Do 45 RPM records need higher anti-skate setting?

While all these discussions are interesting, can you see if one of these ideas or thoughts are incorrect, or are left out, your conclusions will be wrong-sometimes incredibly so.  Lost in all this is how I actually set my anti-skate, and it didn't have to do with the beginning of a record.  It had to do with the end of the record-which turned out to be a compromise.  I could not use the setting that made the end of the record sound its best(I had to use a slightly lower skating force than that, in order to get the best sound over the entire record.).  Some assumptions(that cartridge manufacturers had arrived at recommended levels of anti-skate for their cartridge correctly, and that the anti-skate gauge was correct[or I read, from real life experiences, that it wasn't.].  See omsed's remark about lawyers and doctors.) had to be made by me.  Because so many people on Audiogon disagreed with cartridge manufacturers' anti-skate recommendations, I postulated(with some research on what arms these people were using) that anti-skate settings for unipivot tonearms might be different from the manufacturers' recommendations(which may have been based on gimballed tonearms).

45s are NOT cut with greater modulation (if they were the sound would be louder through the speakers), the goal of the mastering guys is same volume, so the idea that different anti-skate is required is far fetched. Same anti-skate.

I have quite a few 45s that are obviously cut at higher levels. IOW, they play louder. Also, when we cut at 45 on our lathe (I run an LP mastering operation, FWIW) we find that we can cut certain frequencies at higher levels easier than 33. I think where you are having a problem is the assumption that the 'mastering guys' are going for the 'same volume'. We might and we might not. Usually we cut with two goals:

1) see if we can get it all on the side and
2) don't over cut such that the stylus gets knocked out of the groove or the cut goes over the previous adjacent groove.

Its pretty well impossible to overload the cutter system- the main limit is cutting a groove that a cartridge can track without distortion. A lot depends on the signal that is being recorded and they are not all the same else the planet would be a boring place :)

So if friction due to modulation is indeed a factor in skating forces, it would be a mistake to assume that it will be a constant- IOW it is indeed a variable.

I have a device which can show the actual side-forces imposed on the cantilever. Although the instantaneous side-forces are affected by groove drag (and therefore groove modulation), it appears to me that the general side-forces experienced by the cantilever follow the tracking distortion curve.

hth

Rtilden, you surmised correctly that I did not want to respond, it's not worth it. I have graded students that have been sure they have been right until I drew a free body diagram showing all the forces balance, in front of them, and verbally went through it. Then in real time when they offer up their view, I can in real time show the mistakes. This is not feasible in a thread on a forum where you cannot include drawings such as a free body diagram with a vector analysis.

I also realize that I was wrong in thinking everyone wants to learn. Some would just as soon remain ignorant, as long as they can convince some others they are right.

Thanks for your note!

So, over and out for me. Thanks much for your note though.

Hmm. So I used a pencil & fixed a plastic headed straight pin at each end. Let's call the "pivot" proximal, the other, the unconstrained end, "distal". Held the "pivot" pin and placed the other on a Boston Audio Mat2, the plastic pin heads depending from the beam. In a condition described as "overhang", the pencil "beam" was center seeking. As OH was diminished speed of travel also diminished. In a condition of "underhang", the end distal from the crude "pivot" came to rest further from the center of rotation, a state of "equilibrium" was observed. As "underhang" was increased, the distal end eventually ran entirely off the edge of the Mat2.

Running the "pivot" against a straight edge, it seemed to me that the beam remained parallel to its previous location and also seemed to maintain a 90* angle to the guiding straight edge. Movement at point "A" resulted in an equivalent movement at "B" in a most linear fashion.

It also appears these various movements occupied a smaller time-frame as speed of rotation was increased.

'Fraid I lack the background in Physics to prove these actions.

Peace,

Omsed: I am hoping that you do not become disenchanted with the students in the front of the room who are poking you during your teachings. I am the quiet student in the back who is soaking up as much as I can from you. Keep it up as long as you can bear it.

