In about 1970 my wife and I built an “A” Frame cabin on a property in the mountains. As with most A-Frames the sleeping quarters were in a loft and to access the loft I built a circular staircase. The treads for the staircase were cedar planks planed to a 2” finished thickness. Over the years the cabin has changed a lot and is now a more conventional “box”. I saved the parts of the circular staircase and have now found a home for one of the stair treads.
Our “A” Frame getaway in the mountains. The land was one of first purchases as a married couple and we still have it some 50 years later. The little "A" on the right is the outhouse and the '49 Plymouth is a 5 window coupe. At this point there was no power, no telephone, no running water and no sewer. Just quiet!
Over time the “A” Frame gave way to a well insulatde, centrally heated cabin with a generous workshop out back. Since we're 50 years older the plumbing, power, cell service and internet make this a vialble retreat
The salvaged circular staircase made this clock possible.
The Plate for this clock is a tread from the circular staircase. It measures 30” by 12” by 6” and is 2” thick.
This thickness allowed for a single plate that had lots of rigidity
The great wheel has a 3/16” arbor. The first attempt was to use a 1/8” arbor, but with the weight added there was enough flex in the arbor to bind on the pinion
The drive drum turns twice in 24 hours so the one inch drive drum on a 48 inch fall and 12 inches descent in 24 hours gives a 4 day run time.
Winding the clock is as simple as turning the drum which is viable since there is no front plate on the clock.
The gear train is once again taken from Ward Goodrich with 144 teeth to a 12 pinion, 96 teeth to a 12 pinion, 90 teeth to a 12 pinion and a 30 tooth escape.
As can be seen the great wheel is also a 12 hour wheel and the hours have been cut inside the great wheel. The hour hand is stationary on the plate. The rotation is counter clockwise
The second wheel turns once each hour and the minute hand is fixed to the wheel with the four quadrants stationary on the arbor.
The escape wheel is a 4 inch by 30 tooth unit. I opted to design a recoil type escapement. Ward Goodrich says that any number of teeth can be chosen, so I chose 13
15 teeth would be 180º so 13 is 156º. It looks weird but functions really well
I have always had “trouble” getting the correct depthing for the pallets and the escape wheel. I decided to see if I could set up a adjustable pallet arbor - success
Although the pendulum pivots on the escape arbor it is driven by a conventional crutch
Although I could have put almost anything as a bob I chose a pallet that didn’t work out. The bob has very little weight but still functions just fine.
All the wheels and pinions were cut on the CNC machine and its really nice to know that whatever ails a clock it isn’t badly cut teeth.