Why the double third wheel

[caseback]

Hi fellow watch enthousiasts. Could anyone explain what the function/advantage is of the double third wheel I see on the citizen 5470 I'm chasing amplitude on? The only thing I can imagine now, is that it's for stabilizing the seconds pinion perhaps?

 

[oldhippy]

One is for the sweep second.  

[caseback]

Well, both engage the sweep second. Why not a single wheel?

One of the wheels is fixed, the other (when not mounted) can rotate freely.

[nickelsilver]

One is staked to the pinion, one is free. They both engage the sweep pinion, but only the free one engages the 4th pinion.

 

The result is the sweep pinion leaf engaged gets sandwiched; the staked wheel pushes, the free one must turn too, but it is stopped by the 4th pinion. It’s a great system that gives a perfectly stable sweep and doesn't suck amplitude like friction springs.

Edited June 23, 2024 by nickelsilver

[RichardHarris123]

What is this system called? 

[caseback]

20 minutes ago, nickelsilver said:

One is staked to the pinion, one is free. They both engage the sweep pinion, but only the free one engages the 4th pinion.

 

The result is the sweep pinion leaf engaged gets sandwiched; the staked wheel pushes, the free one must turn too, but it is stopped by the 4th pinion. It’s a great system the gives a perfectly stable sweep and doesn't suck amplitude like friction springs.

Thnx! Like I suspected then.