Friction=skating, that's it. I remember back in the 70s some stereo shops had blank LPs for setting anti-skate. They would adjust the anti-skating on the tonearm until it would stay in the middle of the blank record.
45 rpm LPs can have a higher dynamic range, if the recording engineer chooses to apply it. The higher linear speed affords more velocity to be transmitted to the stylus. That means tracking ability of the stylus is further challenged and since the forces are or can be unbalanced a bit to the skating side of things, the first sign of mis-tracking is likely to be heard in the right channel. My 45 rpm direct to disc of the Apassionata can attest to that. My Benz can track it perfectly from beginning to end; but the stylus has to be squeaky clean.

Dear Omsed, This is not a university class or a peer-reviewed forum. Anyone is free to contribute in any way he or she prefers. I can say for myself that when I try to explain something, I am in essence stating my own reasoning of the problem for the express purpose of receiving criticism or correction. I want to learn. Here, I take exception with two of your claims:
(1) Overhang DOES have something to do with the skating force. Because of stylus overhang, the stylus can never be tangent to the groove. That is the root cause of the skating force, because the force of friction is always tangent to the groove. Thus a force vector is created with a direction toward the inward path of the tonearm (the real force is not along the arc of the tonearm, but is inward) that in its net expression becomes the skating force. It also would appear that the offset angle plays a role in determining the direction of the force vector created by lack of tangency, the radial expression of which is the skating force. (Perhaps this is not clear, would need a diagram to demonstrate.)
(2) No one is arguing with your statement that vertical and horizontal movement of the stylus creates the electrical signal that is converted into sound. The point made by me and others was that those vertical and horizontal wiggles that the stylus tip has to trace whilst the linear velocity past the stylus remains constant might in effect alter the coefficient of friction between stylus and vinyl, transiently and variably, so as to contribute to variability in skating force. I am not at all sure that this is a real issue, but it is not nonsensical to contemplate it. And having posited these things, it then would seem possible that a 45, if anything, might induce less skating force than a 33, given that the exact same music is recorded on each. This could certainly be incorrect. Have you measured such phenomena?

By the way, are YOU a physicist? What is your background in what science? I am guessing you are an engineer.

Ralph, Yes, but wouldn't you think that a 45 rpm version of any LP would have relatively lower groove tortuosity/modulation than the comparable 33, because the music signal is allowed more "room" at 45 rpm, per unit of time. Thus, I thought the OPs story that increasing AS helped was not consistent with the notion that groove modulation affected the skating force so as to increase it on average. If anything, I would expect a decrease in skating force, on average. That was a point i made way back up the thread.

Tracking angle error is negligible in the calculation of anti-skate, the magnitude of changing force being very small, tracking error only being +/- about 2 degrees even for a 9.5" tonearm. No arm's anti skate mechanism is within that range of accuracy, you can ignore that amount of change (that due to tracking error).

I have designed several arms, tested nearly any arm you can name, have dynamometers (force gauges) that can pick up the actual numbers. The theory coincides with actual measured results quite well.

We have some folks who are obviously not science people here (meaning not physicists, not engineers) "correcting" good information with misinformation. Overhang is not part of skating forces, RPM is not, 45's are not cut at a higher groove velocity (groove velocity that creates sound is vertical and horizontal movement), it is just the linear velocity past the stylus that is increased.

Atmasphere,
It would seem so.

Lewm,
I think your take on it is right. All I would say is that rather than "headshell" offset angle, it is perhaps better to think of it as "groove" offset angle (which is what gives rise to the tracking angle error, as both the cartridge offset and headshell offsets remain constant while the groove offset angle changes, the error increasing markedly at the innermost radii, giving rise to higher skating forces there).
J
.

45s are NOT cut with greater modulation (if they were the sound would be louder through the speakers), the goal of the mastering guys is same volume, so the idea that different anti-skate is required is far fetched. Same anti-skate.

So the idea that a 45 rpm disc cut with greater modulation to also require slightly greater anti-skate sounds like its not that far-fetched.

