SOLVED: Edison Opera Half-Nut Adjustment

[Raphael]

This Edison Opera, SN. 339, has a problem I've never encountered before. It works just fine until it gets about 85% of the way through a cylinder, and then stops traveling. A little pressure on the half-nut, or on the engagement lever, will allow it to finish the cylinder.

With the machine off, and the engagement lever down, it will still allow the half-nut to move over the feed screw in this range; once it gets further along it "locks on" the way it should.

My first instinct was to increase the pressure on the half-nut they way one would do on, say, a Triumph. But the whole arrangement is different, and I'm unsure how to attack this problem. Rather than adjust first and ask questions later, I thought perhaps the experts here can offer some advice.

thanks,

Raphael

[MisterOpera]

I read your question with interest. Could it be that the feed screw has "dirt" in it at that point? I would check this first. Maybe the ½ nut is worn. also.

Burdette

[Raphael]

Thanks, but I've cleaned and examined the feed screw, and it looks just fine to me. If the half-nut is bad, why would this only occur at one end of the feed screw? And it’s not just one spot on the feed screw, it’s the last 15-20%.

Also, the normal adjustment screw for half-nut tension is fully backed off and there is no way to easily increase half-nut pressure.

Raphael

[drh]

I'm shooting in the dark here, certainly not speaking from actual knowledge, but a thought occurs: could the problem be that the feed screw isn't quite perfectly parallel with the rest of the mechanism, say because of a misadjusted or worn bearing somewhere? If it slopes slightly down from start to finish, the half nut eventually might stop making sufficient contact. One other thought is that a opera's mandrel moves while the reproducer is stationary; could something in the mandrel end of things be binding?

I wish I could be more definitive than speculative, but I hope these ideas may be useful.

[Raphael]

Problem apparently solved. The set screw #2 apparently is used to relieve pressure of the half-nut on the feed screw. I noticed that there was no contact between this set screw and the casting; thus it was at it's maximum position and could not be backed off any further, thus no further pressure could be exerted on the half-nut.  Just below this set screw is yet another set screw, #1, that controls the positioning of the entire piece on a shaft running through it. I backed off on it, and tapped the assembly so that it would reposition itself on the shaft.  Seems to have worked, have played a cylinder all the way through several times and it's not skipping. 

With special thanks to Shawn O'Rourke, Wyatt Marcus and Burdette, who contacted me privately with helpful suggestions, and to the TMF for providing a venue to seek constructive information.

Happy New Year everyone,

Raphael