Angling for 90° - tangential pivot tonearms

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RCruz

RCruz

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Joined 2006
Paid Member
Mark Kelly said:
I can't copy the diagram in question so you'll have to refer to the above post.

With due respect to Horii-san, the diagram in section 2 and the explanation of it are pure bunk.

The stylus friction reaction force occurs because of relative motion between the disc surface and the stylus and it therefore must be in the plane of the record and at a tangent to the groove. The relative magnitudes of the stylus friction reaction force and the downn force are determined by the coefficient of friction between the record and the stylus, not by the geometry of the tonearm.

Since the magnitude of the forces shown in the diagram is completely wrong, the rest of the diagram is useless.
Click to expand...

Admiting the stylus dragging force appears in the plane of the record and tangent to the groove, the force that appears just by friction is up and not down as suggested by our japanese designer. :smash:
 
Esperado

Esperado

Banned
Joined 2011
esperado.fr
RCruz said:
Admiting the stylus dragging force appears in the plane of the record and tangent to the groove, the force that appears just by friction is up and not down as suggested by our japanese designer. :smash:
Click to expand...
You are absolutly right. May-be what means the Japanese designer is that this force (up) applied on the cantilver at the diamond point tend to reduce its angle with horizontal. Same effect than a *down* force applied on the head itself, right ?
Fore once, physical laws are on our side: big modulations increase the friction forces, thus, the pressure on the diamond, increasing slightly the tracking ability ;-)
 

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Nanook

Nanook

Member
Joined 2004
guys, I'm thinking (look out I'm dangerouse)

First some assumptions

the RSLabs tonearm:
  • that the pivot point is 68mm above the '0' record height
  • that a warp is 2mm
  • that the effective length of the arm stays fixed at 239.5mm , but the mounting distance horizontally stays fixed at 230mm
  • that it has a vertical O/S of approximately 16.47° when in the static position

a typical tonearm:
  • the pivot point is approximately 25mm above the static position
  • that any warp is 2mm
  • the effective arm length stays fixed at approximately 230mm
  • the vertical O/S of the tonearm is approximately 6.203° when in the static position

If one considers the forces acting on the stylus tip, then one must look at any possible change in the angle between the pivot point and stylus tip. In the case of the RS Labs tonearm, this results in a change of (approx) .4982°, but a change of only 3.02%. Interestingly for a coventional arm (as per specs stated in assumptions) the change in the angle is essentially the same (which it should be), but as a percentage it jumps to 8.03%

What does it all mean? Any possible speed change due to a warp actually increases more for a "conventional" arm than The RS Labs arm, assuming the compliance of the cartridge deals with these effectively without affecting the speed. It almost seems counter intuitive. For a specific mounting distance the RS labs has a greater vertical offset, and thus lower errors in both the vertical and horizontal directions.

I may be completely wrong here, but I started from first principles and it seemed logical at the time. :)
 
directdriver

directdriver

Member
Joined 2005
Fourth dimension or not, I still like these two dimensional audio porno pictures. :)

This version of the Thales Simplicity is by far my favorite. The gray and silver is so aesthetically satisfying.

thales-simplicity1.jpeg
An externally hosted image should be here but it was not working when we last tested it.



Saw a version with gold trim from the editor of a Hong Kong magazine and it was really tacky and made worse the turntable also has gold trim. Yuck!
 
directdriver

directdriver

Member
Joined 2005
Our friends at Lenco Heaven forum are discussing similar topics about this genre of tonearms, including posts by Frank. So don't miss the chance to check out analysis and discussion over there. One member is partnering with someone named "Conrad" and I have to assume he's the same fellow member, Conrad Hoffman, from this forum and I look forward to seeing their project coming to fruition! Hooray to tangency! :)

Lenco Heaven Forum Tangential Tracking moving pivot tonearm « on: May 08, 2012, 03:36:49 PM »

low pitch: "Sometime back I worked out a locus to keep the stylus in tangent by moving the pivot towards the spindle on a short slide (surprised to find it only required 0.9” travel for a 12” arm). The travel is non linear, but if you mount the pivot on a short arm the non linearity can be offset by the sine. My idea was to have a constant speed of travel, or use a stepper controller (in which case the non-linearity doesn’t much matter). I recently found a collaborator to prototype it with a very sophisticated sensor / control. worked out the general equation just today (OK for linear track – monster for the RT)."

tangentialtrackerrotary.jpg
tangentialtrackerslide.jpg
Click to expand...
 
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directdriver

directdriver

Member
Joined 2005
Transcriptor Transcriber

Here's a curiosity item that I learned about from our friends at LencoHeaven. It's a sliding turntable with stationary tonearm for tangential tracking. I would imagine it uses servo to keep track of tangency.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


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http://i18.photobucket.com/albums/b133/gib48189/Transcriber/160-c_2.jpg

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More pictures at hifi-studio.de.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


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