John, Yes, I just misunderstood the language of your first post on Alexandrovitch. I later figured out what you meant, and there is no disagreement with our earlier conclusion.

I hate to discuss the origin of the skating force, but I love it too. Such is life. My belief is that the prime cause of the skating force is friction of the stylus in the groove coupled with the fact that the cantilever is never tangent to the groove, because of "stylus overhang". "Headshell offset angle" changes the directions of the force vector that results from this. But the net effect is a force that pulls the stylus tip inward along the arc of the tonearm. (Because the tonearm is mechanically stiff and the pivot is anchored, the only way the stylus tip can respond to the forces on it is to "skate" inward on the one permitted path.) This is how I think of it, anyway.

Lewm,
Check out the link to Alexandrovitch and other papers via this link.

He found that with an unmodulated groove, there was no change in friction with radius ie groove speed. With a modulated groove there was an increase in friction, and this increase increased towards the centre, despite, apparently, the reduction in groove speed.

Ct0517,
I don't get the thing in the ET manual regarding the two skating forces. Certainly there is a tiny component of skating force due to the stylus contact point and the cantilever bearing point being in different places, but as far as I am aware that is not a major consideration in terms of the overall picture. But all skating depends on overhang, because it is that which gives rise to the fact that the groove and arm pivot are not in a straight line, thus causing the forces, unlike in the ET which is a linear tracker. If it was set with overhang it would skate too.

John

I've had conversations with several tone arm manufacturers; they seem to agree that there is no standard for anti-skate forces to be applied to an arm. Put another way they all seem to have different ideas about it.

Thats not surprising to me because we are dealing with varying groove modulations from the first track to the last.

I own two pivot tonearms. Anti-skate is a guess.
To be correct therefore pivoted arms need a different anti skate setting for 33 and 45 RPM records and even different positions along the record.

The best explanation I have personally read that describes this phenomena is from someone that actually tested pivot arms and antiskating. From the Eminent Technology ET2 manual. Page 46

"Antiskating and Frequency Modulation Distortion of Different Tonearm Geometric

Pivoted tonearms are designed so that the head shell holds the cartridge at an “offset angle” with respect to an imaginary line drawn through the tonearm pivot to the stylus tip. The arc traced by the stylus tip extends past the record center and is defined as “overhang”.

This design approach minimizes tracking error. There have been many articles written about the geometry of this design approach. Pivoted arms create several side effects which reduce phono cartridge performance. The first is a skating force which results from two different parts of pivoted arm design.

There is a force component (vector) that is directed toward the center of the record. It results from the stylus drag force vector not falling in line with the pivot point of the arm. This force pulls the tonearm inward and the stylus can be observed as bending outward. This force and the resulting bending can be demonstrated by connecting a rubber band to a pivoted arm around the cartridge body and pulling it straight (away) from the tonearm. Note: the motion of the tonearm is inward and results in bending of the rubber band (cantilever).

If you corrected these forces with an anti-skating mechanism such that the stylus did not bend (you can not really do this because the frictional force and resultant bending varies with groove modulation, stylus shape, tracking force, etc...) there still exists another component of skating.
This second skating force results because of overhang. There are frictional force vectors that result which are not directly ahead of the stylus. The surface of the record is not really moving straight ahead with respect to the stylus tip. As a result, there are force components directed ahead and toward the center of the record. The magnitude of the inward force depends upon the degree of overhang. "

We said way back up the thread that groove modulations might in effect alter the coefficient of friction. The only question is and was the magnitude of that effect. I think now it is significant; who could argue with Dr. Alexandrovitch?

But did he really find that "friction remained constant with groove speed"? That speaks to the original question, whether there would be higher skating force at 45 vs 33, and is contrary to our previous conclusion. I can see that the coefficient of friction could go up with decreasing radius, because groove modulations become more tortuous. Have you got an actual copy of this 1961 publication?

