Hi everyone,
I have always liked the appearance of conventional pivoting tone arms, as they sit neatly in the upper right hand corner of any turn table; and the turn table that offers the least space for mounting a tone arm is the Thorens TD-124. Consequently all the tone arms I have designed, were designed to fit that turn table.
Even though I also like straight line tracking tone arms, I just don't like the way they take up so much space. So, in 2022 I designed a compact linear tracking tone arm with a floating head-shell to be able to be mounted on a Thorens TD-124 turn table. It is almost as compact as a conventional pivoting tone arm mounted within the confines of the tone arm mounting board in its "at rest" position. To play an LP, it is swung a few degrees counter clockwise to place the stylus at the beginning of the LP's groove.
I designed the tone arm to travel on a track whose length is ~ equal to one half of the modulated distance measured along the radius of the LP. At the head-shell end of the tone arm, I provided an extra wide cradle to allow the head-shell to travel, a distance also ~ equal to one half of the modulated distance measured along the radius of the LP.
The tone arm would be driven by a geared-down CONSTANT speed DC motor, or my preference, a stepping motor. There would be two limit switches to start and stop the motor, but NO servo.
The design is not yet finished and has not yet been built as I am currently involved in other tone arm designs. If anyone is interested in working with this design, please feel free to do so as long as it is for personal use only. I have solid modelled the tone arm and I am attaching three PDF files.
The head-shell travels on two stainless steel rods carried by four ball bearings with a fifth ball bearing preventing forward movement. Miniature air bearings could be used to support the head-shell.
If the groove pitch of an LP would be constant, it would be easy to compute the lengths of the two tracks but, because of variable pitch, computing the lengths of the tracks would be a little more difficult. What I also have not yet designed is a method to return the floating head-shell to its start position.
Sincerely,
Ralf
I have always liked the appearance of conventional pivoting tone arms, as they sit neatly in the upper right hand corner of any turn table; and the turn table that offers the least space for mounting a tone arm is the Thorens TD-124. Consequently all the tone arms I have designed, were designed to fit that turn table.
Even though I also like straight line tracking tone arms, I just don't like the way they take up so much space. So, in 2022 I designed a compact linear tracking tone arm with a floating head-shell to be able to be mounted on a Thorens TD-124 turn table. It is almost as compact as a conventional pivoting tone arm mounted within the confines of the tone arm mounting board in its "at rest" position. To play an LP, it is swung a few degrees counter clockwise to place the stylus at the beginning of the LP's groove.
I designed the tone arm to travel on a track whose length is ~ equal to one half of the modulated distance measured along the radius of the LP. At the head-shell end of the tone arm, I provided an extra wide cradle to allow the head-shell to travel, a distance also ~ equal to one half of the modulated distance measured along the radius of the LP.
The tone arm would be driven by a geared-down CONSTANT speed DC motor, or my preference, a stepping motor. There would be two limit switches to start and stop the motor, but NO servo.
The design is not yet finished and has not yet been built as I am currently involved in other tone arm designs. If anyone is interested in working with this design, please feel free to do so as long as it is for personal use only. I have solid modelled the tone arm and I am attaching three PDF files.
The head-shell travels on two stainless steel rods carried by four ball bearings with a fifth ball bearing preventing forward movement. Miniature air bearings could be used to support the head-shell.
If the groove pitch of an LP would be constant, it would be easy to compute the lengths of the two tracks but, because of variable pitch, computing the lengths of the tracks would be a little more difficult. What I also have not yet designed is a method to return the floating head-shell to its start position.
Sincerely,
Ralf
Ralf,
I had to go through all the drawings to figure out what you’re up to this time. Your new idea is a little complicated, but kinda fun.
Doug
I had to go through all the drawings to figure out what you’re up to this time. Your new idea is a little complicated, but kinda fun.
Doug
Ralf,
It is a very interesting design. In my opinion, the main benefit of this kind of design is to deal with eccentricity. A servo-controlled linear arm can't handle eccentricity well. The 2nd benefit is to optimally control the total mass of the carriage.
Here are some of my suggestions.
1. It will be nice if the tonearm reaches the end of the groove, the step motor will drive the arm to the rest position as indicated in the following diagram in blue lines. If the arm stays in the center of the base rail, you have to move the arm to one end to play a record.
2. Since the floating head-shell is used for eccentricity only, I suggest shortening the rail for the head-shell as much as possible. I would say 7 mm on both sides should be way enough. In the meantime, you may extend the base rail as long as possible to cover the whole distance from the outermost groove to the innermost groove. In other words, the floating head-shell is used for small movements in both directions caused by eccentricity only.
