I was curious. That’s when things started to get interesting. I have been working on my “wall of clocks”, and noticed that there was always one or another that could be improved in some way. As I tinkered with the clocks they ran better and better so there was less and less to do until finally there was nothing to do but watch them - that is when curiosity set in.
I wondered how few gears you could use and still come up with a workable clock. I suppose you could simply drive an escape wheel but I couldn’t imagine how you would get any run time out of it.
So I turned to the Cycloidal Gear Calculator on the web and fed the following information.
Module = 1.30122 Wheel Teeth 480 Pinion Leaves 8. With this arrangement the escape will turn once per minute on a “seconds” pendulum. That means that the Big Wheel turns once an hour and with 24 wraps on the winding drum - a 24 hour run time.
The layout of the big wheel is on 1/4” plywood that has a diameter of 24 inches.
Oh! for an indexing wheel!
The teeth on the Big Wheel are very fine and although drawn as cycloidal they were effectively cut radially
The wheel cannot be easily swung on the scroll saw - so I drilled the gullets of the gears and then didn’t have to swing.
Normally I cut the spokes after all the teeth are cut but in this case the wheel was heavy and I decided to cut spokes earlier.
With the spokes all cut the wheel was much easier to handle and manipulate to cut the teeth.
The Big Wheel in a bench mount for many of the next phases such as depthing, polishing the teeth and finishing the tips
I started depthing the pinion and wheel at an early stage since I didn’t want to cut 480 teeth and find there was a fatal error.
I used a “one off” depthing tool to get the centers correct, because my normal depthing tool was too small
The escape wheel is a club footed one mostly because I like the look of it.
There are more cuts in a club footed escape wheel but it is quite easy to get an accurate tooth.
The finished escape wheel. The wheel will rotate counter clockwise so there will be no second hand on this clock.
I built up the hub of the gear with a large collet to help keep the gear running true.
The winding drum is a simple ratchet affair with a 1” drum for the cordage. I need 24 wraps per day or 75 inches.
This is the starting point for the “run in”. There is a lot left to go but the big wheel is mounted and the escape pinion is positioned
The escape in full spin. It spins freely until the mark I put on the big wheel hits 11 o’clock when it slows down - but doesn’t stop
Here it is in the escape testing stage. Its hard to get at full view and still see any detail because the pendulum is 6 feet long
The front frame was lightened up by scrolling out a fanciful design.
I made the time train as small as I could cut and the reduction gears “hide” behind the hub on the hands
The hands are old fashioned scrolled ones. The original of this type was usually silver
The pallets were changed to give a little better lift to the pendulum. Next step is to take it all apart and smooth and paint it.
Brass rod was used to mark the hours since I wanted to keep the focus on the “Big Wheel” as much as possible.
I had in mind when I started to include a simple “bong” on the hour and now that has been added.
The actuator is simply a pin on the big wheel hub engaging one on the hammer rod. Electrical conduit makes a nice note
All the working parts are in place - now for the sanding and final finishing - not my favorite part of the job!!