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Turntables & Tonearms Where Analog still Rules

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  #11  
Old 01-08-2020, 09:02 PM
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For a pivoted arm, the effective tone arm length, tracking force, and radius of the record groove itself are the primary variables for skating force.

For example tangential tracking arm has an infinite effective tone arm length and so zero skating force.

The actual and/or effective mass of the tonearm/head shell/cartridge is not part of the equation for skating force.

Assuming that youíve set up the table with a pivoted arm to have two nulls where the cartridge cantilever is parallel to the record groove, you can use a test record to dial in anti-skate in the middle of the record. I use a test record and then listen to fine tune it, knowing that it is an imprecise adjustment that changes with recorded level and also across the surface of the record.

Iíd add that less is more, so dial it in slowly and listen.

Tom
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  #12  
Old 01-08-2020, 09:21 PM
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Tom, I agree wholeheartedly on the approach.

But i canít keep thinking that if the arm is heavy than it takes a heavy weight to move it?

Also. I have been image searching as much as possible, Iíve seen much larger weights on the arm than the weight on my arm. I am beginning to think I simply have an undersized antiskate weight.
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  #13  
Old 01-08-2020, 10:11 PM
mulveling mulveling is online now
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You’re not accelerating the mass of the tonearm in relation to skating forces, so that’s why it doesn’t factor in here. The VTF increases the frictional drag force (proportionally) so it does factor in. Imagine a vertor pointing straight forward from the center front edge of headshell. Then another from the stylus back to the pivot point. The vector difference of these 2 is a vector that points roughly towards spindle and represents the skating force. As tonearm length increases so does the offset angle decrease, and thus the difference vector becomes 0.
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Old 01-08-2020, 10:44 PM
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Quote:
Originally Posted by mulveling View Post
Youíre not accelerating the mass of the tonearm in relation to skating forces, so thatís why it doesnít factor in here. The VTF increases the frictional drag force (proportionally) so it does factor in. Imagine a vertor pointing straight forward from the center front edge of headshell. Then another from the stylus back to the pivot point. The vector difference of these 2 is a vector that points roughly towards spindle and represents the skating force. As tonearm length increases so does the offset angle decrease, and thus the difference vector becomes 0.


Excellent explanation. Thanks!
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  #15  
Old 01-09-2020, 12:42 PM
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Quote:
Originally Posted by mulveling View Post
Youíre not accelerating the mass of the tonearm in relation to skating forces, so thatís why it doesnít factor in here. The VTF increases the frictional drag force (proportionally) so it does factor in. Imagine a vertor pointing straight forward from the center front edge of headshell. Then another from the stylus back to the pivot point. The vector difference of these 2 is a vector that points roughly towards spindle and represents the skating force. As tonearm length increases so does the offset angle decrease, and thus the difference vector becomes 0.
Thanks again for still humouring me on this.

I get the skating force happening at the stylus and the interaction between friction and VTF: 100%. This describes the skating force.

But, as noted "Skating force compensation is provided at the arm pivot. This means that a torque is applied at the pivot..." So, the Anti-Skating Force is applied at the pivot: the pivot supports the mass of the tonearm and counterweight. Even thought the Anti-Skating Force is in theory a purely horizontal vector, does the mass of the system not even play into it?

I keep thinking that a pushing a perfectly balanced chopstick takes less effort than pushing a perfectly balanced tree trunk...?! What part am I missing?
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  #16  
Old 01-09-2020, 12:57 PM
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If you have a friend push on one side of one end of a rod with 1 pound of force, it takes you the same 1 pound of force on the other side to oppose it. It doesn't matter whether the rod is a chopstick or tree trunk.
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  #17  
Old 01-09-2020, 01:06 PM
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Quote:
Originally Posted by mulveling View Post
If you have a friend push on one side of one end of a rod with 1 pound of force, it takes you the same 1 pound of force on the other side to oppose it. It doesn't matter whether the rod is a chopstick or tree trunk.
ok, so once everything is up to speed, it is more-or-less a consistent force that simply needs to be balanced. The counter weight for a lightweight 9" Grace arm would work just as well on a 12" Schick arm.
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  #18  
Old 01-09-2020, 03:03 PM
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Quote:
Originally Posted by Arr_w View Post
ok, so once everything is up to speed, it is more-or-less a consistent force that simply needs to be balanced. The counter weight for a lightweight 9" Grace arm would work just as well on a 12" Schick arm.
Sort of - but depending on how and where the anti-skate weight attaches, one arm may give the same weight more or less leverage versus another arm - and/or may allow for a greater range of adjustment, etc. My Fidelity Research arms fit the weight onto a mini pivoted arm that both allows for a wide range of adjustment (further from the pivot the weight is, the greater the anti-skate force), and continuously decreases the effective lever length (the arm rotates upwards towards 90 degrees, at which point the anti-skate force is 0) as the arm travels towards the inner grooves - which is cool, but since choosing an anti-skate setting is always a compromise anyways, I can't say whether that's better that simply choosing a constant "best average" anti-skate force over the whole record surface (not possible on these FR arms).

Last edited by mulveling; 01-09-2020 at 03:16 PM.
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  #19  
Old 01-09-2020, 04:39 PM
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Right. Exactly. Got it.

I’ll be working on the table this weekend. I I’ll let you know how it goes.

Thanks again for the discussion.
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  #20  
Old 01-20-2020, 03:55 PM
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Finally got to spend some real time on this project. I ran the arm/cart/anti-skate combo up and down the spectrum. My results confirm the discussion and math above. I settled on the nearly the lowest range of tracking force and virtually no anti-skate with the 12" tonearm. The image is very fussy, but moved much more to the centre much more consistently. The music program, energy and LP quality played into the results more significantly than I was expecting.

Thanks again for the help.
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