3. I can't see the bottom view of the floating headshell. The efficiency of the ball bearings is very critical. The performance of the tonearm highly depends on the efficiency of these ball bearings. I can't say anything until I see the proof of the high efficiency of these ball bearings. In my mind, I suspect the efficiency of ballbearings can't meet my expectations. So, have you ever considered Niffy's style wheels?
4. The last point is purely personal preference. Using a pivot structure may make the structure more complicated.
Jim
It is a very interesting design. In my opinion, the main benefit of this kind of design is to deal with eccentricity. A servo-controlled linear arm can't handle eccentricity well. The 2nd benefit is to optimally control the total mass of the carriage.
Here are some of my suggestions.
1. It will be nice if the tonearm reaches the end of the groove, the step motor will drive the arm to the rest position as indicated in the following diagram in blue lines. If the arm stays in the center of the base rail, you have to move the arm to one end to play a record.
2. Since the floating head-shell is used for eccentricity only, I suggest shortening the rail for the head-shell as much as possible. I would say 7 mm on both sides should be way enough. In the meantime, you may extend the base rail as long as possible to cover the whole distance from the outermost groove to the innermost groove. In other words, the floating head-shell is used for small movements in both directions caused by eccentricity only.
3. I can't see the bottom view of the floating headshell. The efficiency of the ball bearings is very critical. The performance of the tonearm highly depends on the efficiency of these ball bearings. I can't say anything until I see the proof of the high efficiency of these ball bearings. In my mind, I suspect the efficiency of ballbearings can't meet my expectations. So, have you ever considered Niffy's style wheels?
4. The last point is purely personal preference. Using a pivot structure may make the structure more complicated.
Jim
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The biggest challenge I see will be vertical effective mass. If the HS is 30g you could end up with 50g or more vertical effective mass with a cartridge installed. This may be ok with very low compliance cartridges like Koetsu and Denon.
Hi,
Thank you everyone for commenting.
I have a sneaking suspicion that I failed you by not making the functioning of my design clearer.
The distance that the stylus of my linear tone arm design has to travel, is 3.690". The tone arm by itself is designed to travel half that distance i.e. 1.845", driven by a constant speed motor. While the tone arm is doing that, the head-shell, driven by the groove, travels the other half of the total distance of 3.690". When the LP is finished, the Tone arm will have traveled 1.845" and the head-shell will have traveled 3.690". To help illustrate the concept, I have included two additional PDF files, which I should have done from the beginning.
If I have insulted anyone who understood the operating principle of my design, my apologies.
The view of the underside of the tone arm, is meant for super10018.
Sincerely,
Ralf
Thank you everyone for commenting.
I have a sneaking suspicion that I failed you by not making the functioning of my design clearer.
The distance that the stylus of my linear tone arm design has to travel, is 3.690". The tone arm by itself is designed to travel half that distance i.e. 1.845", driven by a constant speed motor. While the tone arm is doing that, the head-shell, driven by the groove, travels the other half of the total distance of 3.690". When the LP is finished, the Tone arm will have traveled 1.845" and the head-shell will have traveled 3.690". To help illustrate the concept, I have included two additional PDF files, which I should have done from the beginning.
If I have insulted anyone who understood the operating principle of my design, my apologies.
The view of the underside of the tone arm, is meant for super10018.
Sincerely,
Ralf
Ralf,
I don't think I and warrjon misunderstood your tonearm's operation. In other words, your tonearm is a passive linear arm at 1st 1/4 of the traveling distance. In the 2nd 1/2 of the traveling distance, it is driven by a step motor at a constant speed. It is not servo controlled. The tonearm becomes a passive linear tonearm again at the last 1/4 traveling distance.
Once the tonearm finishes playing a record, it returns to its resting position as follows. But if you want to play the next record, you have to start the step motor to drive the tonearm all the way to the right end of the base rail and manually pull the floating headshell to the right end of the small rail, too. And, turn the tonearm to a proper degree to play. It is not too convenient and has too many steps. This is why I suggested a different resting position.
After seeing the bottom of the floating headshell, it deepens my suspension of the low efficiency of your ball-bearing floating headshell. The good part is that you may effectively control the total mass of the headshell since the counterweight part of the arm is not a part of the headshell. It may improve the efficiency of the ball bearing and reduce friction. I gave up the ball bearing passive linear arm just because I realized that ball bearings are not as efficient as air-bearing and the ball bearings simply have too much friction. I rather let the tonearm has different lateral and vertical effective masses but low friction of the ball bearings. However, for warrjon, he thinks it is more important to have equal lateral and vertical effective masses.
Jim
I don't think I and warrjon misunderstood your tonearm's operation. In other words, your tonearm is a passive linear arm at 1st 1/4 of the traveling distance. In the 2nd 1/2 of the traveling distance, it is driven by a step motor at a constant speed. It is not servo controlled. The tonearm becomes a passive linear tonearm again at the last 1/4 traveling distance.
