It is quite rare to find clocks of this type,Nevertheless, they are very interesting and we can not pass by, although they can not call the language their own language (it's possible to do it manually, in general, but it's very difficult). The principle of work is the following: the spiral is given inslight movement mechanism, the dial remains stationary. When the spiral is scrolled, the position of the ball changes - it moves upwards. The ball shows the time, which is indicated by the numbers on the dial (you can apply a minute scale). When the highest mark is reached, it falls through the hole and returns to the bottom of the spiral along the gutter. This happens twice a day. The complexity of manufacturing a spiral watch is not only the creation of a spiral of the desired shape and size, but in the search for the only correct combination of the parameters of the spiral and the speed of the mechanism. Calculate all this so that the clock is accurate is incredibly difficult.