Anti skate and tonearm damping query

Ok I can see it now.

The coefficient of friction does indeed reduce with pressure but what we haven't established is that the pressure is a linear function of VTA. For that to be the case contact area would have to be constant and it isn't.

I'm not even going to try to explain why not, I have a reasonable grasp on Hertzian contact theory but not good enough to explain it to you. Google Hertzian contact theory and you might see why.

Mark Kelly

Mark,
+++ The frictional force vector is in the direction of relative motion between the stylus and the vinyl. +++
>>>Yes!

When the stylus is following a groove, this direction is tangent to the groove curvature.
>>>Yes!

When the stylus is not following a groove, this direction is tangent to the scribed arc of the stylus on the vinyl.
>>>Yes!
+++

I completely agree with all the above.

I have no idea where you see a: "false dichotomy"
in my statements of: No friction = no skate force, no groove = no "off-set" in the groove (well there is NONE).

The only other angle is that angle between pin-point stylus to pivot and the pivot to centre of rotation. This angle seeks itself to be closed as soon as a friction force is applied.

If indeed it is what you keep referring to, we have no argument only an issue with terminology.

"Off-set angle" is by definition (in my universe and also at least SME's) the angle the head-shell and thereby the stylus is "off-set" in relation to the tone-arm-wand. This "off-set", (specific to each tone-arm) should produces two null-punkt (0 deg tangent angle) spots on the vinyl after correct alignment.

This tangent (tracing) angle is a constantly changing angle whilst the tone arm moves toward the centre of rotation, or end of record.

I am starting to think you are using "off-set" in place of this variable "tangent trace angle"?!

Sen wat we hav here is se problem mit de "Begriffsbestimmungen", oh mein Gott!?

Failure to communicate?

Axel

Axelwahl

You said no groove = no offset. That's not correct.

The tangent to the arc of the stylus traces on the vinyl does not pass through the tonearm pivot. Therefore there is a separate vector pasing through the same point (the stylus contact point) which does pass though the tonearm pivot. The first vector is the stylus frictional reaction force vector, the second is the tonearm restraining force vector.

The angle between these two vectors is the angle I described as the "true offset" and which we are now going to call something else, hopefully slightly less cumbersome than "the angle between the stylus frictional reaction force vector and the tonearm restraining force vector". As explained above, the fact that the stylus frictional reaction force vector doesn't pass through the pivot is what causes skating. That's all there is. Nothing more, nothing less.

Mark Kelly

Axel

I've just read your post more carefully and my first response was too hasty.

I'm not familiar with the term "tangent trace angle" but by your description it is what I described as "true offset angle".

Indeed we may have been suffereing from terminological incommensurability.

Mark Kelly

Mark, regarding Hertz are you saying the contact area of the vinyl is expanding due to deformation with increasing force, (I dont see the stylus deforming), and therefore the contact area might expand more than the force and P becomes smaller even though F increases?