Hello Andy,
I am sorry for the delay. Shooting a video is not as easy as I thought it was.
I managed to shoot two videos, the links to which I'll post in less than two days. One shows the head-shell in action and it is of acceptable quality and the other one shows the tone arm overall on my Micro Seiki turn-table but it is blurry. Today, I'll shoot that one over again, now that I've learned how to set the ISO speed of my video camera to a higher setting.
See you soon,
Ralf
I am sorry for the delay. Shooting a video is not as easy as I thought it was.
I managed to shoot two videos, the links to which I'll post in less than two days. One shows the head-shell in action and it is of acceptable quality and the other one shows the tone arm overall on my Micro Seiki turn-table but it is blurry. Today, I'll shoot that one over again, now that I've learned how to set the ISO speed of my video camera to a higher setting.
See you soon,
Ralf
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No need to apologies
Hope you manage to get something together so we can understand and see how it all works when used.
Cheers
Andy
Videos (better late than never)
Hello All,
I am finally able to post two videos. Not being in possession of video recording equipment, I borrowed a canon digital elf from a friend and spent the next three weeks learning to use it. I managed to make two videos that won't win me any Oscars but they'll get the point across. One video shows the tone arm overall on my Micro Seiki turn table and the other video is a close up of the interaction between the head-shell and the cradle. Because tone arm motion is so slow, I chose a 12"/45 RPM/single LP for the videos. The overall video is useful to observe the motion of the support arm as it carries the tone arm's pivot through its arc. In the close-up I can be seen, jostling the cradle three times with a cotton swab to illustrate how the head-shell stubbornly follows the groove, ignoring any disturbances the cradle might cause. And for you Ray K, please watch the tone arm in the run-out grooves.
The fluctuating numbers on the multimeter's display, show the number of milliamps of current passing through the servo motor coils. Even though the tone arm is finished, I monitor that number to make sure that the tone arm continues to function correctly.
Sincerely,
Ralf
YouTube
YouTube
The attachment manager did't work, so I pasted the links into the reply.
Hello All,
I am finally able to post two videos. Not being in possession of video recording equipment, I borrowed a canon digital elf from a friend and spent the next three weeks learning to use it. I managed to make two videos that won't win me any Oscars but they'll get the point across. One video shows the tone arm overall on my Micro Seiki turn table and the other video is a close up of the interaction between the head-shell and the cradle. Because tone arm motion is so slow, I chose a 12"/45 RPM/single LP for the videos. The overall video is useful to observe the motion of the support arm as it carries the tone arm's pivot through its arc. In the close-up I can be seen, jostling the cradle three times with a cotton swab to illustrate how the head-shell stubbornly follows the groove, ignoring any disturbances the cradle might cause. And for you Ray K, please watch the tone arm in the run-out grooves.
The fluctuating numbers on the multimeter's display, show the number of milliamps of current passing through the servo motor coils. Even though the tone arm is finished, I monitor that number to make sure that the tone arm continues to function correctly.
Sincerely,
Ralf
YouTube
YouTube
The attachment manager did't work, so I pasted the links into the reply.
I certainly had doubts from the start about this wrt the absence of skate force.
Those are gone and this video should have been the first thing to have been posted.
That said, I do have some concerns about the tangency of the "mini rail" of the cradle during servo translations and the effects it might have. That makes me think it is not 100% tangent all the time, but so close it might as well be considered so.
I can't see any obvious force strong enough to cause the headshell to rotate to compensate when the cradle goes off tangent. The obvious pivot point if there was a force to cause it would be the front center bearing but that leads the stylus.
The error could be so small it can safely be ignored though.
My last concern is the bearing count and the stiction possibilities, even the Thales fell afoul of that using the best bearings.
Well done.
An awesome inspired implementation.
Those are gone and this video should have been the first thing to have been posted.
That said, I do have some concerns about the tangency of the "mini rail" of the cradle during servo translations and the effects it might have. That makes me think it is not 100% tangent all the time, but so close it might as well be considered so.
I can't see any obvious force strong enough to cause the headshell to rotate to compensate when the cradle goes off tangent. The obvious pivot point if there was a force to cause it would be the front center bearing but that leads the stylus.
The error could be so small it can safely be ignored though.
My last concern is the bearing count and the stiction possibilities, even the Thales fell afoul of that using the best bearings.
Well done.
An awesome inspired implementation.
Really remarkable results, Ralf. On the video, when the cradle is pushed it is really surprising to see how the headshell continues to track as if nothing had happened. Given the small weight of the cartridge + headshell and consequent minimum inertia, one would expect a hint of movement but instead remains steady. Incredible bearings.
