Can someone comment on this interesting 1970's Bulova movement

[patchwerk]

This is a 100011 Bulova movement from 1978 for a ladies watch. I noticed it has two reverse thread screws including the ratchet wheel! The click mechanism is also spring-less. I think the ratchet wheel touches the top surface of the click and drives it down when the wheel wants to unwind.

When you wind the watch though the ratchet wheel obviously rotates opposite the thread of the ratchet wheel screw potentially loosening it. During me working on it has actually loosened. I guess the option is to really tighten it. 

Does anyone know why they made it like that?

Edited December 31, 2019 by patchwerk
picture upload

[clockboy]

I serviced one of these a few years ago. Nice quality build the only issue I had was over banking and had to fit a slightly weaker mainspring 

[patchwerk]

7 minutes ago, clockboy said:

I serviced one of these a few years ago. Nice quality build the only issue I had was over banking and had to fit a slightly weaker mainspring 

What did you do with the ratchet wheel screw? Just super tighten it so that winding action couldnt loosen it?

[oldhippy]

If you tighten the screw properly it should not un-screw. If it does then look and see if the thread on the screw has worn or the inside of the arbor. 

[patchwerk]

Will do thanks. Anyone know why they chose a reverse thread on the arbor?

[Marc]

The click spring is under the ratchet wheel. 

Clockwise rotation of the crown results in CCW rotation of the crown wheel relative to the screw, so a LH thread ensures that the torque tends to tighten the screw.

CCW rotation of the crown wheel causes CW rotation of the ratchet wheel. However the ratchet wheel is attached to the arbor which has an opposing (CCW) torque from the main spring. The LH thread on the arbor ensures that the CCW torque on the arbor tends to tighten the arbor screw.

[anilv]

Here's the click