Atmasphere, Tonywinsc,
I used to think, as a previous poster, Omsed, posted, that antiskate should be the same irrespective of speed because dynamic friction would apply.
But over the years I have continued to be open to new information I previously wasn't aware of, and willing to modify my ideas if the facts didn't fit them. (Wish that were the case with many scientists).

The OP said all was well with his deck until he played this particular record, and that the problem was solved with an increase in anti skate. If that was the case, then the problem was not with the record, but too little antiskate.

This might fly in the face of conventional engineering opinion, but only if the facts are ignored. The logical answer is that there was more friction, therefore more skating force. And the reason for that would be, as you noted in your example, Tonywinsc, increased modulation, as per studies by George Alexandrovitch, (JAES, 1961). His study showed that on an unmodulated groove, friction remained constant with groove speed, increasing only with downforce. On a modulated groove, friction increased for the same downforce, and also with decreasing radius.

There has been a lot of good, reliable, proven, information on skating forces available for many, many years, which is why virtually every arm was, and is, supplied with antiskate.

John
.

Skating force is generated by the friction between the stylus and the vinyl. That's it. I researched it a few years back and learned that the coefficient of friction, which will determine the friction force generated, varied widely like from 0.1 to 0.5 among different records up until the 50s. Since the late 50s the coefficient of friction has been pretty consistent- about 0.20-0.25. That would result is some milligram differences in skating force from record to record. That being said, I have a couple of records and perhaps it is more about their dynamic range, that I have to turn the anti-skating setting up a tad because I will here a little bit of distortion in the right channel. That does the trick. By the way, one of those records in my mind is recorded at 45 rpm incidentally. It is the Apassionata and it is very dynamic. It is an RCA direct to disc. Very high on the goosebumpometer.

So far John's argument about variable friction does not seem to be addressed, or did I miss something?

I've had conversations with several tone arm manufacturers; they seem to agree that there is no standard for anti-skate forces to be applied to an arm. Put another way they all seem to have different ideas about it.

From a simply pragmatic point of view, the phenomena of the OP is that increasing the force fixed a problem that did not seem to exist at 33 rpm. Was that simply because he had not played anything with that complexity prior? Or was it because the forces on the arm were different?

An object once set in motion...

Ralph, I have spent a lifetime stamping out "centrifugal force", ever since my freshman physics professor hammered it into me about the First Law. I can't stop now. Centripetal force needs my help and support.

Lewm, I think the part about centrifugal force to be a red herring. We don't need to discuss it further.

There is no such animal as centrifugal force. It is fictional. Any object in motion will tend to remain in motion in a line determined by the vector of the force that set it in motion. This is Newton's First Law, and the following is from Wikipedia:

"This is known as uniform motion. An object continues to do whatever it happens to be doing unless a force is exerted upon it. If it is at rest, it continues in a state of rest. If an object is moving, it continues to move without turning or changing its speed. This is evident in space probes that continually move in outer space. Changes in motion must be imposed against the tendency of an object to retain its state of motion. In the absence of net forces, a moving object tends to move along a straight line path indefinitely." (Let me add here that this is true in the absence of gravity and friction.)

To keep an object in circular orbit, one must apply a force directed inward toward the center of the orbit. This force vector is centri-petal, "center-seeking". Think of a sling shot. Before release, the stone travels in a circle because the sling allows you to apply a centripetal force. The moment you let go of the sling, the stone flies off in a line tangential to the radius of its orbit, because that's the direction of the force vector that motivates it. If there really were any such thing as "centrifugal" force (center-fleeing), then the stone would fly away in a line parallel to the radius of the orbit. That does not happen. If David had not understood this, Philistines would rule. He would have missed Goliath by a mile.

Regards, John Gordan: As always, a pleasure to have your informed opinion. I do need to correct my first para., most recent post. Centripetal force *opposes* centrifugal force, to what degree is a variable.

Peace,

Timeltel,
As Omsed said

Skating force remains the same since it is based solely on the magnitude of friction and the offset angle of the tonearm. Same tonearm, same friction, same skating force, so anti-skate should remain the same.

