First impression of the Dual Pivot Kit

Re: First impression of the Dual Pivot Kit

Postby Votan » Wed Dec 05, 2018 5:13 am

Brf wrote:A cartridge that is offset from the main pivot will exhibit azimuth changes in the vertical plane (i.e. warped records) if there is not a corresponding offset in the tone arm’s bearing assembly – this fact is not in dispute and is based on the principles of geometry.

The image that you posted is that of an Origin Live tone arm in which the designer made a conscious and deliberate decision not to offset the bearings as a design compromise to favor frictional bearing tolerance over slight azimuth errors in the vertical plane.

If you google fixed bearing tone arms, it will yield many example of tone arms with offset main bearings i.e. SME, Rega, Jelco, Reed, Kuzma, SAT, etc.

In addition, I am not sure how torque is transferred to the cantilever with the addition of a second pivot, as free rotation is now restricted (constrained) along the longitudinal axis (azimuth) but retains free rotation in both the perpendicular and lateral axis.

In any event, I would urge you to try a dual pivot yourself.

Golear wrote:Hi Votan

If you look at an SME tonearm, you'll see the vertical bearing mounted at an angle to the arm tube. Is this better/worse than what is done on the Conqueror arm? Given the degree of motion (very little) and the speed of motion (very slow), I can't imagine this making the slightest difference.

When it comes to the Dual Pivot, here's an idea on set-up:

1. Install the SoundSmith CounterIntuitive and Dual Pivot.
2. Set VTA then set VTF. Repeat as necessary.
3. Rotate the CounterIntuitive slightly in a clockwise direction, until the stylus wants to point away from the spindle.
4. Set the azimuth, using the Dual Pivot.
5. Align cartridge.

You're all set. You can vary the force on the Dual Pivot by rotating the CounterIntuitive. The VTF will not be affected if all you only rotate the CounterIntuitive. (The force on the Dual Pivot may act as an anti-skate.)
[/quote]

The question is if really the so called “Dual Pivot” is in fact a second pivot point, which together with the main central pivot could form a (more stable) axis for the movements of tonearm-cartridge in wrapped LPs (regardless of whether this axis is in a vertical plane to the arm’s axis or to the offset one’s), or it’s just a stabilizer that may create the mentioned torque to the cantilever.
Because the more pivot it (the Dual Pivot) wants to be, the more pressure in the sliding pant it demands, hence more troubles creates (in the already existing) to anti-skating.
But also and mainly, because as Mat Weisfeld stated in the “New Cuing Device and Dual Pivot Point” topic in Oct 11, 2017 8:02 am:
“After getting a great suggestion from a different form, I'm considering changing the name of the "Dual Pivot" to a "Stabilizer adapter”. Realistically that is exactly what it does, so it might be a more proper name/representative of what it is.”
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Re: First impression of the Dual Pivot Kit

Postby Brf » Wed Dec 05, 2018 8:54 am

Votan wrote:
The question is if really the so called “Dual Pivot” is in fact a second pivot point, which together with the main central pivot could form a (more stable) axis for the movements of tonearm-cartridge in wrapped LPs (regardless of whether this axis is in a vertical plane to the arm’s axis or to the offset one’s), or it’s just a stabilizer that may create the mentioned torque to the cantilever.
Because the more pivot it (the Dual Pivot) wants to be, the more pressure in the sliding pant it demands, hence more troubles creates (in the already existing) to anti-skating.
But also and mainly, because as Mat Weisfeld stated in the “New Cuing Device and Dual Pivot Point” topic in Oct 11, 2017 8:02 am:
“After getting a great suggestion from a different form, I'm considering changing the name of the "Dual Pivot" to a "Stabilizer adapter”. Realistically that is exactly what it does, so it might be a more proper name/representative of what it is.”


I will repeat what I wrote in a previous post.

The VPI tonearm with the dual pivot point installed is what is known as an constrained uni-pivot bearing, whereby, the free rotation around the pivot axis is now restricted (constrained) when compared to a non-constrained uni-pivot which moves freely in both the vertical and horizontal plan.

From a marketing perspective, the term “stabilizer” maybe more consumer friendly and helps to accurately describes the function, but it is a dual pivot in the sense that the main pivot and the stabilizer pivot are attached on the horizontal axis which now governs the arm’s vertical movement (it rides on a dual pivot very similar to a gimbal in the vertical plane).

As previously mentioned, a true uni-pivot has free rotation around the pivot axis. With the addition of a second pivot, the free rotation is now restricted (constrained) along the longitudinal axis (azimuth) but retains free rotation in both the perpendicular and lateral axis.

The term stabilizer is not a misleading or inaccurate statement, but when used with a true VPI uni-pivot tonearm, the arm technically becomes a constrained uni-pivot arm.
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Re: First impression of the Dual Pivot Kit

Postby Votan » Wed Dec 05, 2018 2:49 pm

Brf wrote:
I will repeat what I wrote in a previous post.
………………………………………………………………………………………
The term stabilizer is not a misleading or inaccurate statement, but when used with a true VPI uni-pivot tonearm, the arm technically becomes a constrained uni-pivot arm.


Hi Brf,
No need to argue. It’s the damn that hobby where every hi end guy has its own worldview and defends it to the end! I fully respect your point of view (2rd Pivot), although I will insist on my own (Stabilizer).
Indeed, in order to try to converge and to end all this, I would be grateful if you could clarify the following:

Brf wrote:The VPI tonearm with the dual pivot point installed is what is known as an constrained uni-pivot bearing, whereby, the free rotation around the pivot axis is now restricted (constrained) when compared to a non-constrained uni-pivot which moves freely in both the vertical and horizontal plan.

When the VPI arm works as a non-constrained true a uni-pivot (before someone puts the pivot No 2 in the arm), is there any specific horizontal axis that governs the arm’s vertical movement, who is it and why?

