just according to the groove diameter, not to stylus drag variations.
Home Page
Frankly i doubt that, using permanent magnets in any way, on any kind of tonearms could be possible to achieve such a goal.
To be clearer, saying compensate vs cancel i meant not a quantitative result (compensate < cancel), but a completely different approach.
Compensate is the usual way of adding an opposite torque to the skating force (via magnets weights springs etc) trying to reduce it approximatevely, genearting a double useless force as bonus
Cancel instead means to avoid that the stylus drag (always variable) could produce more side force than what strictly needed for rotation; producing less, and dissipating the rest in always variable pivot frictions.
But don't ask me how: no trade secrets, simply i don't know, but it's intriguing even if offtopic
carlo
Home Page
Frankly i doubt that, using permanent magnets in any way, on any kind of tonearms could be possible to achieve such a goal.
To be clearer, saying compensate vs cancel i meant not a quantitative result (compensate < cancel), but a completely different approach.
Compensate is the usual way of adding an opposite torque to the skating force (via magnets weights springs etc) trying to reduce it approximatevely, genearting a double useless force as bonus
Cancel instead means to avoid that the stylus drag (always variable) could produce more side force than what strictly needed for rotation; producing less, and dissipating the rest in always variable pivot frictions.
But don't ask me how: no trade secrets, simply i don't know, but it's intriguing even if offtopic
carlo
Last edited:
Hello gentlemen,
Just a brief comment regarding the compensation of skating force on the LT. There are several ways to compensate for any remaining skating force that stems from the overall geometry, like changing the proximity of the guide magnet vs. the guide rail over its length.
The main reason why you won't experience the arm showing any tendency to move inwards or outwards when either "riding" a blank record or with a Dual skate-O-meter on a modulated record is the fact that the stylus drag can be countered nearly 100%(within the stylus drag/vinyl friction coefficient variation range) through vertically offsetting the main bearing by the correct amount and in the right direction(180° to the stylus drag vector).
The main arm assembly, which sits on a rotating cantilever(so to speak), can be seen as a pendulum and it will seek the lowest position. The base of the LT allows for not just leveling, but ever so slightly off-setting the arm to generate a force exactly opposing the stylus drag, hence avoiding the generation of a skating force. Cancellation would be the proper term here...
And, quite obviously, such an arrangement wouldn't pass the "attach a string and pull along the cantilever"-test as the generated drag will always be far higher than the stylus drag.
By the way, the magnesium wand version is what the US licensee is offering, all LTs from my workshop still feature treated wooden/wood composite arms.
I still believe that an arm based on this principle is DIY-able. Anyone seriously trying to do so, but running into problems, can contact me privately, - I'll then see if I can point him in the right direction.
Very sorry not to be able to do this more openly here, but said licensee would not approve of it(understandably...)
Great thread still... and I hope more new ideas will pop up
Cheers,
Frank
Just a brief comment regarding the compensation of skating force on the LT. There are several ways to compensate for any remaining skating force that stems from the overall geometry, like changing the proximity of the guide magnet vs. the guide rail over its length.
The main reason why you won't experience the arm showing any tendency to move inwards or outwards when either "riding" a blank record or with a Dual skate-O-meter on a modulated record is the fact that the stylus drag can be countered nearly 100%(within the stylus drag/vinyl friction coefficient variation range) through vertically offsetting the main bearing by the correct amount and in the right direction(180° to the stylus drag vector).
The main arm assembly, which sits on a rotating cantilever(so to speak), can be seen as a pendulum and it will seek the lowest position. The base of the LT allows for not just leveling, but ever so slightly off-setting the arm to generate a force exactly opposing the stylus drag, hence avoiding the generation of a skating force. Cancellation would be the proper term here...
And, quite obviously, such an arrangement wouldn't pass the "attach a string and pull along the cantilever"-test as the generated drag will always be far higher than the stylus drag.
By the way, the magnesium wand version is what the US licensee is offering, all LTs from my workshop still feature treated wooden/wood composite arms.
I still believe that an arm based on this principle is DIY-able. Anyone seriously trying to do so, but running into problems, can contact me privately, - I'll then see if I can point him in the right direction.
Very sorry not to be able to do this more openly here, but said licensee would not approve of it(understandably...)
Great thread still... and I hope more new ideas will pop up
Cheers,
Frank
There's still hope. Thanks, Frank!
Thanks for the graphics. The Esperado arm's segmented lines do not converge to a single point because he was not using the Thales geometry which is not necessary in an arm like that as demonstrated by the Schroeder LT arm. Since the Esperado arm uses the spindle as the reference point, it works out the same. All Birch style arm operation under the same principle except the tail end of the arm moves differently in various designs. Since the Reed T5 arm uses the sensor point at the tail end of arm so the laser must beam at that point as reference as opposed to the spindle or record center.
