Unlike Clocks 1 and 3, but like Clock 2, I plan to make Clock 4 wall mounted.
My wall mounting plans are to use a French cleat, since this makes it easy to remove the clock, and it's sturdy. I attached a cleat to the back of the clock...
... but it was unstable since the plate is wide and the pendulum is off center. So to stabilize, I added a small dowel to the back of the plate that grips the bottom of the cleat on the wall.
This means that I'm confined to use a particular size cleat (on the wall), but other dowel locations can be added easily.
The other thing I wanted was for the clicks and click springs to be carved from a single piece of wood. I tried this on Clock 3 with oak springs, but they were very stiff and eventually broke. Now I'm trying a pair of walnut springs, each a little lighter than the single oak I used previously.
They're glued to the drive wheel. I thought about offsetting them, which would lead to smoother winding, but I had trouble keeping the mechanism stable while setting up the glue. Hopefully they'll stand up to use.
Now that Clock #3's escapement seems to be working, I replaced the center pinion with a v-pulley. I made the v-pulley from two 1/8" plywood disks in which the edges were beveled in the lathe. I used hot glue to adhere the disks together, and used a heat gun to ensure the pulley was evenly glued. The v-pulley was secured to the center wheel by a pin. It seemed that this would grip an 80 lb monofilament fishing line if a counterweight was used. The line settles into the groove for an effective radius of 0.75 inches. The clock ran for over an hour on 3.25 lb drive and 0.5 lb counterweight, which works out to just about 2 inch points of torque on the center wheel.
I also noticed previously that escape wheel wheel drifted up on its arbor, so I added a small wooden washer cap that press fit to the arbor. This seemed to work well enough.
The friction drive I devised earlier for my clock has generally proved to be somewhat unreliable. The drive barrel ended up getting slippery, so I glued sandpaper around it to grip the drive cord. This worked well enough to drive, but winding was then a problem. Although you could release the friction enough to slip the cord upwards to wind, this slowly eroded the cord... and eventually the cord would break!
Since the timer ratchet mechanism seemed to work so well, I figured that might be a good idea. But holding the friction barrel with a ratchet wasn't the first thing that jumped into mind for whatever reason, although in the end, it's what I've chosen to go with. First, I embarked on an experiment to see whether I could use a chain drive with a ratchet mechanism. I found some "sash chain" at the hardware store that was apparently rated for 35 lb, which is more than enough for the clock's weight of 10 lb.
Oddly, no one seems to carry sprockets for sash chain, because it's really for window sashes, which don't actually need to be driven. (There are sash chain pulleys, though.) So I attempted to make my own sprocket, shown above, by cutting a barrel, drilling holes for nails and then pressing nails into the holes for teeth. The nails were originally finishing nails that I cut to size using a cutoff wheel and a jig to ensure they were all the same size.
Although the above picture is just an indication (don't spin with the nails installed!), I cut the barrel to a nice round circle on the lathe. I find I'm using the lathe more and more to ensure accuracy of circles. I find it helpful to grip a large bolt in the three-jaw chuck to use as an arbor for the work.
Here's a picture of the mechanism in place, with a click spring and the chain installed.
Here's another picture with the clock assembled. Notice the large gap to the left... if the winding barrel slips too far to the left, the click disengages and the weight falls!
So, I installed a brass pipe...
... that keeps the barrel pushed to the right against the click.
Unfortunately, the mechanism was nothing but trouble. The placement of teeth is way more critical than I imagined, and the chain kept jumping off the sprocket. Initially, the chain would lift and jam on the gear above it, which was annoying, but not hazardous. But as I got the teeth a little closer, the chain would jump off entirely, sending the weight falling.
So, back to the original friction drive... Here are the parts: a ratchet, barrel, end cap, and brass pipe to keep the barrel in the right spot.
Again, I used the lathe to make perfect circles, and indeed to drill and bore all holes.
Here is the mechanism installed. Time will tell if it proves reliable!
I made considerable progress on my timer over the past two weekends. I started with a pile of parts (after sanding)...
... and ended up with a nearly complete, partially functional timepiece!
Here is how it happened...
Since the design phase, I had left the spacing between the two plates as a yet-to-be determined variable. The key distance was the winding barrel, which had to rotate freely around the main wheel's arbor and engage with the ratchet and click assembly. I wasn't quite sure how much room I'd need, so I built the winding barrel first.
The winding barrel is hollow, and has two transverse pins to anchor the winding ribbon. First, I turned the outside of the winding barrel from 1/4" brass rod. Notice the thicker end (left) to receive the ratchet wheel.
I filed flats on the narrower portions...
And drilled holes to receive the pins in the flats.
I turned the pins from 1/8" brass rod, tapered to fit into the holes.
I pressed the pins into place with the vice.
This wasn't secure enough to keep the pins in place while center drilling, so I also soldered them.
I center drilled the assembled winding barrel in the lathe.