However, if the friction force changes then so does the skating force, so it depends on whether the coefficient of friction remains constant, which is an assumption.

For an ungrooved as opposed to grooved disc, I don't know. For what it's worth, my experience of records skating (mainly in days long gone by) is that I recall them skating at much the same speed whether 33, 45 or 78, judging by the pitch of the scratching sound...

John
.

Omsed,
No one is talking about spinning a complete turntable, or that there is a centripetal force involved in the skating issue, or that the cartridge is spinning with the record. If you read all the posts here and elsewhere I think that is clear. The only reason for using the term at all is in attempting to try and clarify the difference between a force acting toward the centre in the context of an arm being spun or a body in orbit, and a force acting towards the centre in a tonearm in reaction to the friction in the groove.

VTF is, of course, different on each groove face unless anti-skate is used. That's why the skating force is a problem. That is elementary. I don't get what you are saying re the groove faces being identical etc. We are not talking about record cutting, but playback.

Regarding information storage, if I store the same information in a bigger space, that's all I have done. When I retrieve it, I get it back. The point about the bigger space is that I can store more information, otherwise what's the point? Perhaps I am wrong, not being a recording engineer, but I was under the impression that higher speed allowed higher levels, whether it be tape or vinyl. And if there is more information, of whatever kind, the cartridge has to do more work to retrieve it, hence the reference, albeit imprecise, to energy (I take your point about the irrelevance of the platter's kinetic energy).

As you are having difficulty finding proper scientific papers, I've posted a link here. Look at Gilson and Alexandrovitch.

John
.

Regards, Omsed: Let's clarify the difference between centrifugal and centripetal force. Centripetal force is ANY force that acts to prevent an object from moving away from the center of an orbit, see http://www.diffen.com/difference/Centrifugal_Force_vs_Centripetal_Force.

Consider skating phenomena the consequence of two forces acting upon the TA. First, friction along the axis of the TA. This is relative to grove modulation or any stylus "drag" in an unmodulated groove, or even an un-grooved disc.

Any TA (with under or overhang) will be subject to a second vector, this is tangent to the long axis of the TA, and, dependent on wether the stylus is under or overhung relative to the spindle, will exert a lateral force on the stylus. The TA will be inclined to move either away (underhung), or towards (overhang) the center of revolution. The groove constrains the TA movement and serves as a centripetal force.

These actions are observable and repeatable, the same principles that guided Sir Isaac, who also gave definition to centripetal force.

The question remains unanswered, would not a TA tend towards the center of an un-grooved disc more rapidly if spun at 45rpm rather than at 33.3rpm?

Peace,

Timeltel
you said:

A pivoted arm with overhang will seek the center of a blank (ungroved) LP. Would it not move towards the spindle more rapidly if the disc were spun at 78 or 45 rpm than at 33.3?

That depends on the friction generated. All things equal, the friction would be more or less the same, as once the stylus is moving the friction (dynamic as opposed to static) is constant if nothing changes. It is is like when you try to push a heavy box. Static friction makes it hard to get started, but once it is moving it takes more or less the same effort whether it is moving slowly or quickly ). And it is the friction which supplies the force to rotate the arm.

However in any particular modulated groove, the friction changes with velocity (due to the modulation). So in the case of the OP, there may have been a particularly loud passage which indicated that the the existing anti-skate setting was inadequate.

John

Here we go again: VTF cannot be different for each channel. Left wall and right wall are identical - how could they not be given that they are cut by a single cutter?! Each nudge, each bump, each movement of the inside groove wall is duplicated on the outside groove wall. This is the Westerex system.

Horizontal movement is L + R channels. Vertical movement is L - R channel. 45 degree orientation of coils give the sum and difference results of L and R.

Mmakshak,
There is actually a logical default position: namely, that given there is a skating force (which is old, proven, science, well documented, though commonly misunderstood) and which leads to VTF being different on each channel, it should be counteracted.

it is approximately between a fifth and a third of the VTF, depending on stylus profile and other factors.