I join in thanking Frank Schroeder for his uncommon kindness to us diyers, once again demonstrated by these new clarifications. Feeling responsible for the possible misunderstanding that motivated them, I would like to make my point of view a bit clearer.
Much more qualified people than me have shown that all pivoted TAs (including PLTs) generate some skating: it is not an opinion, it is simple vector breakdown, and everyone in this thread had to surrender to that (at least with the famous string test). After some experience with the linear trackers (that generate side force) i've considered the problem even more radically, posting this rhetorical, provocative question.
It's there a way to move a tonearm without a side force? or at least without generating bending?
Against this crude statement someone cited the LT tonearm (often claimed, together with the KL audio, as the only skating-free pivoted) and I reiterated my theoretical doubts, based on available geometry and information.
Now it seems to me that these new clarifications put an end to the topic: LT does not have any detectable skating, as it has sophisticated antiskating devices (variable magnetic guide, pivot slanting) capable to nullify the small residual skating of a PLT. Knowing the theoretical and constructive level of his realizations, there's no doubts about their complete effectiveness.
But if it needs such skating compensations it means that it is not intrinsically, geometrically skating free (that one was my question). It has to introduce forces of opposite sign to correct smartly the skating, it doesn't avoid its existence.
Practically no difference for users, but highly significative for designing.
imho, of course - carlo
Much more qualified people than me have shown that all pivoted TAs (including PLTs) generate some skating: it is not an opinion, it is simple vector breakdown, and everyone in this thread had to surrender to that (at least with the famous string test). After some experience with the linear trackers (that generate side force) i've considered the problem even more radically, posting this rhetorical, provocative question.
It's there a way to move a tonearm without a side force? or at least without generating bending?
Against this crude statement someone cited the LT tonearm (often claimed, together with the KL audio, as the only skating-free pivoted) and I reiterated my theoretical doubts, based on available geometry and information.
Now it seems to me that these new clarifications put an end to the topic: LT does not have any detectable skating, as it has sophisticated antiskating devices (variable magnetic guide, pivot slanting) capable to nullify the small residual skating of a PLT. Knowing the theoretical and constructive level of his realizations, there's no doubts about their complete effectiveness.
But if it needs such skating compensations it means that it is not intrinsically, geometrically skating free (that one was my question). It has to introduce forces of opposite sign to correct smartly the skating, it doesn't avoid its existence.
Practically no difference for users, but highly significative for designing.
imho, of course - carlo
Last edited:
yes, using a motorized tangential system with error sensing. As the arm will be strait, free of all his movements, and its pivot's position blocked by the motor system, end of any parasitic forces on it.
Member
Joined 2019
Hi Tournesol
maybe that question is more challenging than it seems. This is a thread for passive TAs, which I was referring - as said on #2033, and more on # 2048
Beyond my foggy hypothesis, Niffy gave the best answer, if not the only: perfectly centered disc, carriage's uniform motion, zero friction (0 ?) air bearings. No mention of pressurized air tubing, unfortunately.
But if you want to talk about active linears here is the same question, expressly made for those**
What the hell is going to happen to the cantilever, between one step and the next?
(Always talking about angles, or angels - how it's said in english?)
(attachment) i've tried this simulation, based on your graphic: if done correctly, hope it helps to investigate the problems around
Hi Doug
glad to hear you again - I really missed your advice, while venturing the winding paths of the world of linears...
carlo
** Ray's and Ralf's tonearms excluded: active, but coming from another planet
maybe that question is more challenging than it seems. This is a thread for passive TAs, which I was referring - as said on #2033, and more on # 2048
Beyond my foggy hypothesis, Niffy gave the best answer, if not the only: perfectly centered disc, carriage's uniform motion, zero friction (0 ?) air bearings. No mention of pressurized air tubing, unfortunately.
But if you want to talk about active linears here is the same question, expressly made for those**
What the hell is going to happen to the cantilever, between one step and the next?
(Always talking about angles, or angels - how it's said in english?)
(attachment) i've tried this simulation, based on your graphic: if done correctly, hope it helps to investigate the problems around
Hi Doug
glad to hear you again - I really missed your advice, while venturing the winding paths of the world of linears...
carlo
** Ray's and Ralf's tonearms excluded: active, but coming from another planet
Hi Carlo,
I did actually mention the air tube in the post to which you refer.
I said "OK. You will have the resistance due to arm cables (and air line if using a moving bearing type arm) but these are not significant."
When testing my bearings I built a test rig to determine lateral friction. I also took a set of measurements to see how much effect the cables had. I could not determine any difference with the cable added. Based on the resolution of the test rig and how I analysed the data I can confidently say that the resistance due to the cable can be no more than 0.02mN.
I used to think that the air tube in a linear arm would offer significant resistance. A couple of years ago in the linear air bearing thread Jim posted a video of one of his arms. The arm had been neutrally balanced and was sliding back and forth with no discernable resistance to the motion. The arm moved with greater freedom than most pivoted arms I've seen. This video completely changed my mind. Jim had done considerable work finding the best type of tube.