After it was drilled, it was fit friction-tight into the ratchet wheel.
Now that I knew the length of the winding barrel, I could estimate the distance between plates. Here are the two standoffs that hold the plates in place.
I also fabricated four pivots and two hollow bushings for the three arbors.
Here are the main wheel pivots drilled and fit into the frame.
Once that was all in place, I turned the main wheel arbor so that the winding barrel fit around it. I turned this out of a single piece of 1/4" brass rod, which took a while.
Then, I pressed the assembly together -- the winding barrel is permanently captive on the arbor.
With the main wheel assembled, I could align the main wheel pivot and bushing by aligning the two plates. This ensured that the arbor was installed perpendicular to the plates; if I had assembled the plates first, there was the risk that the pivot and bushing centers might be slightly out of alignment.
Next, I started to assemble the winding mechanism. Here is the click in place; I used a short nail with a broad head to attach the click so that it can move freely.
For the spring, I used the drive spring from a broken toy car. (There are lots of toy cars around my house since Theodore loves cars! Whenever a car gets destroyed, I scavenge for useful parts, springs in particular.) The spring was easy to cut with diagonal cutters, and easy to bend to shape with tweezers.
Here is the spring installed with two small finishing nails. I put the nails in first...
... and then trimmed off their points flush with the back of the wheel.
In order to drill the other wheels, I realized that I was struggling to get perpendicular holes since I don't have a drill press. So, I made a clamp assembly for my lathe's flat faceplate. I started with a sheet of steel and drilled four mounting holes. I think that the steel was probably hardened, and I was unable to anneal it with my small propane torch. Anyway, I broke two drill bits. One was a carbide-tipped bit for drilling glass, which cracked -- thankfully after finishing the holes!
Then, came the job of cutting the clamps out. Again, much tool stress later (wore out the teeth on my hacksaw and two jeweler's saw blades), I had my clamps. I filed them neatly, so they wouldn't mark anything.
Here they are, holding the second wheel securely in place. I also made use of a wobble stick to get the center just right.
And with that, turned a simple arbor and fitted the wheel and pinion into the frame.
Now, on to the escape wheel. Again, it was important to get the size of the escape wheel before making its arbor. The escape wheel consists of two three-toothed wheels, held part by three brass pins. Here are the pins, turned from 1/8" brass rod.
The pins are pressed into holes on each of the wheels, forming the escape wheel.
Now, with the escape wheel sized, I was able to figure the length of the arbor. I learned my lesson with the main wheel: turning down a 1/4" brass rod to 1/8" over nearly its entire length so that you have a hub takes long time. To economize on time a bit, I turned the arbor from 1/8" rod brass, and made a separate hub from 1/4" brass rod.
These two items were soldered together, thereby avoiding waste of time and materials.
The escape pinion was pressed on, using my now-standard technique of pressing on the lathe.
As usually happens to me, the depthing for this wheel wasn't perfect. So I opened up the bushing and pivot holes a bit and shimmed them to fit.
Here, the escapement wheel is pressed into place on its arbor. This means that the escape wheel and its pinion are permanently attached to the outer plate.
Trial assembly; most everything seems to fit. The wheels turn (mostly) smoothly, with the escape pinion occasionally binding. That'll be a problem for later, but it will need to be managed... Anyhow, this was the end of the first weekend, probably about 10 hours in total.
The second weekend started with making lots of pins... There are (top to bottom) 2x locking pins, 2x pendulum crutch pins, 2x gravity arm pivots, and a pendulum support.
Here are the locking and crutch pins installed on the gravity arms.
Here are the gravity arm pivots. It turned out that I had made these too short, so I put washers in as a stop-gap measure. Will need to fix later.
The pendulum support rod was set up in the style of what's shown in Gary Mahoney's clock:
I slit my pendulum support rod with a jeweler's saw, filed two flats, and then drilled to receive a screw.
This allows the pendulum to be attached with a flexible hinge of some sort. For the moment, I'm using paper. Maybe I'll use a flat spring.
The whole mechanism is assembled and mounted!
It runs, somewhat intermittently, with 4lb 4oz of weight! It is noisy!
The key issues seem to be that
The escape pinion binds occasionally, stopping the clock
The escape wheel occasionally skips, in which it slips past its locking pin rather than being captured. This is kind of catastrophic since the pendulum receives an out-of-phase impulse; sometimes it can recover, sometimes it can't. I think the cause is the gravity arms slipping along their pivots.
Remaining tasks:
Cap off the ends of the gravity arm pivots. The arms tend to slip around and off the pivots
Fix the gravity arm pivots by either remaking them (preferable) or making custom washers so that they keep the gravity arms the correct distance away from the outer plate.
Fix the depthing of the escape pinion
Fabricate a pendulum bob. The current bob is attached with a rubber band
Replace the pendulum pivot with something a bit stiffer than paper -- the pendulum wobbles axially too much.