Now, while it may vary subtly to some debatable extent across the record and with platter rpm, it is, as Omsed stated, always there and always towards the centre. Applying anti-skate may or may not be audible, but it is designed to compensate for something which could result in record or stylus damage, which is why 99.9% of arms have it in some form.

Users seldom use VTF below cartridge makers recommendations, because the cartridge will mistrack and even if you can't hear that mistracking it is acknowledged as being a bad thing.

However, without anti-skate, the chances are that your cartridge is running below recommended VTF on the right channel.

John

When there is a groove, the inside face restrains the stylus, so there is effectively no such force, because the arm is rotating only minimally (at less than 0.01 rpm), and the stylus has such a tiny mass, that any forces are negligible, and totally overwhelmed by the friction forces by many orders of magnitude.
J
John_gordon (Answers | This Thread)

As a layman, this would most closely resembles my experiences. Well put J.

While science is a good objective parameter, I suggest that trying out the skating force is the best way to determine the answer. I do not see a consensus among the posters of exactly what the science is. If one assumption is incorrect, all conclusions from that are wrong. Or you could conclude that one of the explanations of skating force is correct, and procede accordingly.

Timetel, please read my earlier entries on this thread where I explain the formula for skating force. Skating force remains the same since it is based solely on the magnitude of friction and the offset angle of the tonearm. Same tonearm, same friction, same skating force, so anti-skate should remain the same.

"(Even) if dynamic friction magnitude were dependent upon velocity. Fact is dynamic friction is nearly independent upon velocity."

A pivoted arm with overhang will seek the center of a blank (ungroved) LP. Would it not move towards the spindle more rapidly if the disc were spun at 78 or 45 rpm than at 33.3?

Peace,

Lewm,
If there was no groove, the arm would skate and rotate until there were no forces acting to make it do so, so there would be, for a short while, a "conventional" centripetal force acting on the stylus and arm along the stylus to pivot axis caused by the rotation.

When there is a groove, the inside face restrains the stylus, so there is effectively no such force, because the arm is rotating only minimally (at less than 0.01 rpm), and the stylus has such a tiny mass, that any forces are negligible, and totally overwhelmed by the friction forces by many orders of magnitude.
J

Omsed, Point taken. Sorry.

John, The tonearm is stationary, resisting the force of friction on the stylus tip which would tend to want to pull the tonearm clockwise in the direction of LP rotation. But I have privately wondered about a tiny centripetal force exerted by the LP on the stylus tip, as the grooves spiral inward. I think it's overcome or negated by the skating force.

1. The difference in sound between 33 and 45 has nothing to do with the amount of energy being put into the stylus or the energy in the system. It has to do with less information density on the groove. There is greater length groove per second of musical signal. Lower information density, which is storing the same information in a greater storage area/length/volume (depending on the technology) gives greater fidelity. This is true in records, tape (30ips instead of 15ips, for instance), photography (a 4" x 5" negative compared to 35mm, which is 1" x 1.5", movie film....any analog medium.

This is a huge thing, and it is why more tape run by the head, more groove length under the stylus, and greater info on a negative enlarged to the same size all yield great improvements. The record does not play louder with a 45, which it would with higher modulation, the tape does not play louder.

2. As for energy, you are mixing energies. Energy put into moving the cantiliver is the same or volume would be louder. Kinetic energy of the platter is higher, yes, but that has nothing to do with playback and has nothing to do with more energy put into the cartridge, which is not done.

But, there is more kinetic energy in the platter. You are wondering about it. Well, where it came from is the energy put into it by the motor. That kinetic energy came from the torque required to get it up to speed over the period of time of acceleration. That energy is = i(w x w) where w (omega) = rotational velocity and i is the moment of the inertia of the platter. That energy stays constant, and when the switch is turned off the energy gets bled off, turning into heat, in the bearings and motor "off torque". That amount of energy during deceleration = the amount of acceleration = the kinetic energy while the platter was turning. Thus, energy is neither created nor destroyed, but is conserved, only changing forms. Newton is satisfied. Or at least his laws are, I trust he is dis-satisfied about how much physics is twisted and mutilated in this industry!

