[Wayner]

Thanks Turkey (that sounds bad!), but it's your AC name.

ListentoTubes,

As you know, the natural tendency for a tonearm during play is to drive towards the spindle. That is because the stylus has an offset angle in relation to the tonearm. It acts like a rudder. To compensate for this action, we need an equal but opposite reaction, hence the anti-skate counter weight. It is applied to the tonearm body with a certain measured amount of weight to put a counter-force on the tonearm to "neutralize" this effect. If you look at the Empire picture, you will notice a very tiny nylon thread (it's not fishing line, it's smaller). The thread is connected to the front non-functioning anti-skate control of the Empire, wraps around the pivot body, goes thru the fishing lure "down-rigger" and is tied to the measured amount of lead weight. There is also an 'E' guitar string that goes up thru the same hole in the weight to keep the weight from swinging.

The setup for the Empire is so well balanced, that I can put the tonearm anywhere on a blank disc (a must have), that the arm will simply sit in that position (with the platter spinning). I guessed right the first time I made the set-up, needing only a slight amount of filing to get the tonearm behavior totally under control. Now if I put a different weight cartridge in I will have to do the process all over again.

This will also be the same process for the Rega R200 arm. I'm betting it will be different as the weight of the arm, style will all have an influence.

Hope that makes sense for you.

Wayner

[Mountain-ear]

Wayner -

Maybe I've been wrong all these years, but my understanding was that centrifugal force sent the tonearm to the outside edge of the groove.  The anti-skate counterweight was, therefore, suspended over the inner side of the tonearm to offset that tendency.

Nice looking table nonetheless.  Have fun!

Steve

[Listens2tubes]

Thanks Wayner

[Wayner]

Steve,

If it didn't have a stylus, it would surely fling righ off the platter as you describe.

Wayner

[turkey]

Thanks Turkey (that sounds bad!), but it's your AC name.

I figure that sooner or later someone will call me names, and this way I give them something to start with.

Actually, I had just exchanged some e-mail with someone who's living in Turkey now, and had also read his blog about what the religious zealots are doing over there lately, and thought "What a bunch of turkeys there are in Turkey!"

Plus it was getting close to Thanksgiving, so when I signed up at AC and needed to pick a name - turkey it was.

[turkey]

From wikipedia:

"As the tonearm tracks the groove, the stylus exerts a frictional force tangent to the arc of the groove and since this force does not intersect the tone arm pivot, a clockwise rotational force (moment) occurs and a reaction skating force is exerted on the stylus by the record groove wall away from center of the disc. Modern arms provide an anti-skating mechanism, using springs, hanging weights, or magnets to produce an offsetting counter-clockwise force at the pivot, making the net horizontal force on the groove walls near zero."

[rcag_ils]

The centripetal force of a rotating record tends to pull the tone arm toward the center of the platter. Adding an "anti-skate" force equal to the tracking force will keep the arm from "skating" toward the center, will need a blank disk to calibrate it accurately.

However, if you have good hearing, you can hear the difference if the anti skate force is not correct.

[turkey]

The centripetal force of a rotating record tends to pull the tone arm toward the center of the platter. Adding an "anti-skate" force equal to the tracking force will keep the arm from "skating" toward the center, will need a blank disk to calibrate it accurately.

Centripetal force would only come into play if the stylus were rotating about the center of the record.

The classic example is to take a weight, tie a string to it, and whirl it around. The weight experiences "centripetal force."

In the case of a phonograph record, the record itself experiences centripetal force, but the stylus and tonearm do not.

[tgp06]

Actually, the weight is experiencing centrifugal force (outward). The string is applying centripetal force (inward), keeping the weight rotating about the center. Not really sure what happens in the case of a tonearm and a rotating record!?

[turkey]

Actually, the weight is experiencing centrifugal force (outward). The string is applying centripetal force (inward), keeping the weight rotating about the center.

Yes, this is exactly right. I wrote it poorly.