Brf wrote:From a marketing perspective, the term “stabilizer” maybe more consumer friendly and helps to accurately describes the function, but it is a dual pivot in the sense that the main pivot and the stabilizer pivot are attached on the horizontal axis which now governs the arm’s vertical movement (it rides on a dual pivot very similar to a gimbal in the vertical plane).

After someone have installed the Pivot No 2 in the VPI arm making it a constrained uni-pivot, who exactly is the horizontal axis you mention, that now governs the arm’s vertical movement, from which exact points (pivots) is defined as horizontal and why?
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Re: First impression of the Dual Pivot Kit

Postby Brf » Wed Dec 05, 2018 3:35 pm

Votan wrote:
Brf wrote:
The VPI tonearm with the dual pivot point installed is what is known as an constrained uni-pivot bearing, whereby, the free rotation around the pivot axis is now restricted (constrained) when compared to a non-constrained uni-pivot which moves freely in both the vertical and horizontal plan.


When the VPI arm works as a non-constrained true a uni-pivot (before someone puts the pivot No 2 in the arm), is there any specific horizontal axis that governs the arm’s vertical movement, who is it and why?


No, the arm is free to move in all axis but uses mass so that when a cartridge is excited by a modulated groove and attempts to move the arm the inertia of the arm holds it steady.

Votan wrote:
Brf wrote:From a marketing perspective, the term “stabilizer” maybe more consumer friendly and helps to accurately describes the function, but it is a dual pivot in the sense that the main pivot and the stabilizer pivot are attached on the horizontal axis which now governs the arm’s vertical movement (it rides on a dual pivot very similar to a gimbal in the vertical plane).

After someone have installed the Pivot No 2 in the VPI arm making it a constrained uni-pivot, who exactly is the horizontal axis you mention, that now governs the arm’s vertical movement, from which exact points (pivots) is defined as horizontal and why?


Think of a gimbal arm whereby the horizontal bearing controls the vertical axis and the vertical bearing controls the horizontal. When you install a dual pivot, you have effectively created a horizontal bearing with dual points, just like a gimbal, which controls the vertical axis. The arm is still free to rotate unrestricted in the horizontal plane, but its movement along the longitudinal plane (azimuth) is now restricted by the dual pivot.
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Re: First impression of the Dual Pivot Kit

Postby Votan » Wed Dec 05, 2018 5:58 pm

Brf wrote:
Votan wrote:After someone have installed the Pivot No 2 in the VPI arm making it a constrained uni-pivot, who exactly is the horizontal axis you mention, that now governs the arm’s vertical movement, from which exact points (pivots) is defined as horizontal and why?


Think of a gimbal arm whereby the horizontal bearing controls the vertical axis and the vertical bearing controls the horizontal. When you install a dual pivot, you have effectively created a horizontal bearing with dual points, just like a gimbal, which controls the vertical axis. The arm is still free to rotate unrestricted in the horizontal plane, but its movement along the longitudinal plane (azimuth) is now restricted by the dual pivot.

In the VPI uni-pivot tonearm equipped with the stabilizer (so called “Dual Point” or Pivot No 2) in contact to its sliding plate, sorry, but I can’t understand which way is created the horizontal bearing you mention (that controls the arm’s- cartridge’s vertical movements) from those two specific pivot points, given that the Pivot No 1 (the factory central pivot) is too much higher than the Pivot No 2 (the contact point to its plate), forming an acclivitous axis that has nothing to do to horizontal!
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Re: First impression of the Dual Pivot Kit

Postby Brf » Wed Dec 05, 2018 7:47 pm

Votan wrote:
Brf wrote:
Votan wrote:After someone have installed the Pivot No 2 in the VPI arm making it a constrained uni-pivot, who exactly is the horizontal axis you mention, that now governs the arm’s vertical movement, from which exact points (pivots) is defined as horizontal and why?


Think of a gimbal arm whereby the horizontal bearing controls the vertical axis and the vertical bearing controls the horizontal. When you install a dual pivot, you have effectively created a horizontal bearing with dual points, just like a gimbal, which controls the vertical axis. The arm is still free to rotate unrestricted in the horizontal plane, but its movement along the longitudinal plane (azimuth) is now restricted by the dual pivot.

In the VPI uni-pivot tonearm equipped with the stabilizer (so called “Dual Point” or Pivot No 2) in contact to its sliding plate, sorry, but I can’t understand which way is created the horizontal bearing you mention (that controls the arm’s- cartridge’s vertical movements) from those two specific pivot points, given that the Pivot No 1 (the factory central pivot) is too much higher than the Pivot No 2 (the contact point to its plate), forming an acclivitous axis that has nothing to do to horizontal!


I should have been more precise. I use the term "horizontal" to reference the two independent bearing points on a constrained unipivot that control the vertical tonearm axis. The two horizontal pivot points do not need to be 180 degree diametrically opposed and perpendicular to the vertical pivot (central) to control the arm's vertical axis due to the fact that they are vertically supported.

A gimbal arm relies on diametrically opposed bearings due to the fact that they are supported horizontally, therefore, creating a need for a continuous plane.

Although the implementation of a horizontal bearing between a constrained unipivot and gimbal are different, their end function is the same (in the vertical plane)

Again, I urge all users who are unsure of the dual pivot to try one out. I have never seen a used dual pivot for sale, therefore, if you are not happy, it would be an easy resale.
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Re: First impression of the Dual Pivot Kit

Postby Johnny » Thu Dec 06, 2018 8:55 am

Brf, always a gentleman and gracious with his time as always. Thanks for the insight on the dual pivot

Votan, welcome to the VPI forum. Btw, no need for bold, underlining, and exclamation points in your post.
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