Re: [ARSCLIST] Spoke Pattern

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad


JOHN HALL wrote of personal experience:

> The Skully lathe table shaft had a single steel ball at the bottom of the
> table shaft. As it would distort after much use.

----- could we imagine that the end of the shaft would then "knead" the ball
around?

Removing it and inserting a
> nylon or teflon insert, and putting a point on the bottom of the shaft was the
> method used by some owners. Finding a machine shop that had a lathe big enough
> to handle the table (85lb ) was a problem. The advance ball did not stop the
> vertical spokes. Some times it would reduce the debth and sometimes it made it
> worse. This was more of a problem with the variable pitch mod. than with fixed
> pitch.

----- the precise number 54 spokes indicating precisely 30 Hz somehow calls
for an electrical explanation with 60 cycles mains. A simple rectification of
60 Hz gives a unidirectional impulse at 30 Hz, but that would then need to be
transferred to a vertical force. If rubber mounts were sagging, conceivably a
mechanical rectification of something vibrating at 60 Hz could occur, but
where? The magnetostriction that causes the audible hum is a 120 Hz effect.
And if advance ball does not help, there must be an unhealthy resonance
somewhere. Certainly something a service engineer ought to have looked into.

This was spoken (no pun inteded) by someone without personal experience with
Scully lathes.

Kind regards,


George