The string applies centripetal force to the weight, which balances out the centrifugal force.

[Wayner]

All I know is the tone arm will run, not walk to the spindle with anti-skate turned off. With the exception of the AR-XA tonearm that was very well damped from side to side movement and did not require anti-skating.

What is Wikipedia talking about?

Wayner

[rcag_ils]

The classic example is to take a weight, tie a string to it, and whirl it around. The weight experiences "centripetal force.

In the case of phono record, the record is the string, the arm is the weight, the arm experiences the "centripetal force",  Hence anti skate weight generates centrifugal (outward) force to balance it to 0.

[geezer]

Wayner -

Maybe I've been wrong all these years, but my understanding was that centrifugal force sent the tonearm to the outside edge of the groove.  The anti-skate counterweight was, therefore, suspended over the inner side of the tonearm to offset that tendency.

Nice looking table nonetheless.  Have fun!

Steve

My understanding is that "centrifugal force" applies to something that is (or is "trying" to) move on a curved path. The force tends to push it in the direction perpendicular to the path and away from the center of curvature. For example, if you put a dime on a turntable and start it up, the dime would slide off the turntable (away from the center). But the stylus is not moving with the turntable, and there is no centrifugal force pushing it away from the center (which is the meaning of "centrifugal").

[rcag_ils]

When a record is spinning and you place a dime on it, the dime will be thrown off the record by the centrifugal force with the dime's velocity that's perpendicular to the record's arc.

When a record is turning, and the stylus tip (not a dime) is held in a spiral groove at one end and the tonearm is fixed on it's pivot, a force will be exercised on the arm and cartridge. This force is centripetal force which will move the cartridge towards the spindle.

The arm can only move in a radial way as it is held in position by the pivot. The result is that there will be an increased pressure on the left channel groove wall. In order to neutralize this force, and to give both channel groove walls equal pressure, a bias weight is need.

[geezer]

When a record is spinning and you place a dime on it, the dime will be thrown off the record by the centrifugal force with the dime's velocity that's perpendicular to the record's arc.

When a record is turning, and the stylus tip (not a dime) is held in a spiral groove at one end and the tonearm is fixed on it's pivot, a force will be exercised on the arm and cartridge. This force is centripetal force which will move the cartridge towards the spindle.

The arm can only move in a radial way as it is held in position by the pivot. The result is that there will be an increased pressure on the left channel groove wall. In order to neutralize this force, and to give both channel groove walls equal pressure, a bias weight is need.

Actually the dime will leave the turntable with whatever velocity it has at the moment it begins to slip, which will be tangential  to the arc not perpendicular.

[turkey]

But the stylus is not moving with the turntable, and there is no centrifugal force pushing it away from the center (which is the meaning of "centrifugal").

Agreed.

The quote from Wikipedia explains nicely how skating happens, and how to compensate for it.

[BobM]

Whatever the physics explaination is, the fact is that an arm will tend to skip toward the center of the record. Anti-skate pulls the arm outward to reduce this tendency. A good arm will have some means of varying this outward pull, increasing it slightly as the arm moves more toward the center of the record, where the force increases.

Reducing the force on the stylus as it tends to press on the inward facing wall will, and seat the stylus more in the center of the groove, will definitely improve certain aspects of the sound. Some hear this more than others and there is much debate on the need for this. Some arms must need it more than others, and to varying degrees.

But as with any fine instrument, and a tonearm surely qualifies, the ability to adjust this by the end user to improve their listening pleasure only makes sense.

Bob

[rcag_ils]

tangential  to the arc not perpendicular.

the line of the velocity intersects with the point on the record arc at 90 degrees.

[geezer]

tangential  to the arc not perpendicular.

the line of the velocity intersects with the point on the record arc at 90 degrees.

Nope. Check any freshman physics book.

[rcag_ils]

Nope. Check any freshman physics book

The velocity is 90 degrees to the point to tangency of the record arc, therefore perpendicular to the point.