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 Post subject: Edison feedscrews
PostPosted: Fri Jul 20, 2018 9:22 am 
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Victor I
Joined: Wed Jul 30, 2014 9:34 am
Posts: 168
Location: Spain
Hi all

Testing my 2 clip Edison Standard with the Standard Speaker reproducer I've found that with some cylinders it skips a groove every more or less one inch.

As this recorder/reproducer has zero sideways play, the only explanation I can find is that some cylinders have their grooves not cut with the exact same space than the feedscrew.

This led me to go to my spare parts boxes and measure 2 spares feedscrews I have. To my surprise, one has 50 threads per inch and the other 49.

Measuring the one on the phonograph revealed that is has 50 threads also.

So my question is: Its only a case of manufacturing tolerances or the standard for 2 minute cylinders changed from 50 to 49 at some moment?

Thank you in advance,

Pedro Martínez


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 Post subject: Re: Edison feedscrews
PostPosted: Sat Jul 21, 2018 1:36 am 
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Victor V
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Joined: Tue Dec 14, 2010 1:17 am
Posts: 2917
Location: Where there's "hamburger ALL OVER the highway"...
As far as I know, all standard 2 minute cylinders were 100 tpi: I do not know of any change in gearing that would reduce at the feed screw on an Edison Standard from 50 to 49.

The Standard Speaker, because of its lack of horizontal movement, became obsolete, due to the necessity of readjusting it when it periodically got out of track. Such is the nature of the beast.

What cylinders are you playing on it? Moulded cylinders may perhaps vary slightly; but the usual culprits are celluloid cylinders, such as Indestructibles, since they tend to shrink with age.

Bill


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 Post subject: Re: Edison feedscrews
PostPosted: Mon Jul 23, 2018 3:36 am 
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Victor I
Joined: Wed Jul 30, 2014 9:34 am
Posts: 168
Location: Spain
Thank you Bill for the information.

The 50 TPI feedscrew turning ½ the speed of the mandrel gives the correct tracking speed for the 100 TPI 2 minutes sylinders.

I've tested on all kinds of cylinders with varying grades of success. I think it is what you say, if they have shrink or deformed after a century this causes the problem.

Still puzzles me the 49 TPI feedscrew I also have.

Regards,

Pedro Martínez


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