Once the tonearm finishes playing a record, it returns to its resting position as follows. But if you want to play the next record, you have to start the step motor to drive the tonearm all the way to the right end of the base rail and manually pull the floating headshell to the right end of the small rail, too. And, turn the tonearm to a proper degree to play. It is not too convenient and has too many steps. This is why I suggested a different resting position.
After seeing the bottom of the floating headshell, it deepens my suspension of the low efficiency of your ball-bearing floating headshell. The good part is that you may effectively control the total mass of the headshell since the counterweight part of the arm is not a part of the headshell. It may improve the efficiency of the ball bearing and reduce friction. I gave up the ball bearing passive linear arm just because I realized that ball bearings are not as efficient as air-bearing and the ball bearings simply have too much friction. I rather let the tonearm has different lateral and vertical effective masses but low friction of the ball bearings. However, for warrjon, he thinks it is more important to have equal lateral and vertical effective masses.
Jim
Hi Jim,
I don't think the arm needs equal EM I think this arm will have much higher vertical EM than horizontal. Our Linear trackers are the opposite they have higher horizontal EM. I think the high vertical EM is going to cause issues with warps and even with a clamp if you look closely the cartridge is moving vertically. The fast movement of the irregularities will cause unwanted modulation.
Hi super10018,
I guess I was right, you don't understand how my design works.
The tone arm does not play a record in quarters and halves.
I wrote in my first post that there would be limit switches.
The procedure of playing a record would be identical to playing a record with a conventional tone arm.
You swing the tone arm to the start of the groove and actuate the lift/lowering device. That starts the carriage motor at ~50% of groove pitch while the head-shell is driven by 100% of groove pitch. They both arrive at the circular part of the run-out groove at ~ the same time, waiting to be raised by the user. Returning the tone arm to the rest position, actuates the carriage motor to return the carriage to the rest position. The slight bump caused by the carriage when it stops, is enough to return the head-shell to its start position.
The ABEC-5 ball bearings I have been using are more than adequate for the task. I have been using them since 2019
The whole scheme can be accomplished with a few 7400 TTL logic chips.
Ralf
I guess I was right, you don't understand how my design works.
The tone arm does not play a record in quarters and halves.
I wrote in my first post that there would be limit switches.
The procedure of playing a record would be identical to playing a record with a conventional tone arm.
You swing the tone arm to the start of the groove and actuate the lift/lowering device. That starts the carriage motor at ~50% of groove pitch while the head-shell is driven by 100% of groove pitch. They both arrive at the circular part of the run-out groove at ~ the same time, waiting to be raised by the user. Returning the tone arm to the rest position, actuates the carriage motor to return the carriage to the rest position. The slight bump caused by the carriage when it stops, is enough to return the head-shell to its start position.
The ABEC-5 ball bearings I have been using are more than adequate for the task. I have been using them since 2019
The whole scheme can be accomplished with a few 7400 TTL logic chips.
Ralf
Ralf,
I don't see there is any fundamental difference. My suggestion still stands. The only difference is you may use automation to reduce manual steps. That will be nice. The resting position is in the middle of the rail for the step motor. It has to be moved to the end of the rail manually or automatically to play a record.
ABEC-5 ball bearings by themselves may look like it is adequate for a linear arm. However, the problem is a combination of various factors, such as the construction of the rail, the material of the rail, and the total mass of the carriage. Once everything comes together. It will be different. Sure, they will make a sound. But they will sound differently.
I don't see there is any fundamental difference. My suggestion still stands. The only difference is you may use automation to reduce manual steps. That will be nice. The resting position is in the middle of the rail for the step motor. It has to be moved to the end of the rail manually or automatically to play a record.
ABEC-5 ball bearings by themselves may look like it is adequate for a linear arm. However, the problem is a combination of various factors, such as the construction of the rail, the material of the rail, and the total mass of the carriage. Once everything comes together. It will be different. Sure, they will make a sound. But they will sound differently.
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Ralf,
My 2nd suggestion stands as well. My suggestion was to extend the rail for the step motor to cover the whole traveling distance. In this way, the floating headshell will move once eccentricity is present. Otherwise, the floating headshell is stationary or makes very small movements to reduce the movements associated with the low-efficient ball bearings.
In addition the reasons above, as I said before, I am not a fan of a constructed headshell. The best headshell is a simple solid block of metal.
My 4th suggestion is good, too. I just don't see the benefits of a pivoted linear tonearm because the reason to make pivoted linear tonearm is purely psychological one. Of course, you may do whatever you like to do. But a pivoted linear tonearm doesn't have any advantages for playing back the reocrds.