And finally, here is the bit of wrong information on the forum John sent us to, written by a "John" on that forum.

There is no centripetal force involved, as the arm is not rotating with the record. Now, if we put the whole turntable and tonearm mechanism on a rotating sub table and rotated the subtable then the cartridge would indeed try to fly outward.

But I know of nobody spinning their ENTIRE turntable setup while playing a record, so there is not such force.

It is a great optical illusion: stylus on a rotating record, so it must fly outward! False illusion. Spin the platter faster and faster and faster and there still is no centripetal force: only the platter is spinning! There can be no such force as the velocity of the stylus/cartridge/headshell in the tangential direction is essentially zero.

Don't worry about getting this wrong, most first year physics students would. A lifetime studying and working in physics and engineering: there's no substitute for that plus the education beforehand. Nobody should feel bad about that, I do not feel bad about not knowing as much about their respective fields as my doctor and lawyer do!

Omsed,
You need to read and assimilate before spouting. Otherwise you may be
considered a wanker.
[quote] This greater acceleration does not exist. And more energy is NOT
being put into the system or the volume would be louder on a 45![/quote]

So would you care to enlighten us otherwise why anyone would use 45 rather
than 33 1/3 other than to be able to have a disc with higher modulation?
As far as my (possibly inferior) knowledge is aware, that a body revolving
faster has more energy than one revolving slower. I thought this was
something to do with kinetic energy?
Therefore permitting higher signal levels to the cartridge.
Of course you may not have noticed any difference between 45s and 33s, in
which case get yourself some and listen....

Re centipetal force - think about it. The only revolving item other than the
platter, is the tonearm, which is the item under discussion, and there are
minimal, and irrelevant, centripetal forces acting on it, which is what I have
said in the blog.
John

Misunderstanding: it was the blog about anti-skate that an above poster referenced which mentioned centripetal force, which makes the science credentials of the blogger suspect.

Oh yes, it was you to whom I was responding, Omsed. It was you who used the term "centrifugal". So what's your point? I did find my response, and I don't see where I ever said anything that could be construed as attributing skating to a centripetal force. Indeed, as noted above, I was just discussing the physics of a body in orbit.

Dear Omsed,
The question was around the two terms "centrifugal" and "centripetal". I was pointing out that in Newtonian terms there is no such thing as centrifugal force, that the force holding a body in circular orbit around an origin is centripetal (center-seeking, not center-fleeing). I cannot recall my exact words, nor do I wish to search for them, but I had no intention of implying that there is centripetal force involved in skating, if that's what you mean here.

I still would like a clue about your credentials in the audio/engineering business, just because you sound like an interesting and experienced person from whom we can learn.

Just read the antiskate blog. There is no centripetal force in any part of the system. The guy is taking the facts that the record rotates, that an arm is on the record, and falsely extrapolating the conclusion that there is centripetal force. Does not exist in this system.

Could not find the Gilson papers, if someone wants to give a link I'll read them.

Plain wrong statement: "45 presenting the cartridge with the problem of tracking a groove which makes the stylus accelerate at a greater rate"

This greater acceleration does not exist. And more energy is NOT being put into the system or the volume would be louder on a 45!

This poster is confusion lateral and vertical groove velocity with linear groove velocity.

In reality, for the same lateral or vertical velocity (the signal-generating directions) the angles on the groove are more gentle, as the same displacement of the stylus in the vertical and lateral directions happen over a greater (linear) length of the record groove.

Zavato,

Just noticed this.
Your mistracking is most likely caused by the 45 presenting the cartridge with the problem of tracking a groove which makes the stylus accelerate at a greater rate. This puts it at the edge of its tracking envelope, therefore the influence of the skating force (which is always present in a pivoted arm) more apparent, resulting in distortion on one channel.

