After the clock ran for about 24 hours it lost about 3 minutes. I noticed in my reading about them that you can adjust the speed by changing the height of the pendulum. There is a nut under the weight to raise and lower it. I had moved it before when experimenting with it. I then raised it as high as it would go and in a few hours it had gained 4 min. It seems to be a fairly sensitive adjustment but it adjusts too fast and too slow so I know the proper spot is somewhere in the middle. I better be careful this might be the start of another hobby.