Jim
My 2nd suggestion stands as well. My suggestion was to extend the rail for the step motor to cover the whole traveling distance. In this way, the floating headshell will move once eccentricity is present. Otherwise, the floating headshell is stationary or makes very small movements to reduce the movements associated with the low-efficient ball bearings.
In addition the reasons above, as I said before, I am not a fan of a constructed headshell. The best headshell is a simple solid block of metal.
My 4th suggestion is good, too. I just don't see the benefits of a pivoted linear tonearm because the reason to make pivoted linear tonearm is purely psychological one. Of course, you may do whatever you like to do. But a pivoted linear tonearm doesn't have any advantages for playing back the reocrds.
Jim
The headshell will follow eccentricity because it's floating on rails. There's no need to widen the tracking radius because the base will slide horizontally in a non-servo way.
This is not a pivoted linear arm.
This is not correct. Let's assume the speed the stylus travels is A. So, the speed of the step motor is about A/2. The floating headshell is constantly traveling with the step motor. Both the cartridge and the step motor will reach the left end of the rails at the same time. That means that the floating headshell is moving all the time no matter whether there is eccentricity or not.
If possible, I suggest expanding the rail for the step motor to cover the whole traveling distance with the pivoted retrieving mechanism, in the meantime, to reduce the length of the rail on the floating headshell. In other words, the speed of the stylus travels is equal to the speed of the step motor. So, the headshell doesn't move unless the existence of eccentricity.
The retrieving mechanism is a pivoted one. Using a pivoted mechanism is purely for psychological satisfaction. The cost for that is a complicated structure.
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I am NOT saying if it is right or wrong. I used the word, suggestion. I am merely suggesting better options based upon my opinion. The designer has the right to completely ignore that and it is fine with me.
As Warrjon pointed out the vertical mass is already high as is and widening the rail structure will only add even more mass.
Years ago I had thought of a similar passive design in another thread with a fixed wide structure but Carlo pointed out the issue of high vertical mass that ultimately I agreed with him and abandoned the idea. Ralph's motorized design with half width rails is one way to combat that issue.
Years ago I had thought of a similar passive design in another thread with a fixed wide structure but Carlo pointed out the issue of high vertical mass that ultimately I agreed with him and abandoned the idea. Ralph's motorized design with half width rails is one way to combat that issue.
You completely misunderstood my suggestion. Please see the image below. The tonearm in red lines is what I suggested and the tonearm in blue lines is my version at the rest position. The tonearm in light gray lines is Ralf's original design.
So, the step motor covers the whole traveling distance while the floating headshell makes small movements in both directions in the case of eccentricity. In fact, my version reduces the vertical effective mass. The rail for the step motor has nothing to do with the vertical effective mass at all.
I guess my version may be simpler to make since it is fine as long as the speed of the step motor matches the speed of the cartridge. But I could be wrong because I don't know the construction details for Ralf's original design.
Additional words about the resting position. It is nice that the step motor will drive the tonearm all the way back to the right end of the rail once you lift the tonearm when it reaches the end of the groove. So, the tonearm should sit on the right end side of the rail when it is at the resting position.
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I apologize for the misunderstanding on the widening of the headshell rails instead of the sliding base. I was thinking out loud of my own design that projected onto your suggestion. A Freudian slip, I suppose. But at the same time what you suggested has been made already in the other Ralph's invention, the servo quasi-Birch arm in the other forum thread except in articulated pivoting base form. This is a non-servo design moving in fixed pitch, like a fixed pitch record lathe, in the second half of the travel, hence the rather wide headshell rails are necessary. Matching the motor with the speed of cartridge would require a servo system in which this is not. What you suggested essentially became a modern Rabco/Goldmund (minus horizontal pivot) with a floating headshell.
PS, I personally like the floating headshell idea because it floats with eccentricity and the only thing on my wishlist is to have a completely passive non-servo non-motorized version without the vertical mass issue. Sorry, I'm spitballing again!
PS, I personally like the floating headshell idea because it floats with eccentricity and the only thing on my wishlist is to have a completely passive non-servo non-motorized version without the vertical mass issue. Sorry, I'm spitballing again!
What I suggested is not a servo-controlled system. It should be the same moving mechanism as Ralf's original design. I understand there are some exceptions and the gaps between the groove may vary, such as Telarc Tchaikovsky: 1812 Overture. But such instances may be only in 0.1% chance. In 99.9% of cases, it should be ok. Even the gaps between the groove vary a little. There is still some room to compensate for the difference in the floating headshell.
This is the groove of Telarc Tchaikovsky: 1812 Overture.
Utter waste of time this contraption.
When commercial designs have already done research and development on suitable turntables for decades.
And the TD124 with that contraption is just not suitable, nor reasonable to provide any benefits.
When commercial designs have already done research and development on suitable turntables for decades.
And the TD124 with that contraption is just not suitable, nor reasonable to provide any benefits.