Hi guys,

Please excuse my ignorance, but can somebody point out this "Guillaume Balance" for me, on any of the above pictures?
I have been trying to locate it but seems I can't find any differences between the pictures of movements with and without it!

Thank you very much both for your efforts to bring knowledge to this forum!!!

Ioannis

Please note in the pictures below the RED circle.  Note also that in the first 2 pictures the length of the rim between the wheel arm and the "split" is much longer than as shown in the third picture.  These 2 are Guillaume alloy, while the third is traditional.

Within is seen the wheel arm and the section of the rim which is "split".  Because the wheel rim is made of 2 different metals (brass and a white alloy, easily seen in the first 2 pictures) which expand and contract differently with temperature, this "split" allows the wheel rim to deform from a perfect circle as the temperature changes.  Interaction with the air thereby causes the motion to slow or increase.

With a normal split bimetallic wheel, improvements are made over a solid balance at the coolest and warmest temperatures.  The Guillaume wheel seeks to maintain this, and also improve the "middle" temperature accuracy.