The gear train is now complete. The way it is set up, the mainwheel turns once per day. This means that the ratio between the mainwheel and the center arbor (which holds the minute hand) is 1 to 24, since there are 24 hours in one day.
The 120-tooth mainwheel turns a pinion of twenty on the second arbor, for a ratio of 6. The 80-tooth second wheel turns a pinion of 20 on the center arbor for a ratio of 4. Four times six is twenty-four.
There will be a winding drum of 1/2" diameter on the mainwheel arbor which will hold 8 turns, or about 12.5" of cable. This is the maximum that a weight can drop inside the glass dome of the case. The dome is 16" high, but one must allow some for the height of the weight itself, plus the clearance of the main arbor under the top of the dome.
There is a ratio of 1 to 15 between the center arbor and the escape arbor. The 60-tooth center wheel drives a 20-tooth pinion on the contrate wheel arbor, for a ratio of one to three. The 60-tooth contrate wheel drives a pinion of 12 for a ratio of one to five. Three times five is fifteen.
The escape wheel has 16 teeth, and it drives a balance wheel turning at 4 RPM which means that the escape wheel turns once every four minutes. The center arbor (holding the minute hand) turns once every 60 minutes, which is a ratio of 4 to 60 or 1 to 15, as shown in the calulations above. Tedious math, but there's no way around it.
I usually make the pinions when I make the arbors themselves.
Since the train is made, I can now use the actual dimensions of the gears themselves to finish drafting the plates and the rest of the layout of the clock. The actual sizes of the gears themselves and the gear ratios are shown in the gear map
Next, I'll build the plates, pillars and columns. When those are finished, I'll build the escapment, followed by planting the gear train between the plates. Lots of interesting and challenging work.
Todays' link: