Anti skate and tonearm damping query

Axelwahl

I think I have confused you by trying to simplify things. The angle I referred to as the true offset is the angle between the groove tangent and the line between the stylus and pivot. The frictional force acts along the tangent so this is the angle between the frictional force vector and the restraining force vector. The true offset angle varies with groove radius for ordinary pivoted arms and the offset angle of the arm is an approximate average of the true offset angles.

I can see how this is confusing and I should probably have used a different term.

Perrew

You are confusing force and pressure. The force is set by the VTF and the groove angle, so the sum of the forces on the sidewall is SQRT 2 times the VTF (for 90 degree groove). The pressure is this divided by the contact area. Larger contact area = lower pressure for a given VTF.

Mark Kelly

Mark, so increasing the VTF would increase the pressure and the skate force would decrease, all else equal? Wouldnt this imply that high VTF means anti-skate can be ignored?

Mark,
ja now fine, and so we have even more discrepancies since I, for the sake of TRUE simplification, been talking over and again about BLANK vinyl, and the stylus point riding on this smooth surface --- AND THEREBY taking any of this groove tangent stuff OUT OF THE EQUATION.

There IS a skate force WITHOUT any groove! Therefore NO tangent, what so ever comes into play as I tried real hard to get across.

Taking things into the groove, with all this stuff Perrew is on about is no good, if the basics are not cleared up, yes?

So, again, NO friction force, NO skate force, period.

Tangent has NOTHING to do with it at this point, *if we are NOT in any groove*!
As such all this talk about tangent, or off-set, etc. only serves to cloud the basics of the skate force issue --- unless you are much more deeply into the details then at this point was my understanding.

As such, and going back to the SIMPLE, *no groove*, model Dertonarm is NOT right in assuming a zero skate force at a 0 groove tangent angle.
I can prove that, as soon as there is friction, there is a skate force.
His (Dertonarm's) point is such only of any relevance, if at 0 tangent groove angle -- and as he assumes --- there be less friction force than at any other angle.
If this be so in the first place (and I have no explanation why it should be so!), it be so minute a difference, as to have no measurable effect.

Therefore off-set is as little part of the PRACTICAL equation as is Over-Hang. If one groove side is traced a micro-millimetre later (or earlier) then the other --- what be the increased friction due to that?
None! for a spherical stylus, and none for most any other stylus as well, even it the sides be a sharp as it gets.

It will make a mess of the signal, oh yes, but that is another discussion all together i.e. correct cart alignment.

Axel

Perrew

I cannot see how you can get to that conclusion.

Axelwahl

I love how you can take a simplification and twist it until it becomes a complexity. Your jump from "no groove" to "no tangent" is unjustified.

The frictional force vector is in the direction of relative motion between the stylus and the vinyl. When the stylus is following a groove, this direction is tangent to the groove curvature. When the stylus is not following a groove, this direction is tangent to the scribed arc of the stylus on the vinyl.

The rest of your post rests on this false dichotomy so it also falls (except for the bit about our befuddled friend DT not knowing what he's talking about. That I agree with)

Mark Kelly

Mark you said, P=F/A and "The breakdown takes the form of a pressure dependent coefficient of friction; the coefficient decreases with increasing pressure "
Still an example with your choice of tonearm would be helpful.