Back on topic.
I've been studying the patent for the schroder arm. What a brilliant piece of design work it is. I haven't had a chance to do any calculations and have been trying to picture the forces just based on the diagrams in the patent. On the skating force front it is very clever. Unlike most pivoted tangential arms it would appear that skating force increases towards the end of the record, most decrease towards the centre. The way the arm works would produce much lower skating force than virtually any other arm. The amount of skating will be so low that any additional biasing will be completely unnecessary.
Of all the pivoted tangential arm designs that I've seen this is by far my favourite. It's construction is simple offering a good clean path for energy to disipate from the arm, good mechanical grounding. I would have preferred the use of vee jewel bearings rather than ball races in order to maximise the grounding and to minimise the possibility of chatter. Not having any bearings at the headshell has got to be a major advantage. I think this is the worst place to put a bearing.
All in all a great design.
Niffy
I did actually mention the air tube in the post to which you refer.
I said "OK. You will have the resistance due to arm cables (and air line if using a moving bearing type arm) but these are not significant."
When testing my bearings I built a test rig to determine lateral friction. I also took a set of measurements to see how much effect the cables had. I could not determine any difference with the cable added. Based on the resolution of the test rig and how I analysed the data I can confidently say that the resistance due to the cable can be no more than 0.02mN.
I used to think that the air tube in a linear arm would offer significant resistance. A couple of years ago in the linear air bearing thread Jim posted a video of one of his arms. The arm had been neutrally balanced and was sliding back and forth with no discernable resistance to the motion. The arm moved with greater freedom than most pivoted arms I've seen. This video completely changed my mind. Jim had done considerable work finding the best type of tube.
Back on topic.
I've been studying the patent for the schroder arm. What a brilliant piece of design work it is. I haven't had a chance to do any calculations and have been trying to picture the forces just based on the diagrams in the patent. On the skating force front it is very clever. Unlike most pivoted tangential arms it would appear that skating force increases towards the end of the record, most decrease towards the centre. The way the arm works would produce much lower skating force than virtually any other arm. The amount of skating will be so low that any additional biasing will be completely unnecessary.
Of all the pivoted tangential arm designs that I've seen this is by far my favourite. It's construction is simple offering a good clean path for energy to disipate from the arm, good mechanical grounding. I would have preferred the use of vee jewel bearings rather than ball races in order to maximise the grounding and to minimise the possibility of chatter. Not having any bearings at the headshell has got to be a major advantage. I think this is the worst place to put a bearing.
All in all a great design.
Niffy
I think I made an error in my previous post. With the Schroder arm skating torque does decrease towards the center of the record. The difference is that the skating torque is anticlockwise where with most arms it is clockwise.
I had been having some difficulty wrapping my head around one aspect of this arm.
As the arm tracks to the left the effective length (between the main pivot and the stylus) increases in line with the direction of the stylus drag. The force required to extend the arm being derived from the drag. With an eccentric record the arm spends a large percentage of the time travelling to the right. Whilst moving to the right the effective length of the arm decreases against the direction of stylus drag. Where does the force required to shorten the arm against the drag come from? I had thought that the only logical source must be the side force that pushes the arm to the right. This would mean that the arm had higher resistance to movement in one direction than the other.
Then it hit me. The skating torque is anticlockwise, this tries to push the arm to the right. Is the skating torque being used as the motive force to move the arm to the right?
I think the amount of force required to move the arm to the right might also decrease towards the center of the record.
Whether the two forces can be balanced and how this effects the arm when it isn't moving to the right I haven't figured out yet. I am working all this out in my head so I'm probably missing an important piece of the puzzle.
Intriguing possibility. If this is what Frank has done then he's even more clever than I thought and I always thought he was exceedingly clever.
Niffy
I had been having some difficulty wrapping my head around one aspect of this arm.
As the arm tracks to the left the effective length (between the main pivot and the stylus) increases in line with the direction of the stylus drag. The force required to extend the arm being derived from the drag. With an eccentric record the arm spends a large percentage of the time travelling to the right. Whilst moving to the right the effective length of the arm decreases against the direction of stylus drag. Where does the force required to shorten the arm against the drag come from? I had thought that the only logical source must be the side force that pushes the arm to the right. This would mean that the arm had higher resistance to movement in one direction than the other.
Then it hit me. The skating torque is anticlockwise, this tries to push the arm to the right. Is the skating torque being used as the motive force to move the arm to the right?
I think the amount of force required to move the arm to the right might also decrease towards the center of the record.
Whether the two forces can be balanced and how this effects the arm when it isn't moving to the right I haven't figured out yet. I am working all this out in my head so I'm probably missing an important piece of the puzzle.
Intriguing possibility. If this is what Frank has done then he's even more clever than I thought and I always thought he was exceedingly clever.
Niffy