Not knowing nothing about servos, just a curiosity: what you use follows the movements (like a "normal" servo) or prevents them, as an auto-pilot of a boat, that "learns" the rudder behavior and anticipates it (on waves or wind gusts)?
carlo
Not knowing nothing about servos, just a curiosity: what you use follows the movements (like a "normal" servo) or prevents them, as an auto-pilot of a boat, that "learns" the rudder behavior and anticipates it (on waves or wind gusts)?
carlo
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Hello 2wice,
I am attaching a PDF file to better illustrate my responses.
If you look at the PDF, you will notice a theoretical line I call "stylus path". The stylus path is located at a fixed distance from the tone arm's vertical pivot and crosses the cradle at 90 degrees to the cradle's center line. When the tone arm/cradle sweeps across the LP, the stylus path continues to intersect the platter center precisely. This is accomplished by a cam and cam follower arrangement at the tone arm's pivot. (covered by my US Patent No. 4,722,080) Because of the fact that the head-shell/cartridge has only two degrees of freedom relative to the cradle, the cartridge's cantilever remains perfectly parallel to the cradle's center line.
The head-shell cannot rotate in the horizontal plane because of the fact that the two bearings that support the head-shell at its rear are slanted. In order for the head-shell to rotate, it would have to rise against gravity.
I have been using my tone for over a year now, first by moving it manually and later with the servo, without any problems. When I purchased the bearings, I first washed the grease out of them, using a solvent that leaves no residue. You can order ball bearings without lubricants but it would be expensive for small quantities.
Sincerely,
Ralf
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Thank you kindly for your reply.
Does this mean the arm has a horizontal pivot independent from the servo?
Hello Carlo,
The servo I use is of the closed loop type. The head-shell/cartridge follows the groove and totally ignores the tone arm/cradle. When LP friction increases, the tone arm/cradle moves toward the label, which causes the Hall effect sensor to move away from the magnet. That action causes the servo to increase the control force on the tone arm/cradle which then returns to its position centrally under the head-shell. When friction decreases, the opposite takes place. During normal operation, i.e. no one is messing around with a cotton swab, the cradle's correcting motion is hardly noticeable. The beautiful thing about that system is that, the cradle's correcting motion has no effect on the head-shell's precise tangential trackability.
Sincerely,
Ralf
Hi Ralf
How is the LP friction transferred to the tonearm if the cartridge is independent?
Regards
Trenton
Hi, Ralf
I have been watching this thread with interest even though some of the technical aspects of your arm design are beyond my skill set. Having had the privilege of visiting you a few years ago and actually holding and looking at your analog marvel, and viewing your other mechanical, engineering talents was a true eye opener to this hobby machinist. Your modesty about your design shills, mechanical engineering, machining capabilities etc. are grossly under stated to say the least. I just want the people reading this thread to know how talented you really are. Your arm should be as good or better than any arm on this planet, period. I hope you manage to get the funding necessary to bring your novel, beautiful, and technically superior arm to market. Best of luck with your arm and have a wonderful Thanksgiving !!
Best wishes,
Joe
I have been watching this thread with interest even though some of the technical aspects of your arm design are beyond my skill set. Having had the privilege of visiting you a few years ago and actually holding and looking at your analog marvel, and viewing your other mechanical, engineering talents was a true eye opener to this hobby machinist. Your modesty about your design shills, mechanical engineering, machining capabilities etc. are grossly under stated to say the least. I just want the people reading this thread to know how talented you really are. Your arm should be as good or better than any arm on this planet, period. I hope you manage to get the funding necessary to bring your novel, beautiful, and technically superior arm to market. Best of luck with your arm and have a wonderful Thanksgiving !!
Best wishes,
Joe
Hello Trenton,
The friction between the rotating LP and the stylus, pulls the head-shell/cartridge against the single vertical bearing at the front of the cradle. Because the head-shell tracks tangentially, that drag force is co-linear with the center line of the cradle which in turn is located to the right of the tone arm's pivot, as viewed from the stylus end of the tone arm. That condition in turn causes the tone arm/cradle to move forward and rotate clock wise toward the label until it is checked by the servo.
Sincerely,
Ralf
Hello Joe,
Thank you for your kind words.
If you're visiting the CES early next year, maybe you could stop by again?
Then I could better explain the functioning of my tone arm, now that I have a fully functioning servo.
After my work on my tone arm, I may do some work on a bearingless turn table idea.
I hope that you had a wonderful Thanksgiving too.
Sincerely,
Ralf