Sunday, January 25, 2015


The pendulum is attached directly to the arbor holding the anchor.  The anchor arbor was described before.  Once the position of the anchor along the arbor was found by fitting it with the escape wheel, I applied a small amount of glue to hold it.  I would have really preferred not to do this (I can adjust a friction fit, but not a glued one), but the anchor appears to slip a little too much.

To clamp the pendulum on to its arbor, I drilled two perpendicular holes -- one for a tightening bolt nearer to the end, and one for the arbor a little farther in.  Then, I slit the end of the pendulum.  Here is the assembly with a 8-32 bolt with washers in place.  Tightening the bolt grips the arbor more strongly.

The tightening bolt is accessible when the pendulum is in the frame.  Here it is as it is installed.

In order to test the workings of the mechanism, I mounted the frame against a set of sturdy shelves with a clamp.

In this position, I was able to give the pendulum a push and apply some weight by hand to the center wheel.  The mechanism appears to run, though some of the gears occasionally bind.  Usually, it looks like the fourth wheel pinion is the culprit, but sometimes the third wheel pinion binds.  With a small weight attached to the end of the pendulum (a pair of vice grips) and a 3 lb drive weight it will consistently run for about 15-20 seconds before stopping.

Saturday, January 17, 2015

Aliging the tailstock

I'm going to need to drill a pipe for the hour hand on my clock.  But since I know that the tailstock on my lathe is misaligned, I could run into trouble since the pipe is 1" long. 

After a little examination, it looks like the headstock edge of the quill tube is about 1/16" down from where it should be.  (Seems like a lot of wear, honestly.  Maybe something else is amiss...)  It seemed like a small shim ought to fix the problem, so I put a small brass shim of about this size under the tailstock runner.

I checked the alignment with the live center just touching a rod I had trued in the headstock. 

I slid the shim in just far enough to get the vertical alignment about right, and then used the alignment screws on the side of the tailstock to correct the horizontal alignment.  This disrupted the vertical alignment, so I iterated a few times.  Being wary that the overall problem is that the axis of the quill is not parallel to headstock axis, I checked the alignment both with the quill retracted and fully extended before being satisfied that everything was in order.  This worked, so I think the shim does actually make the axes coincident.

I then marked the shim's location by scratching it with the graver along the edge of the tailstock.

To move the tailstock, I just have to remember to take the shim along with it.  Since the runners are well lubricated, this mostly means keeping a finger on the exposed part of the shim as I slide the tailstock. 

Sunday, January 11, 2015

Winding mechanism

The winding mechanism for the clock follows the design shown in Huygens' endless chain mechanism.  The pulley is attached to the center wheel arbor and can have a max diameter of 1.5".  It's a tight fit to the center wheel arbor and is secured with glue.  The ratchet wheel can have a diameter of 2.5" and is offset from the main axis, and its arbor is clear of the center wheel.  The ratchet wheel needs its own arbor and a click.  (I expected to need a spring to keep the click seated, but that appears to be unnecessary.)  Here are the wooden parts for the ratchet wheel (left) and pulley (right).

The ratchet wheel also has an arbor and bearings, though that's perhaps unnecessary, it seemed appropriate.

The ratchet wheel bearings are placed offset from the train, as shown below:

The pulleys are friction-fit onto their arbors.  Unlike all of the gears that I attached before (which required several attempts with the lathe to turn the arbors to the correct size, then undershooting and building back up with solder), I tried a different approach.  Simply grip the arbor in the lathe, and then use an empty drill chuck in the tailstock to push the part onto the arbor with the lathe off.  This worked very smoothly!

It took several iterations to set the position of the ratchet wheel's pulley along its arbor, so that there is enough clearance between the center wheel and the ratchet wheel.

The pulleys both have several parts glued together.  Here is the initial gluing setup for each.

I just used Elmer's wood glue, and weighted the pieces.

I attached the click to the middle plate with a small nail.

I had expected to need a spring to keep the click secured while winding.  However since I located the click near the top of the ratchet wheel, gravity is sufficient to keep it anchored.  This also makes it easy to release the click should I need to.

Here is the cord attached.  I'm using 1/8" nylon braided rope with two single sheave pulleys for the weights.  Even with two turns on each pulley, the cord seems to slip, but it is sufficient to demonstrate that the mechanism is correct.

(Update 2014-01-17) One thing that is also slipping is the center wheel on its arbor when a large torque is applied to the drive pulley.  To fix this, I applied a small amount of glue to attach the pulley to the center wheel.

Thursday, January 1, 2015

Center wheel and pendulum arbor

I modified the plans for the center and pendulum arbors to fit the dimensions of the frame, now that the frame has been constructed.
As noted on the previous iteration of the plans, one end of the center arbor is supported by a thrust bearing of the kind manufactured yesterday.  The other end is supported by a ring.  The ring was cut from 1/4" brass rod, after being center drilled with an 11/64" hole.  The ring was made 3/8" long, and afterwards the edges were deburred in the lathe with the graver.  The center arbor itself was cut as per the plan above.  The arbor and bearing are shown below.
The arbor was fitted to the center wheel...

and test-fit in the frame with the other wheels.

I had to file the third wheel pinion to ensure smooth rotation, because it looks like the depth of the center wheel is slightly off.

Here's the pendulum arbor attached to the anchor.

And the pendulum in place engaging with the escape wheel.