The point about it not being gearing was that the increment from 30 to 40 is the same as the increment from 50 to 60. The error would be proportional to speed if it were just a gearing problem. You may have to tweak the return spring and needle position to get it in line. As far as the effect of the earth's rotation goes, consider that the surface of the earth is moving at a little over 1,000 mph just from rotation. Then factor in the movement of the entire solar system through deep space. I will stick with speed relative to surface, thank you.
