Why does my mechanical clock run faster as the spring becomes looser? In the weekly cycle of winding, the clock keeps perfect time for the first 2 days or so, but as the spring becomes looser, it runs ahead of time or becomes faster by up to 7 minutes. What is the answer to this phenomenon?
Thank you,
Brenda Haggai

The internet is full of info you can Google but I would prefer you consult with a professional for any cleaning and ADJUSTMENTS.

You never said which kind of clock or how old it is.

Odd... its usually the other way around. Got me curious about this now. Wild guess thrown out...perhaps the fully wound spring places a greater friction load that results in a minuscule difference on the escapement mechanism that converts that spring tension into rotational motion? Would or might explain why as it winds down it might actually speed up a small amount.

Not solution you want to hear, but if you can't find a good clock person, wind every 2 days or so. Good Luck

This does seem strange. For a coil spring (which I assume is what is in your clock) the torque that the spring exerts is roughly proportional to the tightness of the coil. Stated another way: the torque is inversely proportional to the radius of curvature of the spring material. As the spring unwinds and gets loser, the radius of curvature increases and the torque decreases. So one would expect that the escapement mechanism would run slower as the spring unwinds. Most clock designs try to avoid this by not letting the coil unwind too far (i.e., try to keep the radius of curvature fairly constant).

I'm wondering if the issue may be that the teeth of the escapement wheel are worn to the point where at slower speeds it can turn freely, without properly engaging the lever?