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Re: Which proves that the stylus does not melt the vinyl

Posted by John Elison (A) on April 16, 2007 at 09:26:16

In Reply to: Re: Which proves that the stylus does not melt the vinyl posted by M.Stojek on April 16, 2007 at 06:23:09:

> Skating force is proportional to friction and also proportional to distance
> between the friction point (stylus) and center of the rotating disk.

Skating force is proportional to friction, but it is not proportional to the distance between the stylus and the center of the disk. On the other hand, skating force changes slightly as the tonearm traverses the record as a result of the changing angle between the groove tangent at the stylus and a line from the tonearm pivot to the stylus. Therefore, the following equation will describe skating force for an unmodulated groove.

Skating Force = sin(θ)•VTF•µ

Where:

θ = The angle between the groove tangent at the stylus and a line from the tonearm pivot to the stylus

VTF = Vertical Tracking Force

µ = Coefficient of Friction

For a tonearm aligned to Baerwald's 66-121-mm null-point geometry, both θ and skating force will be maximum at the outermost groove. As the tonearm moves inward, θ decreases and so does skating force. The minimum skating force occurs in-between the null-point after which both θ and skating force begin increasing again all the way to innermost groove.

To put this into perspective for a 9-inch tonearm, skating force decreases by nearly 11% to its minimum value in-between the null-points. Then it begins increasing again to the innermost groove where it is still 4% lower than its original value at the outermost groove.

Best regards,
John Elison

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