Normally, with insufficient anti-skate, the VTF is enough to cope with most groove modulation. When there is more energy in the system, that is not the case and shows up the imbalance in downforce on each face of the groove, which anti-skate is designed to compensate.

Omsed,
you said

when you think you know it all start looking for your mistakes!

Have a look a R.J Gilson's paper in Wireless World Oct 1981 for some more reasons why you might wish to increase antiskate disproportionately as the arm approaches the inner grooves. Also, watch you don't fall into the trap of regarding anti-skate as a setting governed by a "I can't hear a difference with anti-skate, so why bother using it" attitude.

As an aside, regarding 45rpm records, if we had been talking about 7" singles rather than 12" LPs, that is another thing altogether. (see my blog
for more on this and on anti-skate generally.)

Omie, What do you research and what do you design? Inquiring minds want to know.

Going to try to be bowing out from the forums now guys. I see that they are addictive to me! Wow, it takes a lot of time to try to be clear, and I have my real job, research and design to do.

Try to remember, when you think you know it all start looking for your mistakes! You'll find them.

@ Ralph: You ask "Also, if the platter is at rest there will be no skating force at all. That was the basis for my response above; are you saying there is zero(0) change regardless of rotational speed?"

Answer: The difference in the rest condition and the dynamic condition are not relative to each other. Skating force is the result of dynamic friction, which requires movement. So the rest condition is irrelevant. One cannot extrapolate changes due to increases in relative velocity based on the change from no velocity to some velocity. The comparison between the no velocity condition and some specific positive velocity condition is a non-sequitur. That would be the case even if dynamic friction magnitude were dependent upon velocity. Fact is dynamic friction is nearly independent upon velocity.

Let's put some physics and math to it for Ralph.

1. Skating force is always in the same direction, never changing from + to -. If we denote the inward radial force (skating force) as positive then it remains positive.

2. The magnitude of the vector changes in relation to the error in tangency of the stylus to the groove. Since the angle relative to tangency of a pivoted arm changes then the magnitude of the skating force changes.

3. Though skating force always remains positive (in my convention of positive meaning toward center) the DEVIATION in skating force goes from positive to negative to positive across the record as it is played from the outer groove.

However, the deviation in his force is pretty small, given that skating force can vary from record to record a bit anyway, and given that the antiskating mechanisms of arms are not perfectly linear.

4. The magnitude of change in skating force for an arm with a 23 degree headshell angle would be +7%, -4%, if the arm uses Baerwald geometry. The percentages are deviations from when the arm is at true tangency (null points).

5. Let's look at the magnitude of those percentage changes. Based on my detailed and repeatable experiments to determine actual skating forces I am confident we are looking at deviations of approximately two HUNDREDTHS of a gram! A small Post-It note weighs TWENTY times that!

Now, this is where experience can be helpful. Try as I might, I cannot reliably detect a sonic difference by changing the antiskate force by those amounts. I cannot detect a tracking ability change by changing antiskate by those amounts.

4. With poor tracking pivoted arms, yes, tracking is worse at the center of the record. But, since the best arm I can find is free of this, I have to conclude that there are many problems at work with those arms, including geometry (one low cost, ubiquitous brand uses their own geometry that nobody can figure out), resonances, and other matters that I'm not about to spend time figuring out.

Based on all of the above, I have concluded that variations in skating force across the record due to geometrical considerations are not a material concern in the sound reproduction of a pivoted tonearm.

Ralph, Re the original question, friction (between the stylus tip and the groove) is the prime source of the skating force, and friction is independent of velocity. It's as simple as that.
The only difference between a 33 and a 45 might be if the two LPs were made of different vinyl compounds that gave different coefficients of friction. There might be an additional very small contribution related to groove tortuosity, as I wrote before Omsed.

Yes, skating force is not constant across the surface of the LP, but not because of the platter speed. Inconstancy has more to do with headshell offset angle and the arc traversed by the stylus as it moves from outer to inner.